349

KEYWORDS

ISSN: 0974 - 0376

NSave Nature to Survive

: Special issue, Vol. III:

www.theecoscan.inAN INTERNATIONAL QUARTERLY JOURNAL OF ENVIRONMENTAL SCIENCES

Prof. P. C. Mishra Felicitation Volume

Paper presented in

National Seminar on Ecology, Environment &Development

25 - 27 January, 2013

organised by

Deptt. of Environmental Sciences,

Sambalpur University, Sambalpur

Guest Editors: S. K. Sahu, S. K. Pattanayak and M. R. Mahananda

Ajit K. Misra et al.

Residual mercury

Mercury pollution

Chlor-alkali industry

Physico-chemical parameters

Estuary

River and plants

349 - 366; 2013

MERCURY POLLUTION IN AND AROUND A CHLOR-ALKALI

INDUSTRY: A REVIEW

350

AJIT K. MISRA1*, ALAKA SAHU2, SURYASMITA KANWAR, DEORAJ SARMA3 AND A. K. PANIGRAHI

Environmental Science Division, Department of Botany, Berhampur University,

Berhampur-760 007, Odisha. INDIA1T. T. College, Puroshattampur, Ganjam, Odisha

2R. N. College, Dura, Berhampur. Odisha3TSR and TBK College, Gajuwaka, Visakhapatnam, Andhra Pradesh

E-mail: drakpanigrahi@gmail.com

INTRODUCTION

Indian industrial sector is ranked as the tenth biggest in the world in gross industrial

output. Pollution problems arising from the industries, at least in India, are partly

because of their location about 80% of her industries are concentrated in 10 or

12 big cities forming isolate pockets. Dispersal location of industries may have

helped to reduce the amount of a pollutant at a specific location. But realistically

“dilution is not the solution” as far as pollution problems are concerned (Panigrahi

and Sahu, 2012). The rapid growth of industries has resulted in the production

and use of substances some of which create health hazards. A significant amount

of these compounds (wastes) are released into the environment, affecting the

flora and fauna. Waste is defined as any gaseous, solid or liquid material that is

discarded because it has no further apparent use for the industrial manufacturer.

These wastes are pollutants cannot be eliminated but must be disposed of and

contained within the global environment. Industrial waste is in the form of gases,

solids, liquid effluents and slurries containing a range of organic and inorganic

chemicals. Industrial processes are continually changing, as new and modified

technologies are developed. Consequently products, plant and premises may

become obsolete and worn out, so causing waste disposal and dereliction

problems. In general term, solid waste can be defined as waste not transported by

water that has been rejected for further use. The chief aspect of land pollution is

basically caused by solid and semi-solid waste disposal methods, the presence of

hazardous chemicals in the environment and the despoilation and degradation

of the land surface. Hazardous wastes are those, which could be harmful to the

human health, other organisms and the environment. Many inorganic elements

as Mercury (Hg), Lead (Pb), Cadmium (Cd), and Arsenic (As) are biological poisons

at concentrations in the parts per billion (ppb) range. Once the chemicals find

their way into the environment, a major portion reaches the soil and sediment,

which in turn serve as sink. Leaching of waste chemicals discharged from the

chlor-alkali industry pose ground water contamination problems (Panigrahi and

Sahu, 2012). Plants absorb these toxic leached chemicals along with water and

other nutrients and accumulate in different tissues. These plants store chemicals

in their body and these chemicals pass through the food chain from one trophic

level to the other higher trophic level. These toxic chemicals are poorly excreted,

hence retained as residual chemicals in the body. A significant build up of the

toxic chemicals in different organs / tissues of the organisms are achieved through

the process of bioconcentration and biological magnification (Panigrahi and Sahu,

2012). Metals differ from other toxic substances in that they are neither created

nor destroyed by humans. Nevertheless, utilization by humans influences the

potential for health effects in at least two major ways. First, by environmental

transport that is by anthropogenic contributions to air, water, soil and food and

NSave Nature to Survive QUARTERLY

The study indicated that Ganjam Rushikulya

estuary and the surrounding area of Jayashree

Chemicals Pvt. Limited, a caustic soda plant

released huge amount of mercury into the

environment. Evaporated mercury from the

Mercury cell house contaminated the

surrounding biota leading to elevated mercury

levels beyond prescribed limit is the major

concern at present. The discharged mercury

in the effluent of the industry contaminated

the Rushikulya River and estuary lead to

elevated mercury level in aquatic plants and

animals. The sediment from the treatment tank

and effluent channel contained a significant

amount of mercury which was dumped in

nearby places raised the residual mercury

concentration in all types of plants (producers)

and in animals (consumers). The mercury

pollution in and around the industry a

significant problem up to 2006 was grim and

grave. But due to change in technology in the

industry, the mercury concentration declined

significantly in the effluent channel. The

decline in mercury level in water, sediment

and effluent channel, solid waste dumping site,

available plants and animals at present when

compared to earlier reports is a positive sign

for the area. But our concern rests on the

future, as all mercury discharged from the

industry ultimately entered in to Bay of Bengal

by rain run off water, by leaching from the

solid waste dumping sites, by leaching from

the effluent stocking pond near the river basin.

ABSTRACT

*Corresponding author

351

MERCURY POLLUTION AROUND CHLOR - ALKALI INDUSTRY

second, by altering the speciation or biochemical form of the

element. Human industrial activity may greatly shorten the

residence time of metals in ore, form new compounds and

greatly enhance worldwide distribution. It is estimated that

mercury or its compounds are used in at least 80 industries

and in more than 3000 different ways.

