DELINEATION OF CADMIUM CONTAMINATED SOILS AROUND BUDDAH NALLAH (LUDHIANA) AND

REMEDIAL MEASURES OF AFFECTED SOILS

Thesis

Submitted to Punjab Agricultural Universityin partial fulfillment of the requirements

for the degree of

MASTER OF SCIENCE

in

SOILS(Minor Subject: Agronomy)

By

Dharamvir Singh Kambo

(L-2008-A-77-M)

Department of Soil Science

College of Agriculture

© PUNJAB AGRICULTURAL UNIVERSITYLUDHIANA-141004

2011

1

CERTIFICATE – I

This is to certify that the thesis entitled, “Delineation of cadmium contaminated soils around Buddah Nallah (Ludhiana) and remedial measures of affected soils” submitted for the degree of M.Sc. in the subject of Soil Science (Minor Subject: Agronomy) of the Punjab Agricultural University, Ludhiana, is a bonafide research work carried out by Dharamvir Singh Kambo (L-2008-A-77-M) under my supervision and that no part of this thesis has been submitted for any other degree.

The assistance and help received during the course of investigations have been fully acknowledged.

(Major Advisor)

Dr. MPS. KHURANA

Senior Soil Chemist

Department of Soil Science

Punjab Agricultural University,

Ludhiana- 141004 (India)

CERTIFICATE- II

2

This is to certify that the thesis entitled, “Delineation of cadmium contaminated

soils around Buddah Nallah (Ludhiana) and remedial measures of affected soils”

submitted by Dharamvir Singh Kambo (L-2008-A-77-M) to the Punjab Agricultural

University, Ludhiana, in partial fulfilment of the requirements for the degree of M. Sc.

in the subject of Soil Science (Minor Subject: Agronomy ) has been approved by the

Student’s Advisory Committee along with the Head of Department after an oral

examination of the same.

___________

Head of the Department Major Advisor

(Dr. Charanjit Singh) (Dr.MPS Khurana)

_________________________

Dean, Post-Graduate Studies

(Dr. Gursharan Singh)

3

Acknowledgements

First of all, I bow my head to “AKAL PURKH” the ALMIGHTY by whose kindness I

have been able to clear another chapter of my life.

Words are compendious in expressing my profound sense of gratitude to my

revered Major Advisor Dr. M P S Khurana, Sr. Soil Chemist, Department of Soil Science,

Punjab Agricultural University, Ludhiana, for his constant guidance, constructive

criticism, encouragement and unstinting moral support provided during this

investigation. Working under his expertise has been a great learning experience.

I am highly thankful to the respected members of my Advisory Committee,

Dr.U S Sadana, Professor of Soil fertility, Department of Soil Science, Dr. B S Brar, Sr. Soil

Scientist Department of Soil Science and Dr. Raj Kumar Pedologist, Department of Soil

Science and Dr. S S Walia Agronomist, Department of Agronomy for their valuable

suggestions, continuous support and going through the manuscript.

I duly acknowledge the research facilities provided by the Head, Department of

Soil Science, Punjab Agricultural University, Ludhiana.

I am falling short of words to express my feelings of obligation toward my

parents who always stand by me during the testing times of my life. Their everlasting

inspiration, support and affection enable me to face difficult situations in my life.

I am highly thankful to my senior Mr. Sanjeev Kumar and my friends, Jasbir,

Arshdeep, Sukhwinder, Satnam, Gurpreet, Sandeep and Remander, for their pleasant

association and co-operation during the hours of need.

Invaluable help rendered by laboratory and field staff of the Department of Soil

Science is fully acknowledged.

I feel proud to be a part of PAU, Ludhiana where I learnt a lot and spent some

unforgettable moments of my life.

Needless to say, errors and omissions if any are all mine.

Date__________ ______________Place: Ludhiana Dharamvir Singh Kambo

4

Title of the thesis : Delineation of cadmium contaminated soils around Buddah Nallah (Ludhiana) and remedial measures of affected soils

Name of the student and Admission No.

: Dharamvir Singh Kambo L-2008-A-77-M

Major Subject : Soil ScienceMinor Subject : AgronomyName and Designation of Major Advisor

: Dr. MPS Khurana, Sn. Soil Chemist

Degree to be Awarded : M.Sc.Year of award of degree : 2011Total pages in thesis : 80Name of the University : Punjab Agricultural University,

Ludhiana – 141 004, Punjab, India

ABSTRACT

Cadmium is potentially toxic metal and is highly carcinogenic that enters the food chain from the soil through crop uptake resulting from various anthropogenic activities. The surface sewage irrigated soils collected laterally around Buddah Nullah irrespective of the sites had DTPA extractable cadmium 5.2 times more than the adjoining tube well irrigated soils. Considering the threshold value of 3 mg Cd kg-1 soil, about 11.3 per cent soils have crossed this limit and needs cleanup operation. However management option to rehabilitate such soils depends on pools of Cd responsible for phyto-toxicity and use of amendments able to influence these pools. A screen house experiment was conducted to assess the effect of (0, 2.5, 5 10, 20 and 40 mg Cd kg-1 soil) and CaCO3 (2.5 and 5%), FYM (1 and 2 %) and Phosphorous (20 and 40 P2O5 mg kg-1 soil) on the growth of pigweed on soil having DTPA-Cd 0.36 mg kg-1 soil. Dry matter yields decreased as a consequence of phytotoxic effect of Cd emanating from increased availability of Cd in soils and plants. The rate at which significant declined occurred was 10 mg kg-1. However application of different amendments viz (Calcium carbonate, FYM, Phosphorus) exhibited variable behavior as far as their remediation potential was concerned. Application CaCO3, FYM and phosphorous at their highest rate reduced DTPA- Cd by 52.6 percent, 37.1 percent and 45.1 percent respectively. Consequently maximum enhancement in dry matter yields was observed with application of 5% CaCO3 among other amendments. The upper critical toxic level in soil and shoots of pig weed was found to be 4.38 mg kg -1 soil and 14.6 µg g-1 dry matter respectively. The interaction of Cd with Zn and Fe was found to be rate dependent. Cu and Mn in both shoots and roots was negatively correlated to the added Cd. All the fractions of Cd in soils increased significantly with cadmium application. Amendments decreased the EX+WS fraction, the maximum depressing effect observed with 5% CaCO3 because of concomitant increase in CARB fraction. FYM application decreased the CARB fraction where as it encouraged both OM-Cd and oxide bound fractions. Phosphorus application was effective in transforming Cd in to oxide bound fractions with little influence on carbonate and organic.

Key words: Cadmium, Delineation, Amendments, Critical levels, Cadmium fractions

________________________ ___________________Signature of the Major Advisor Signature of the Student

5

CONTENTS

CHAPTER TOPIC PAGE

I INTRODUCTION 1-3

II REVIEW OF LITERATURE 4-21

III MATERIALS AND METHODS 22-27

IV RESULTS AND DISCUSSION 28-62

V SUMMARY 63-66

REFERENCES 67-80

6

CHAPTER - I

INTRODUCTION

Increasing public awareness over the effects of environmental pollution during recent decade

was a result of enhanced understanding of the risk to human health. Contamination of

elevated-heavy metals in soils can adversely affect soil ecology, agricultural productivity,

quality of agricultural products, water resources, human and animal serious health problem

(Raicevic 2005). Agricultural lands show elevated levels of pollutant elements due to various

anthropogenic activities such as continuous use of sewage water largely contaminated with

industrial effluents, sewage sludge and fertilizers (Rattan et al 2002; Patel et al 2004). It is

released into environment by power stations, industries engaged in electroplating, pigments,

plastics, stabilizers and nickel cadmium batteries (Sanita di Toppi and Gabrielli 1999).

Increasing awareness of the environmental and public health hazard of toxic metals

pressurizes society to develop management strategies to remediate or restore the contaminated

area.

Among the pollutant elements, cadmium (Cd) is of great environmental concern as it

is easily absorbed by the plants from the contaminated soils and frequently accumulated by

agriculturally important crops with a significant potential to impair animal and human health.

Cadmium is a pollutant and potential toxin that has no known function in any biological

organism (Wagner 1993). This warrants close attention as it is a cumulative poison. This has

led the International Food Standards Organization, Codex Alimentarious Commission to

propose a 0.1 mg Cd kg-1 limit for cereals, pulses and legumes. The maximum tolerable intake

of cadmium for humans recommended by FAO/WHO is 70 ug/day. Therefore demarcation,

delineation and mapping through global poisoning system of cadmium contaminated soil in

the highly industrialized town of Punjab (Ludhiana) is urgently required to know the extent of

pollution.

Among remediation options, physical methods such as vitrification and evacuation of

polluted soils and its disposal to land fill sites are quite expensive. The major problem

associated with phyto-remediation is low metal removing rates (McGrath et al 2002).

Chemical stabilization appears to be an alternative technique that is seen as cost-effective and

environmentally sustainable. The principal aim of stabilization is the reduction in the bio-

available fraction of the metal either through increased metal sorption and/or precipitation, or

through the formation of insoluble complexes.

Hence; there has been an increasing interest in the immobilization of the metals using

range of inorganic and organic material like lime, phosphate, organic manures, and zeolites

(Singh et al 1989; Khurana and Kansal 2000). However, use of lime, phosphate, and farm

yard manure (FYM) is cost-effective option. Lime provides adsorptive surfaces and facilitates

7

pH induced precipitation. The FYM as metal ameliorant has also been studied as it off sets the

toxic effect of pollutant elements. On the contrary, Narwal and Singh (1998) reported an

increase insolubility of metals in soils amended with organic material.

Further speciation in to various geochemical forms of heavy metals including

cadmium in contaminated soils affecting their solubility is gaining importance to understand

fully the behavior of this metal in soils which directly influence their availability to plants.

Although the total metal concentration in many contaminated soils may be high, the phyto-

available fraction is usually very low due to the strong association of metal with organic

matter, Fe–Mn oxides, and clays, and precipitation as carbonates, hydroxides, and phosphates

(McBride 1995). The magnitude of these forms is not only controlled by pH, organic matter,

cation exchange capacity, calcium carbonate content of the soil through dissolution,

adsorption, precipitation and chelation reaction but also on the rates of metal loading from

inorganic or organic sources and climate.

Once, these heavy metals are incorporated in to the soil, their extractability decreases

with time indicating a possible change of their forms in the soil (Bell et al 1991). If the crop is

planted following the application of heavy metals and amendments (Calcium carbonate, FYM

and Phosphorus), the change in chemical form any influence the uptake by plants and help to

reduce the toxicity. Effect of different inorganic amendments on fractionation and availability

of Cd to wheat was evaluated by Ghafoor et al (2008). Inorganic amendments viz. lime,

gypsum, diammonium phosphate (DAP) and potassium dihydrogen phosphate was used at

different rates were found to effective in retaining Cd in non available pools and substantial

decrease in exchangeable fraction of Cadmium. Sequential extraction data thus indicated that

amendments were equally effective in transforming readily available Cd to less mobile

fractions (carbonate, Fe/Mn oxide). There is paucity of information pertaining to speciation

(various fractions) controlling and contributing towards the availability of cadmium to the

crops particularly grown on sewage irrigated soils. This study was to examine the effect of

amendments on fractionation and bioavailability of Cd in soil in order to the alleviate its toxic

effects of cadmium on vegetables crops.

In Punjab, vegetables crops are grown mostly on sewage irrigated soils and are

known to accumulate large amounts of heavy metals in their shoots and roots because of their

high biomass and root proliferation. Chalai (Pig –weed Amaranthus tricolor) is generally

found growing on sewage irrigated soils for edible purposes because of the low production

cost and high productivity per unit area, this is considered to be the low cost vegetable in the

Indian market and often described as poor man’s food. As it is consumed as green vegetable,

amount of Cd present in it has direct bearing on human health. Although various amendments

has been tried for different crops but the work on efficient and cost efficient ameliorative

8

measure affecting the availability of cadmium to this crop is still not elucidated. There for it

was felt desirable to examine different amendments on the bioavailability of Cd to this crop.

Objectives

1) To delineate Cd contaminated soil for its lateral distribution in order to assess its

extent of pollution.

2) To assess relative suitability of different amendments for minimizing Cd pollution

in contaminated soils and plants.

3) To establish the upper threshold limit of toxicity of Cd for pig weed.

4) To study the effect of various amendments on the transformations of Cd in soil.

9

CHAPTER II

REVIEW OF LITERATURE

The review pertinent to present investigation had been reviewed under the following heads

2.1 Influence of sewage water / sludge application on accumulation of heavy metal in

soils and plants

2.2 Effect of cadmium on growth, concentration and uptake in different plant species:

2.3 Effect of different amendments on cadmium uptake

2.4 Transformation of heavy metals in soils

2.1 Influence of sewage water / sludge application on accumulation of heavy metal in

soils and plants

Repeated use of waste water for irrigation to crops resulted in build-up of heavy-

metals in the soil (Singh et al, 1985; Mapanda et al 2005; Rattan et al. 2005; Liu et al. 2005;

Mitra and Gupta 1999; Zhang et al 2008). Elevated levels of different heavy-metals in soils

regularly irrigated with sewage water than ground water have also been found (Siebe 1998;

Aghabarati et al. 2008). Siebe (1998) reported significant increase in DTPA-extractable-Pb

and Cd up to 30 cm soil layer with the application of sewage water, consecutively for 80

years than the soils irrigated with ground water. El-Arby and Elbordiny (2006) reported

concentrations of DTPA-Fe, Mn, Zn, Cu, Co and Ni in the sandy soil receiving treated waste

water averaged 3.2, 122, 129, and 186 which was 22.0, 14.5 and 10.5 fold than soils receiving

ground water as irrigation, respectively. Mapanda et al (2005) studied the magnitude of

contamination and annual loadings of soils with Cu, Zn, Cd, Ni, Cr and Pb at three sites in

Harare (Zimbabwe) where waste water irrigation was practiced in vegetable gardens for last

ten years. They reported that heavy-metal concentrations in sandy and sandy–clay soils

ranged from 7.0 to 145 mg kg−1 for Cu, 14 to 228 mg kg−1 for Zn, 0.5 to 3.4 mg kg−1 for Cd,

<0.01 to 21 mg kg−1 for Ni, 33 to 225 mg kg−1 for Cr and 4 to 59 mg kg−1 for Pb up to 20 cm

soil depth. Annual heavy metal loading rates showed that all studied heavy-metals exceeded

their permitted limits in soils, depending on site.

Mitra and Gupta (1999) reported that total and DTPA–extractable concentration of

Pb, Cd, Cr, Co and Ni were significantly higher in soils of East Calcutta irrigated with sewage

water than the tube well water irrigated soils of Baruipur farm. Concentration of Pb, Cd and

Cr were found to be above the permissible limits in sewage irrigated soils.

Singh et al (2010) reported that continuous application of waste water and clean

water site as have led to higher concentrations of heavy metals in the soil at waste water

irrigated site as compared to clean water irrigated site which were higher by 109 % for Cd,

152 % for Cu, 25 % for Pb, 32 % for Zn, 161 % for Ni and 52.8 % for Cr.

10

Kansal and Khurana (1999) observed that DTPA–extractable and total Cd

concentration of sewage irrigated soils were higher than tube-well irrigated soils in the

industrial towns of Punjab.

Kürsad Türkdo et al (2003) reported 2 to 50-fold higher concentration of Cd, Pb, Cu

and Co, ~40-fold higher Zn concentration in volcanic soils irrigated with waste water

compared to ground water in Van region of Turkey. Liu et al (2005) reported metal

enrichment factor of Cd (1.8), Cr (1.7), Cu (2.3), Zn (2.0), Pb (1.9) and the metal

contamination factor of Cd (2.6), Cr (1.5), Cu (2.0), Zn (1.7), and Pb (1.6) in soil that

received the sewage water irrigation.

Rattan et al (2005) reported that sewage waste water irrigation for 20 years resulted

in significant build-up of DTPA-extractable Zn (208%), Cu (170%), Fe (170%), Ni (63%)

and Pb (29%) in sewage waste water irrigated soils over ground water irrigated soils, whereas

Mn content was depleted by 31%. Fractionation study indicated relatively higher build-up of

Zn, Cu, Fe and Mn in bio-available pools of sewage waste water irrigated soils. In contrast,

Rusan et al (2007) reported non-significant (p≤0.05) differences in soil available Pb and Cd

content in soils of Jordan with the application of municipal waste water even up to 10 years.

Mohammad and Mazahrez (2003) also reported inconsistent variation in heavy-metal content

of soil with industrial waste water application.

Khurana et al (2003) found that mean values of DTPA- Pb, Ni, Cd Zn, Mn and Fe in

surface (0-15cm) soils of highly industrialized city of Ludhiana irrigated largely with sewage

effluents were 4.21, 3.58, 0.30, 11.9, 25.4 and 49.2 as compared to 2.76, 0.40, 0.12, 2.10,

8.34, 10.88 in less industrialized city of Sangrur indicating higher loading of soils of

Ludhiana with heavy metals through sewage irrigation. The increase in heavy metals content

of soils with continuous application of sludge/ sewage water has also been reported by Brar et

al (2002) and Kuhad et al (1989).

Taywade and Prasad (2008) observed that in sewage water irrigated soils are

associated with relatively higher concentration of DTPA-Fe, Mn, Cu, Zn, Pb, Cr and Cd as

compared to the corresponding non-irrigated soils.

In a study Dheri et al (2007) reported that Pb, Cr, Cd and Ni were significantly higher

in sewage water irrigated soil compared to tube well irrigated soil .The concentration of Pb,

Cr, Cd and Ni in sewage irrigated soils were 1.8, 35.5, 3.6 and 14.3 times higher than their

concentration in tube well irrigated soils respectively. The build up of Cr (35.5 times) and Ni

(14.3 times) in this study was so high that these elements may cause phyto-toxicity to crop

plants with continuous application of sewage effluents.

The investigation carried by Sikka (2003) found that the mean content of available

cadmium, lead and nickel where Buddah Nallah (a sewage channel passing through the

interior of Ludhiana City) water has been continuously used were 0.8, 4.7 and 1.9 mg kg-1 soil

11

which were 530, 361 and 296 percent higher than the adjoining fields where tube well water

has been used for irrigation. In earlier study Sharma and Kansal (1986) noted that available

cadmium was three to five times higher in Nullah irrigated soils where it ranged from 0.119 to

0.253 mg kg -1 soil as against its content which ranged from 0.085 to 0.115 mg kg -1 soil in

tube-well irrigated

Gupta and Mitra (2002) studied the effect of long-term use of sewage waste water in

soils of Calcutta (India) and reported 2.43, 46.5, 3.81, 0.86, 93.0, 15.9, 3.88, 2.44 and 6.61

fold increase in total-Fe, Zn, Cu, Mn, Cd, Pb, Co, Ni and Cr concentration in comparison to

soils receiving ground water for crops. In an another study in El-Sadat City of Egypt on the

use of industrial for 5 years, El-Arby and Elbordiny (2006) reported significant increase of

1.72, 2.48, 2.72, 4.49, 4.24, 1.90 and 2.36 times increased concentration of total-Fe, Mn, Zn,

Cu, Co, Ni and Pb over ground water irrigated soils (0-15 cm) has been reported. Patel et al

(2004) compared the build-up of total heavy-metal content in soils irrigated with mixed

sewage and industrial effluents and those irrigated with effluents from paper mill industry.

