vertical profile of heavy metal concentration in core...

Indian Journal of Geo-Marine Sciences

Vol. 40(1), February 2010, pp.83-97

Vertical profile of heavy metal concentration in core sediments of Buckingham

canal, Ennore

Usha Natesan and B. Ranga Rama Seshan1

1Centre for Environmental Studies, Anna University Chennai, Chennai – 600 025. India

[E-mail: [email protected]]

Received 20 October 2009; revised 14 January 2010

Down core variations in heavy metal concentrations at every 2.5cm increment was determined. Four cores were

collected to assess the heavy metals - Cd, Cr, Cu, and Mn in the Ennore creek and one core was collected from the sea. Mn

is present in highest concentrations in all cores ranging 0.9 to 4ppm. Results were processed used correlation and factor

analysis. Results of statistical analysis show that positive correlation exists among fine grained particles and heavy metals.

Correlations of OM with heavy metals is also observed. Results confirm that fate of heavy metal in sediment is influenced

by many parameters. Sediment pollution assessment was carried out using geoaccumalation index, anthropogenic,

enrichment and contamination factor. Muller’s Igeo classification places Ennore under class

0 - uncontaminated except C3 which falls under class 6 (very highly contaminated). EF places Ennore under minimal

contamination. According to Pollution Load Index calculations Ennore shows low to moderate degree of contamination.

[Key words: Core, Ennore, Heavy metal, Pollution, Sediment]

Introduction Sea, and more particularly the aquatic systems

(e.g. estuaries), are the ultimate repository of

anthropogenic wastes. Highly dynamic nature of the

marine environment allows for very rapid assimilation

of these materials by processes such as dilution,

dispersal, oxidation, degradation or sequestration into

sediments. However, the capacity for such assimilation

is limited thereby leading to pollution. Increase in

urbanisation and industrialisation has led to increase in

marine discharges and, therefore, the total load of

pollutants being delivered to the sea1. These discharges

contain heavy metals among a host of other pollutants.

Various complex diagenetic processes can also

influence sedimentary trace metal concentration

profiles. Diffusion of metal to a sink located below

the sediment–water interface can occur if dissolved

metal concentrations are higher in the water column

than in porewaters2&3

; this can create subsurface peaks

in sedimentary metals that could be erroneously

attributed to variations in metal deposition. Trace

metals can also be mobilized after their deposition

and then either relocalized in the sediment column4-6

or diffuse to the water column7. The upper layers of

sediments can be mixed by physical processes due to

the burrowing and feeding activities of benthic

organisms; these mixing processes tend to

homogenize metal concentrations in the mixing zone8.

The geochemical mobility of toxic metals in

sediments depend on how and type of sediment phase

they are bound to and their chemical form, which, in

turn, is related to the physicochemical and biological

characteristics of the environmental system. In

general the mobility of heavy metals in sediment is

severely limited by strong sorption reactions between

metal ions and negatively charged particles of

sediments9. However, several long-term experiments

have evidenced an enhanced mobility of metal ions in

organic matter rich sediments10-13

.

Organic matter together with pH is the most

important parameter controlling heavy metal

behaviour in sediment. Heavy metals bound on

insoluble humic substances are relatively immobile.

On the other hand, binding onto smaller organic

molecules may increase metal mobility and

bioavailability14

. Humic carboxylic -COOH and

phenolic -OH groups are mainly involved in the

formation of metal-humic complexes15&16

.

With Ennore being a major industrial complex,

there is a need to assess the status of the marine

environment around Ennore. The study of core

________________

Corresponding author : Dr. Usha Natesan

E-mail: [email protected]

Phone : +91 44 22203195/ + 91 44 22203032

Fax: +91 44 24472547/ + 91 44 22354717

INDIAN J. MAR. SCI., VOL. 40, NO. 1, FEBRUARY 2011

84

samples gives an historical record of concentration of

heavy metal i.e bottom sediments and the surface

sediments representative of pre-industrial and recent

times respectively. Apart from analysis of heavy

metals, since the fate and transport of these metals are

governed by sedimentological parameters such as pH,

grain size, sediment composition and organic matter,

these were included in the study.

Materials and Methods Study area

Study area covers the North Chennai region

consisting of the coastal waters and the Ennore creek.

Ennore Creek is a complex fresh/brackish water system,

which is nearly 800m wide and elongated in the

NE-SW direction. (Fig. 1). Ennore creek drains the

Kortalliyar River watershed. Southern arm of the

creek is well developed with industries, utilities,

suburban residential areas and fishing hamlets.