Chlor-alkali industry (one of the large source of mercury

discharge):

One of the major users of metallic mercury is the chlor-alkali

industry, in which chlorine and caustic soda (NaOH) are

simultaneously produced by the electrolysis of brine solutions

using a flowing cathode of metallic mercury. The sodium ion

(Na+) which amalgamates with mercury at the cathode is

converted to NaOH in presence of water and the released

mercury is recycled into the cell. The schematic reaction for

the Chlor-alkali process is (Bouveng, 1968) as follows:

NaCl (soln.) → Electrolysis → Cl2(anode)↑+NaHg

x (Cathode)

NaHgx →

H

2O → NaOH + Hg + ½ H

2↑

If chlorine and hydrogen are given off together, an explosive

mixture can result. So, to prevent this, mercury-sodium

amalgam is pumped into a second reaction vessel, where,

water is introduced and hydrogen and sodium hydroxide are

formed. Due to the demand of pure caustic soda (i.e. having

fewer chlorine ions) the chlor-alkali industries switched from

the use of diaphragm cell to mercury cell process. Because of

mercury’s unusual property to form an amalgam with the

reduced sodium metal derived from salt brine, the mercury

cell process results in a very pure grade of caustic soda (NaOH).

Mercury is lost in different routes, (I) solid wastes or sludges -

brine purification sludge; (ii) water; (iii) product hydrogen,

caustic; (iv) handling loss, (v) unknown losses including loss

of Hg of vapour in cell room and (vi) washing of mercury

cathode as washings. Brine mud generation is around 30kg/

tonne caustic soda in India which is more than double the

international average, indicating higher impurities in the salt.

Further, the mercury content in brine mud ranges from 2.5 to

30 mg. g-1. The quantity of Hg lost in water is fairly low but

much higher than acceptable limits for direct disposal. Thus,

among the different routes by which Hg is lost nearly 65% of

the total loss ends up in brine mud or sludge. Losses occur

due to the volatility of mercury, its presence in suspension

and solution in brine, in caustic soda, spillage during operation

and maintenance of the cells and with solid wastes from brine

purification and NaOH filtration. The caustic soda produced

by this method will contain varying amounts of mercury at

the trace level, depending on the degree of purification. There

is also a risk of secondary contamination in the environment

through the fallout of mercury around the industry as a result

of losses to the atmosphere, through the ventilation of air and

the hydrogen gas produced. The products of the industry

such as sodium hydroxide also give rise to secondary

contamination depending on their further uses.

The most significant source of mercury availability in the

environment is mostly due to the chlor-alkali industries

(Bouveng, 1968; Hortung and Dinman, 1974; Skei, 1978;

and Sahu et al., 1987; Panigrahi and Sahu, 2012). In 1969,

15-19 metric tonnes of mercury were discharged into the air

from Swedish chlor-alkali factory. Loss of mercury from the

mercury cell processes has been estimated in the order of

0.172kg for each ton. of chlorine so produced. A typical

modern 30 m2 mercury cell of a chlor-alkali industry can

contain up to 12,000 lb of Hg which is circulated in a closed

system and reused indefinitely. However, due to circumstances

of its operation, there is a loss of 150-250g of Hg per 1000kg

chlorine produced (Mitra, 1986). Mercury emissions from

chlor-alkali plants were assumed to consist mostly of Hg vapour

as elemental (metallic) mercury (Hgº) and bivalent Hg (Hg II as

HgCl2). About 65% of total chlorine production in the U. S. A.

makes use of the mercury cells process instead of diaphragm

process. Mercury cells account for over 80% of chlorine /

caustic soda production in Japan and the European countries.

In India at the beginning of 1984 the total installed capacity for

caustic soda was 9, 09, 900 tonnes per annum of which 88%

came from mercury cells and the rest from diaphragm cells. In

1983, the total quantity of caustic soda made from mercury

cells was 5, 14, 700 tonnes (64.2% of capacity). It is estimated

that the rate of mercury consumption is 394 gm per tonne of

caustic against the targeted value of 350 g Hg per tonne it is

90g Hg per tonne in industrialized countries. Pollution of

surrounding biota through the discharges of effluents and solids

wastes from chlor-alkali industries have been amply

demonstrated (Shaw et al., 1986a, b; 1989a, b; 1990). Wallin

(1976) reported that samples of the carpet forming moss

Hypnum cupressiforme from sites around six Swedish chlor-

alkali plants all contained higher mercury levels. It was highest

close to the industry and decreased with the increasing distance

from each industry. Reports of mercury dispersion and

contamination in Yatsushiro Sea (Kudo and Miyahara, 1983)

and Lake Superior region (Glass et al., 1986) are available.

Suckcharoen (1978 and 1980) reported residual mercury in

the vegetation around a caustic soda plant in Thailand. Shaw

et al. (1985, 1986a, 1988a, b and 1989a, b) reported the

residual mercury accumulation in different biotic systems

available in and around a chlor-alkali industry. Shaw et al.

(1988a, b) reported the changes in aquatic primary productivity

of the estuary contaminated with the effluent of the chlor-alkali

industry. The monitoring and assessment of mercury pollution

in the vicinity of a chlor-alkali plant has been done by Panda

et al. (1989).