They reported that soil irrigated with paper mill effluents accumulate 2.4, 4.5 and 3.8 mg kg -1

less Fe, Zn and Cu, respectively but 2.1 and 18.6 mg kg-1 more Mn and Pb, respectively than

mixed sewage and industrial effluents.

Chen et al (2009) analyzed the total concentrations and chemical speciation of heavy

metals including Cd, Cr, Cu, Zn and Ni in sewage–irrigated soils in the eastern suburb of

Beijing, China. The results showed that there was remarkable buildup of Cd, Cr, Zn and Cu in

sewage-irrigated top soils compared to reference topsoils. Among the four metals, Cd was

more mobile and bioavailable in the sewage-irrigated topsoils than in the reference topsoils.

Higher Cd contents in sewage-irrigated soils may constitute potential risk on food security

and human health.

Prabu et al (2009) conducted an experiment to assess the extent of heavy metal

contamination of vegetables due to irrigation with polluted Akaki river water, Ethiopia on

agricultural land. The results showed that the heavy metals in Akaki water were higher than

the natural elemental levels in freshwater. The concentration of Cr in all vegetables was more

than the maximum limit. The Cd accumulation was more in leafy vegetables than other

vegetables under study. Metal transfer factors from soil to vegetables were significant for Zn,

Mn, Cu, Fe and Cd and accumulation of Cr and Ni was comparatively less while that of Zn,

Fe, Cu and Mn was more in vegetable plants.

Mapanda et al (2005) studied the contamination of leafy vegetables (Brassica

species) with copper (Cu), zinc (Zn), cadmium (Cd), nickel (Ni), lead (Pb) and chromium

(Cr) and their subsequent risk to human exposure in the City of Harare, where waste water

was used for irrigating vegetables and concluded that it was not safe and might not be

12

sustainable in the long-term. They also reported elevated concentrations of Cu, Zn, Cd, Ni, Cr

and Pb in the topsoil of sites irrigated with waste water.

Lokeshwari and Chandrappa (2006) studied to assess the extent of heavy metal

contamination of vegetation due to irrigation with sewage-fed lake water on agricultural land.

Samples of water, soil and crop plants have been analyzed for seven heavy metals, viz. Fe,

Zn, Cu, Ni, Cr, Pb and Cd using atomic absorption spectrophotometry. The results showed the

presence of some of the heavy metals in rice and vegetables, beyond the limits of Indian

standards. Metal transfer factors from soil to vegetation are found significant for Zn, Cu, Pb

and Cd. Comparing the results of heavy metals in water, soil and vegetation with their

respective natural levels; it was observed that impact of lake water on vegetation was found to

be more than the soil.

Gupta et al (2007) investigated the effects of municipal waste water irrigation on the

accumulation of heavy metals ( Pb, Zn, Cd, Cr, Cu and Ni ) in soil and vegetables and

revealed that heavy metal-contaminated vegetables grown in wastewater-irrigated areas may

pose public health hazards.

Mishra and Tripathi (2008) conducted a study to determine the heavy metal

contamination in soil with accumulation in plants in waste water irrigated areas. Results

revealed that waste water contained lower concentrations of Cr, Zn, Cu, and Pb except Cd

than the permissible limits prescribed by the World Health Organization (WHO). The

maximum metal concentrations occurred in Brassica oleracea. The metal enrichment and

degree of contamination showed that accumulation of the five toxic metals increased during

sewage irrigation as compared with the reference values, other Indian regions and globally.

However, based on WHO standards for heavy metal contamination of soil and irrigation

water, our data does not ensure safe levels for food.

2.2 Effect of Cadmium on growth, its concentration and uptake in different plant species

Cadmium is a non essential element that negatively affects plant growth and

development. It is recognized as an extremely significant pollutant due to its high toxicity and

large solubility in water (Pinto et al 2004). It is easily taken up by plants and can interfere

with many physiological processes associated with normal growth and development (Artexe

et al 2002). It inhibits root and shoot growth, affects nutrient uptake and synthesis of

chlorophyll, protein, carbohydrate, free amino acids, and RNA etc Greger et al (1991) and

reduces crop yields (Jing and Logan 1992; Lune Van and Zwart 1997). The uptake of

cadmium by higher plants depends on its concentration in the soil and its bioavailability,

modulated by the presence of organic matter, pH, redox potential, temperature and

concentration of other elements. Cadmium easily penetrates the root through the cortical

tissue and is translocated to the above ground tissues (Yang et al 1998). In general, cadmium

13

is toxic to a number of plant species at relatively low soil and plant concentration.Visible

symptoms of cadmium toxicity in plants include chlorosis, leaf rolls and stunting.

Patel et al (1980) reported that high level of Cd produced 50% or more yield decrease

in bush bean plants (Phaseolus vulgaris) in highly calcareous desert soil. Further, they

reported that increasing Cd levels caused significant decrease in the yield of crop.

Borges and Wollum (1981) reported that application of Cd decreased the dry matter

production of tops, roots and nodules of soybean plants. Nutrient imbalance in the presence of

Cd was observed. They suggested that the interaction of Cd with some nutrients may be

responsible for Cd toxicity. They further found most pronounced Cd effect on Fe and Mn

rather than Zn.

Page (1981) found that Cd was usually lowest in grain and fruit crops, intermediate in

root crops and highest in leafy crops. The most important soil factors influencing crop Cd

were the concentration in soil and soil pH. Cataldo et al (1981) also reported that following

root absorption, Cd was strongly retained by roots with only 2% of the accumulated Cd being

transported to leaves, as much as 8% was transported to seeds during seed filling.

Khan and Khan (1983) studied the effect of Cd on the nutrient concentration of

tomato and egg plant. The application of Cd was found to effect the nutrient concentration

and their uptake by plants. Cadmium decreased Zn in both crops and increased Mn, Fe and

Cu in tomato and decreased in egg plant.

Chernykh (1991) noticed the effect of different concentrations of Pb and Cd on the

uptake of major and trace elements by barley and Vicia sativa cv which were grown in pots

taking various types of soils. The low concentrations of Cd or Pb didn’t alter plant material

uptake, but higher heavy metal concentrations disrupted mineral uptake and translocation.

Reductions in the uptake of P, Ca, Mg, Cu and Fe were more pronounced in Vicia sativa than

in barley at high heavy metal concentration. Among the various soils, the effect of Pb and Cd

were more visible in acid sod-podzolic soil than in uncultivated sod-podzolic and least in

chernozem.

Haghiri (1973) studied the growth and cadmium concentration of soybean and wheat

tops as influenced by soil applied Cd. In both the crops, Cd concentration increased while

yields decreased with increasing level of applied Cd. Cadmium toxicity (2.5 ppm) of applied

cadmium. He also assessed the effect of soil applied Cd at 0-10 ppm on the yield and

cadmium uptake of radish, lettuce, capsicum and celery. Cadmium tolerance and uptake

varied widely among crops, lettuce having the highest concentration and radish roots the

lowest. The largest relative reduction in growth was shown by lettuce followed by radish,

green pepper and celery. Maclean (1976) found that addition of 5 ppm of Cd decreased the

yield of lettuce in all the five soils selected during the study. Rana and Kansal (1985) reported

that application of Cd to soil showed adverse effect on plant growth. The fresh yield of

14

barseem fodder decreased significantly with Cd application to soils. The higher rate of Cd

application even lead to mortality of plants immediately after germination.

Koreak and Fanning (1978) added Cd to soil (2 mg Cd kg-1 soil) in the form of

inorganic salt (CdSO4) and an equivalent amount in the form of municipal sewage sludge and

determined the amount of Cd absorbed by corn (Zea mays). Even though, the pH of the soil

amended with sewage sludge was lower (pH 6.0) than that of same soil amended with CdSO4

(pH 6.5), the amount of cadmium accumulated by the corn foliage from CdSO4 was 5 to 18

times greater than the amount accumulated by the foliage from the soil amended with sewage

sludge.

Maclean (1976) observed reduction in yield of lettuce in all the five soils when Cd

was added at the rate of 5 ppm. Sadana and Singh (1987) found that increasing level of Cd up

to 8.0 mg kg-1 soil reduced significantly (40 percent) dry matter yield of spinach. The

corresponding increase in Cd content of spinach was from 0.6 to 38.4 μg g -1 dry matter. Singh

and Nayyar (1991) observed 15 to 79 percent reduction in dry matter yield of wheat at 45

days of growth at different rates of Cd application.

Saini and Kansal (1990) revealed that yield of maize fodder decreased significantly

with the application of cadmium. The higher yield of 9.24 g pot-1 was obtained without Cd

which was significantly reduced to 7.30 g pot-1 when the rate of Cd application was increased

to 5 μg g-1 soil. Singh and Nayyar (1989) reported a significant decrease in mean dry matter

yield of corn with 30 mg Cd kg-1 soil application in a pot culture experiment on coarse

textured soil.

Juwarkar and Shende (1986) obtained 32 percent reduction in grain yield of wheat on

calcareous vertisol due to toxic effect of high level of Cd (400 ppm) applied through sewage

sludge. Walker et al (1979) reported a significant linear effect of Cd upon the concentration

of Zn, Mn, Cu, K, Ca and Mg except P which decreased with increased Cd conducted on low

pH soil application in soyabean plants while Mahler et al (1982) from a green house trial

reported that Cd additions to the soil decreased Zn in lettuce, tomato, corn and swiss chard,

decreased Mn in Swiss chard and lettuce, it increased in tomato but showed little or no effect

in corn. Further, application of Cd didn’t affect P, Fe, Ca, Mg, S and K uptake.

Jeng and Bergseth (1992) reported that high total content of heavy metals is not

synonymous with increased plant uptake. Jasiewicz (1993) sampled carrots, beetroots,

parsley, celery, leeks, onions, cabbages and lettuces taken from numerous localities and

analyzed for Cd, Ni and Pb levels in the aerial parts as well as in roots. In the majority of

samples, Cd and Ni accumulated more in the roots as compared to Pb which was more in the

aerial parts. The contents of Cd and Pb exceeded the permitted levels.

In a green house experiment, Lehoczay et al (1996) studied the influence of Cd

concentrations (0, 50 or 100 mg kg-1 soil) on biomass production and Cd contents of maize,

15

garlic and spinach by taking two soil types i.e. Eutric cambisol and Gleycluvisol. The Cd

contents of all three crops increased with increasing concentrations of Cd in the soil. The

concentrations of Cd in plants grown in the strongly acidic gleycluvisol soil were many times

higher than those of plants grown in the neutral Eutric cambisol soil. With regard to biomass

accumulation spinach was most sensitive to Cd.

Arauja et al (1997) reported that Cd contents in plants like Carinata and Duronegro

increased with increased cadmium levels in the nutrient solutions. Applied cadmium

decreased contents of Zn and Mn in roots with little or no effect on the contents of these

elements in the shoot. Copper content in plants remained unaffected by Cd levels in the

nutrient solution except for the Cd content in roots of Carinata, Fe contant was altered only in

the roots of duronegro.

Bipasha et al (1997) reported that Cd alone significantly decreased shoot bud

formation and shoot elongation, with the higher concentration having greater effects, but

addition of equal concentration of Zn overcame the toxicity of Cd to some extent. Tolerant

plants could be regenerated in a culture medium containing both metals and showed greater

uptake of Cd in the roots than shoots, whereas Zn was translocated from roots to shoots. Ebbs

and Kochain (1998) screened twenty two grasses and cereals in hydroponic culture indicated

that oats (Avena sativa) and barley (Hordeum vulgare) tolerated higher levels of Cu, Cd and

Zn as evidenced by elevated concentrations of these metals in the plant shoots.

Khurana et al (2006) reported significant decrease in mean dry matter yield of maize

cultivars namely Sartaj and Parkash with 10 mg Cd kg-1 soil. Lehoczky et al (1998) assessed

the effect of increasing Cd concentration on biomass production of lettuce and noticed a

decrease in biomass production as Cd rate was increased. Similar results were obtained by

Singh and Aggarwal (2005).

A study was conducted by Shafiq (2008) to determine the effect of different

concentrations of lead and cadmium on seed germination and seedling growth of Leucaena

leucocephala. Seed were grown under laboratory conditions at 25, 50, 75 and 100 ppm of

metal ions of lead and cadmium. Both lead and cadmium treatments showed toxic effects on

various growth indices of L. leucocephala. Seed germination and root length significantly

(p<0.05) decreased at 50 ppm treatment of cadmium as compared to control. The seedling dry

weight also significantly (p<0.05) reduced at 25 ppm treatment of lead and cadmium.

2.3 Effect of different amendments on cadmium concentration and its uptake

Stabilization/solidification techniques are developed to convert contaminants into less

soluble, immobile or less toxic forms. Stabilization aims to immobilize contaminants by

adding immobilizing agents enhancing adsorption, complex binding or precipitation

(Kumpiene et al 2008). Typical immobilizing agents in field studies amendments are: limes,

16

phosphates, organic matter induced additives (peat, manure) and industrial co-products based

Synthetics (Guo et al 2006)

2.3.1 Effect of phosphorus amendment on cadmium concentration and its uptake

The application of different amendments is well known for their effectiveness to

reduce toxicity of heavy metal to crop plant in contaminated soils. The use of phosphorus

amendment has gained an increasing interest to minimize heavy metal toxicity through

chemical immobilization of Cd in crop plant. The reduction in phyto toxicity of heavy metal

has been observed due to their immobilization in soil.

The role of phosphorus amendments to reduce Cd toxicity occurred through the

formation of Cd–phosphate complexes. This may be due to sorption mechanisms such as

surface fixation, ion exchange, precipitation and co-perception when different phosphorus

source are added to Cd contaminated soils. These processes led to lowering the phyto

availability of Cd to crop plants. Chemical immobilization of heavy metal with phosphate

may thus be a good remedial measure to reduce Cd toxicity to crop plants in contaminated

sites. Phosphate-based additives forms secondary phosphate precipitates that are relatively

insoluble and stable in a wide range of conditions. Solubility of both metals and phosphates

remains low under neutral conditions and acidity has to be added for an efficient metal

immobilization (Chen et al 2003).

Levi-Minzi and Petruzzelli (1984) observed that phosphate induce variation in soil

pH influenced the solubility of Cd in soils. They noticed that that while the effect phosphorus

on pH and cadmium was less evident in an organic soils with high pH buffering capacity, the

addition of diammonium phosphate increase soil ph thereby reducing solubility of Cd in

mineral soils with low pH buffering capacity. Bolland et al (1977) reported that the specific

adsorption of phosphate anions increased the negative charge of variable surface which may

result in the increasing retention of metal cat ion such as Cd +2, Cu+2 and Zn+2. Naidu et al

(1996) also reported an increase in net negative charge of surface due to specific adsorption of

phosphate anions.

Bolan et al (1999) observed that retention of Cd+2, Cu+2and Zn+2 ions increased with

increase in specific adsorption of phosphate ions through P amendment. Bolan et al (2003)

reported that with addition of KH2PO4 as a source of amendment to the contaminated soils, the

plant growth of Brassica juncia increased with application of P amendment in the Cd

contaminated soils and also phosphorus application decrease the Cd concentration in plants.

The reduction in phyto toxicity of Cd due to phosphate induced immobilization of Cd in soils,

which could be explained by precipitation of Cd as Cd(OH)2 and Cd3(PO4)2.The mechanism

involved in phosphate induced Cd adsorption included increase in pH , increase in surface

charge, co-adsorption of phosphate and Cd as an ion pair and surface complex formation of

Cd on phosphate compound.

17

Ma et al (1994) reacted Pb and synthetic hydroxyl apatite (HA) in the presence of

various levels of Al, Cd, Cu, Fe, Ni or Zn at different pH levels and observed a significant

reduction in Cd concentration in solution. They suggested that mechanisms for reducing Cd

concentration in soil solution were likely the formation of amorphous mixed-metal

phosphates (Cd-phosphates or Ca-Pb-Cd phosphates), sorption on apatite surfaces, or ion

exchange reactions. Laperche et al (1996) reported that addition of phosphorus may reduce

phytoavailbility of Cd through a combination of several mechanisms, such as sorption,

precipitation or co precipitation. Valsami-Jones et al (1998) studied the reactions of synthetic

HA and natural apatite with aqueous Pb and Cd and found that Cd concentration were

reduced in the aqueous solution. They also suggested similar mechanism of formation of

amorphous mixed–metal phosphate as well Chen et al (1997) suggested that reduction in

aqueous Cd concentration with apatite addition occurs primarily because of sorption

mechanism such as surface complexsation and ion exchange rather than precipitation of Cd

phosphate. Laperche et al (1997) investigated the effect of different apatite amendments on

Pb availability to sudan grass and reported that in the absence of apatite, the Pb concentration

in sudan grass were as high as 170 mg Pb kg-1 which got reduced to 3mg kg-1

Basta and McGoven (2004) studied that the evaluation of three chemical

immobilization treatments i.e. agriculture limestone (AL), mineral rook phosphate and

diammonium phosphate (DAP) to reduce heavy metal (Cd, Zn, Pb) transport in a smelted

contaminated soil. They observed that DAP treatment was superior to all other materials for

reducing Cd, Zn and Pb concentration. Application of DAP @ 10g kg -1 was most effective

treatment for immobilization of Cd, Pb and Zn with reduction of 94.6, 98.9and 95.8

respectively.

Brown et al (2004) reported that with application of phosphorus amendments, the

phytotoxicity of Cd was reduced which led to higher plant yield in tall fescue grass and

observed that 1 % H3PO4 treatment was the most effective to reduce plant Cd concentration.

Hettiarachchi and Pierzynski (2002) studied the effect of various P amendments on

plant growth of Sudan grass and Swiss chard. They reported that Cd concentrations in both

the crops were reduced significantly by triple super phosphate (TSP) but did not change with

the addition of rock phosphate indicating thereby that plant growth was enhanced by the

presence of soluble phosphorus source due to formation of mixed metal-phosphates. The

lower solubility of these metal phosphates could have restricted metal uptake by plant. Cao et

al (2003) also reported that with the application of phosphorus through phosphate rock, the

Pb, Zn and Cu concentration in roots of Augustine grass was decreased.

Raicevic et al (2005) studied that in situ immobilization of toxic metals, using

inexpensive `reactive` amendments, is considered as a simple and cost effective approach for

the treatment of soils, contaminated by the presence of heavy metals as compared to ex situ

18

and costly techniques. The stabilization of heavy metals in contaminated soils and ground

water by addition of apatite minerals has the potential to be a successful and widely

applicable remediation strategy for the case of Cd, Pb as will as for other heavy metals

existing in polluted soils. The theoretical analysis of stability, regarding the apatite/Cd or

apatite/Pb systems and relevant results of sorption experiments, pointed out two different

mechanisms for the immobilization of Cd and Pb by use of apatite to remediate the

contaminated soils.

Strong antagonism between P and Cd has been reported by Brown et al (2004).

Restricted Cd availability due to P application was also confirmed by Panwar et al (1999,

2001) and Datta et al (2007).