Northern section of the creek is connected to the

Pulicat Lagoon and has two major developments -

North Chennai Thermal Power Core (NCTPS) and

Ennore Satellite Port. Construction of the Ennore

Satellite Port has choked the mouth of the Ennore

Creek. Raw municipal sewage, industrial trade

effluents, industrial cooling waters, oil from boat

repairs; aquaculture wastewater all of them make it

through Buckingham canal, Ennore and eventually

into the Bay of Bengal off North Chennai coast. In

view of these activities about 25km stretch of

Buckingham canal i.e from Ennore creek in the south

to Pulicat in the north was chosen.

Fig. 1 Study area showing sampling locations

USHA & SESHAN: VERTICAL PROFILE OF HEAVY METAL CONCENTRATION IN CORE SEDIMENTS

85

Core collection and analysis

Cores were collected from 5 locations as shown in

Figure 1. The sampling locations were selected based

on the prevailing stresses. Core 1 (C1) is close to the

creek where the coolant water and fly ash from

NCTPS is discharged. There is a second inlet to the

canal which is permanently closed and Core 2 (C2)

was collected close to this inlet. Discharges from

various industries can be seen at southern side of the

creek, this has been fixed as Core 3 (C3). Pulicat

where the environmental condition is relatively

pristine has been fixed as Core 4 (C4). Core 4 is

considered as reference for this study. A core was

collected from the Bay of Bengal, Core 5 is located

(C5) at a distance of about 2km from the coast to

determine if the heavy metals from Ennore have been

dispersed and deposited in the Bay of Bengal.

Core collection was done by acid washed PVC

coring tube of 10cm diameter and 1m length which

was presealed on one side was used. A boat was hired

and the sampling locations were fixed with Global

Positioning System (Table 1). The pre-labeled core

was inserted into water sediment interface. Pressure

was applied to ensure the core penetrates to the

maximum depth. After reaching the bottom, the core

was slowly retrieved back and closed. Core was

marked indicating the upward direction. Cores were

collected within the canal viz Ennore creek and

Second inlet inner side; from Pulicat Lagoon and

industrial discharge on 18.07.08. Sea core was

collected with the help of NIOT Research Vessel

Sagar Purvi on 03.06.08.

During sampling, the water depth was measured

using a tide pole. Salinity, temperature and dissolved

oxygen (DO) of surface water were recorded in the

field using a probe. DO was measured using WTW

Oxi 330/SET, salinity using Cyberscan Con/TDS with

0.1 mS resolution and temperature was measured

using a standard thermometer. The cores were frozen

for a period of four days and then sliced horizontally

at 2.5 cm interval. Sediment samples were stored in

clean labeled polythene covers.

Sediment samples were dried at 70-80°C for 48

hours prior to analysis. The shells present in the dried

samples were handpicked. The clumps present in the

samples were broken down with a help of mortar &

pestle. Sediments were analysed for their composition

with the help of the procedure adopted by Krumbein

and Pettijohn17

. Grain size analysis was carried out for

the surface subsamples using a set of 10 sieves spaced

from 2000mm to 45µ. Samples were sieved for

15minutes in Rotop sieve shaker. Sediment retained

on each sieve was carefully removed and weighed.

Cumulative weight % retained with the help of

GRADSTAT directly calculated the grain size

distribution18

. pH of the sediment samples were

determined using Cyberscan PCD 5500 pH meter

having a carbon glass electrode with resolution 0.01.

Determination of calcium carbonate and organic

matter in sediment were done following the procedure

of Loring and Rantala19

and Gaudette20

respectively.

Geoaccumalation index was calculated using an

equation given by Müller (1979). Anthropogenic

factor was calculated for the cores collected. With the

help of this it was possible to differentiate between

geogenic and anthropogenic input of heavy metals.

For digestion of heavy metals, the sediment

samples were sieved through 230µ mesh sieve and

was acid digested. The extraction was performed with

1g of sediment. Trace metals were determined by

digestion with HF, HNO3, and H2SO4 in a sealed

Teflon vessel (Teflon bomb) using a hot plate21&22

.

Digested samples were filtered with Whatman Grade

“A” filter paper and the filtrate was analyzed for Cd,

Cr, Cu and Mn in Optima emission spectrophotometer

Optima 2100 Dy. Chemicals of high purity (Merck,

Germany) were used for the analysis and standard

solutions were prepared from 1000mg/L stock

solution for each metal. Quality assurance testing

relied on the control of blanks and a yield for

chemical procedure was quantitative at 100 ± 5.2%.