Research work done on Chlor-alkali wastes

There is no doubt that chlor-alkali industries are seriously

polluting the surrounding environments. But comparatively

very few reports are available on the toxicity and toxicological

effects of chlor-alkali industrial wastes on different biotic

systems. Mishra and Misra (1984) studied the changes in

morphological behaviour of rice seedlings grown in solid waste

extract of a chlor-alkali industry. Using the same solid waste,

Mishra et al. (1985 a, b) investigated the chances of reclamation

with Blue-green algae in paddy field but no significant results

were obtained regarding decontamination of polluted

environments. Nanda et al. (1986) demonstrated the toxic

effects of the solid waste extract of a chlor-alkali industry on

the changes in pigment concentration of a crop plant,

Phaseolus aureus, Roxb. Mishra (1986) investigated the

changes in growth and morphological variables of a crop plant

exposed to saturated waste extract. Sahu et al. (1987, 1988,

1990), Shaw et al. (1988, 1989 a, b) and Sahu and Panigrahi

352

(2000) studied the toxicity of the effluent and solid waste of a

chlor-alkali industry containing mercury on different blue-

green algae and reported the toxicity of mercury at higher

concentrations and also indicated that at sub-lethal

concentrations of mercury, stimulation in growth of BGA was

noticed. Panda et al. (1989) studied the bioconcentration,

bioavailability and geno-toxicity of mercury from the solid

waste of a chlor-alkali industry. Berndt and Bavin (2012) studied

the methyl mercury and dissolved organic carbon relationships

impacted by elevated sulfate from mining. Wiener et al. (2012)

studied the risks of mercury in yellow perch a species important

in trophic transfer of methyl mercury in the Laurentian Great

Lakes region.

Industry under study (M/S Jayashree Chemicals Pvt. Ltd.,

Ganjam):

The chlor-alkali industry M/S Jayashree Chemicals Pvt. Ltd., is

situated at Ganjam, on the Bank of Rushikulya estuary about

1.5 km. Away from the sea, Bay of Bengal, on the East and 30

km. North of Berhampur city (Fig. 1 and 2) on the south-eastern

side of India at 84º53’E L and 19º16’N L. The industry was

established in 1962 and started manufacturing caustic soda,

liquid chlorine and hydrochloric acid by using a sheet of

elemental mercury as a mobile cathode for the electrolysis of

brine water (saturated sodium chloride solution) since August

1967.

In the process of manufacture of chemicals the factory

discharges the effluent containing mercury and chlorine, into

the estuary and deposits solid waste (brine mud, enriched

with mercury) on the adjacent land areas. Mercury is thus,

discharged into the environment through effluent and solid

waste routes, contaminating the adjacent aquatic and terrestrial

ecosystems, respectively. This addition of mercury is the

primary contamination. The secondary contamination occurs

through the chimney into the atmosphere and its fall out by

the process of precipitation. All these discharges collectively

seem to cause a major environmental threat to crop production

and also to fisherman engaged in fishing both in the river and

also in the estuary. So this industrial pollution affecting the

human health, agriculture and economy of the locality became

he cause of public resentment which led to the filing of a

petition on July 25, 1977 at the Rajya Sabha (the upper house

of the Parliament) by the residents of Ganjam town and

neighboring villages with an appeal for protection of human

life and environment from the industrial pollution.

Consequently, a Parliamentary Committee was formed which

after an investigation released a 20 point remedial

recommendation and felt the need of a more in-depth scientific

study of the pollution problem.

Mercury - an environmental pollutant

Mercury pollution of the environment has created some serious

hazards for mankind. As mercury has been used since ancient

times, mercury poisoning also has a long history. The most

significant incidents of the toxicity of this metal from the

scientific and epidemiological points of view have been those

in Japan in Minamata (1953-60) and Niigata (1965); these

were caused by industrial release of mercury and its

compounds into Minamata Bay and the Agano River

respectively (Fujuki, 1973; Tsubaki and Irukayama, 1977).

Again during 1971-72, the largest outbreak of methyl mercury

poisoning ever recorded occurred in Iraq as a result of

consumption of home bread prepared from wheat seed treated

with methyl mercury fungicide. Alkyl-mercury fungicide used

for seed dressings are important original sources of mercury

in terrestrial food chains (WHO, 1976). Even today the dreadful

repercussion of 1956 Minamata disease is still prevalent

among the population.

Movement of mercury in the environment

Because of its high volatility, mercury becomes dispersed over

a very large fraction of the atmosphere. It is dispersed as vapour

or as particles associated with dust, smoke, volcanic gases,

and the natural degassing of soils. Any mercury deposited

back into the soil may be revolatilised in aerobic terrestrial

environments. The high volatility of the metallic phase and of

Figures 1 and 2: Photograph showing the position of Jayashree Chemicals Pvt. limited at Ganjam, Odisha, Rushikulya estuary, Bay of Bengal

in India and a portion magnified showing the study sites at Ganjam)

AJIT K. MISRA et al.,

353

inorganic (mainly mercuric chloride) and organic compounds(mainly monomethyl or dimethyl mercury) leads to wideranging transport of mercury in air. Annually more than 8000tones of mercury are mined and processed for use in industry.Mercury is released into the atmosphere when fossil fuels areburnt and ores are roasted. Besides chemical and otherindustrial activities, agricultural and mining contribute majoramounts of mercury to the ecosystem, including land (soil),water and air, via bacterial action, a portion of this would beconverted to methyl mercury and some would be concentratedin fish. Fish eaters then accumulate mercury in their bodies.The amount of mercury in air varies with height but is often 10to 20 times greater at ground level than at 120m.The mercuryreleased can either stay close to the source for long periods orbe dispersed world wide within several weeks.

The sea water, air and also the hair of the people, of thenorthern hemisphere are found to contain greater amounts ofmercury than those in the southern hemisphere. This isbecause of the greater industrialization in the north via globalcycling mercury finally accumulates in the sea. The sea servesas the ultimate sink for mercury. However, small amounts of

mercury may be released from sea and aquatic systems by

bio-methylation and volatilization into the air and finally

become fixed in aquatic sediments. It was indicated that the

presence of a water table above mercury deposits does not

greatly reduce the rate of mercury loss by vaporization. This

suggested that land surface is the principal source of mercury

in the atmosphere. Little information is available as to the

extent of the reactions of gaseous mercury with earth materials.