Matusik at el (2008) study the In situ immobilization of heavy metals in polluted

soils using phosphates leads to formation of products which are highly insoluble and

thermodynamically stable over a broad pH and Eh range. The highest reduction of cadmium

concentration (>99%), owing due to the formation of cadmium phosphates, was observed for

all used phosphorus sources within pH range of 6.75–9.00.

Mark et al (2000) suggested that, due to low solubility, the formation of metal

phosphates in soils contaminated by metals may represent a cost-effective, sustainable, in situ

method for the remediation of metal contaminated soils. A variety of laboratory and field

experiments have been carried out to investigate this proposition and these are reviewed. In

laboratory studies carried out by the authors, and summarized here, bone meal (ground bone)

was used as a phosphorus source. Low concentration bone meal additions to metal

contaminated soils resulted in the immobilization of lead, zinc, nickel and copper, and

increases in the pH of the soils. The relatively low cost of bone meal means that bone meal

amendments could be a cost-effective treatment for metal contaminated soils

2.3.2 Effect of CaCO3 on Cd concentration and its uptake

Lime and other alkaline amendments raise pH that leads to a higher affinity between

soil and metal species, but also leads to formation of precipitates and secondary minerals that

decreases metal solubility and transport (Basta and Mcgoven 2004)

Singh and Nayyar (2001) reported that with applied calcium carbonate at the rate of

2.5 percent to the soil, both DTPA-extractable and plant Ni decreased which helped in

mitigating the toxic effect of Ni as evidenced by the increase in dry matter yield of cowpea.

Increased levels of Ca2+ can decrease the amount of Cd that is assimilated by plants

(Larlson et al 2000). Because of their similar size, Ca (II) is almost in distinguishable from

Cd (II) (Ochiai 1995). A higher affinity for the essential trace metal Ca results in the

decreased uptake of Cd into the plant. A similar relationship exists between P and Cd. John et

al (1972) showed that the addition of 1000 ppm of phosphorus to a Cd contaminated soil

19

decreased the concentration of Cd 43% in the roots of oats. Trace metal deficiencies in plants

have been associated with increases in heavy metal uptake (Khan and Frankland 1983).

Peles et al (1998) concluded that the addition of lime to contaminated soils

(essentially increasing the pH) decreased the uptake of heavy metals. In unlimed soils

Ambrosia trifida accumulated 13.6 μg Cd g-1 of tissue and in limed soils A.trifida

accumulated 2.5 μg Cd g-1 of tissue.

Tlustos et al (2008) reported the influence of the addition of CaO and CaCO3 in

contaminated soil containing 7.14 mg Cd kg -1, 2174 mg Pb kg -1, and 270 mg Zn kg-1 on

element availability for spring wheat in pot experiment. The ameliorative materials were

added into the pots containing 5 kg of soil in amount of 3 g CaO, and 5.36 g CaCO3 per kg of

the soil. Soil pH increased to 7.3 in lime treatments compared to 5.7 in control soil. Mobile

portion of soil elements (0.01 mol l-1 CaCl2 extractable) dropped by 80% for Zn, 50% for Cd,

and 20% for Pb, respectively. In both straw and grains of wheat reduced content of elements

was observed in limed pots compared to the control ones.

Han and Lee (1996) observed reduction in uptake of Cd and Pb in Raphanus sativa L.

var. Paekyong using the application of lime. Soils treated with 1.52 mg kg –1 Cd and 25.37 mg

kg –1 Pb, respectively was grown in greenhouse pots and amended with lime at five rates of 0,

0.25, 0.5, 1.0 and 2.0% by dry soil weight. Plants were harvested at 25, 50, and 75 days after

sowing and the roots and shoot separated. Liming decreased Cd uptake markedly at its highest

level.

Xian (1989) reported that exchangeable and carbonate constituted 55 and 11% of

total Cd respectively and he also observed that potential bioavailability was strongly

controlled by their chemical forms related to solubility and exchangeable and carbonate forms

were the most important forms for heavy metal uptake by plant. Ma and Gade (1997)

obtained 57 to 100% reduction in water soluble Pb with the application of crushed rock

phosphate to a lead contaminated soils.

Lee (2004) study the effect of soil amendments, including compost, zinc oxide,

calcium carbonate, calcium carbonate mixed with zinc oxide, and calcium carbonate mixed

with compost. The amended soils were incubated for six months under 60% of water holding

capacity. Following incubation, wheat was grown for four months in greenhouse. Analyses of

Cd concentration demonstrated a significant decrease in soil solution concentration and

DTPA or EDTA extractable in soils amended with calcium carbonate or calcium carbonate

mixed with ZnO (or compost) (p < 0.01). These amendments can significantly reduce the Cd

concentration in the grain, leaf and stem, or reduce the total Cd uptake in all parts of wheat

species grown in highly contaminated soil amended with calcium carbonate or calcium

carbonate mixed with ZnO (or compost) (p < 0.01).

20

2.3.3 Effect of FYM on cadmium concentration and its uptake

The heavy metal concentration in soil and may lead to the phyto toxicity to crop

plants. Various organic and inorganic amendments are applied to contaminated soils to reduce

the toxic effects of heavy metals in soils as well as plants. Organic compounds like Farmyard

manure, biosolids and poultry manure are known to decrease the phytotoxity of different

heavy metals like Cd, Cr and Cu etc. FYM is easily available source of organic matter, cost

effective.

Hiroyuki et al (2010) conducted a field experiment and observed efficiency of cattle

waste compost (CWC) in reducing Cd uptake by spinach (Spinacia oleracea L.). Spinach was

grown in a field that had been treated by having cattle, swine, or poultry waste compost

incorporated into the soil before each crop throughout 4 years of rotational vegetable

production. Cadmium concentration was 34–38% lower in spinach harvested from the CWC-

treated soils than in the chemical fertilizer-treated soil.

The risks related to municipal solid waste compost application in comparison to

farmyard manure and mineral fertilizers on durum wheat were investigated on a short-term

experiment by Lakhdar et al (2008). Compost was applied at 40 t ha -1 and 80 t ha-1 with or

without chemical fertilizers. Analogously, farmyard manure was applied at 40 t ha -1. Both

compost and farmyard manure improved plant growth and nutrient uptake. However, compost

amendment showed more effectiveness, especially at 80 t ha-1. Alternatively, this dose of

compost involved an increase of plant copper, cadmium, and zinc concentrations in plant

tissues. Metal accumulation did not thwart the enhancement of wheat yield.

Putwattana (2010) conduct a pot experiment and study the effect of cow manure on

the cadmium uptake and dry matter yield and result showed an increase in dry biomass

production by factors of 4.7 and 1.7 in plants grown in soil supplemented with cow manure

(20% w/w) and silicate fertilizer (20% w/w), respectively by Ocimum basilicum (sweet basil)

grown on in Cd contaminated soil (20 mg/kg Cd)

Singh et al (1992) Studied that in a screen house experiment that Cd concentration in

plants decreased with the addition of organic matter at all cadmium levels.

Dahiya et al (1987) studied the effect of Cd and FYM on dry matter yield of maize

and found that FYM application increased significantly dry matter yield of maize by

decreasing the concentration of Cd in maize plants. Khurana and Kansal (2000) studied the

bio-availability of Cd to maize crop as influenced by Cadmium and Farm Yard Manure. They

found that addition of FYM increased organically and oxide bound but decreased the

exchangeable + water soluble and carbonate bound fraction. Increase in comparatively

insoluble fractions of Cd helped to mitigate the toxic effect of Cd as evidenced by increase in

dry matter yield.

21

2.4 Transformation of heavy metals in soils

Increasing amount of pollutant elements are entering the soil plant system through

anthropogenic activities, sewage waste and fertilizers. Once these elements specially Cd .,Pb

and Ni (found commonly in soils in toxic amounts around the industrial towns) enter the soil

plant system, they interact with its organic and inorganic constituents. Then they get

transformed into various forms like soluble, exchangeable bound to carbonates, Fe and Mn

oxides, organic matter and residual (Bell et al 1991). Sequential procedures have been used to

identify these forms (McLaren and Crawford 1973; Cottenie et al 1979). Researchers have

often noted that metal added to soils as reagent grade inorganic salts were more readily

available to plants than those present in sewage sludge. Once these heavy metals are

incorporated into soil, their extractability appears to change with time indicating a possible

change of their chemical form. So metal toxicity depends on chemical associations in soils.

For this reason determining the chemical form of a metal in soils is important to evaluate its

mobility and bioavailability.

Ghafoor et al (2008) study the effect of different inorganic amendments on

fractionation and availability of Cd to. Inorganic amendments viz. lime, gypsum,

diammonium phosphate (DAP) and potassium dihydrogen phosphate (KH2PO4) was used at

different rates. Maximum reduction in Cd in grain (75%) and straw (64%) was observed

where KH2PO4 were applied at 2000 mg kg-1 followed by the treatment, where DAP was

applied at the rate of 2000 mg P kg-1. Lime application significantly decreased Cd

concentration by 54% and 64% in straw and grain as compared to control, while decrease

with gypsum 41% in straw and 61% in grains

Kuo et al (1983) observed that 30-60 per cent of total Cd was found to be in

exchangeable fraction (Soluble in MgCl2). This per cent was found to be much greater than

that of other elements including Fe and Mn. Most of the Cu, Zn and Mn were present in an

oxalate extractable fraction but only small amounts were extractable by citrate dithionite-

bicarbonate (CDB) solution. Cu, Zn and Mn were strongly associated with amorphous Fe

oxides with only small amounts being occluded in crystalline iron oxides. It appeared that Cd,

Ni and Zn were shifting to residual forms. The occurrence of metals in residual forms in the

soil after sludge incorporation, contributed to the lack of metal movement in the soil profile.

Berthet et al (1984) assessed that levels of exchangeable and easily reducible Cd were

very low in sewage sludge than in the soil. Levels of Cd associated with organic matter were

high and moderately reducible forms were frequent in both soils and sludge. Almost half the

Cd in sewage was in stable forms unavailable to plants.Cd concentration in the plants being

generally higher in treatments than controls.

Lake et al (1984) reported that following the application of municipal sewage sludge

to agricultural soil, the metals were being predominantly associated with solid phases, soluble

22

exchangeable species generally represent < 10 per cent of total metals. Speciation in sludge

amended soil initially reflected that of sludge itself although changes with time had been

observed.

Gibson and Farmer (1986) studied various fractions of cadmium and zinc and found

that 32 per cent of Cd was associated with the exchangeable + carbonate fractions, 29 per cent

of zinc with the organic fraction, 42 and 46 per cent of the total Cd and Zn were found in the

residual form.

A sequential extraction procedure incorporating I M KNO3, 0.5 M KF, 0.1 M

Na2P207, 0.1 M EDTA and I M HNO3 had been used to fractionate metals in to exchangeable,

adsorbed, organically bound, carbonate bound, and sulphide forms respectively (Stover et al

1976). Carbonate constituted 49 per cent of Cd, 32 per cent of Ni and 61 per cent of Pb on

average while 35 per cent of Cu was present in sulphide form, 50 per cent of Zn was

organically bound. For Cd, Cu, Pb and Zn adsorbed and exchangeable fraction accounted for

only 17 per cent.

In sandy loam soils treated with sewage sludge, Sposito et al. (1982) found that Zn,

Cd and Pb were mainly present in carbonate form, Cu in organic form and Ni in sulphide

form. Irrespective of sludge application rate, exchangeable metals averaged between 1.1 and

3.7 per cent. Soon (1981) revealed that soils treated with sludge increased the amount of

exchangeable cadmium but reduced the amount of complexed Cd compared with fertilizer

soil. Cadmium retention by cation exchange became more dominant with the increasing

amount of Cd in the soil. He postulated that with addition of 50 µg Cd g-1, its precipitation as

CdCO3 was at pH>7.6. Cadmium adsorption increased with increasing pH. The difference in

Cd adsorption between different soil treatment were attributed mainly to the change in soil pH

(6.9 to 7.9) induced by sludge application. Alekseev and Zyrin (1982) found that water

soluble and exchangeable forms of cadmium were transformed into more stable form with

time. They also observed that mobility of cadmium and its availability for plants were

substantially greater in acid soil than in non calcareous, neutral and alkaline soils.

According to Silviera and Sommers (1977), water soluble and exchangeable metals

(Cu, Zn, Cd and Pb) comprised a small per cent of the total metal concentration in the sludge

and in soil-sludge mixture incubated for 7 to 28 days. The DTPA extractable fraction of the

total Cu, Zn, Cd increased with time but DTPA extractable Pb remained unaffected.

Emmerich et al (1982) employed sequential extraction procedure for applied sewage sludge

and uncontaminated soil samples. They reported that less than 35 per cent of each metal (Cu,

Ni, Zn Cd) in sewage sludge was in the residual form but the soils contained greater than 65

per cent of each metal studied in this form. It appeared that Cd, Ni and Zn were all shifting to

residual forms. The occurrence of metals in the stable organically bound, carbonate and

23

residual forms in the sludge coupled with a shift towards the more stable form (residual) after

soil incorporation, contributed to the lack of metal movement in the soil profile.

Soon and Bates (1982) studied the chemical pools of cadmium, nickel and zinc in

polluted soils and extracted the soil with 1M ammonium acetate to remove soluble plus

exchangeable metals, with 0.125 M copper acetate to remove complexed metals and with I M

HNO3 to dissolve chemisorbed or occluded metals and precipitates such as oxides and

carbonates. Expressed as a per cent of metal so extracted, exchangeable Cd>Zn and Ni,

complexed Cd and Zn >Ni, and Ni>Zn> Cd in the acid soluble pool. With a few exception

(soils with high organic matter content or low pH) at least 50 per cent of extracted metal was

in acid soluble form. But when soil 1 and 2 were treated with CdCl2 (samples I-A and 2-A)

more of added Cd was soluble and exchangeable compared to treatments which received

similar amount of Cd from sewage sludge.

Xian and Shokohifard (1989a) investigated the effect of pH on chemical forms and

plant availability of heavy metals in three polluted soils. Heavy metals were portioned in to

five operationally definite chemical fractions: exchangeable, carbonate, Fe–Mn oxides,

organic and residual. When soils pH values were decreased from 7.0 to 4.55, levels of Cd, Zn

and Pb in exchangeable forms increased but decreased in carbonate and Fe-Mn oxides forms.

Their levels in organic and residual forms were unchanged.

Khan and Frankland (1983) reported that a very high proportion of Cd and Pb added

to the soil became water insoluble fraction within one hour of contact with the soil, although

most of the water insoluble fraction was EDTA soluble.

Miller and McFee (1983) sequentially extracted the heavy metals with I M KNO3,

Sodium pyrophosphate, 0.1 M EDTA, 0.1 M hydroxyl amine hydrochloride and 0.01 N nitric

acid, 0.27 N sodium citrate + .1N sodium bicarbonate + 0.25 g Na2S2O4, I N HNO3, and

HNO3 + H2O2 for removing water soluble exchangeable, organically bound, carbonate / non

crystalline Fe occluded Cd, Mn oxides occluded, crystalline Fe oxides occluded, sulphide and

residual to study the distribution of cadmium, zinc, copper and lead in soils of industrial north

western Indiana. The result showed large amounts of relatively labile metals associated with

exchange site (KNO3 extractable), 23, 10, 1 and 8 per cent of total Cd, Zn, Cu and Pb

respectively, bound by soil organic matter (Na2P2O7 extractable : 21, 33, 24 and 41 per cent of

total Cd, Zn, Cu and Pb) and associated with carbonates and/or non crystalline Fe oxides

(EDTA-extractable : 12, 8, 26 and 28 per cent of total Cd, Zn, Cu and Pb). Minimal amount

of the metals were within small amount of crystalline Fe and Mn oxides present in these soils.

Non extractable (residual) metals amounted to 26, 32, 23 and 41 per cent of total Cd, Zn, Cu

and Pb.

Xian (1989b) reported that the exchangeable fraction contained 55 and 13 per cent

and carbonate fraction 11 and 10 per cent of the total Cd and Zn respectively. The highest

24

amount of zinc (42 per cent) was detected in residual form. Cadmium distribution to organic

and residual was small especially in paddy soils. Metals level in cabbage plants were in

accordance with their levels in the soil. He also observed that potential bioavailability of

heavy metal was strongly controlled by their chemical forms related to solubility and

exchangeable and carbonate forms were the most important forms for heavy metal uptake by

plants. Okamoto et al (1990) found that the heavy metals were mostly in the carbonate and

Fe-Mn oxides forms with low mobility and availability in soil amended with sewage

sludge .When the sludge application was interrupted, and the soil was treated with acid

fertilizers, the chemical forms of the heavy metals changed from carbonate or Fe-Mn oxides

to soluble and exchangeable forms, with an increase in availability and mobility due to

decrease in soil pH

Dudka and Chlopecka (1991) observed that mobility and plant availability of zinc

and cadmium in sludge treated soil were associated mainly with the exchangeable fraction.

Jeng and Singh (1993) studied partitioning and distribution of cadmium and zinc in selected

cultivated soils in Norway. These soils were analysed by sequential extraction to isolate five

fractions of Cd and Zn. On average, 47, 4, 33 and 5 per cent of the total Cd fractions were

classed as weakly adsorbed (F1), adsorbed (F2), strongly adsorbed (F3) and very strongly

adsorbed (F4) forms of elements respectively. 11 per cent was regarded as incorporated in

resistant mineral (F5). The relatively high proportion of F1 fraction indicated that much of Cd

under these conditions was available to plants. For Cd, F1 and F3 were directly correlated with

organic carbon and total iron. Organic carbon also seemed to be important in retaining F 4,

where as F5 correlated best with clay.

Pierzynksi and Schwab (1993) studied the sequential fractionation of Cd. Soil

samples were extracted with 0.5 M KNO3, deionized water three times, 0.5 M NaOH, 0.05 M

Na2EDTA and 4 M HNO3. The sum of KNO3 and water extractable metals were assumed to

represent the most liable metal pool, the NaOH fraction were assumed to represent the

organically bound pool, EDTA to represent metal from inorganic precipitates and HNO3

fraction was residual. They further studied the effect of lime stone, cattle manure, poultry

manure, N-vivo, K2HPO4 and (NH4)2HPO4 on these fractions. Lime stone treatment was

clearly the most effective in reducing bioavailable (KNO3, H2O and NaOH) fraction of Zn and

Cd. But NaOH-Cd was significantly increased by cattle manure, poultry manure and K2HPo4

treatment as compared to control. Lime stone treatment significantly increased EDTA-Cd

fractions as compared to control. Corresponding to reduction in NaOH–Cd with increasing

lime stone rates, was a significant increase in EDTA-Cd suggesting an increase in precipitated

Cd in the presence of lime stone. Significant increase in NaOH-Cd observed with addition of

manure might be attributed either to Cd additions with manure or partitioning of Cd into

organic fractions with increasing organic additions.

25

Ramos et al (1994) employed sequential extraction procedure to partition the Cd, Pb,

Cu and Zn in soils representing three different areas in Spain, i.e. marshes, stabilized sand and

mine. Marshes had the greatest total levels of four metals due to the influence of a mine

located 40 km away while the stabilized sand was non polluted. The bioavailable fraction of

Cd represented > 50 per cent of total Cd in the soils. The total amount of Cu, Pb, Cd and Zn

in the soils and their distribution in the five fractions depended on the total metal content, soil

type and soil properties. Mobilities of the metals were in the order of Cd > Zn > Pb > Cu.