Relative chemical standard solutions

(Merck’s Multielement Standard Solution IV,

Germany) were run to check the precision of the

Table 1 Core Details

Core Number Core

Latitude (N)

Longitude (E)

Water Depth in m

Core retrieval

depth in cm

Number of

subsamples

1 Ennore Creek 13°14.120' 80°19.896' 1.25 35.0 13

2 Second inlet inner side 13°22.296' 80°19.642' 1.68 35.0 13

3 Industrial discharge 13°13.413' 80°19.139' 0.16 42.5 16

4 Pulicat lagoon 13°24.411' 80°19.505' 0.9 40.0 15

5 Ennore Sea 13°14'5''.04 80°20'39''.33 20.0 8


86

instrument throughout the analysis. Results obtained

for all analysed samples were within ± 2.25% error

limit with a precision of 95%.

Results And Discussion Surface Water Quality

Temperature, salinity and DO of surface water

details are outlined in Table 2. C1, records maximum

temperature (36°C) due to the discharge from

NCTPS. Kalaivani (2007)23

reported that this station

records remarkably higher temperature with an

average increase of 9°C compared to other stations.

Consistent high temperature is due to the coolant

water discharge from NCTPS. Minimum DO of

0.7mg/L is recorded at Industrial Discharge (C3).

Accumulated sludge could have contributed to the

reduction in DO by decreasing the rate of dissolution

of atmospheric oxygen which in turn may enhance the

rate of biochemical oxidation24

. DOD (2001)25

report

showed that Ennore creek is contaminated by sewage

released from Buckingham Canal with nil to low DO

and values of other elements were more or less within

limits. The salinity value recorded is less compared to

the other Cores. Surface water quality characteristics

could not be obtained for the core collected from

Ennore Sea.

Sediment Texture And Composition

Grain size analysis using GRADSTAT software

shows that the sediment samples have a sandy texture.

Fig. 2 shows graphical variations in grain size for

each core. Ennore creek comprises of coarse sand

with a d50 value of 621.1µm. At C1 around 95 – 99%

of sand is recorded (Fig. 3). C1 is composed of coarse

sand due to the constant tidal exchange between the

creek and the Bay of Bengal which brings in coarse

sand particles whereas the other cores have medium

sand. Silt content in the vertical profile ranges

between 0.3 and 5%. Negligible amount of clay was

present. A slight decrease in sand content was

observed at a depth of 35cm which is compensated by

increase in the silt content. Ennore Sea and Industrial

discharge consists of poorly sorted fine sand but

Ennore sea sand domination is observed whereas silt

forms the highest fraction in C3 due to the huge

amount of sludge from industrial discharge. High silt

and clay was observed in C3 and similarly high

concentration of heavy metals in the top in 7.5cm

indirectly indicating greater extent of pollution during

the recent times. As indicated by Doyle and Shields26

d50 i.e. median bed material grain size best represents

grain size distribution and thus was included in the

analyses. The least d50 value is observed in C4

(293.5µm). Table 3 gives the detailed description of

the nature of the sediments. C3 and C4 are mesokurtic

whereas C2 and C5 are platykurtic and only C1 is

very leptokurtic in nature. In C5 although sand was

found to be dominating there is a reduction from 90%

to 80% owing to the nature of sediments in the Pulicat

lagoon. It is compensated by subsequent increase in

both clay and silt. Sediments with a high percentage

of small grains, such as silt and clay, have high

surface-to-volume ratios and can adsorb more heavy

metals than sediments composed of large grains, such

as sand27

.

pH

pH of sediment controls the solubility of different

metals as opined by Ahrland28

. There is not much

down core as well as Core to Core variations in pH

(Fig. 4). It lies between slightly acidic to neutral to

slightly basic. The apparent unevenness length wise is

due the variations in core retrieval depth for each

Core. C3 has neutral to basic pH whereas all the other

locations the pH lies between 6-7 or in few cases less

than 6 viz C4 at a depth of 25cm and 45cm the pH

drops to 5.82 and 5.97 respectively. Industrial

discharge shows a basic pH throughout the core.

Metals such as copper, cadmium, lead, and zinc can

be mobilized during oxidation of anoxic or at low pH

sediments through oxidation of sulfide phases29

and

oxidation of organic matter30

. C3 shows a greater

basic nature with a corresponding decreased Cd

concentration. Cu is totally absent in all cores.