Noble metals such as platinum, gold and silver readily form

amalgams with mercury. Organic matter and clays absorb

gaseous mercury and therefore the atmospheric mercury level

is continually being decreased by reaction with air borne

particulate matter and land surfaces. Some of the mercury

bound up in wet soil can be revolatilised as the soil dries,

while some may be trapped by humus material. A considerable

amount of Hg released into the atmosphere from soil and

mineralized land areas and by volcanic activity. The rate of

vaporization of mercury and its compounds follows the

patterns:

Hg > Hg2Cl

2 > HgCl

2 > HgS > Hgº

Role of biota in movement of mercury

Microbes play an important role in the movement of mercury

in nature, especially in the soil, sediments and aqueous

environments. The main result of microbial action on mercury

seems to be its volatilization, whether it involves reduction of

the mercuric ion or methyl or phenyl mercury compounds to

volatile Hgº, or whether it involves conversion of the mercuric

ion to dimethyl mercury or of the phenyl mercuric ion to

diphenyl mercury. The mercuric ion (Hg2+) may be methylated

by bacteria and fungi to give methyl mercury [(CH3) Hg+],

which is water soluble. Some bacteria may further methylate

methyl mercury and convert it to dimethyl mercury, which is

volatile and escapes into the air.

Upon weathering, mercuric sulphide (cinnabar, HgS) is

converted to mercuric sulphate and becomes disseminated in

soil and water. Bacteria, fungi, and humic acid reduce Hg2+

and cause a wider range of distribution. Methyl mercury, as

well as phenylmercury, may again be enzymatically reduced

to volatile Hgo by bacteria. This causes detoxification of soil.

Phenyl-mercury, which is usually anthropogenic in origin,

may be reduced by soil bacteria and converted to diphenyl

mercury. Biogenic H2S may convert the mercuric ion to HgS,

again under anaerobic conditions. The mercury bio-cycle is

as in the Fig. 5.

Following the application of mercury fungicides, the metal is

transferred to fruits, tubers or seeds in plants. Foliar

applications of phenyl mercuric acetate to rice resulted in the

3a 3b

Figure 3: 3a. Map of Ganjam area showing the chlor-alkali industry,

Jayashree Chemicals; 3b. Effluent stocking pond near the Rushikulya

Rive

Figure 4: Photo showing the industry (pin point), effluent channel

(triangle), three study sites in the river and one study site at the

estuary

Ph2Hg PhHg+ Hgº

Hg2+HgS

biogenic H2S

weathering

fungi

Bacteria MeHg+ MeHgBacteria H2S

chemical reaction

UV-lightBacteria

Bacteria

Figure 5: Mercury Transformation by microbes and chemical or

physical agents

MERCURY POLLUTION AROUND CHLOR - ALKALI INDUSTRY

354

transfer of mercury to the grain. Terrestrial animals accumulate

mercury mainly from their food. Birds accumulate mercury

mainly by eating seeds and grain treated with mercurial

fungicides etc. Mercury is transformed into methyl mercury,

mainly by micro-organisms, and eventually becomes

concentrated in large fish. A very limited conversion of mercury

components to methyl mercury occurs in hens. A methyl

mercury-fed hen laid eggs containing only methyl mercury.

Mercury tends to accumulate in the growing feathers, claws

and beaks of birds and all of the bodily content of mercury is

eventually deposited in feathers and other keratinous

structures.

Study Site and Sample collection at M/S. Jayashree Chemicals

Pvt. Limited at Ganjam, Odisha

Eco- toxicological effects of mercury

Toxicity is the inherent property of a chemical molecule to

produce injury on reaching a susceptible site on or in an

organism. The toxicity of a pollutant to living organisms (plants

and animals) can be evaluated by exposing a small group of

them under controlled laboratory conditions. Dose is the single

most important factor that determines the degree of injury

produced by a toxicant. Some of the possible mechanisms

through which toxic agents can impair important biochemical

processes and physiological functions in living organisms are

cell membranes, enzymes, lipid metabolism, protein

biosynthesis, microsomal enzyme systems, regulatory

processes and growth, carbohydrate metabolism and

respiration etc. (Bruin, 1976).

Eco-toxicity is the effect of toxic substances on ecosystems

which can be through a number of different ways. But in

simplest form two basic types of effect are possible. (1) Acute

lethal toxicity, over a short time period due to discharge of a

toxic substance, or treatment of an area with a toxic material

on a single occasion. (2) Chronic sub-lethal effects can occur

in an area due to exposure to sub-lethal concentrations over a

longer time period on a continuous or intermittent basis.

Assessment of the ecological impacts of toxicants are derived

from spot observations of the fields receiving different wastes,

sewage, industrial discharges or sludges containing sufficient

toxicant content to which toxicity can be assigned. Grain seeds

dressed with mercury based agrochemicals accumulate

mercury via translocation. Hens fed with crop seeds, pretreated

with mercurial compounds could concentrate the metal in

their livers and eggs. Mercury is concentrated up through the

food chain due to biological magnification amounts only slightly

above those ordinarily found in sediments, could be potentially

dangerous. The inorganic form of mercury is toxic, but it is

much more toxic in its organic form (Olson and Panigrahi,

1991). Rai et al. (1981) showed reduction in the chlorophyllcontent of Chlorella vulgaris exposed to HgCl

2. Hg increased

the length of the lag phase, during the growth of the green alga

Scenedesmus quadricauda and blue-green algae (Sahu, 1987;

Shaw, 1987). Organomercurials retard the growth and viability

of several species of marine algae more effectively than

inorganic mercury. The chronic toxicity of HgCl2, MMC

(Methylmercuric chloride) and PMA have been studied on

Daphnia magna. Panda et al. (1989) have assessed the

distribution, bio-availability, bio-concentration and

genotoxicity of mercury from some waste and sediment

deposits of a chlor-alkali plant by Allium Micronucleus (MNC)

assay. The growth, biochemical composition, Hill activity and

pigment content in different algal forms is quite prominent on

the presence of mercury (Rath et al., 1983, 1985; Mishra et

al., 1985; Shaw et al., 1989, a).Toxicity of various salts of

mercury is related to cationic mercury per se whereas solubility,

biotransformation and tissue distribution are influenced by

valency state and anionic component. Metallic or elemental

mercury volatilizes to mercury vapour at ambient air

temperature and most human exposure is by inhalation.