The distribution of the chemical forms of Cd and Cu in four inceptisols was studied

using a sequential extraction procedure by Ahumada and Schalscha (1994). The metals were

separated into five fractions: water soluble, exchangeable, reducible, DTPA extractable and

insoluble organically bound forms. Cadmium was recovered mostly in the insoluble organic

matter fraction. The addition of extra Cd did not affect this distribution. Copper was

recovered mostly in the reducible and the Fe and Mn oxides bound forms. By increasing the

redox potential of soils from –150 to +50 mV and then to 300 mV, the proportion of

exchangeable metals decreased while the proportion of the reducible form increased. The

proportion of plant available Cd was unaffected and the distribution of Cu forms was

unchanged.

Asami et al (1995) fractionated soil Cd, Zn, Pb and Cu in 38 soil samples from 11

soil profiles of industrially polluted and nearby non polluted areas in Japan. On average 45

per cent of Cd was present in CaCl2 (Ca) soluble fraction where as corresponding values for

other metals were less than 10 per cent. The per cent of each metal in the CA fraction

followed the order Cd>Zn>Pb>Cu. The same order was observed for acetic acid soluble

fraction. Approximately 30 per cent of total Pb and Cu and only 10 per cent of total Cd and

Zn were present in the pyrophosphate soluble fraction. Approximately 20 per cent of total Zn

or Pb and 10 per cent of Cd or Cu were present in the free oxides fraction. Only 20 per cent of

Cd and between 40-50 per cent of other three metals were present in the residual fraction. The

result showed that Cd was more labile than other metals.

Taylor et al (1995) conducted fractionation of residual cadmium, copper, nickel, lead

and zinc in soils that had received previously two types of sludge at two different rates,

fertilizer and control. The content of cadmium, copper, nickel, lead and zinc fractions in

previously sludge amended soils were governed by total content of these metals in the sludges

applied and by the rate of sludge application. The contents of these metals were higher in soils

that received the Chicago sludge as compared to that received the Hunstsville sludge.

Furthermore, soils that received 20 t/ha/year of sludge for 5 years generally had higher levels

of these metals than those receiving a single dose at 100 t ha-1. The per cent of total content in

water soluble and exchangeable forms was very low. The application of sludge tended to

reduce the residual fraction and increased the organic and carbonate fraction. Overall, the

26

predominant forms of metals in the sludges were as Cd, Ni, Pb and Zn carbonate and Cu

organic fractions.

Sadamoto et al (1995) assessed the heavy metal pollution in terms of chemical forms

especially Cu, Zn and Cd. Extraction with H2O2 and acetic acid (2.5 per cent v/v) recovered

greater quantities of metal than 0.1M potassium pyrophosphate. Oxalic acid + UV radiation

incompletely extracted metals occluded by Fe oxides whereas oxalic + ascorbic acids reduced

the oxides enabling extraction of the occluded metals. Acetic acid (2.5 per cent v/v) extracted

metals sorbed by geothite and gibbsite. The residual fraction comprised 50 per cent of soil Cu,

60-70 per cent of soil Zn. Cadmium however was found predominantly in exchangeable forms.

Liu et al (1997) studied the desorption mechanisms and chemical forms of Cu and Cd

in major Taiwan agricultural soils, high in organic matter and Fe-Mn oxides contents to

evaluate the fate of heavy metals. The result showed that Cu was mainly associated with Fe-Mn

oxides (29.4 per cent), carbonate (23.8 per cent) and organic matter (17.0 per cent) while Cd

existed mainly as water soluble and exchangeable forms (68.6 per cent). All the results showed

that Cd pollution might had greater impact on plants and environment than Cu pollution.

Singh et al (1998) characterised the surface soils near some disposal sites in Belgium

for total metal contents and various fractions. Residual fractions were low compared to total

content (2-4 per cent for Cd, 25-35 per cent for CO, 7-18 per cent for Mn, 4-22 per cent for

Zn, 11-42 per cent for Pb). High metal concentration in the acid extractable and reducible

fractions indicate pollution hazards. Singh et al (1995) extracted the heavy metals with DTPA

and NH4NO3 at different pH values in a clay loam and loam soil. They found that the DTPA

extractable and NH4NO3 extractable Cd had decreased with increasing soil pH and the effect

was more pronounced with NH4NO3 extractable Cd. Both extractants were found equally

effective in relation to Cd concentration in plants.

The review of literature presented in the preceding pages indicated that application of

metal contaminated sewage water, sewage sludge, solid wastes and fertilizers and caused

significant contamination of agriculture soils with heavy metals including cadmium. Review

also suggested that separation of various forms in soils had been useful in studying the

retention and release of elements by the soil to the plant and was particularly more important

for pollutants added through waste materials. The addition of amendments influenced the

chemical forms of cadmium in a soil and therefore, helped to reduce the toxicity of cadmium.

Studies pertaining to the use of farm yard manure, CaCO3 and phosphorus were rather scanty.

Therefore present study was undertaken to investigate the effect of these amendments on

transformations of this element to evaluate its bioavailability.

27

CHAPTER – III

MATERIAL AND METHODS

Keeping in view, the objectives mentioned in chapter-1, the materials used and the methods

followed during the course of study have been reported under the following heads.

I) Surveys Studies

II) Screen house studies

III) Laboratory studies

I) Survey studies

Ludhiana city was founded on a ridge of Buddah Nallah, which once was a bed of the

river Satluj. The urban area is lying between 30o 51'10" to 30o 57' 20"N latitude and 75o 46'00" to

75o56'20"E longitude, the average height above mean sea level is 247 m. Previously the urban

area was confined south of it but due to burgeoning population, the low lying area between

Buddah Nallah and the river Satluj is fast getting urbanized

In order to determine pollution potential, surface (0-15cm) soil samples receiving

waste water irrigation at a distance of 50, 250, 500, 750 and 1000 meters (5 sites) were

collected laterally on either side (Right and left) along the Buddah Nallah from each village

(six in number) which were approximately 4-5 kilometers from each other with the help of

global positioning system in the month of December. The six villages selected for this

purpose were Bhamian khurd, Saidan, Saleem tabri, Pratapsinghwala, Talwara and Jain pura.

It was not possible to collect samples from all the sites of the all the villages due to built area.

Details of sampling sites from each village is mentioned in table 4.1 Thus, in total, 53 soil

samples were collected for this purpose.

Surface (0-15cm) soil samples were also collected from nine villages namely

Bhamian Kalan, Baranhara, Balloke, Ladian Khurd, Bagha Khurd, Jhamat, Ayali khurd,

Malikpur, Rajowal where no sewage water was applied. These sampling sites are

schematically shown in map (fig 1)

II) Screen house studies

Bulk soil sample (0-15 cm surface) was collected from sewage irrigated soil near to

the Buddah Nallah (Ludhiana). Soil was air dried ground and passed through a 2 mm stainless

steel sieve. The physico – chemical characteristics of processed soil are given in table 3.1.

The processed soil was thoroughly mixed and used for screen house studies.

28

Table 3.1. Physico-chemical characteristics of the soil.

Characteristics Contents

pH(1:2)* 7.02

EC(ds m-1)* 0.54

Organic Carbon (%) 0.24

Calcium carbonate (%) 0.20

Macro nutrients (Kg ha-1)

N 278.4

P 15.7

K 137.8

DTPA extractable (mg kg-1 soil)

Cadmium 0.36

Zn 1.38

Fe 12.6

Mn 5.40

Cu 1.00

Mechanical Composition

Sand (%) 75.2

Silt (%) 15.0

Clay (%) 9.80

Texture Loamy Sand

*( 1:2, soil: water suspension)

Experiment: 1

Treatments

Level of cadmium (6) : 0, 2.5, 5, 10, 20, 40 mg kg-1 soil

Levels of amendments (7) : 0, 2.5%, 5 % (Calcium carbonate), 1%, 2%

(FYM) and 20, 40 mg P2O5 kg-1soil (CaH2PO4)

Replications : 4

Crop : Chalai(Pig weed-Amaranthus tricolor)

Experimental Design : Completely randomized factorial design

No .of pots : 6 x4x 7 =168 pots

29

Treatment imposition and fertilizer application: Bulk surface (0-15cm) soil sample was

collected from the sewage irrigated soil. This sample was air dried ground and sieved. Nine kg

of this processed soil was taken in each polythene pot. Cadmium at the above rates were applied

through cadmium chloride and amendments (Calcium carbonate: 2.5 and 5 %, FYM: 1 and 2%

Phosphorus: 20 and 40 mg P2O5 kg-1 soil through CaH2PO4. The soil in the pots was subjected

to alternate wetting and drying cycles for 30 days to attain equilibrium. Thereafter,

representative soil samples from each pot was taken, processed and stored in polythene bags for

chemical analysis. After application of basal recommended doses of N, P and K, the seeds of

Pig weed (Amaranthus tricolor) was sown in pots under optimum moisture conditions. After

germination, thinning was done to maintain 6 plants. The soil in the pots was irrigated as and

when required. The crop was harvested after 45 days of sowing. Shoot, root and soil samples

were collected from each pot. The shoot and root samples were analyzed for total Cd as well as

for Cu, Fe, Mn and Zn while soil sample was be analyzed for DTPA-Cd .The upper threshold

value of Cd in soil and crop was determined by employing suitable method .

Harvesting, collection and processing of shoot and root samples: The shoot samples were

harvested with the help of stainless steel blade. For harvesting and collection of root samples the

polythene bags were taken out from the pots. The soil was washed with tap water from each

polythene bag. The roots were separated and put in the stainless steel sieve and washed with tap

water pressure, water jet, acidified deionized water and finally with double distilled water. The

harvested shoot samples were also washed with acidified deionized water, distilled water and

with double distilled water. The washed shoot and root samples were first air dried by keeping

them in paper bags and then in oven at 65±2 oC. Thereafter, the shoots and roots were weighed

for dry matter yield. Shoots and roots of the plants were ground by stainless steel grinder and

stored in polythene bags separately. Cadmium as well as Fe, Mn, Zn and Cu were analysed in

shoots and roots.

Post harvest soil sampling: After harvesting the crop, composite soil samples from each pot

were taken with stainless steel tube augar. These soil samples were air dried, ground, sieved and

stored in polythene bags for their chemical analysis.

2 Laboratory studies

Sequential extraction of soil samples: A seven step sequential extraction procedure given in

Table 3.2 was applied to evaluate the association of metals with soil constituents. The different

chemical forms of fraction of Cd were exchangeable + water soluble, carbonates, organic mater

complexed, Mn-oxide bound, occluded in amorphous and crystalline Fe oxide and residual

mineral fraction. Several methods of fractionation of heavy metals have been proposed by several

workers (Chao 1972; Gupta and Chen 1975; Tessier et al. 1979; Chao and Zhou 1983; Shuman

1985). Here sequential extraction procedure adopted by Singh et al (1988) was used with some

modifications to simulate the conditions, which is described in Table 3.2. Reagents used in

30

fractionation scheme were selected from those cited in the literature as being selective for specific

chemical from in soil. All procedures were carried out in triplicate. Five gram of each soil sample

was taken in centrifuge tube then centrifuged and filtered after fulfilling the essential conditions

such as shaking, boiling, digestion etc. the soil residue was washed twice with double distilled

water.

Residual metal analysis: Residual from C-FeOX extraction was washed twice with double

distilled water. It was subsequently dried and ground to pass through a 2mm stainless steel sieve.

A 0.5g sample was digested with 10 ml concentrated HF and 2-3 ml concentrated HClO4

remaining material was taken up in 6N HCl and volume was made to 25 ml.

Analysis methods:

The following methods were used for soil analysis:

1) Mechanical analysis was done as per International pipette method (Piper 1950).

2) pH and electrical conductivity were determined in 1:2 soil water suspension with the

help of glass electrode pH meter and conductivity meter bridge respectively.

3) Organic carbon was estimated by Walkley and Black’s rapid titration method as

described by Jackson (1973).

4) Calcium carbonate was estimated by following the method of Puri (1949).

5) DTPA extractable polyvalent transition metals were extracted by using the procedure

of Lindsay and Norwell (1978) and estimated on AAS.

Total heavy metals: A sample of soil was ground to pass through 2 mm stainless steel sieve. A

0.2 gram sample was digested as per method described in residual fraction (Tessier et al

1979).The amount of other metals and Cd in each fraction were estimated by atomic absorption

sepectrophotometry (AAS).

Analysis of (FYM): One gram of oven dried FYM sample was digested in 20 ml of

distilled concentrated nitric acid at low heat on a hot plate to oxidise organic matter and

digested the mixture with 20 ml of perchloric acid until dense white fumes of acid

appeared. Diluted the digest with double distilled water to known volume

Analysis of roots and shoots: In order to determine Cd and other heavy metals in shoots

and roots, 0.5g of ground and well mixed plant material was digested in a diacid mixture of

nitric acid and perchloric acid (4:1). After digestion, the volume was made to 25 ml with

double distilled water, filtered and stored in well washed plastic bottles. All the estimations

in the aliquot were made by using Atomic Absorption Spectrometer.

Statistical analysis: Factorial CRD was employed to study the effect of different treatments

in various experiments (Panse and Sukhatme, 1967). The analysis was carried out with the

help of a computer. The effects of treatments were compared with the help of interaction with

CD (Critical Difference).

31

Table 3.2 a. Sequential extraction methods used for post harvest distribution of Cd

Sr. No.

Fractions Solution Soil (g)

Solution (ml)

Conditions Reference

1 Exchangeable + Water soluble (EXCH+WS)

1 M Mg(NO3)2 5 20 Shake 2 hrs at 25°C

Shuman (1985)

2 Carbonates (CARB) 1 M NaOAC (pH 5.0 CH3COOH)

5 20 Shake 3 hrs at 25°C

Tessier et al (1979)

3 Organically bound (OM)

0.7 M NaOCl (pH 8.5)

5 20 Shake 30 min in boiling water bath, stir occasionally, repeat extraction

Shuman (1983)

4 Mn-Oxides bound (MnOX)

0.1 M NH2OH.HClSol. in 0.01 M HNO3 (pH 2.0)

5 25 Shake 30 min Chao (1972)

5 Amorphous Iron Oxide bound (A-FeOX)

0.25 M NH2OH.HCl + 0.25 M HCl

5 25 Shake 30 min in boiling water bath, stir occasionally

Chao and Zhou (1983)

6 Crystalline Fe-oxide bound (C-FeOX)

0.2 M (NH4)2

C2O4 + 0.2 M H2C2O4 (pH 3.0) + 0.4 M ascorbic acid

5 25 30 min in boiling water bath, stir occasionally

Shuman (1982)

Table 3.3: Chemical composition of farm yard manure (on oven dry weight basis)

32

Characteristics Content

Organic carbon (percent) 20.18

pH* 8.0

EC (dS/m)* 3.16

Total metals content (mg kg-1 soil)

Iron 2140

Manganese 280

Copper 9.40

Zinc 72.4

Cadmium 0.38

*1:4 farm yard manure: water suspension

33

CHAPTER IV

RESULT AND DISCUSSION

The experiment results pertaining to the present investigation have been presented and

discussed under the following heads.

4.1 Survey studies:

4.1.1 Delineation, demarcation and mapping of cadmium polluted soils along a

sewage channel (Buddah Nullah) in Ludhiana district.

4.2 Influence of different levels of Cd and and various amendments on

4.2.1 Dry matter yield of shoots of chalai (pig-weed)

4.2.2 Dry matter yield of roots of chalai (pig-weed)

4.2.3 Cadmium concentration in shoots and shoots of chalai (pig-weed)

4.2.4 Cadmium uptake in shoots and shoots of chalai (pig-weed)

4.2.5 DTPA – extractable Cd in equilibrated soils

4.2.6 DTPA – extractable Cd after the harvest of crop

4.3 Micronutrient cations concentration in shoots and roots of chalai (pig-weed)

4.4 Upper critical level of Cd in

Soil

Plant

4.5 Effect of various amendments on the transformations of Cd in soils (laboratory

studies)

4.1 Survey studies

Study Area

Buddah Nallah, a narrow unlined canal, is the city’s sole surface water

resource.  It originates from Chamkaur Sahib (district Ropar) and merges in the River

Sutlej. It is an important drainage line of Ludhiana district, receives waste water from

diverse type of industries such as machine tools, electroplating, bicycles and woolen

& hosiery manufacturing units. The daily disposal of such waters, which are both of

industrial and domestic origin, is quite high. The large volume of domestic and

industrial waste water has converted the canal to a virtually sewage drain. In the late

nineteenth century, it was a clean water stream as reported in the gazetteer of 1904.

4.1.1 DTPA extractable cadmium: Diethylene triamine pentaacetic acid (DTPA) and more

precisely 0.005M DTPA + 0.01MCaCl2+ 0.1M tri ethanol amine (pH 7.3) has been used to

measure available form of Cd. Elevated concentration of DTPA extractable Cd was found in

sewage fed soils as compared to normal soils at all the locations. Overall mean (average of 10

34

values) DTPA extractable Cd in surface sewage irrigated soils of Bhamian khurd, Saidan,

Saleem tabri, Pratapsinghwala, Talwara and Jain pura were 0.11, 0.21, 0.18, 0.18 and 0.13 mg

kg-1 soil respectively irrespective of distance from the polluting point indicating high

accumulation in surface soils (Table 4.1). The respective mean values of DTPA extractable

Cd in the surface layer in tubewell irrigated soils of of Bhamian Kalan, Baranhara, Balloke,

Ladian Khurd,Bagha Khurd, Jhammat , Rajowal, Malikpur, Ayali Khurd were 0.06, 0.04,

0.06, 0.02, 0.02, 0.04, 0.02, 0.02 and 0.02 mg kg-1 soil, respectively. When mean value of

DTPA-Cd for all the samples (53 in number) of surface sewage irrigated soils was taken, it

was found to be 5.2 times greater than the normal soils. The increase in Cd content of soils

with continuous application of sludge has been reported by many workers (Singh et al 1985;

Mapanda et al 2005; Rattan et al 2005; Liu et al 2005; Mitra and Gupta 1999; Zhang et al

2008; Siebe 1998; Aghabarati et al 2008).

4.1.2 Lateral distribution of Cd on either side of Budah Nallah: The data in Tables (4.1)

revealed that mean DTPA extractable Cd in surface sewage irrigated soils was highest near

the proximity and decreased as the distance increased laterally (Table 4.1). In general it was

highest at 50 meter distance on either side of Buddah Nallah and decreased as the lateral

distance on either side of the sewage channel increased to 250, 500, 750 and 1000 meters

respectively. Perusal of data in table revealed that at village Bhamian khurd, the amount of

DTPA extractable Cd in soil sample receiving sewage irrigation collected at 50 meter away

on right side of the sewage channel was 0.14 mg kg-1 soil which decreased to 0.12, 0.10 and

0.08 mg kg-1soil in soil samples collected at a distance of 250, 500 and 750 meter. Similar

trend was observed for other sites /location of various villages. Such behavior of enrichment

is due to farmers practice of growing vegetables near the proximity of sewage channel which

are largely and preferentially irrigated with sewage water laden with heavy metals including

cadmium. Secondly, it has been noticed that sampling area at the time of sampling up to 100

meters on either side get submerged with water off and on due to overflow of water during

rains .