Calcium Carbonate And Organic Matter

The down core variations in calcium carbonate is

shown in Fig. 5. C1 showed the highest CaCO3 with

6% at the surface and drops to about 4% at a depth of

15cm and then again increases and varies from 5 to

4%. The source of calcium carbonate is dead

organisms – molluscs, foraminifera, coccoliths and

their shells lying all along the shores. The second

Table 2 Surface Water Quality

Core Temperature (°C) DO (mg/L) Salinity (ppt)

1 36.0 6.0 33.2

2 28.8 4.4 27.4

3 29.0 0.7 27.2

4 30.6 4.7 30.6

5 - - -


87

Fig. 2 Grain Size Distribution


88

Fig. 3 Sediment Composition

Table 3 Description of Sediments

Core d50 µm Description Sorting Skewness Kurtosis

1 621.1 Coarse Sand Moderately Sorted Symmetrical Very Leptokurtic

2 353.3 Medium Sand Moderately Sorted Symmetrical Platykurtic

3 408.3 Medium Sand Poorly Sorted Symmetrical Mesokurtic

4 293.5 Medium Sand Poorly Sorted Coarse Skewed Mesokurtic

5 315.0 Medium Sand Poorly Sorted Coarse Skewed Platykurtic


89

highest CaCO3 % is observed in C5. Presence of

CaCO3 here can be attributed to the presence of

shelled organisms in the marine environment and

moreover Indian coastline falls in the category of

calcareous ooze and has 50% to less than 50% by

weight of calcium carbonate31

, upon the death and

decay of shelled organisms below the Carbonate

Compensation Depth, dissolution takes place and

calcium carbonate gets deposited. Least concentration

of CaCO3 is observed at C3, this being the site for

industrial discharge chances of shell deposition is

minimal due to the heavy sludge loading. The

remaining two Cores, viz C2 and C4, lying within the

canal supports a rich biodiversity including shelled

organisms thereby showing the presence of CaCO3.

At a depth of 25-35cm in C4 CaCO3 is present at 2%.

Taking into account its high specific surface area,

organic matter can form complexes with heavy metal

and consequently influence their distributions32

. Clays

have high specific surface area and can directly trap

heavy metals, but they also may act as a substrate for

organic matter flocculation33

that in turn adsorbs

metals. Cores C2, C3 and C4 have high organic

matter of 2-9% (Fig. 6) and they are the ones that

have relatively higher concentration of heavy metals.

The source for organic matter within the canal is due

to the fine nature of sediments, high rate of

sedimentation and larger supply of organic matter

from river runoff34

. C1 recorded the highest

concentration of organic matter (10.175%).Sea core

shows relatively lower organic matter content ranging

from 1.7 – 4.7%. It is observed that in all the cores the

surface subsamples have higher organic matter

content compared the bottom subsamples.

Vertical Profile Of Heavy Metals

Fig. 7 shows the trend in down core variation in

heavy metal concentrations. Adsorption of heavy

metal ions and complexes on clay minerals occurs as

a result of ion exchange, surface complexation,

hydrophobic interaction and electrostatic interaction.

Clay minerals play an important role in accumulation,

adsorption/desorption, as well as exchange processes

Fig. 4 pH variations

Fig. 5 Variations in Calcium carbonate


90

of metal ions35

. The elemental sequence of heavy

metal concentration expressed in ppm is as follows:

Mn (1 to 4ppm) > Cu (0.1 to 7ppm) > Cr

(0.1 to 1.5ppm) > Cd (0 to 0.023ppm).

C1 is relatively less polluted in comparison with

other Cores. This can be to due to the highly dynamic

nature of creek with continuous tidal action and

dilution with seawater thereby reducing the chances

of passage of heavy metals from water to sediment.

Moreover enhanced mobility of metal ions is

observed in organic matter rich soils and the nature of

the creek sediments being sandy makes it incapable

for the metal to bind to the soil. In the creek, Cu is

present in higher concentration compared to other

metals (0.434 - 2.886ppm). Globally, the average

concentration of Cu in river-borne solids transported

in estuaries is relatively higher (2500ppm) than that of

near shore sediments36

(48ppm), whereas in all the

other cores Mn is present at higher concentration

(0.777 - 1.326ppm). Cd and Cr are present at

concentrations barely exceeding 0.05ppm. Mn is

present at about 1 ppm. Cu is present as high as

2.9ppm. The trend in Cu is variable compared to the

other metals.