Bioassays for toxicity testing

A bioassay is conducted to find out the toxicity of a substance.

The laboratory bioassay technique is generally favoured

because experimental conditions can be controlled and the

response of test organisms observed or monitored to a greater

degree. Response of test organisms can be of 3 types.

(1) an acute effect; (2) a sub-acute effect and (3) a chronic

effect.

In practice, most bioassay results are expressed in terms of

acute lethal toxicity which measures certain sub-lethal

responses in test organisms over a specified period of time.

For sub-lethal measurements the results may be expressed as

the “Median effect concentration” in which 50% of the test

organisms display the response being measured. Toxicity tests

such as acute lethality tests, chronic toxicity tests for

reproduction effects and tests on bioconcentration /

bioaccumulation are useful for assessing chemical hazards to

aquatic life. So, bioassays using aquatic organisms have a

long history of use in estimating the toxicity of industrial wastes

In many bioassays, microorganisms are used because of their

rapid growth rates, easy to handle, faster production of results

and ubiquitous distribution in aquatic and terrestrial

environments. Of all aquatic life, algae offer the best possible

tool as biological indicator because (1) One can study a largenumber of individuals and species without disturbing thenatural communities; (2) Individuals are small and can easilybe collected and transported; (3) Microbial species usuallyrepresents the major productive biomass in aquatic systemsand are having extremely important characteristics. The releaseof hazardous wastes into the aquatic ecosystems produces avariety of complex responses, apart from lethality, to specificorganisms (Christman et al., 1973). Hidden injury such asinhibition of photosynthesis or alteration in oxygenconsumption most significantly affect the role that a primaryproducer plays in the phytoplankton - zooplankton - copepod- minnow - sunfish - bass, pyramid (Ammann and Terry, 1985).When the sub-lethal concentration condition exists, suddenelimination of organisms may not occur, but as growth and

reproduction of a species are affected over a period of time

the final result could well be the same. Growth and

photosynthesis are intimately related, each being a function

of the utilization of light and nutrients. Recent studies have

shown that blue-green algae alter their pigment concentrations

as a function of changes in light (Jones and Myers, 1965),

temperature and CO2 concentration (Eley, 1971). So pigment

concentration should not be considered as a reliable indicator

of cell numbers for these organisms.

Inhibition of photosynthesis and respiration in plant cells by

AJIT K. MISRA et al.,

355

solution of mercury and zinc salts has been reported (Overnell,

1975; Filippis and Pallaghy, 1976 and Rath et al., 1985).

Photosynthetic rate is a valuable indicator of energy expanded

to meet the demands of an environmental alteration.

Assessment of the photosynthetic rate of exposed algae offers

the best and most rapid method of evaluating the impact of

any toxicant or industrial wastes introduced in an aquatic

system, affecting primary producers. The effects of industrial

wastes on photosynthesis rate of algae have hardly been

reviewed. Shaw et al. (1988, 1990, 1991a, b) reported the

effect of chlor-alkali industry effluent on the oxygen evolution

rate of the blue-green algae, W. prolifica, Janet. But the present

work was designed to investigate the effect of the effluent of

the industry on the photosynthetic rate of the BGA. The

assimilation of xenobiotic chemicals within organisms at sub-

lethal or lethal levels may induce a sequence of biological

effects, ranging from molecular interference with biochemical

mechanisms to interactions with cellular organelles (e.g. DNA

and RNA molecules), through pathological changes at the

cellular, tissue and organ levels. Finally, these result in an

integrated functional or behavioral response, experienced at

the whole organism level, which may be reversible or

irreversible. So the change in biochemical profile may be

considered as an index of pollution status in the pollution

assessment. It is already an established fact that disturbances

in growth and growth substances are always related with

metabolic changes inside the plant (Levitt, 1972; Poljakoff-

Mayber and Gale, 1975). Several biochemical changes

precede any change in growth because growth is the

culmination of many biochemical processes; andphysiological and biochemical effects are the underlying causeof measurable whole organism effects. Effect of the toxicantson growth may be studied by examining the macromoleculesinvolved in growth, such as dna, rna, protein, free amino acids

(a precursor of protein) as well as glycogen which is a reserve

food in case of bga, like animals. Heavy metals specifically

mercurials have long been recognized as agents which poison

and interact with proteins in general and enzymes in particular

(Fox et al., 1975). In living cells, there are so many proteins,

polypeptides and substances belonging to other classes of

biochemical which do contain-SH groups that mercury and

mercurials would seem to affect more structures, enzymes

and co-factors than they leave unaffected. Therefore, when a

mercurial compound acts on a living cell, it is usually an

exceedingly difficult task to establish the quantitative

relationship between the primary site of action and an observed

toxic effect. Methyl-mercury is known to cause chromosomal

damage and induces hepatic protein synthesis in rats. Reactions

of proteins with mercurials were reviewed by Webb (1966).