35

Table 4.1: Cadmium DTPA and total cadmium concentration around Buddah Nallah along with their geographical locations

 S no

 Ludhiana Soil Samples

Distance from Buddah Nallah

DTPA -Cd

Total Cd

  Lattitude Longitude Village Name      1 N-30º55.217' E-075º54.781' Bhamian khurad 50 m 0.12 1.642 N-30º55.305' E-075º54. 809' Bhamian khurad 250 m 0.12 1.603 N-30º55.377' E-075º54. 841' Bhamian khurad 500 m 0.10 1.504 N-30º55.480' E-075º 54. 868' Bhamian khurad 750 m 0.08 1.54        Mean 0.11 1.575 N-30º55.207' E-075º54. 779' Bhamian khurad 50 m 0.14 1.726 N-30º55.160' E-075º54. 815' Bhamian khurad 250 m 0.10 1.67 N-30º55.102' E-075º54. 852' Bhamian khurad 500 m 0.10 1.548 N-30º55.047' E-075º54. 846' Bhamian khurad 750 m 0.08 1.28        Mean 0.11 1.549 N-30º55.118' E-075º53.662' Sadian 50 m 0.16 1.8410 N-30º55.078' E-075º53.670' Sadian 250 m 0.12 1.6411 N-30º55.012' E-075º53.687' Sadian 500 m 0.1 1.612 N-30º54.995' E-075º53.714' Sadian 750 m 0.1 1.62        Mean 0.12 1.6813 N-30º55.131' E-075º53.664' Sadian 50 m 0.18 1.7614 N-30º55.181' E-075º53.676' Sadian 250 m 0.14 1.5415 N-30º55.256' E-075º53.690' Sadian 500 m 0.12 1.5216 N-30º55.340' E-075º53.705' Sadian 750 m 0.12 1.4617 N-30º55.390' E-075º53.711' Sadian 1000 m 0.1 1.24        Mean 0.12 1.4418 N-30º55.718' E-075º50.653' Saleem tabri 50 m 0.24 3.2419 N-30º55.751' E-075º50.632' Saleem tabri 250 m 0.2 3.1220 N-30º55.808' E-075º50.581' Saleem tabri 500 m 0.22 3.121 N-30º55.860' E-075º50.571' Saleem tabri 750 m 0.18 1.922 N-30º55.980' E-075º50.558' Saleem tabri 1000 m 0.14 1.84        Mean 0.19 2.4923 N-30º55.718' E-075º50.823' Saleem tabri 50 m 0.28 3.44

24 N-30º55.524' E-075º47.527' Partap sinhg wala 50 m 0.22 3.0225 N-30º55.613' E-075º47.498' Partap sinhg wala 250 m 0.22 2.7626 N-30º55.762' E-075º47.523' Partap sinhg wala 500 m 0.18 2.4227 N-30º55.882' E-075º47.526' Partap sinhg wala 750 m 0.14 2.2228 N-30º55.934' E-075º47.530' Partap sinhg wala 1000 m 0.14 2.2        Mean 0.17 2.4029 N-30º55.507' E-075º47.529' Partap sinhg wala 50 m 0.26 3.2230 N-30º55.454' E-075º47.534' Partap sinhg wala 250 m 0.22 2.8831 N-30º55.427' E-075º47.525' Partap sinhg wala 500 m 0.16 2.3432 N-30º55.345' E-075º47.510' Partap sinhg wala 750 m 0.16 1.9833 N-30º55.220' E-075º47.497' Partap sinhg wala 1000 m 0.14 2.32        Mean 0.17 2.38

36

34 N-30º56.275' E-075º46.182' Talwara 50 m 0.22 2.2435 N-30º56.338' E-075º46.240' Talwara 250 m 0.2 1.9436 N-30º56.409' E-075º46.267' Talwara 500 m 0.16 1.8837 N-30º56.507' E-075º46.310' Talwara 750 m 0.16 1.938 N-30º56.590' E-075º46.360' Talwara 1000 m 0.14 1.72        Mean 0.17 1.8639 N-30º56.260' E-075º 46. 160' Talwara 50 m 0.2 2.3640 N-30º56.240' E-075º 46. 139' Talwara 250 m 0.2 2.241 N-30º56.170' E-075º 46.057' Talwara 500 m 0.18 1.8442 N-30º56'120' E-075º 46. 048' Talwara 750 m 0.2 1.7643 N-30º56.098' E-074º 46. 029' Talwara 1000 m 0.14 1.8        Mean 0.18 1.9044 N-30º56.551' E-075º44.920' Jain pura 50 m 0.18 1.9845 N-30º56.617' E-075º44.925' Jain pura 250 m 0.14 1.8846 N-30º56.676' E-075º44.921' Jain pura 500 m 0.14 1.7247 N-30º56.735' E-075º44.920' Jain pura 750 m 0.1 1.4648 N-30º56.822' E-075º44.924' Jain pura 1000 m 0.06 1.38        Mean 0.11 1.6149 N-30º56.525' E-075º44.911' Jain pura 50 m 0.2 1.8650 N-30º56.433' E-075º44.872' Jain pura 250 m 0.16 1.851 N-30º56.352' E-075º 44.835' Jain pura 500 m 0.14 1.6452 N-30º56.272' E-075º44.805' Jain pura 750 m 0.08 1.2653 N-30º56.198' E-075º44.770' Jain pura 1000 m 0.1 1.34        Mean 0.12 1.5154 N-30º54'57.04" E-075º56'47.67" Bhamian kalan   0.06 0.9855 N-30º56'14.21." E-075º46'58.18" Baranhara   0.04 0.8456 N-30º56'26.19" E-075º48'25.40" Balloke   0.06 1.2857 N-30º56'49.19" E-075º47'17.13" Ladian khurd   0.02 1.0258 N-30º57'01.34" E-075º46'03.80" Bagga khurd   0.02 1.159 N-30º54'57.04" E-075º45'44.17" Jhammat   0.04 1.2560 N-30º57'19.43" E-075º45'30.54" Rajowal   0.02 0.8161 N-30º55'37.50" E-075º44'38.53" Malikpur   0.02 0.5862 N-30º55'02.49" E-075º45'57.51" Ayali khurd   0.02 0.78        Mean 0.03 0.86

4.1.3 Total Cd: In general, high concentration of total cadmium was observed in the polluted

soils at all sites. Data in tables (4.1) showed that the content of total Cd decreased as the

lateral distance increased being maximum at 50 meter and minimum at 1000 meters at all the

sites on either sides of sewage drain (Table 4.1). On right side of Buddah Nallah it varied

from 1.64 to 1.54, 1.76 to 1.24, 3.24 to 1.84, 3.02 to 2.2, 2.24 to 1.72 and 1.98 to 1.38 mg kg-1

as the distance increased from 50 to 1000 meters with a mean value of 1.57, 1.68, 2.49, 2.40,

1.86 and 1.61 mg kg-1 soil in sewage irrigated soils of Bhamian khurd, Saidan, Saleem tabri,

Pratapsinghwala, Talwara and Jain pura respectively. Same trend was observed on left side of

Buddah Nallah. Maximum concentration of total cadmum was observed in village Saleem

tabri followed by Pratapsinghwala, Talwara, Saidan, Jain pura and least in Bhamian khurd.

37

Fig: 1

38

The increase in total Cd content with sewage water irrigation was dependent upon the

rate of loading and chemical composition of sewage water as well as “in situ” properties of

soils (Williams et al 1980; Thakur and Kansal 1992). Elevated concentration of total Cd in

the soils of industrial towns of Punjab might also be attributed to the atmospheric fall out of

heavy metals since these lie in close proximity to industrial activities. Griffiths and

Wardsworks (1980).

In order to demarcate Cd polluted soils, guidelines based on total metal content were

considered. As per guidelines of Kabata and Pendias (1984), 3-8 mg total Cd kg -1 soil is

considered to be the critical limit above which toxicity of Cd is possible. In the present study,

6 (representing the sites Saleem tabri and Partapsinghwala) out of 53 soil samples reached

this threshold value of 3 mg Cd kg-1 soil. ). Thus it appeared that about 11.3 percent soils have

become polluted as a result of continuous irrigation with sewage water. These soils require

immediate attention and needs to be ameliorated urgently.

There is the possibility that rest of the soils might approach this critical limit in a few years

if same level of irrigation with sewage water continued.

In another standard adopted in U.K, as prescribed by G L.C (Greater London Council), total

Cd concentration ranging from 0 to 1, 1 to 3, 3 to 10, 10 to 50 and >50 mg kg -1 soil were

categorized as typical uncontaminated, slightly contaminated, contaminated and heavy

contaminated soils, respectively. According to this system therefore, most of the investigated

soils fell under slightly contaminated category indicating thereby that clean up operation is

definitely required. So there is an urgent need to work out the critical limit for Cd toxicity in

the Punjab soils on a wider scale

4.2 Influence of different levels of Cd and various amendments on

4.2.1 Dry matter yield of shoots of chalai (pig weed)

4.2.1.1 Effect of Cadmium: Gradual reduction in mean dry matter yield of chalai (pig weed)

occurred with increasing levels of cadmium irrespective of the amendments but the

significant decrease was observed at and above the application rate of 10 mg kg -1soil. The

adverse effect of the added Cd was more marked at highest rate of its application (Table

4.2.1and Fig 2). Mean dry matter yield of chalai in soil at 45 days of growth, significantly

decreased from 21.7 g pot-1 to 18.0, 15.4 and 11.5 g pot-1 when the rate of cadmium was

increased to 10, 20 and 40 mg kg-1soil irrespective application of amendments. The reduction

in dry matter yield of chalai shoots was 1.1, 2.3 16.8, 28.9 and 46.9 percent with the

application of cadmium at the rate of 2.5, 5, 10, 20 and 40 mg kg -1soil. The reduction in shoot

growth was in accord with the amounts of extractable Cd in the soils and Cd content in plants

(Tables 4.2.5 and 4.2.3). The detrimental effect of Cd on yield was consistent with the results

of others in different crops (Singh and Nayyar 1991; Dahiya et al 1991; Narwal et al 1990;

Cieslinski et al 1996; Bipasha et al 1997; Gupta and Gupta 1988, Khurana et al 2006 and

39

Sidhu and Khurana 2010). This was probably due to marked and significant increase in

available Cd which resulted in the increased amount of metal being absorbed by the plants.

Atrexe et al (2002) have elucidated that normal growth and development was

impaired with Cd which is readily taken up by plants. Cadmium, even at very low

concentration results in respiratory and photosynthesis (Lee et al 1976) and structural

disorders (Lamoreaux and Chaney 1977). In pea, a number of toxic effects of Cd on

metabolism have been reported, such as inhibition of various enzymes activities (Obata et al

1996, and induction of oxidative stress (Sandalio et al 2001) including alterations in enzymes

of antioxidant defense system (Romero –Puertess et al 2002). The basic cause of Cd toxicity

in plants probably lies in much higher affinity of Cd for thiol groupings (-SH) in enzymes and

other proteins. Reduced plant growth due to Cd addition might also be attributed to reduced

photosynthetic rate and internal water deficit in vascular system caused by reduced

conductivity of stem and poor root system development (Alloway 1990).

Despite the marked reduction in dry matter yield beyond application rate of 10 mg Cd

kg -1 soil, the pig weed plants did not exhibit any visual symptoms of Cd toxicity. Therefore, it

may be hypothesized that reduction in dry matter yield had resulted solely from the toxicity of

the cadmium and not of nutrient imbalance as no visual symptoms were observed.

4.2.1.2 Effect of amendments: There was significant effect of different amendments on dry

matter yield of shoots of pig weed. Different amendments behaved variably as far as their

remediation potential was concerned at a particular level of Cd application. Application of

various amendments viz (CaCO3, FYM and P) at all the levels mitigated the toxicity of

cadmium as is evident by the increase in dry matter yield of the crop irrespective of Cd levels.

A significant enhancement in dry matter yield of chalai was observed with all the

amendments. Lime @ 2.5 and 5% increased mean dry matter yield from 16.4 (Control) to

18.2 and 19.1 g pot-1, respectively. FYM at the rate 1 and 2% produced mean dry matter yield

of 18.4 and 19.4 g pot-1 while 17.6 and 18.4 g pot-1 respectively with phosphorus (P2O5)

application of 20 and 40 mg kg-1 soil regardless of Cd levels. Increase in yield may be

attributed to alleviating Cd toxicity in soil owing to amendments application (Bolan et al

2003a & b) Our findings are conformity with those of Chen et al (2000); Friesel et al (2004)

and Zhu et al (2004) who also reported that application of lime and phosphate amendments

significantly increased dry matter yield of fescue grass (Fescue rubra L.) and wheat (Triticum

aestivum L.) compared to un-amended control. Among the various amendments, application

of CaCO3proved very effective followed by phosphorus (P2O5) and FYM in alleviating the

40

4.2.1: Effect of rates of Cadmium and amendments on dry matter yield of shoots of pig weed.

Cd rates (mg kg-1

soil)

Amendment

Control

CaCO3 (%) FYM (%)Phosphorus (P2O5

mg kg-1 soil)

Mean2.50 5 FYM 1 FYM 2 20 40

0 20.68 21.62 21.92 21.89 22.43 21.35 21.88 21.68

2.5 20.09 21.25 22.31 22.12 22.53 20.84 20.99 21.45

5 19.14 21.36 21.95 21.48 22.22 21.02 21.14 21.19

10 15.81 17.69 19.15 18.26 19.53 16.93 18.85 18.03

20 13.27 15.22 16.93 15.38 17.07 14.45 15.54 15.41

40 9.38 12.00 12.28 11.52 12.40 11.20 11.75 11.50

Mean 16.39 18.19 19.09 18.44 19.36 17.63 18.36  

Cadmium levels = 0.75CD(p=0.05) Amendments = 0.81 Cadmium X Amendments = NS

Fig 2: Effect of rates of Cadmium and amendments on dry matter yield of shoots of pig weed.

Cd toxicity in soil as Cd concentration in shoots decreased maximum with application rate

of calcium carbonate (2.5 and 5 % ) and intermediate with phosphorus (20 and 40 mg P2O5

kg-1 soil) and minimum with FYM (1 and 2%). Brown et al (1998) reported that Cd in the

sludge amended plot was less available to lettuce than the Cd in the unsludged plot.

41

Maximum mean dry matter yield of the shoots of pig weed was obtained in the

treatments involving FYM amendments in spite of the fact it was less effective in decreasing

the concentration of Cd in pig weed shoot compared to other amendments. It might be

possible that some other useful constituents of FYM were effective in enhancing the yield.

The plant appeared healthier in all the FYM treated pots throughout the growing season.

Similar effects of compost in growth media has been found in other studies (Atiyeh 2001;

Perez Murcia et al 2006) which were mainly due to the improvement of soil structure by

increasing porosity, water holding capacity and aeration. Ram and Verloo (1985) also

observed that addition of different organic material like FYM, peat, humic acid and tetra

ethylene penta amine (Tetren) to a polluted Belgian soil enhanced the dry matter yield of

corn, resulting in reduced availability of heavy metals due to formation of insoluble metallo-

organic complexes. Clemente et al (2007) found that FYM decreased metal availability in

contaminated soils due to formation of insoluble complexes during mineralization of organic

matter. Gupta et al (1989) reported that straw and grain yield of wheat grown in highly

contaminated soil improved with the increasing levels of FYM in the soils. McBride (1995)

observed that substantial fraction of the applied organic matter remains and the elevated

organic matter content of soil could limit the activity and bio availability of some heavy metal

The increase in shoot yield due to phosphorus application indicated its usefulness and

effectiveness to reduce Cd toxicity. Bolan et al (2003) observed that P application reduced

phytotoxicity of Cd, resulting in higher yields of Brassica juncea. An enhanced biomass

production of Sudex and Swiss chard was reported by Hettiarachhi and Pierzynski (2002) in

an experiment conducted on heavy metal pollted soils (Cd, Pb and Zn) with application of

soluble source of phosphorus. Basta et al (2001) and Hettiarachchi and Pierzynski (2002)

reported that plant –tissue concentration of Cd was consistently reduced in the presence of

soluble P, possibly through the formation of mixed metal phosphates, which could have

restricted metal uptake by plants. The result of present study indicated that in situ

immobilization of Cd occurred probably due to the phosphate –induced Cd adsorption and

precipitation of Cd as Cd (OH)2 and Cd3(PO4)2 with the addition of mono calcium carbonate.

This corroborated result of (Bolan et al 2003).

Amendment in the form of CaCO3 was found to be most effective. It was probably due

to formation of less soluble compounds like CdCO3 (Bolan et al., 2003a) mitigated the

toxicity of cadmium. An other explanation may be that increased levels of Ca2+ through the

application of calcium carbonate can decrease the amount of Cd that is assimilated by plants

(Larlson et al 2000) because of their similar size (Ochiai 1995). A higher affinity for the

essential trace metal Ca results in the decreased uptake of Cd into the plant. These findings

find support from the work of Singh and Nayyar (2001) who reported that 2.5 percent

application of CaCO to the soil resulted in the decrease in both DTPA-extractable and plant Ni

42

which helped in mitigating the toxic effect of Ni and subsequently increased dry matter yield

of cowpea. Peles et al (1998) concluded that the addition of lime to contaminated soils

(essentially increasing the pH) decreased the uptake of heavy metals including cadmium. Lee

et al (2004) and Zhu et al (2004) reported that lime and phosphorus significantly decreased

the concentration of heavy metals including Cd in wheat shoots. Ram and Verloo (1985)

found that FYM and peat soil enhanced the mobility of Cd at lower pH and decreased it at

higher pH.

4.2.2 Dry matter yield of roots as influenced by Cd and amendments application

4.2.2.1 Effect of Cadmium: Roots dry matter yield of pig weed followed the same trend as

that case of shoot. The dry matter yield of roots started declining even with the application

rate of 5 mg Cd kg-1 soil. However, a significant decrease was observed with 10 mg Cd kg-1

soil onwards. Further, application of 20 and 40 mg Cd kg-1 soil showed significant sharp

decline in root dry matter yield. This indicated that root yield recorded by the addition of 20

and 40 mg Cd kg-1 soil was significantly lower than the root yield recorded with 10 mg Cd kg -

1 soil. The reduction in dry matter yield of pigweeds root was 16.0, 28.2 and 45.9 percent with

the application of cadmium at the rate of 10, 20 and 40 mg kg -1soil. So the yield reduction in

response to Cd was of similar proportions in the roots as for the aboveground part of the

plants. The reduction in root growth was in accord with the amounts of extractable Cd .The

magnitude of reduction in root biomass was comparable to the shoot biomass (Tables 4.2.2 &

4.2.1and Fig 2 & 3)

4.2.2.2 Effect of Amendments: The effect of different amendments on root growth was

similar to that reported for the above ground part of the plants. Different amendments helped

to ameliorate the toxicity of Cd to varying extent and subsequently enhanced the dry matter

yield. As in case of shoot, all the amendments registered significant increase in dry matter

yield of the crop

A significant enhancement in dry matter yield of roots of chalai was observed from

5.4 to 5.9, 6.2; 6.1, 6.3; 5.8 and 6.0, respectively with application rate of calcium carbonate

(2.5 and 5 % percent), FYM (1 and 2%) and phosphorus application (20 and 40 mg P2O5 kg-1

soil) regardless of Cd levels. Calcium carbonate amendment was proved to be most effective

among all the treatments as it offset the toxic effect of cadmium more efficiently. Similarly

maximum dry biomasses of the roots were obtained with FYM amendments as in case of

shoots. Same reasoning can be put forth for the behavior of different amendments as case of

the roots.