In C2 all the metals are present at about 2ppm

whereas Mn is present at a concentration of 3ppm

Fig. 6 Variations in Organic Matter

Fig. 7 Vertical Profile of Heavy Metals concentrations


91

which indicates Mn is present at higher concentration

in the canal than the coastal environment. The present

trend is in agreement with study carried out by

Jayapraksh in 200237

. This core being near second

inlet which is permanently closed shows the extent to

which pollutants are being transported within the

canal. Cd is absent throughout the vertical profile. Cr

shows almost a uniform trend with concentration

varying between 0.3 to 0.7ppm. Followed by C3, Cr is

occurring in C2 at a slightly higher concentration

compared to other cores (0.4-0.6ppm as compared to

0.2-0.4ppm). Cu and Mn do not follow any trend,

their vertical profile is variable. The heavy metals can

be from various industrial wastewaters that drain into

the Buckingham canal, Ennore.

C3 being industrial discharge location, heavy

metals are found to vary from 0.004 – 3.8ppm. Cd

being the least and Mn being the highest. The source

for the heavy metal is discharges from the industries.

The surface sediments show higher concentration of

heavy metals rather than bottom sediments suggesting

accumulation of these heavy metals is human induced

and the phenomena is a recent one. Even in C3 Cu

concentration is negligible, up to the depth of 37.5cm

Cu is present at concentration range of 0.004 to

0.023ppm beyond that Cu is absent.

C4 is taken as reference since it is relatively

pristine devoid of influence from human activity.

Even in Pulicat Mn is seen at higher concentration

thereby indicating the natural presence of Mn in the

marine environment of Ennore. The same pattern is

observed in C5 hence proving its natural occurrence

rather than being an input from an anthropogenic

source. Overall C4 shows lower concentration in all

heavy metals except Cu concentration which varies

between 0.3-0.9ppm and shoots upto 7.8ppm at

32.5- 35.0cm and from there on the concentration

again decreases but not as low as the surface

sediments (1-1.5ppm). The source for this heavy

metal content is unknown, dating of the sample

might provide an indication of its presence but

dating is beyond the scope of this study. Other than

this peculiar trend observed with Cu, the lower

concentration of heavy metal in C4 vouches for the

fact that Pulicat is unpolluted when compared to

Ennore. A similar behaviour is observed in C5 viz

low concentration of heavy metal which indicates

that there is not much spatial dispersion of

Fig. 7 Vertical Profile of Heavy Metals concentrations


92

pollutants and the pollutants have not reached to a

distance of 2km into the sea from the coast.

Correlation indexes were calculated for similarities

in composition of samples from different locations.

Cd was considered for statistical analysis only in C1

and C3. From the correlation matrix it is evident that

clay and silt (fine grained fraction) reveals good

correlation with heavy metals except in C3 (Table 4).

Weak association of Cd and Cr with fine grained

fraction in C3 indicate that they are not controlled by

grain size. In C4 and C5, Cr and Mn are positively

correlated. In C3 and C4, Cr and Cu are positively

correlated. Notably, the correlation and geochemical

associations of metals reveal a significant source of

contamination reflecting a common origin of similar

nature existing from the industrial effluents38

. Organic

matter also has good positive correlation with heavy

metals.

Geoaccumulation Index

The Geoaccumulation Index (Igeo) introduced by

Muller39

was used to assess metal pollution in

sediments of Ennore (Table 5). Igeo is expressed as

follows:

Igeo = log2 (Cn /1.5 * Bn ) where

Cn - measured concentration of heavy metal in the

sediment,

Bn - geochemical background value in average

shale40

of element n,

1.5 is the background matrix correction in factor

due to lithogenic effects.

Igeo calculation was carried out only for the surface

sediment in each core. The calculated values for

Ennore and its surrounding marine environment are

given in Table 6. As far as pollution due to Cd is in

Ennore is concerned, it is uncontaminated. C3 for Cr

and Cu falls under the class very highly contaminated.

C4 is the only core that shows moderate

contamination the rest of the cores show

contamination to a greater extent which provides

evidence that C4 is comparatively uncontaminated.

Anthropogenic Factor

In order to evaluate the data in detail the

anthropogenic factors (AF) of elements in the Cores

were calculated according to the formula,

AF = Cs/Cd

41 where

Cs and Cd refer to the concentrations of the

elements in the surface sediments and at depth in

sediment column.

According to Ruiz-Ferna´ndez42

, if AF is >1 for a

particular metal, it means contamination exists;

otherwise if AF is ≤ 1, there is no metal enrichment of

anthropogenic origin. AF for the Cores collected in

Ennore is tabulated in Table 7.