De et al. (1985) reported that the highest dose of mercury in

the form of HgCl2 (20.0 mg/L) in Pistia stratiotes promoted

plant senescence by decreasing chlorophyll content, protein,

rna, dry wt., catalase and protease activities and by increasing

free amino acid content. Heavy metals and other chemical

agents affect the DNA, RNA and protein content of cell and

cause DNA damage, in vivo. Singh and Singh (1984) reported

decrease in the levels of DNA, RNA and protein in a blue-

green alga exposed to sodium metabisulphite. Filippis and

Pallaghy (1976) reported increase in the levels of DNA, RNA

and protein in Chlorella treated with HgCl2. DNA and RNA

synthesis in intact cells were inhibited by MeHg. But during

the study of nucleic acid synthesis in vitro in isolated nuclei, it

was found that MeHg specifically stimulated RNA synthesis

by RNA polymerase II but inhibited RNA synthesis catalyzed

by polymerase I and III, as well as DNA synthesis.

The alteration in the enzyme activity can serve as a sensitive

index of pollution, as the xenobiotic agents affect several

systems. The abnormal enzymatic disorders always result in

abnormal biochemical change. In general toxic chemicals,

attack the active sites of enzymes, inhibiting essential enzyme

function. Heavy metal ions, in particular, Hg2+, Pb2+ and Cd2+

act as effective enzyme inhibitors. They have affinity for

sulphur containing ligands (-SH). The mercurials occupy a

special niche in the subject of enzyme inhibition. They are

useful for demonstrating the presence of SH groups in enzyme

reactions, but lack specificity towards particular enzymes or

classes of enzymes. Since so many enzymes contain reactive

-SH groups at or near the active center, the mercurials would

seem to inhibit more enzymes than they leave unaffected.

When mercurial acts on living cells, one cannot state which

enzymes are affected most readily (Webb, 1966). Within cells,

mercury may bind to a variety of enzyme systems, including

those of microsomes and mitochondria producing non-

specific cell injury or cell death. Complexes between Hg2+

and certain purines and pyrimidines, especially thymine, are

quite stable. It is widely believed that active transport processes

in biological membranes are driven by the energy, stores in

ATP and released by the activity of ATPase. It has been

reported that a significant depression of Na+, K+ -ATPase is

associated with excessive absorption of mercury (Panigrahi

and Misra, 1978a, b; 1980; Sahu et al., 1987, 88, 90). Mercuric

ions and their organic derivatives serve as probes in

investigations of membrane transport, when they are used to

block carrier sites. ATP can be used as a measure of living

phytoplankton carbon in the aquatic system. De et al. (1985)

reported that the highest dose of Hg (20.0 mg/L) in the form of

HgCl2 promoted plant senescence by decreasing chlorophyll

content, protein, RNA, dry wt., catalase and protease activities.

Microbial ecosystems can drastically alter the fate of metals in

the lithosphere or hydrosphere. Bacteria and fungi can alter

the valency state of the metal via methylation, chelation,

complexation, absorption, oxidation and reduction. Thus,

microorganisms affect the bioavailability and dispersion of

metals in both aquatic and soil ecosystems; ultimately

influencing the movement of the metals into and up the food

chain. The existence and significance of atmospheric transport

and dispersion of Hg as well as its deposition to the ecosystem

has been documented over many years. In comparison to the

concepts of aerial transport and deposition of Hg, the notion

of re-emission of this contaminant from environmental surfaces,

such as water, soil and vegetation is of more recent origin. The

first information gathered on microbial alteration of mercurial

compounds was based on observations of decreased biocidal

properties of Hg containing fungicides in both aquatic and

soil environments. Mercuric ion is volatilized from the soil or

the sediment and these volatile forms enter the atmosphere or

the water column. When uptake of a toxic substance occurs,

microorganisms are frequently able to perform detoxification,

thereby yielding a product that can be more toxic to higher

MERCURY POLLUTION AROUND CHLOR - ALKALI INDUSTRY

356

AJIT K. MISRA et al.,

organisms. It is true for the bacteria production of methyl

mercury, which may be regarded as a means of resistance

against mercurials by conversion to an organic form and

subsequent secretion. It thus appears that microorganisms do

not require mercury, but rather deal with it when present in

their food supply. The ability to transform mercury compounds

is not restricted to a small group of microorganisms; aerobic

and anaerobic bacteria, as well as fungi, but on the basis of

numerous laboratory experiments (supported by a rather

limited number of in situ field measurements strong evidence

exists for volatilization of Hg from a large variety of vascular

plants, leguminous seeds, non-vascular plants such as lichens

and mosses, algae, phytoplankton, the oceanic surface, at least

in biologically productive, up-welling equatorial locations,

various types of mercuriferous and non-mercuriferous soils

(Lindberg et al., 1979) and Hg-containing solid waste deposits.

Objective of the review

The present review was designed to discuss the impact and

fate of mercury in the effluent discharged from the chlor-alkali

industry. The present review focuses on the mercury pollution

problem at Ganjam and Rushikulya estuary of Bay of Bengal.

Aquatic and terrestrial contamination

The effluent which when released from the factory finds its

way into the Rushikulya river estuary, was found to contain

very high amount of mercury (Table 1). Out of twelve analyses

carried out in twelve months, only once, in the month of

March, a lower concentration of mercury (0.0268 mg 1-1) was

observed. Though the concentration in March was low, the

value was in itself much higher than the permissible limit of

0.01 mg 1-1. Maximum concentration of mercury, as recorded

in the month of January, was to the tune of 1.5487 mg 1-1.