43

Table 4.2.2: Effect of rates of Cadmium and amendments on dry matter yield of roots of pig weed

Cd rates (mg kg-1

soil)

Amendments

CaCO3 (%) FYM (%)Phosphorus (P2O5 mg kg-1

soil) Mean

Control 2.5 5 1 2 20 40

0 6.82 6.94 6.98 7.12 7.22 7.04 7.0 7.02

2.5 6.58 7.0 7.24 7.26 7.34 6.81 6.88 6.96

5 6.38 7.00 7.14 6.98 7.26 6.78 6.92 6.92

10 5.26 5.80 6.20 6.03 6.32 5.54 6.18 5.90

20 4.42 4.90 5.50 5.04 5.62 4.74 5.08 5.04

40 2.88 3.90 4.00 4.10 4.12 3.78 3.86 3.80

Mean 5.40 5.92 6.18 6.08 6.32 5.78 5.98

Cd levels = 0.33 CD(p=0.05) Amendments = 0.36 Cd levels X Amendments = NS

Fig 3: Effect of rates of Cadmium and amendments on dry matter yield of roots of pig

weed

44

4.2.3 Effect of Cd and amendments levels on Cd content (µgg-1) in shoots and roots of pig

weed

4.2.3.1 Effect of Cadmium: The mean concentration of Cd in the shoots increased

successively with increasing rates of Cd application irrespective of applied amendments. The

application of even the lowest rate of 2.5 mg Cd kg -1 soil significantly increased the Cd

content in crop over control. The mean Cd concentration increased from 1.3 in control

treatment to 4.7, 6.0, 14.1, 21.8 and 46.4 µg g-1 dry matter when rate of Cd application was

raised to 2.5, 5, 10, 20 and 40 mg kg-1 soil. The difference of Cd content among the treatments

were also significant. This was probably due to marked and significant increase in available

Cd (Table 4.2.3 and Fig 4) which resulted in the increased amount of metal being absorbed by

the plants.

Compared to its value in shoot, contents of cadmium in roots were invariably higher

at all levels of added cadmium i.e consistently higher concentration of Cd was detected in

roots as compared with shoots (Table 4.2.3 and Fig 5). Since roots are the primary plant

organs which remain in contact with soil solution and thus accumulate comparatively higher

amount of heavy metals. An application rate of 5 mg Cd kg-1 soil was required to

significantly increase the root Cd content in pigweed over control regardless of amendments

levels. It is pertinent to note here that although this level significantly increased the Cd

content in both shoots and roots but they failed to cause a significant reduction in the dry

matter yield of the crops, indicating that Cd is less phyto-toxic at these level. The highest Cd

concentration was obtained with 40 mg Cd kg-1 soil both in shoots and roots. These results

find support from the work of several workers namely, Maclean (1976); Mahler et al (1978);

Singh and Nayyar (1989); Narwal et al (1993); Khurana et al (2006) and Sidhu and Khurana

(2010) who also reported higher Cd content in different crops due to Cd application.

4.2.3.2 Effect of Amendments: Cadmium concentration both in roots and shoots showed

decreasing trend with supply of amendments. However, there was considerable difference in

magnitude of different amendments in alleviating Cd toxicity by bringing decrease in Cd

concentration in both shoots and roots of the crop.

All the amendments significantly decreased the concentration of Cd in shoot and

roots of pigweed (Table 4.2.3 and Fig 4 & 5) The concentration of Cd in shoot with lime @

2.5% and 5% treated soils decreased from 20.7 to 14.2 and 12.8 µg g-1 dry matter which was

31.5 and 37.8% lower than that in the control plants, respectively irrespective of Cd levels.

FYM addition @ 1 and 2% reduced concentration of Cd in shoot from 20.7 (control) to 16.8

and 15.3 which comes out to be 18.8% and 26.2% lower that in control. Addition of

phosphorus @ 20 and 40 mg P2O5 kg-1 soil decreased shoot Cd concentration by 22.7 and

30.2%, respectively compared to that in the control plants.

45

Table 4.2.3: Effect of rates of Cadmium and amendments on concentration of Cadmium in shoots and roots of pig weed.

Cd rates

(mg kg-1

soil)

Amendments

Shoots

CaCO3 (%) FYM (%)Phosphorus (P2O5 mg kg-1

soil)

MeanControl 2.50 5 1 2 20 40

0 1.60 1.20 1.02 1.28 1.20 1.32 1.28 1.26

2.5 6.04 4.18 3.64 5.02 4.64 4.88 4.64 4.72

5 8.06 5.72 4.52 6.50 5.88 6.06 5.50 6.04

10 18.66 12.40 11.44 15.38 13.82 14.68 12.34 14.10

20 29.06 20.08 16.76 24.10 21.16 22.34 19.10 21.80

40 60.58 41.30 39.77 48.36 44.80 46.52 43.66 46.42

Mean 20.66 14.16 12.86 16.76 15.26 15.98 14.42

Roots

0 2.18 1.60 1.42 1.66 1.54 1.58 1.60 1.66

2.5 9.28 5.20 4.48 7.36 6.30 6.28 5.74 6.38

5 13.22 7.02 5.98 10.18 9.00 8.94 8.10 8.92

10 24.80 16.78 14.26 19.74 17.72 19.06 16.22 18.38

20 39.38 27.24 22.12 31.02 26.66 30.40 26.75 29.08

40 79.34 50.04 46.90 51.98 51.00 54.24 52.10 55.10

Mean 28.04 17.98 15.86 20.32 18.72 20.08 18.42

Cadmium levels (shoots) = 0.69CD(p=0.05) Amendments (shoots) = 0.74 Cadmium X Amendments (shoots) = 1.82

Cadmium levels (roots) = 0.86CD(p=0.05) Amendments (roots) = 0.93 Cadmium X Amendments (roots) = 2.28

46

Fig 4: Effect of rates of Cadmium and amendments on concentration of Cadmium in shoots of pig weed

Fig 5: Effect of rates of Cadmium and amendments on concentration of Cadmium in

roots of pig weed

47

Similarly reduction in mean Cd content due to application of various amendments

was registered in roots as for the above ground part of the plants. The amendments had

significant effect in decreasing the concentration of Cd in roots compared to that in the

control plants. Lime @ 2.5% and 5% decreased root Cd concentration by 35.9 and 43.4

compared to that in control samples. FYM addition @ 1 and 2% declined it by 27.5% and

33.2% compared to that in the control samples. The mean concentration of Cd in root

samples in the presence of 20 and 40 mg P2O5 kg-1 soil was 28.4 and 34.3 % lower than that

in the control, respectively. The decrease in concentration may be due to growth dilution,

which occurred with an increase in biomass production since there was an increase in yield

owing to application of lime, P2O5 and FYM (Lee et al 2004) and partially decreased Cd

concentration in soil solution with all the amendments through formation of less soluble

compounds like Cd3(PO4)2 and CdCO3 (Bolan et al 2003a). Lee et al (2004) and Zhu et al

(2004) reported that lime, compost and phosphorus significantly decreased the

concentration of heavy metals including Cd in wheat grain and straw compared to that of

control plants. Similarly a decrease in Cd concentration through P application were

obtained by Dheri et al (2007) and Hettiarachchi and Pierzynski (2002) in spinach and

swiss chard (Beta vulgaris (L). Clemente et al (2007) and Mc Bride (1995) demonstrated

the effectiveness of FYM in decreasing Cd concentration due to formation of insoluble

complex.

4.2.4 Effect of Cd and various amendments levels on Cd uptake of shoots and roots

4.2.4.1 Effect of cadmium: The data on the Cd uptake as affected by added Cd and various

amendments in the shoots are presented in table 4.2.4. The mean Cd uptake in the shoots of

pig weed increased significantly with increasing level of Cd application regardless of Cd

application. The Cd uptake in pigweed increased from 27.5 µg pot -1 in control to 100.8,

126.8, 251.9, 331.9, 528.2 µg pot-1with 2.5, 5, 10, 20 and 40 mg Cd kg -1 in soil respectively.

Compared with no Cd (control) a 9.7 fold increase in its uptake was observed by applying

10 mg Cd kg-1. It suggested that applied Cd was readily absorbed by crop and was easily

translocated from roots to above ground plant parts. Raising the Cd level to 20 mg kg -1 soil

did not increase the Cd uptake to an extent similar to that observed with 10 mg Cd kg -1 soil.

In fact applying 20 mg Cd kg-1 soil, only 1.3 times increase in Cd uptake was observed over

that recorded at 10 mg Cd kg -1 soil. This kind of Cd uptake pattern was consequence of both

reduction in yield due to Cd toxicity and increased uptake of Cd at higher application rate

as a reduction in yield was compensated by higher Cd absorption.

Lower uptake of cadmium in roots of pig weed as compared to shoots, inspite of its

high Cd concentration had resulted from the lower dry matter yield of the roots (Table 4.2.2

& 4.2.3). The mean uptake of Cd by roots increased significantly and progressively with

increasing levels of Cd (Table 4.2.4 and Fig 6 & 7). The increase in mean uptake of Cd in

48

roots of pigweed was about 3.9, 5.3, 9.3, 12.5 and 17.8 times higher than control at 2.5, 5, 10,

20 and 40 mg Cd kg-1 soil application

4.2.4.2 Effect of Amendments: Application of different amendments decreased Cd uptake in

both shoots and roots of pig weed significantly. As explained earlier, application of various

amendments had depressed the availability of Cd (Table 4.2.3) and increased the dry matter

yield, thereby a reduced Cd uptake in pigweed plant was observed. The uptake of

Table 4.2.4: Effect of rates of Cadmium and amendments on uptake of Cadmium by shoots and roots of pig weed.

Cd rates

(mg kg-1

soil)

Amendments

Shoots

CaCO3 (%) FYM (%)Phosphorus (P2O5 mg kg-1

soil)

MeanControl 2.50 5 1 2 20 40

0 32.3 25.7 22.8 27.9 27.3 28.2 28.0 27.5

2.5 120.9 88.2 80.8 111.4 105.2 101.8 97.5 100.8

5 154.0 122.1 98.7 138.7 130.5 127.1 116.6 126.8

10 294.7 219.3 218.8 280.5 269.4 248.9 231.4 251.9

20 383.8 305.4 284.2 370.6 360.4 322.0 296.9 331.9

40 569.4 496.1 487.1 556.1 555.3 521.1 512.4 528.2

Mean 259.2 209.5 198.7 247.5 241.4 224.8 213.8

Roots

0 14.5 11.2 10.0 11.8 11.2 11.2 11.1 11.6

2.5 61.1 36.2 32.5 53.8 46.4 42.8 39.4 44.6

5 84.3 49.0 42.6 71.2 65.6 60.5 55.7 61.3

10 130.6 96.8 88.8 118.4 111.4 105.9 99.6 107.3

20 172.7 133.4 121.9 156.5 150.3 144.0 135.7 144.9

40 229.1 195.2 186.5 212.9 210.0 204.5 202.0 205.7

Mean 115.4 87.0 80.4 104.1 99.1 94.8 90.6 Cadmium levels (shoots) = 13.58CD(p=0.05) Amendments (shoots) = 14.67 Cadmium X Amendments (shoots) = NS

Cadmium levels (roots) = 9.19CD(p=0.05) Amendments (roots) = 9.93 Cadmium X Amendments (roots) = NS

49

Fig 6: Effect of rates of Cadmium and amendments on uptake of Cadmium by shoots of pig weed

Fig 7: Effect of rates of Cadmium and amendments on uptake of Cadmium by roots of pig weed

Cd in shoot decreased from 259.2 µg pot-1 (control) to 209.48 (lime @ 2.5%), 198.7 (lime @

5%); 247.5 ( FYM @ 1% ), 241.4 (FYM @ 2% ); 224.8 (P @ 20 mg P2O5 kg-1 soil) and

213.8 µg pot-1 (P @ 40 mg P2O5 kg-1 soil). Application of lime @ 2.5% and 5% decreased it

by 19.2 and 23.3 % lower compared to control plants, respectively irrespective of Cd levels.

FYM addition @ 1 and 2% reduced uptake of Cd in shoot by only 4.5 and 6.9 percent lower

that in control. Addition of phosphorus @ 20 and 40 mg P2O5 kg-1 soil decreased shoot Cd

50

concentration by 13.3 and 17.5 per cent respectively compared to that in control. Application

of various amendments viz (FYM, CaCO3, and Phosphorus) at all the levels reduced the

uptake of cadmium which reflected in the increase in dry matter yield of the crop

irrespective of Cd levels (Tables 4.2.1 and 4.2.2). A significant reduction in uptake of

cadmium was observed with all the amendments. Lime @ 2.5 and 5% decreased it by 28.4

and 35 µg pot-1 respectively with respect to control. FYM at the rate 1 and 2% declined it by

11.3 and 16.2 µg pot-1 while 20.5 and 24.8 µg pot-1 reduction in uptake of the crop

respectively was obtained with phosphorus application of 20 and 40 mg P2O5 kg-1 soil) with

respect to control regardless of Cd levels. Singh et al (1991) observed that when Cd was

applied with FYM, the uptake of Cd decreased with increasing level of FYM. Similar

decrease in Cd uptake with increasing application of FYM had also been reported by Dahiya

et al (1987). The decrease in DTPA extractable Cd (Table 4.2.5) in soils with calcium

carbonate may be result of directly through stronger binding and precipitation of this metal

with CaCO3 and indirectly rise in pH of the soils (Singh and Nayyer 1993). Liming can lead

to the precipitation of metals as metal-carbonate and significantly decrease the exchangeable

fraction (Table 4.4b) of metals in contaminated soil (Knox et al 2001) which could reduce the

uptake by plants. Ma and Uren (1998) observed marked decrease in DTPA extractable with

addition of CaCO3 through its effect on increase in pH Cd contents in wheat after addition of

lime to soil were significantly decreased and proposed that CaCO3 can help in mitigating the

toxic effects of Cd on wheat.

4.2.5 DTPA extractable Cd before sowing of crops: Effect of Cd on DTPA extractable Cd

in soils after equilibrium is presented in table (4.2.5 & Fig 8). The data showed that

extractable Cd increased markedly and significantly with graded rates of Cd application

irrespective of amendments before sowing of crop. The increase was significant with 5 mg Cd

kg-1 soil application over control. The content of DTPA–Cd in soil after completion of

equilibrium time were 0.27, 0.65, 1.68, 3.18, 7.37, and 14.91 mg kg -1 soil at 0, 2.5, 5, 10, 20

and 40 mg Cd kg-1 soil application. A perusal of data in table (4.2.5) showed that the

maximum extraction of Cd by DTPA with 40 mg Cd kg-1 soil application was approximately

60.4 percent in the absence of amendments which was less than 70 to 80 percent of applied

Cd that reported by Haq et al (1980). Singh and Nayyar (1989) also obtained about 60 to 80

percent of added Cd in coarse textured soil. Cieslinski et al (1996) reported 13.7, 26.7, 51.9

mg Cd kg-1 soil DTPA extractable Cd where the application rates were 15, 30 and 60 mg kg -1

soil. This showed high rate of cadmium extractability, which is a cause of concern.

51

Table 4.2.5: Effect of rates of cadmium and amendments on DTPA-Cd in soil at equilibrium

Cd rates (mg kg-1

soil)

Amendments

CaCO3 (%) FYM (%)Phosphorus (P2O5

mg kg-1 soil)

MeanControl 2.5 5 1 2 20 40

0.00 0.36 0.20 0.15 0.31 0.30 0.28 0.25 0.27

2.50 1.13 0.48 0.32 1.02 0.64 0.60 0.56 0.65

5.00 2.34 1.34 1.22 1.92 1.81 1.66 1.48 1.68

10.00 5.27 2.44 2.02 3.43 3.22 3.06 2.75 3.18

20.00 11.02 6.08 5.28 8.08 7.62 7.37 6.14 7.37

40.00 24.17 12.21 11.82 14.86 14.30 13.92 13.08 14.91

Mean 7.38 3.80 3.50 4.94 4.64 4.41 4.05

Cadmium levels = 0.71CD(p=0.05) Amendments = 0 .76 Cadmium X Amendments = 1.87

Fig 8: Effect of rates of cadmium and amendments on DTPA-Cd in soil at equilibrium

4.2.5.1 Effect of amendments: Applied amendments were found to be significantly

effective in declining the content of DTPA–Cd in soil over control after the completion of

equilibration period. The content of DTPA-Cd decreased by 3.58 mg kg-1 soil (lime @

2.5%), 3.88 (lime @ 5%); 2.44 ( FYM @ 1% ), 2.74 (FYM @ 2% ); 2.97 (P @ 20 mg P2O5

kg-1 soil) and 3.33 µg pot-1 (P @ 40 mg P2O5 kg-1 soil) as compared to control.

Corresponding percent decrease comes out to be 48.5, 52.6, 33.1, 37.1, 40.2 and 45.1

52

respectively with application rate of calcium carbonate (2.5 and 5 % percent), FYM (1 and

2%) and phosphorus application (20 and 40 mg P2O5 kg-1 soil) regardless of Cd levels

respectively. The increase in soil pH with lime (Table 4.5.1) might cause in precipitation of

Cd with carbonates and reduced the solubility of Cd in soil. Decrease in DTPA-Cd with

phosphorus may be caused by significant increase in Cd 2+ adsorption. Similar reasoning has

been put forth by Naidu et al. (1996) and Bolan et al. (1999) that increasing rate of phosphate

application significant increase in Cd 2+ adsorption by soil colloids. Therefore, decrease in

DTPA extractable Cd may be attributed to an increase in negative charge to affect more Cd

adsorption. The precipitation of Cd as Cd(OH)2 and Cd(PO4)2 has also been reported by Bolan

et al. (2003a) with the application of P amendments. Formation of insoluble oregano metallic

complexes may be the reason behind the reduction of DTPA-Cd in soil with FYM application

(Clemente et al 2007).