AF values suggest that all metals except for Cd in

the core samples of Ennore are anthropogenic. AF is

also seen to depend on the core sample location with

maximum AF observed for Mn followed by Cu at C3.

Enrichment Factor

The extent of sediment contamination can be

assessed using the enrichment factor (EF). EF is a

good tool to differentiate the metal source between

anthropogenic and naturally occurring43,44,45,46

.

According to this technique metal concentrations

were normalized to the textural characteristic of

sediments. It is standardization of a tested element

against a reference. A reference element is the one

characterized by low occurrence variability. The

common reference elements are Sc, Mn, Ti, Al and Fe

47, 48, 49, 50, 51, 52. In the present study Mn was used as

the reference metal.

EF = sample

reference

(Me/Mn)

(Me/Mn)

where Me/Mn is the ratio of the metal (Me) to Mn in

samples of interest and Me/Mn Reference is the natural

reference value of the metal to Mn ratio. EF values

were interpreted as suggested by Birch53

. The

enrichment categories are outlined in Table 8.

EF values vary within the Buckingham canal,

Ennore with minimal to significant enrichment

(Table 9). Cd is consistent throughout the study area

with minimal enrichment. Cr at C3 shows moderate

enrichment the rest being minimal enrichment.

Significant enrichment is observed at C1.

Assessment Of Sediment Contamination By

Comparision Of Concentartion With Those Of

Background Sediments

Hakanson54

had suggested a contamination factor

(Cif) and the degree of contamination (Cd) to describe

the contamination of given toxic substance given by

Cif = C

i 0-1/ C

i n and Cd = Σ7

i=1 Cif


93

Table 4 Correlation coefficient matrix of sedimentalogical parameters and heavy metals from Ennore, Southeast coast of India

(P <0.05)