Concentration of mercury in the effluent was found to be much

Plants around the industry Sample size Mean Mercury level,

mg.g-1 dry weight

1986 2010 1986 2010

Cynodon dactylon 11 15 14.83±2.12 22.6±4.5

Cyperus rotundus 17 16 25.17±2.61 28.3±4.9

Eragrostis ciliata 17 22 15.77±3.11 18.1±3.2

Ipomoea digitata 14 18 7.9±0.85 14.2±5.4

Lippia nodiflora 15 18 40.17±3.25 42.6±6.5

Pandanus odoratissimus 17 14 3.57±0.66 11.6±2.8

Plants around the solid waste deposits

Plants Sample size Mean Mercury level

1986 2010 1986 2010

Jatropha gossypifolia 12 19 19.7±3.91 24.6±8.2

Justicia simplex 15 22 13.83±2.87 17.93.4

Calotropis procera 12 18 9.73±1.42 14.32.6

Acalypha indica 14 16 5.33±1.01 7.8±1.8

Amaranthus spinosus 18 15 4.08±0.85 4.9±0.8

Mimosa pudica 17 14 4.00±0.91 5.6±1.2

Croton sparsiflorus 25 18 2.17±0.22 4.9±0.7

Amaranthus viridis 14 12 2.13±0.31 5.2±1.1

Azadirachta indica 17 11 1.87±0.28 4.9±0.8

Argemone mexicana 20 16 1.32±0.19 5.4±0.7

Boerhaavia repens 18 21 1.23±0.09 3.6±0.9

Plants from the nearby populated localities

Amaranthus spinosus 18 14 2.12±0.14 3.45±0.8

Solanum melongena 8 12 1.58±0.22 2.66±0.5

Hibiscus sabdariffa 17 14 1.13±0.14 2.55±0.4

Luffa cylindrica 10 15 0.90±0.31 1.84±0.3

Zizyphus jujuba 13 18 0.82±0.26 1.92±0.4

Vigna sinensis 11 17 0.82±0.18 0.96±0.3

Azadirachta indica 16 16 0.76±0.19 0.82±0.2

Ocimum basillicum 9 12 0.74±0.17 0.81±0.3

Justicia simplex 11 14 0.71±0.11 0.63±0.2

Phaseolus vulgaris 15 9 0.58±0.21 0.44±0.1

Dolichos lablab 8 11 0.58±0.32 1.23±0.5

Phaseolus mungo 12 9 0.58±0.19 1.86±0.4

Acalypha indica 8 6 0.58±0.12 0.66±0.2

Euphorbia prostrata 10 12 0.56±0.09 0.540.4

Psidium guayava 14 13 0.54±0.02 2.911.4

Momordica charantia 15 20 0.54±0.11 1.540.8

Cucurbita maxima 15 20 0.42±0.06 1.310.7

Oryza sativa 12 25 0.42±0.04 2.120.8

Croton sparsiflorus 12 14 0.38±0.01 0.850.2

Table 2: Residual mercury level (mg kg -1 dry wt) in different plant

species collected from the contaminated area within 1 km radius of

the factory. Data are mean of samples±standard deviation

fluctuating having a mean value of 0.4474 ± 0.0426 mg 1-1 in

1986. In 1996, the value depleted to 0.3894±0.0258 mg.L-1,

where 12.96% decrease was recorded. Out of the four stations

selected for studying mercury dynamics in the estuary, station

II, which is the junction point was found to be having the

highest amount of mercury in comparison to other stations.

The range was 0.0176 mg 1-1 in the month of March to 0.4838

mg 1-1 in the month of February with a mean value of 0.1690

± 0.1536 mg 1-1 (Table 1). Mercury levels at this station were

found to be dependent on the levels of mercury in the effluent

to some extent except in the month of January in 1986. In

1996, the mean mercury level increased by 1.42% and

0.1714±0.0844 mg of Hg. L-1 was recorded (Table 1). Levels

of mercury at other stations were lower in comparison to station

II. Out of the three stations, station IV was found to contain the

lowest amounts of mercury (Table 1). Levels of mercury at

station I and III were nearly identical with a tendency of little

Stations Mean ± S.D. (1986) Mean ± S.D. (1996) % change

Water (mg of Hg. L-1)

I 0.0374 ± 0.0359 0.0321 ± 0.0217 -14.17

II 0.1690 ± 0.1536 0.1714 ± 0.0844 ±01.42

III 0.0346 ± 0.0315 0.0380 ± 0.0118 ±09.80

IV 0.0273 ± 0.0269 0.0133 ± 0.0035 -51.28

E 0.4474 ± 0.0426 0.3894 ± 0.0258 -12.96

Sediments (mg of Hg. Kg-1 dry weight )

I 0.98±0.81 1.16±0.64 +18.37

II 369.25±169.19 288.44±65.88 -21.89

III 0.96±0.68 2.26±0.35 +135.42

IV 0.78±0.60 1.05±0.28 +34.62

E 929.39±405.23 658.32±64.58 -29.17

Water (mg of Hg. L-1 )

I 0.0321±0.0217 0.0211±0.0112 -34.26

II 0.1714±0.0844 0.0952±0.0234 -44.45

III 0.0380±0.0118 0.0214±0.0119 -43.68

IV 0.0133±0.0035 0.0096±0.0024 -27.81

E 0.3894±0.0258 0.1128±0.0542 -71.03

Sediments (mg of Hg. Kg-1 dry weight )

I 1.16±0.64 0.74±0.32 -36.21

II 288.44±65.88 132.85±18.36 -53.94

III 2.26±0.35 1.08±0.24 -52.21

IV 1.05±0.28 1.35±0.34 +28.57

E 658.32±64.58 486.54±38.19 -26.09

Table 1: Mercury concentration in water and sediment at different

stations in 1986, 1996 and 2006 and percent change of mercury

when compared to 1986 and1996 value

357

When compared to 1996 mercury levels, in 2006, at Station-

I- 34.26% decrease; in station-II-44.45% decrease, in station-

III-43.68% decrease, in station-IV- 27.81% decrease and in

the effluent channel, Station-E, 71.03% decrease in mercury

level was recorded. The significant decrease in mercury

concentration in all the 5 sites was probably due to the change

of technology from Electrolytic cell process to Diaphragm

process by the industry. Sediment analysis showed the

presence of a remarkable quantity of mercury (Table 1).