4.2.6 DTPA extractable cadmium in post harvest soils: Compared to its content in

equilibrated soil (table 4.2.5), the DTPA – Cd in general decreased in soil after the harvest

(Table 4.2.6). Perusal of data in table (4.2.6) revealed lower values of DTPA-Cd in all the

treatments after the harvest of the crop compared to its value at equilibrium. The contents of

Table 4.2.6: Effect of rates of Cadmium and amendments on DTPA-Cd in soil after crop harvest

Cd rates (mg kg-1

soil)

Amendments

CaCO3 (%) FYM (%)Phosphorus (P2O5

mg kg-1 soil)

MeanControl 2.5 5 1 2 20 40

0 0.20 0.12 0.07 0.13 0.13 0.16 0.14 0.14

2.5 0.63 0.29 0.26 0.62 0.46 0.38 0.33 0.42

5 1.98 1.14 1.08 1.70 1.55 1.40 1.31 1.45

10 3.86 1.88 1.62 2.60 2.35 2.26 2.09 2.38

20 9.24 5.18 4.59 6.72 6.30 6.09 5.41 6.22

40 19.81 9.95 9.52 12.54 11.66 11.54 10.80 12.26

Mean 5.95 3.09 2.85 4.05 3.74 3.64 3.35

Cadmium levels = 0.65CD(p=0.05) Amendments = 0.68 Cadmium X Amendments = 1.69

53

Fig 9: Effect of rates of Cadmium and amendments on DTPA-Cd in soil after crop

harvest

DTPA–Cd in soil after crop harvest were 0.14, 0.42 , 1.45 , 2.38 6.22, 12.26 mg kg -1 soil as

against 0.27, 0.65, 1.68, 3.18, 7.37, and 14.91 mg kg-1 soil at 0,2.5, 5, 10, 20 and 40 mg kg-1

soil application at equilibrium. This might be due to removal of Cd by the crop as well as

transformations in to relatively insoluble forms.

The minimum and maximum amount of DTPA – Cd left after the harvest was 2.85

and 4.05 mg kg-1soil with application of 5 percent calcium carbonate and 1 per cent FYM

respectively. It was apparent from the data in table (4.2.6 & Fig 9) that the amount of DTPA

left in soil after the crop harvest in the presence of amendments was significantly lower as

compared in their absence.

4.3: Effect of Cd levels on micronutrient contents (μg g–1 dry matter) in pig weed: Plant

samples were collected from the treatments involving various levels of Cd in order to study

the effect of these levels on concentrations of micronutrients (Fe, Zn, Cu and Mn)

Table 4.3.1: Effect of Cd on the Fe content (μg g-1 dry matter) in the shoots and roots of pigweed

Cd rates Pigweed

Shoots Roots

0 313.3 396.4

2.5 322.9 405.8

5 330.9 417.0

10 349.9 441.5

20 338.8 427.6

40 324.2 420.2

CD(p=0.05) 9.9 11.0

54

4.3.1 Iron

The iron concentration in the roots and shoots of pig weed revealed a synergistic

relationship between Cd and Fe up to 10 kg –1 soil and an antagonistic relationship at higher

levels (20 and 40 mg Cd kg –1 soil). It showed increasing trend in shoot from 313.34 in

control to 349.94 µgg-1 when the levels of Cd were raised to 10 mg kg -1 soil and This is

further supported by the high positive correlation between Cd and Fe in the shoots (r = 0.91

Cd kg –1 soil) and roots (r = 0.93). The mean Fe concentration in the shoots and roots showed

a decreasing trend beyond an application rate of 20 mg Cd kg–1 soil. Negative correlation (r =

-0.80 in shoot and -0.65 in roots) further lend support to These findings are in conformity

with the results of Khan and Khan (1983); Koshino (1973); Root et al (1975) and Rupp et al

(1985), who reported similar behaviour in tomato and egg plant, rice, corn and grapevine,

respectively. Gupta and Dixit (1992), on the other hand, reported that the Fe content

decreased due to the application of Cd in soybean and wheat, while Mahler et al (1982) found

no influence of Cd application on the leaf Fe concentration of lettuce or Swiss chard.

Table 4.3.2: Effect of Cd on the Cu content (μg g-1 dry matter) in the shoots and roots of pigweed

Cd rates Pigweed

Shoots Roots

0 12.4 14.7

2.5 11.6 13.9

5 10.7 12.3

10 8.7 10.6

20 8.0 9.7

40 7.7 9.2

CD(p=0.05) 1.4 1.9

4.3.2 Copper

The copper concentration in the roots and shoots of pig weed was negatively affected

by the application of Cd at all levels (Table 4.3.2). There was a gradual decrease in Cu

concentration in the shoots and roots of the crop when the levels of cadmium were raised

from 0 to 40 mg kg-1soil. It decreased from 12.35 µg g-1 to 11.55, 10.7, 8.75, 8.05 and 7.65 µg

g-1 when the levels of Cd were raised to 5, 10, 20, 40 and 80 mg kg -1 soil. The correlations

between these metals were found to be highly negative both in the shoots (r = –0.77) and in

the roots (r = –0.75). This may be ascribed to antagonism between the two elements. The

copper content in the roots of the crops was generally higher than in the shoots. These

55

findings are in conformity with the results of Khan and Khan (1983). The antagonistic effect

of Cd accumulation on the levels of essential nutrients in the leaves was also observed in

chelator-buffered nutrient solution (Adhikari et al 2006).

4.3.3 Zinc

The data in table 4.3.3 revealed consistent increase in the mean Zn concentration with

increasing levels of Cd up to 10 mg kg–1 soil, while the higher rates (20 and 40 mg kg–1 soil)

depressed the zinc concentration in both the roots and shoots of the crops. This showed that

low levels of cadmium have a synergistic effect on the zinc concentration in the shoots and

roots while high levels have an antagonistic effect. A significant positive correlation was

observed between the rate of Cd application and the Zn concentration of the shoots (r = 0.90)

and roots (r=.89) up to the 10 mg Cd kg–1 soil rate. At higher rates, however, highly

significant negative correlations were obtained for both the shoots (r = –0.92) and the roots (r

= –0.94). The increase in shoot zinc concentration with the application of Cd up to 10 mg kg –

1 soil may be due to the concentration effect, because the dry matter yields of the shoots and

roots were decreased by cadmium. Other possible explanation for this apparent synergism

was that Cd dissociated zinc fixed from the binding sites in the soil due to competition for the

same sites.

Table 4.3.3: Effect of Cd on the Zn content (μg g-1 dry matter) in the shoots and roots of pigweed

Cd rates Pigweed

Shoots Roots

0 52.5 69.6

2.5 56.6 73.9

5 58.4 77.8

10 62.8 83.2

20 60.1 78.6

40 50.9 66.8

CD(p=0.05) 2.14 3.70

Other workers (MacLean 1976; Singh and Steinnes 1976 and White and Chaney

1980) did not report any interaction between Cd and Zn in lettuce, barley and soybean

respectively. However Abdel-Sabour et al (1988) observed decreased Cd content with Zn

application in maize. Oliver et al (1994) investigated the accumulation of cadmium by wheat

grown at nine sites of South Australia as affected by zinc application and found a marked

decrease of Cd concentration in wheat grain. The result clearly indicated their antagonistic

56

relationship But Iwai et al (1975) observed that Zn added to substrate had no effect of Cd

content of corn.

4.3.4 Manganese

There was a consistent decrease in the mean Mn concentration of the shoots with

increasing levels of cadmium, which could be interpreted as a clear cut case of antagonism

between Cd and Mn (Table 4.3.4). The application of 5,10, 20 and 40 mg Cd kg-1soil

decreased significantly mean Mn concentration in the shoots crop by 5.7, 14.1, 27.1 and 31.6

percent respectively as compared to control Similarly In the roots, the application of 5 mg

Cd kg–1 soil significantly decreased the Mn concentration. These findings were corroborated

by the negative correlation detected in both the shoots (r = –0.89) and the roots (r = –0.87).

Cataldo et al. (1983) found that pearl millet and green gram showed a depression in the Mn

Table 4.3.4: Effect of Cd on the Mn content (μg g-1 dry matter) in the shoots and roots of pigweed

Cd rates Pigweed

Shoots Roots

0 73.2 81.3

2.5 71.9 80.2

5 68.9 76.3

10 62.8 69.2

20 53.4 58.9

40 50.1 55.4

CD(p=0.05) 4.5 4.5

content when 10 and 20 mg Cd kg–1 soil was added. These authors attributed this to the fact

that Cd competitively inhibited Mn absorption, suggesting a common transport site or

process. Patel et al (1976) also observed that the Mn concentration decreased due to Cd

application. On the other hand, Khan and Khan (1983) and Narwal et al (1993) reported that

the Mn concentration increased with the addition of cadmium, in contrast to the findings in

the present study

4.4) Upper critical level of Cd in soil and plant

4.4.1 Soil

4.4.2 Plant

4.4.1 Toxic level of Cd in soil: The toxic or upper critical level of Cd is defined as its lowest

concentration in tissue or soil at which its presence led to reduction in yield. The critical

concentration can be calculated by interpolating the concentration at which yield is reduced

by some arbitrary amount usually 10 to 30 percent. For finding the upper critical level, the

57

regression equations were worked out where the value of percent reduction in dry matter yield

was regressed with corresponding DTPA- Cd in soil. Different mathematical and regression

models such as linear, quadratic and exponential were tested using MS excel (Windows 2007)

to find out the best fit for establishing the critical level. There was excellent fit to the data

with quadratic model as revealed by significant coefficient of determination (R2)

From these equations, the toxic level of DTPA – Cd at which 20 percent reduction in dry

matter yield occurred, were then estimated. The toxic levels of DTPA – Cd was found to be

4.38mg kg-1 soil for pig weed

Table 4.4: Upper critical levels of cadmium in soil and plant in pig weed

Equation Coefficient of

determination (R2)Soil

Linear

Quadratic

Exponential

y = - 1.1053+0.4084 X1

y= 0.9168+ 0.0234 X1 +0.0073 X12

y= 0.8035e0.0681x1

0.91

0.93

0.84

Plant

Linear

Quadratic

Exponential

Y1=0.039+.0.995X1

Y1=3.91+0.253X1+0.014X12

Y1=3.678e0.0558x1

0.92

0.90

0.86

4.4.2 Toxic levels of Cd in shoot of pig weed:. Same method as used for shoot was

employed for finding the toxic level of Cd in soil for a crop through regression equations

where the values of percent reduction with Cd levels in dry matter yield of shoot of crop were

regressed with corresponding tissue Cd concentration. The toxic levels of Cd were then

estimated from the equations at 20 percent reduction. Here also, excellent fit to the data

was found with quadratic model as indicated by significant coefficient of

determination (R2)The toxic levels of Cd in shoots of pig weed at grand growth stage

through quadratic model was found to be 14.6µg g-1 dry matter respectively.

4.5 Laboratory Studies: The soil samples treated with various levels of Cd and amendments

(Calcium Carbonate @ 5%, FYM @ 2% and Phosphorus @ 40mg kg -1 soil) were collected

after pooling the replications treatment wise at equilibrium and after the harvest of the each

crop. Physico chemical characteristics of the soil samples (24 at equilibrium and harvest) such

58

as pH, organic carbon and CaCO3 pertaining to above treatments were determined and are

presented in table 4.5a.

These soil samples (24 at equilibrium and harvest) were then subjected to sequential

fractionation to determine fractions such as Exchangeable + water soluble (EX+WS),

carbonate bound (CARB), Organic bound fraction (OM), Mn oxide bound (MnOX),

Amorphous Fe oxide bound (A FeOX), crystalline Fe-oxide bound (C FeOX) and Residual

(RES). Influence of various amendments was studied on the distribution and transformations

of cadmium and results are discussed as under:

Table No 4.5.1: Physico chemical characteristics of the soil as influenced application of with Calcium carbonate, FYM and Phosphorus at equilibrium

Treatments pH Organic carbon(%) CaCO3 (%)

CaCO3 5.0 %

FYM 2.0 %

Phosphorus 40 mg kg-1

Control Soil

7.92 0 .20 4.62

7.10 0 .65 0.16

7.00 0.24 0.18 7.02 0.24 0 .18

4.5.1 Effect of amendments on Physico chemical characteristics of the soil: Soil

pH, calcium carbonate, organic matter: Among factors controlling the concentration of Cd in

soil, pH, CaCO3 and organic matter are probably among the important parameters

(Christensenn 1984; Ghafoor et al 2008). Addition of various amendments viz calcium

carbonate @ 5 % percent, FYM @ 2% and phosphorus @ 40mg kg-1 soil altered original

properties of the soil. Soil pH increased markedly in soils treated with calcium carbonate at

the rate of 5 percent respectively but to lesser extent with application of other amendments.

As expected, addition of calcium carbonate 5 % resulted in increase of CaCO3 content of the

soil. The increase in organic content was especially noticeable in soils treated with and FYM

@ 2%. This material contained 20.18 percent of organic carbon (Table: 3.3)

59

Table 4.5.2: Distribution of Cd in different fractions as influenced by Cadmium and amendments at equilibrium

Control

Rates of CdEX+WS-

Cd CaCO3-Cd OM-CdMnOX-

CdA FeOX-

CdC FeOX-

CdRES-Cd

0 0.06 0.12 0.32 0.57 0.88 0.57 1.39

2.5 0.40 0.18 0.39 0.60 1.72 0.88 1.69

5 0.95 0.38 0.78 0.68 1.38 1.26 2.61

10 1.85 0.60 1.42 0.98 3.14 1.35 4.08

20 2.98 1.12 2.84 1.65 5.28 1.80 7.62

40 4.54 2.05 5.24 5.79 8.74 4.18 12.60

CaCO3 (5 %)

Rates of Cd

EX+WS-Cd CaCO3-Cd OM-Cd

MnOX-Cd

A FeOX-Cd C FeOX-Cd

RES-Cd

0 0.03 0.26 0.08 0.70 1.00 0.58 1.30

2.5 0.16 0.51 0.16 1.18 1.34 0.94 1.67

5 0.32 0.85 0.43 1.40 1.46 1.34 2.35

10 0.78 1.99 0.78 1.72 3.18 1.38 3.98

20 1.02 3.46 1.68 2.04 5.58 1.88 7.98

40 1.54 6.54 2.88 6.12 9.02 4.28 13.10

FYM (2 %)

Rates of Cd EX+WS-Cd

CaCO3-Cd OM-Cd MnOX-Cd

A FeOX-Cd

C FeOX-Cd

RES-Cd

0 0.03 0.03 0.40 0.78 1.00 0.59 1.08

2.5 0.22 0.09 0.54 1.18 1.32 0.91 1.43

5 0.44 0.16 1.52 1.32 1.50 1.24 1.86

10 0.98 0.32 2.42 1.72 3.78 1.44 2.60

20 1.22 0.53 5.08 2.28 6.02 1.89 6.08

40 2.00 1.43 8.12 6.68 9.32 4.48 10.78

60

Phosphorus (P2O5 40 mgkg-1 soil)

Rates of Cd

EX+WS-Cd

CaCO3-Cd OM-Cd MnOX-Cd

A FeOX-Cd

C FeOX-Cd

RES-Cd

0 0.03 0.10 0.20 0.68 0.98 0.60 1.35

2.5 0.20 0.23 0.52 1.02 1.24 0.92 1.84

5 0.34 0.38 0.99 1.12 1.42 1.32 2.48

10 0.84 0.69 1.45 1.32 3.22 1.42 4.65

20 1.04 1.16 3.04 2.28 5.86 1.88 8.10

40 1.80 2.11 6.02 6.62 9.18 4.44 12.91

61

Fig 10: Distribution of Cd in different fractions as influenced by Cadmium and amendments at equilibrium.

Distribution of Cd in different fractions as influenced by Cadmium and amendments (at equilibrium and post harvest):

4.5.2: Exchangeable + Water soluble fraction (EX+WS)

4.5.2.1 Effect of cadmium: Exchangeable and water soluble Cd increased with increasing

levels of cadmium (Table 4.5.2). It increased from 0.06 to 4.54 mg Cd kg -1 when Cd

application was increased from 0 to 40 mg kg-1 at equilibrium. After the crop harvest there is

slight decrease (0.04 to 3.94) in this fraction. This might be due to the crop removal or

transformation of this pool to the other pools

4.5.2.2 Effect of Amendments: Application of amendments decreased the amount of Cd in

this fraction to the varying degree of magnitude at equilibrium and after harvest. At 40 mg Cd

kg-1soil, it decreased from 4.54 to 1.54 mg kg-1 soil with application of CaCO3 at the rate of

5percent, to 2.00 mg kg-1 soil with FYM at the rate of 2% and to 1.80 mg kg-1 soil when

62

phosphorus was applied at the rate 40 mg kg-1 soil. Liming decreased the amount of EX+WS

fraction due to increase in pH (Table 4.5.1). These observations are in line with those of Chen

et al (2000); Bolan et al (2003b; Zwonitzer et al (2003) and Zhu et al (2004). Narwal and

Singh (1998) observed that application of cow and pig manure decreased the exchangeable

and water soluble cadmium in soils. They argued that formation of organic complexes was

more important than CEC in reducing this fraction. Iwegbue et al (2007) suggested that the

organic compounds bound more trace metals than held on the exchange sites.

4.5.3: Carbonate bound fraction (CARB-Cd)

4.5.3.1 Effect of cadmium: An increasing trend was noticed in the amount of carbonate

bound fraction with increasing rates of Cd application levels (Table 4.5.2) at equilibrium. It

increased from 0.12 to 2.05 mg Cd kg-1 soil when Cd application was increased from 0 to 40

mg Cd kg -1soil which amounted to 2.95 and 4.76 percent at the above rates respectively.

After the crop harvest there was slight decline (2.60 to 4.27 percent) in this fraction. This may

be due to transformation of this fraction into the other fraction with time.

4.5.3.2 Effect of Amendments: The amendments differed to affect carbonate bound

Cadmium Maximum amount of applied Cd at all the rate of its application associated itself in

this fraction was observed in the treatment having 5% CaCO3 followed by, phosphorus @

40mg kg-1 and FYM at the rate of 2 percent. At 40 mg kg-1soil applied Cd, this fraction

accounted for 15.04, 4.90 and 3.36 percent in treatment involving 5% CaCO3, 40 mg P2O5 kg-1

soil and 2% FYM. This revealed that application of amendments in the form of calcium

carbonate (5%) and phosphorus (40 mg P2O5 kg-1) soil helped to increase this form where as

FYM decreased this fraction. In limed soils, the activities of free Cd2+ and OH- ions, CO2

partial pressure, control the precipitation of Cd as CdCO3 (octavite), Cd(OH) and CdCO3

particularly in a sandy soil having low organic matter and low CEC (Street et al 1978).

Pierzynksi and Schwab (1993) reported that lime stone treatment significantly increased

EDTA-Cd fractions which assumed to represent metal from inorganic precipitates as

compared to control. An increase in carbonate bound Cd after lime and P application was

also observed by Bolan et al (2003a) and Zwonitzer et al (2003). Singh and Nayyar (1992);

Rana and Kansal (1985) also observed that cadmium carbonate controlled the activity of Cd

in such soils. After crop harvest CARB-Cd showed very slight decreasing trend. The

corresponding values of the fraction were slightly higher prior to sowing of crop which

declined marginally with cropping (Tables 4.5.2 and 4.5.3).

4.5.4: Organic bound fraction (OM-Cd)

4.5.4.1 Effect of cadmium: Amount of this fraction at equilibrium increased with increasing

rates of Cd steadily from 0.32 in control to 5.24 mg kg-1 soil when it was applied at the rate of

40 mg kg-1 soil at equilibrium. It constituted 8.2, 6.7, 9.7, 10.2, 12.2 and 12.2 percent of the

total at 0, 2.5. 5, 10, 20 and 40 mg kg -1 soil in respectively.