C1

n = 15 pH Sand Silt Clay CaCO3 OM Cd Cr Cu Mn

pH 1.00

Sand 0.57 1.00

Silt -0.55 -0.98 1.00

Clay -0.35 -0.46 0.29 1.00

CaCO3 0.29 0.37 -0.32 -0.28 1.00

OM -0.76 -0.32 0.34 0.29 -0.23 1.00

Cd -0.27 -0.57 0.63 -0.07 -0.33 0.03 1.00

Cr -0.15 -0.04 0.05 -0.15 0.02 0.05 0.42 1.00

Cu 0.45 0.22 -0.22 -0.01 0.26 -0.30 -0.22 -0.01 1.00

Mn 0.15 0.25 -0.30 0.12 -0.29 0.08 -0.39 -0.27 -0.50 1.00

C2

n = 13 pH Sand Silt Clay CaCO3 OM Cr Cu Mn

pH 1.00

Sand 0.82 1.00

Silt -0.71 -0.94 1.00

Clay -0.83 -0.98 0.86 1.00

CaCO3 0.13 0.03 -0.04 -0.03 1.00

OM -0.57 -0.45 0.32 0.49 0.48 1.00

Cr 0.22 0.18 -0.03 -0.24 0.30 -0.13 1.00

Cu 0.12 0.47 -0.54 -0.42 -0.02 -0.08 -0.48 1.00

Mn 0.20 0.22 -0.19 -0.23 0.53 0.05 0.33 0.35 1.00

C3

n = 16 pH Sand Silt Clay CaCO3 OM Cd Cr Cu Mn

pH 1.00

Sand -0.48 1.00

Silt -0.09 -0.64 1.00

Clay 0.69 -0.50 -0.35 1.00

CaCO3 -0.12 -0.54 0.62 -0.04 1.00

OM -0.68 0.77 -0.44 -0.44 -0.48 1.00

Cd -0.41 0.59 -0.38 -0.30 -0.54 0.70 1.00

Cr -0.61 0.68 -0.40 -0.38 -0.31 0.87 0.45 1.00

Cu -0.69 0.48 -0.09 -0.48 -0.10 0.73 0.39 0.91 1.00

Mn 0.84 -0.44 -0.08 0.62 0.13 -0.68 -0.53 -0.54 -0.66 1.00

C4


pH 1.00

Sand -0.12 1.00

Silt -0.02 -0.93 1.00

Clay 0.35 -0.85 0.6 1.00

CaCO3 0.04 0.34 -0.4 -0.1 1.00

OM -0.26 0.33 -0.23 -0.39 0.15 1.00

Cr -0.3 0.03 0.05 -0.22 -0.69 0.19 1.00

Cu 0.35 -0.08 0.09 0.02 -0.39 -0.27 0.07 1.00

Mn -0.3 0.22 -0.16 -0.31 -0.34 0.29 0.88 -0.22 1.00

C5


pH 1.00

Sand 0.46 1.00

Silt -0.26 -0.73 1.00

Clay -0.42 -0.72 0.05 1.00

CaCO3 0.65 0.09 -0.16 0.02 1.00

OM -0.26 -0.38 0.43 0.12 -0.63 1.00

Cr -0.19 -0.54 0.08 0.71 0.07 0.08 1.00

Cu -0.52 0.23 -0.09 -0.24 -0.28 -0.28 -0.62 1.00

Mn 0.38 -0.09 -0.20 0.33 0.33 0.06 0.77 -0.88 1.00


94

Table 9 EF of Ennore

C1 C2

Depth (cm) EF (Cd) EF (Cr) EF (Cu) Depth (cm) EF (Cd) EF (Cr) EF (Cu)

0.0-2.5 0 1.05 7.39 0.0-2.5 0 1.01 1.05

2.5-5.0 0 1.35 7.42 2.5-5.0 0 0.92 1.57

5.0-7.5 0 1.32 10.62 5.0-7.5 0 1.42 1.28

7.5-10.0 0 1.13 8.11 7.5-10.0 0 1.21 0.98

10.0-12.5 0 1.12 11.64 10.0-12.5 0 0.79 4.18

12.5-15.0 0 0.84 3.09 12.5-15.0 0 0.76 0.68

15.0-17.5 0 1.08 6.48 15.0-17.5 0 0.96 2.46

17.5-20.0 0 0.73 2.27 17.5-20.0 0 1.22 3.99

20.0-22.5 0 0.76 7.45 20.0-22.5 0 0.88 3.83

22.5-25.0 0 0.77 6.49 22.5-25.0 0 0.86 2.69

25.0-27.5 0 1.00 9.39 25.0-27.5 0 0.93 1.99

30.0-32.5 0 0.93 12.14 30.0-32.5 0 0.96 1.33

32.5-35.0 0 0.74 0.22 32.5-35.0 0 0.72 0.07

35.0-37.5 0 0.84 0.62

37.5-40.0 0 1.76 1.15

C3 C4

Depth (cm) EF (Cd) EF (Cr) EF (Cu) Depth (cm) EF (Cd) EF (Cr) EF (Cu)

0.0-2.5 0 2.11 2.20 0.0-2.5 0 1 1

2.5-5.0 0 2.99 2.47 2.5-5.0 0 1 1

5.0-7.5 0 2.68 3.01 5.0-7.5 0 1 1

7.5-10.0 0 1.62 1.29 7.5-10.0 0 1 1

10.0-12.5 0 1.23 1.23 10.0-12.5 0 1 1

12.5-15.0 0 0.78 0.22 12.5-15.0 0 1 1

15.0-17.5 0 1.01 0.59 15.0-17.5 0 1 1

17.5-20.0 0 1.00 0.90 17.5-20.0 0 1 1

20.0-22.5 0 0.97 0.88 20.0-22.5 0 1 1

22.5-25.0 0 0.82 0.63 22.5-25.0 0 1 1

25.0-27.5 0 0.79 0.55 25.0-27.5 0 1 1

30.0-32.5 0 0.91 0.49 30.0-32.5 0 1 1

32.5-35.0 0 0.77 0.03 32.5-35.0 0 1 1

35.0-37.5 0 1.33 0.29 35.0-37.5 0 1 1

37.5-40.0 0 1.47 0.63 37.5-40.0 0 1 1

40.0-42.5 0 1.61 0.55 40.0-42.5 0 1 1

42.5-45.0 0 1 1

Table 5 Geoaccumalation index classes to assess sediment

quality

Igeo Class Igeo Value Quality of Sediment

0 < 0 Uncontaminated

1 0 - 1 Uncontaminated to moderately

contaminated

2 1 - 2 Moderately contaminated

3 2 - 3 Moderately to highly contaminated

4 3 - 4 Highly contaminated

5 4 - 5 Highly to very highly contaminated

6 > 5 Very highly contaminated

Table 6 Igeo classification for Ennore

C1 C2 C3 C4 C5

Cd Igeo Class 0 0 0 0 0

Cr Igeo Class 1 2 6 2 3

Cu Igeo Class 6 3 6 2 2

Mn Igeo Class 1 3 3 2 4

Table 7 Anthropogenic Factor (AF) in Core Samples of Ennore

C1 C2 C3 C4 C5

Cd 0.14 0 0 0 0

Cr 0.51 1.26 1.03 1.03 0.83

Cu 1.55 1.1 0.92 0.3 1.04

Mn 1.15 1.17 1.05 1.39 1.06

Table 8 Enrichment categories

EF class Extent of Enrichment

< 2 Deficiency to minimal enrichment

2 -5 Moderate enrichment

5 – 20 Significant enrichment

20 - 40 Very high enrichment

> 40 Extremely high enrichment


95

where, Ci0-1 is the mean content of the substance;

Ci

n is the reference value for the substance.