63

4.5.4.2 Effect of Amendments: Amendments had effect of varying magnitude on organic

matter bound Cd. Maximum concentration OM-Cd was observed with 2% FYM application

and intermediate with 40 mg P kg-1 soil and minimum with 5% CaCO3. At 40 mg Cd kg-1 soil

application, the relative percent distribution of Cd in to organic bound fraction was 12.2

percent of the total which decreased to 6.6 (Table 4.4.2) with lime @ 5 % of the total Cd.

FYM @ 2% and 40 mg P2O5 P kg-1 soil increased it to 19 and 13.9 % of the total Cd,

respectively. Ahumada and Schalscha (1993) observed that Cd was recovered mostly in

insoluble organically bound form. The increase due to FYM addition was probably due to

addition of Cd (0.38 mg kg-1 FYM) in FYM. Sposito et al (1982) observed that there was an

increase in NaOH (organic) Cd with an increase in sludge rates. Pierzynksi and Schwab

(1993) studied the sequential fractionation of Cd as influenced by lime stone, cattle manure

and poultry manure. Lime stone treatment was clearly the most effective in reducing

bioavailable (KNO3, H2O and NaOH) fraction of Cd. But NaOH-Cd was significantly

increased by cattle manure and poultry manure as compared to control.

With time organic form showed very slight decreasing trend. The corresponding

values of the fraction were slightly higher prior to sowing of crop which declined marginally

with cropping (Tables 4.5.3). The decline in organic form might be attributed to its

conversion into less available fractions.

Table No 4.5:3 Distribution of Cd in different fractions as influenced by Cadmium and amendments at post harvest

Control

Rates of Cd

EX+WS-Cd

CaCO3-Cd OM-Cd MnOX-Cd

A FeOX-

Cd

C FeOX-Cd

RES-Cd

0 0.04 0.10 0.10 0.68 0.98 0.58 1.36

2.5 0.31 0.15 0.25 1.14 1.30 0.92 1.64

5 0.76 0.30 0.52 1.18 1.42 1.28 2.54

10 1.74 0.54 0.94 1.58 3.22 1.38 3.98

20 2.46 0.96 1.98 2.50 5.70 1.98 7.54

40 3.94 1.84 4.58 6.95 9.14 4.26 12.28

CaCO3 (5 %)

Rates of Cd

EX+WS-Cd

CaCO3-Cd OM-Cd MnOX-Cd A FeOX-

Cd

C FeOX-Cd

RES-Cd

0 0.02 0.23 0.06 0.74 1.04 0.60 1.25

2.5 0.12 0.48 0.14 1.24 1.38 0.94 1.62

5 0.28 0.81 0.38 1.46 1.48 1.38 2.31

64

10 0.68 1.89 0.64 1.64 3.28 1.41 3.94

20 0.82 3.41 1.42 2.14 5.98 1.80 7.93

40 1.46 6.43 2.68 6.24 9.12 4.34 12.99

FYM (2%)

Rates of Cd

EX+WS-Cd

CaCO3-Cd

OM-Cd MnOX-Cd

A FeOX-Cd

C FeOX-Cd

RES-Cd

0 0.03 0.03 0.36 0.78 1.02 0.60 1.04

2.5 0.18 0.10 0.52 1.20 1.36 0.90 1.40

5 0.42 0.15 1.48 1.34 1.54 1.28 1.82

10 0.94 0.36 2.36 1.80 3.32 1.45 2.58

20 1.12 0.48 4.88 2.34 6.12 1.90 6.04

40 1.96 1.38 7.38 7.02 9.42 4.62 10.60

Phosphorus (P2O5 40 mgkg-1 soil)

Rates of Cd

EX+WS-Cd

CaCO3-Cd

OM-Cd MnOX-Cd

A FeOX-Cd

C FeOX-Cd

RES-Cd

0 0.03 0.07 0.16 0.85 0.98 0.59 1.22

2.5 0.19 0.20 0.48 1.15 1.27 0.94 1.74

5 0.32 0.36 0.91 1.30 1.47 1.38 2.28

10 0.78 0.66 1.34 1.46 3.34 1.44 4.53

20 0.98 1.14 2.93 2.34 5.99 1.96 7.87

40 1.68 2.10 5.85 6.68 9.42 4.52 12.81

65

66

Fig11: Distribution of Cd in different fractions as influenced by Cadmium and

amendments at post harvest

4.5.5: Metals associated with oxides

4.5.5.1Effect of cadmium: At equilibrium, the amount of Cd in manganese oxides (MnOX),

amorphous Fe oxides (A FeOX) and crystalline Fe oxides (C FeOX) bound forms increased

with increasing rates of cadmium. At 40 mg kg-1 soil application, these forms constituted

about 13.4, 20.3 and 9.7 per cent respectively of the total Cd in soil. Relative higher value of

oxides (MnOX, A FeOX and C FeOX) fractions compared to the others fractions suggested

that Cd was mostly found occluded in these fractions. Keller and Vedy (1994) indicated that

Cd was mainly associated with Fe- Mn oxides. Bruemmer et al (1988) suggested that higher

amount of Cd in this fraction was due to its specific adsorption on Fe-Mn oxides or

incorporated inside the oxide particles. Jenne (1968) reported that concentration of heavy

metals was inclined to be controlled by sorption to hydrous oxides After harvest, with time,

amount of Cd bound to MnOX, A FeOX and C FeOX ) were 6.95, 9.14 and 4.49 mg kg -1soil

which were higher compared to their values of 5.79, 8.74, 4.18 mg kg-1soil of the above

fractions respectively at equilibrium. Logan and Chaney (1983) indicated that over time a

Cd salt solution reacted with soil and reverted to less available or more insoluble oxidised

form.

4.5.5.2 Effect of Amendments: At equilibrium, increasing trend for all oxide (MnOX, A

FeOX, C FeOX) fractions was observed with all the added amendments. However a slight

difference in Fe, Mn bound Cd existed among amendments. Amount of MnOX-Cd increased

from 13.42 to 14.08 percent with the application of calcium carbonate. Same trend was found

in A FeOX-Cd which increases from 20.26 to 20.75 and in C FeOX fraction from 9.69 to 9.84

percent. Application of FYM encouraged Cd to be accumulated more in this fraction FYM @

2 % registered higher values of all oxide bound fractions (6.68, 9.32 and 4.48 mg kg -1soil ) as

compare the equilibrium (5.79, 8.74, 4.18 mg kg -1soil). This was most likely due to

predominance of dithionite extractable iron and manganese oxides (Free Fe and Mn oxide )

having a mean value of 0.64 per cent and 156 mg kg-1 soil. Shuman (1988) reported that

amorphous Fe oxide Zn increased with the application of organic matter. Application of

phosphorus @ 40 mg kg-1soil resulted in the increase of Cd bound pools MnOX-Cd, A FeOX-

Cd and C FeOX-Cd to 6.62, 9.18 and 4.44 mg kg-1soil respectively from 5.79, 8.74, 4.18 mg

kg-1soil. After harvest of crop, amount of Cd bound to MnOX, A FeOX and C FeOX ) were

6.68, 9.42 and 4.52 mg kg -1soil as against 6.62, 9.18 and 4.44 mg kg-1soil indicating thereby

that cropping did no affect this form. Ghafoor et al (2008) also reported increase in FE/Mn

bound fractions with KH2PO4 and lime.

67

4.5.6: Residual fraction (RES-Cd)

4.5.6.1 Effect of cadmium: There was an increase in residual Cd with increasing level of

Cadmium. Application of 40 mg kg-1 soil increased the amount of Cd in this pool from 1.39

to12.60 mg kg-1.

4.5.6.2 Effect of amendments: Lime application influenced this fraction and encouraged Cd

to be more associated with this fraction. However P application ineffectually increased

residual Cd in soil. Application of FYM inefficiently decrease this fraction. This is in

conformity with Chen et al (2000), Bolan et al (2003a & b) and Zhu et al (2004) who

reported that lime, P and compost increased residual Cd in soil. It is assumed that metal

fraction lost from the Exch+WS was recovered in the /oxides and residual fractions (Knox et

al 2001)

The results of the present study in the preceding pages indicated that among the three

amendments (FYM, Calcium carbonate and Phosphorus), calcium carbonate was found to be

most effective in mitigating the toxicity of cadmium followed by phosphorus and FYM. It is

quite possible that application of calcium carbonate may cause deficiency of some essential

micronutrients which is a cause of concern. Considering soil health as of paramount and vital

importance, application of FYM appears to most suitable amendments as it not only offset the

adverse effect of cadmium but also causes improvement in soil structure by increasing

porosity, water holding capacity and aeration. Other useful constituents of FYM also help to

sustain soil productivity.

Further, there is need to characterize organic matter as in some cases higher fulvic

content encourage plant uptake of pollutants. Application of phosphorus may also antagonize

zinc availability under certain situations. Considering the above facts, choice of amendments

has to be made carefully. So, there is need to conduct further experiments to study the

effect different types of both inorganic and organic ameliorants under specific

situations depending on the severity of pollutant toxicity so that their availability

could be kept at the minimum.

68

CHAPTER V

SUMMARY

There is unabated contamination of soils with heavy metals including Cd through sewage

water, city garbage, and untreated industrial effluents as a result of rapid industrialisation and

urbanisation in Punjab in the recent past. High amount of cadmium has been reported to cause

health hazards and disorders in human beings. In Punjab, leafy vegetables including Chalai

(Pig weed- Amaranthus tricolor) are generally grown on the outskirt of the cities and irrigated

frequently by sewage water contaminated largely by industrial effluents. There is need to

develop appropriate decontamination technology using range of inorganic and organic

materials for minimizing its pollution in agricultural soils and crops grown on these soils.

There was paucity of information on the transformation and availability of Cd in the presence

and absence of amendments (lime, phosphate and organic manure). In view of all this,

objective of the of the present study were;

1. To delineate Cd contaminated soil for its lateral distribution in order to assess its extenent

pollution.

2. To assess relative suitability of different amendments for minimizing Cd pollution in

contaminated soils and plants.

3. To establish the upper threshold limit of toxicity of Cd for pig weed.

4. To study the effect of various amendments on the transformations of Cd in soil.

Survey Studies

In order to determine pollution potential, surface (0-15cm) soil samples receiving

waste water irrigation at a distance of 50, 250, 500, 750 and 1000 meters (5 sites) were

collected laterally on either side (Right and left) along the Buddah Nallah from each village

(six in number) which were approximately 4-5 kilometers from each other with the help of

global positioning system in the month of December. These were analysed for DTPA and

total Cd

Mean value of DTPA-Cd irrespective of sites of surface sewage irrigated soils was

0.154 mg kg-1 soils which was found to be 5.2 times greater than the normal soils

In order to demarcate Cd polluted soils, guidelines based on total metal content were

considered. As per guidelines of Kabata and Pendias (1984), 3-8 mg total Cd kg -1 soil is

considered to be the critical limit above which toxicity of Cd is possible. In the present study,

6 (representing the sites Saleem tabri and Partapsinghwala) out of 53 soil samples reached

this threshold value of 3 mg Cd/kg soil. Thus it appeared that about 11.3 percent soils have

become polluted as a result of continuous irrigation with sewage water. These soils require

immediate attention and needs to be ameliorated urgently. There is the possibility that rest of

69

the soils might approach this critical limit in a few years if same level of irrigation with

sewage water continued.

In another standard adopted in U.K, as prescribed by G L.C (Greater London

Council), total Cd concentration ranging from 0 to 1, 1 to 3, 3 to 10, 10 to 50 and >50 mg/kg

soil were categorized as typical uncontaminated, slightly contaminated, contaminated and

heavy contaminated soils, respectively. According to this system therefore, most of the

investigated soils fell under slightly contaminated category indicating thereby that clean up

operation is definitely required. So there is an urgent need to work out the critical limit for Cd

toxicity in the Punjab soils on a wider scale

Screen house studies

A screen house experiment was conducted to assess the effect of six levels of Cd (0,

2.5, 5 10, 20 and 40 mg kg-1 soil) and CaCO3 (2.5 and 5%), FYM (1 and 2 %) and

Phosphorous (20 and 40 mg kg-1 soil) in a factorial complete randomized design on the

growth of pigweed on sandy loam soil having DTPA extractable Cd 0.36 mg kg -1 soil. The

soil in the pots was equilibrated for 21 days at field capacity moisture level after applying

above treatments. The crop was then planted and harvested at grand growth stage. Dry matter

yield of shoot and roots the crop was recorded and plant samples of both shoots and roots

were analyzed for Cd and micronutrients cations. The soil samples collected after equilibrium

and crop harvest were analyzed for DTPA- extractable Cd. A laboratory study was also

conducted to determine different pools of cadmium and their transformations as influenced by

amendments.

The result of the screen house study revealed that with the increasing rates of Cd

application, there was significant and progressive increase in DTPA -Cd at equilibrium. The

application CaCO3, FYM and phosphorous declined the content of DTPA- Cd in soils at all

level of its application.

DTPA-Cd decreased from 7.38 mg kg-1 soil ( control) to 3.8 (lime @ 2.5%), 3.5

(lime @ 5%); 4.9 ( FYM @ 1% ), 4.64 (FYM @ 2% ); 4.4 mg kg-1 soil (P @ 20 mg P kg-1

soil) and 4.0 mg kg-1 soil (P @ 40 mg P kg-1 soil), thereby indicating the superiority of

applying CaCO3 as an ameliorant over other amendments for mitigating the toxicity of

cadmium

Cadmium content in the shoots increased with increasing rates of Cd application. The

application of even the lowest rate of 2.5 mg Cd kg -1 soil significantly increased the Cd

content in crop over control. The mean Cd concentration increased from 1.26 in control

treatment to 4.72, 6.04, 14.10, 21.80 and 46.42 µg g-1 dry matter when rate of Cd application

was raised to 2.5, 5, 10 20 and 40 mg kg-1 soil. It implied now that the decrease in dry matter

yield had resulted from the phyto toxic effect of Cd in pigweed emanating from the increased

availability of Cd in soil and plants as a result of its application. A gradual reduction in mean

70

dry matter yield of chalai (pig weed) occurred with increasing levels of cadmium irrespective

of the amendments but the significant decrease was observed at and above the application rate

of 10 mg kg-1soil. However different amendments viz (Calcium carbonate, FYM, Phosphorus)

exhibited variable behaviour as far as their remediation potential was concerned at a

particular level of Cd application and their application at all the levels mitigated the toxicity

of cadmium as is evident by the increase in dry matter yield of the crop irrespective of Cd

levels. A significant enhancement in dry matter yield of chalai was observed with all the

amendments. Lime @ 2.5 and 5% increased mean dry matter yield from 16.39 (Control) to

18.2 and 19.1 g pot-1, respectively. FYM at the rate 1 and 2% produced mean dry matter yield

of 18.4 and 19.34 g pot-1 while 17.6 and 18.4 g pot-1 respectively with phosphorus application

of 20 and 40mg kg-1 soil regardless of Cd levels. The dry matter yield of roots started

declining even with the application rate of 5 mg Cd kg-1 soil application. However, a

significant decrease was observed with 10 mg Cd kg-1 soil onwards. Further, application of 20

and 40 mg Cd kg-1 soil showed significant sharp decline in root dry matter yield. The

reduction in dry matter yield of pigweeds root was 15.9, 28.2 and 45.7 percent with the

application of cadmium at the rate of 10, 20 and 40 mg kg-1soil. So the yield reduction in

response to Cd was of similar proportions in the roots as for the aboveground part of the

plants. The reduction in root growth was in accord with the amounts of extractable Cd .The

magnitude of reduction in root biomass was comparable to the shoot biomass. Maximum

mean dry matter yield of the shoots of pig weed was obtained in the treatments involving

FYM amendments in spite of the fact it was less effective in decreasing the concentration of

Cd in pig weed shoot compared to other amendments. Amendment in the form of calcium

carbonate was found to be most effective. With amendments (calcium carbonate) through

formation of less soluble compounds like CdCO3 mitigated the toxicity of cadmium.

There was excellent fit to the data with quadratic model as revealed by significant

coefficient of determination (R2) From these equations, the toxic level of DTPA – Cd at

which 20 percent reduction in dry matter yield occurred, were then estimated. The toxic levels

of DTPA – Cd was found to be 4.38 mg kg-1 soil for pig weed

The toxic level of Cd in shoots of pig weed at grand growth stage through quadratic

model was found to be 14.6 µg g-1 dry matter.

Applied cadmium at lower levels (0 to 10mg Cd kg-1 soil) increased Zn concentration

in roots and shoots of crop showing synergistic interaction. It indicated that, one helps in the

absorption of the other at lower levels. However at higher levels (20 and 40 mg kg -1 soil) of

Cd application, Zn concentration decreased relative to control indicting antagonistic

interaction. Like zinc, mean Fe concentration in the roots and shoots of crop showed

increasing trend with the application of Cd at lower levels but depression at higher levels. The

concentration of copper and manganese in the roots and shoots of pig weed was negatively

71

affected by the application of Cd at all levels as evident from the significant negative

correlation coefficients between these metals and cadmium.

Different pools of Cadmium as influenced by Cd and amendments application at equilibrium

All the fractions of Cd increased significantly with increasing levels of cadmium

irrespective of amendments at equilibrium before seeding of crop. Application of

amendments had a depressing effect on the amount of cadmium in the EX+WS fraction.

Manure application decreased the amount of cadmium in carbonate where as it encouraged

the Mn oxide, organic bound and amorphous Fe oxide crystalline FeOX bound Cd.

Application of calcium carbonate at the rate 5% increased the amount of carbonate

substantially but had a non significant effect on all other forms. Phosphorus application was

effective in trasnsforming Cd in to less available forms (Mn oxide, amorphous Fe oxide and

crystalline FeOX bound Cd).

Different pools of Cadmium as influenced by Cd and amendments application at post harvest

There was a decreasing trend of extractability of exchangeable + water soluble,

carbonate bound and organic bound fraction with time both in the presence and absence of

amendments. The decline in these forms might had been caused partly by its progressive

removal by plants or due to possible shift to other forms. In all the treatments (with and

without amendments) with time/cropping there was an increasing trend of Cd to be associated

more in the MnOX, A FeOX and C FeOX fractions. The value of this fraction was

comparatively higher after the harvest of the crops compared to at equilibrium.

72

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VITA

Name of the student : Dharamvir Singh Kambo

Father’s name : Sh. Amarjit Singh

Mother’s name : Smt. Balwinder Kaur

Nationality : Indian

Date of Birth : 28th July, 1986

Permanent home address : VPO Phulewala. Teh. Bagha purana Distt. Moga

Educational Qualification

Bachelor’s degree : B.Sc (Ag.) Hons

University : Punjabi University, Patiala

Year of award : 2008

% of marks : 64.7%

Master’s degree : M.Sc. (Soils)

OCPA : 7.58/10

Year of award : 2011

Title of Master’s Thesis : Delineation of cadmium contaminated soils around Buddah Nallah (Ludhiana) and remedial measures of affected soils

Awards and distinctions : MET Scholarship (2008)

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