Table 10 gives details about the terminology used

to describe contamination factor. Contamination

factor and degree values for core sediments of Ennore

are shown in Table 11. Mn and Cr in C3 and C5 fall

under the category of moderate degree of

contamination, whereas the other two metals in core

samples of Ennore show low degree of contamination.

Cd calculation places Ennore under low degree of

contamination.

Assessment Of Pollution By Calculating Pollution

Load Index (Pli) Tomlinson

55 had employed a simple method based

on pollution load index (PLI) to assess the extent of

pollution by metals in estuarine sediments56

. Sediment

pollution load index (PLI) was calculated using the

equation

CF = Cmetal/Cbackground

(PLI = n√CF1 × CF2 × CF3 × ........ CFn)

where, CF is the contamination factor,

Cmetal is the concentration of pollutant in sediment

Cbackground is the background value for the metal

n the number of metals.

The PLI value of > 1 is polluted whereas < 1

indicates no pollution. PLI values calculated is

summarized in Table 12.

With respect to PLI Ennore is polluted as far as Cr,

Mn are concerned whereas there is no pollution for

Cd and Cu.

Conclusions

Sand domination is observed in all Cores except

C3 where silt domination is observed. C3 shows

highest d50 value (408.3µm). The pH of the core

samples lie in a close range of 5-8 without much

variations with depth. Organic matter enrichment is

found in cores collected within the canal. C3 shows

least concentration of organic matter. Down-core

variations of heavy metals studied here shows that

Ennore and its surrounding environment have been

subjected to pollution over-time. The highest

occurring metal is Mn. Cd is absent throughout or

occurs at a minimal concentration of 0.02-

0.0014ppm. Cores C4 and C5 show less pollution.

The heavy metals of Ennore according to Igeo (Cd,

Cr, Cu and Mn) show moderate contamination

except at the industrial discharge, southern side of

the Ennore creek which shows very high

contamination owing to discharges from various

industries situated in Ennore. The reference site

Pulicat shows low degree of contamination whereas

core samples from within the canal and the Ennore

Sea sample shows moderate degree of

contamination which gives a valid evidence for

choosing Pulicat as reference site in the present

study. On the whole it can be said that Mn and Cr

are present at higher concentration that Cu and Cd

in Buckingham canal, Ennore.

Table 9 EF of Ennore

C5

Depth (cm) EF (Cd) EF (Cr) EF (Cu)

0.0-2.5 0 0.76 0.54

2.5-5.0 0 0.96 0.55

5.0-7.5 0 0.87 0.61

7.5-10.0 0 0.75 0.40

10.0-12.5 0 0.74 0.77

12.5-15.0 0 0.63 0.79

15.0-17.5 0 1.00 0.70

17.5-20.0 0 1.08 1.16

20.0-22.5 0 0.96 1.02

Table 10 Terminologies used to describe the contamination

factor

Cif Cd DESCRIPTION

Cif < 1 Cd < 7 Low degree of contamination

1< Cif < 3 7< Cd < 14 Moderate degree of

contamination

3 < Cif < 6 7< Cd < 28 Considerable degree of

contamination

Cif > 6 Cd > 28 Very degree of contamination

Table 11 Contamination Factor and Contamination Degree

Cif

Core 1

Cif

Core 2

Cif

Core 3

Cif

Core 4

Cif

Core 5

Cd 0.00 0.00 0.00 0.00 0.00

Cr 0.59 1.43 2.49 1.00 1.77

Cu 1.48 1.05 0.92 1.00 0.59

Mn 0.60 1.56 1.96 1.00 2.26

CONATMINATION DEGREE - Cd

Core 1 Core 2 Core 3 Core 4 Core 5

2.67 4.04 5.37 3.00 4.61

Table 12 Pollution Load Index

Metal PLI

Cd 0

Cr 1.39

Cu 0.96

Mn 1.42


96

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vertical profile of heavy metal concentration in core...

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