Maximum amount of mercury was found in the sediment from

the effluent channel. The levels of mercury fluctuated much,

the maximum being 2053.3 mg kg-1 dry wt in the month of

July and the minimum 456.67 mg kg-1 dry wt in the month of

Season Solid waste deposit area Station Direction I Direction II Direction III Means for each station

along different direction

Pre- monsoon 87.08± 6.93 a 19.58±1.24 12.28±1.58 11.76±0.89 14.54

b 2.48± 0.14 2.78±0.26 1.28±0.04 2.18

c 0.58± 0.18 0.48±0.04 0.39±0.04 0.48

Monsoon 77.06±1.58 a 12.67± 0.26 6.67±0.36 7.76±0.38 9.03

b 2.28± 0.06 1.98±0.04 0.98±0.15 1.75

c 0.54± 0.04 0.55±0.07 0.41±0.03 0.50

Post-monsoon 90.12±5.78 a 15.81± 0.96 8.28±0.26 10.78±0.39 11.62

b 2.68± 0.04 2.18±0.06 1.01±0.08 1.96

c 0.56± 0.04 0.63±0.13 0.31±0.03 0.50

Table 3: Residual mercury level in the Cynodon dactylon samples (mg kg-1 dry wt) collected along different directions and in different seasons

from the area within 2 km radius of the factory (Shaw et al., 1986 a, b and Sahu, 1987)

Name of the Plant Soil Root Stem Leaf Fruit

Croton sparsiflorus 1 610.00±17.32 4.61± 0.11 5.00± 0.25 24.03± 0.35 3.15± 0.16

2 576.67±11.55 3.52± 0.06 4.6± 0.26 18.03± 0.23 2.16± 0.08

3 660.00±14.25 7.4± 0.45 10.43± 0.23 27.9± 0.2 3.52± 0.03

4 613.33±11.55 2.48± 0.06 3.42± 0.13 15.43± 0.12 1.14± 0.06

5 2.13± 0.25 1.55± 0.15 2.93± 0.14 2.32± 0.14 0.39± 0.07

Jatropha gossypifolia 1 82.67±5.77 10.07±0.25 16.33± 0.29 18.25± 0.26

2 12.17±1.33 0.97± 0.03 1.38± 0.06 2.32± 0.14

3 503.33±25.17 8.85± 0.14 12.37±0.29 14.38± 0.41

4 9.02± 0.52 1.78± 0.13 1.28± 0.21 2.88± 0.06

Ipomoea digitata 1 288.67±5.77 4.6± 0.26 2.12± 0.20 7.07± 0.14

2 202.00±5.00 15.07± 0.51 4.62± 0.20 19.87± 0.91

3 210.28± 3.80 13.18± 0.41 3.18± 0.18 17.06± 0.7

Argemone mexicana 1 5.2± 0.17 3.92±0.13 3.82± 0.41 4.27± 0.23 3.82 ± 0.4

2 3.87± 0.12 3.02± 0.14 3.02± 0.14 3.44± 0.13 2.77± 0.14

3 4.60± 0.11 3.42± 0.10 3.25± 0.22 4.15± 0.19 3.05± 0.14

Calotropis procera 1 893.33±11.55 15.07± 0.50 10.7± 0.36 38.83±1.44

2 130.00± 5.2 3.33± 0.06 2.43± 0.14 14.73±0.25

3 210.00± 8.45 7.67± 0.41 3.84± 0.09 23.24± 0.89

Table 5: Levels of mercury in the soil and root, stem, leaf and fruit of the plants at different sites (Conc. of Hg in mg kg-1 dry wt.). Data

presented, Means of five samples±standard deviation. (Shaw et al., 1986 a, b and Sahu, 1987)

higher levels at station I than at station III, except in the month

of April when the value was less than at station III. No particular

trend of increase or decrease in the levels of mercury was

noted at any of the station. However, all the three stations

showed their minimum and maximum levels in the monsoon

and pre-monsoon seasons, respectively. The levels of mercury

during monsoon season at these stations were much less and

very similar to each other. The trend of decrease or increase in

the levels of mercury was also similar. When compared to

1986 mercury levels, in 1996, at Station-I, 14.17% decrease;

in station-II,1.42% increase in station-III,9.8% increase in

station-IV, 51.28% decrease and in the effluent channel,

Station-E, 12.96% decrease in mercury level was recorded.

Table 4: Mercury level in the soil samples (mg kg-1 dry wt) collected along different directions and in different seasons from the area within

2km radius of the factory. (Data presented, Mean of five samples ±standard deviation. Station- a, b and c are stations at ½ km, 1km and 2km

distance from the industry respectively.) (Shaw et al., 1986 a, b and Sahu, 1987)

Season Solid waste deposit area station Direction - I Direction -II Direction -III Means for each station

along different direction

Pre- monsoon 610.98 ± 30.98 a 70.28±5.98 48.99±3.96 45.28 ±2.98 54.85± 13.49

b 5.92±1.02 4.98±0.98 4.91 ± 0.86 5.27±0.56

c 0.78±0.10.04 0.68±0.13 0.58 ±0.09 0.71±0.15

Monsoon 599.96 ± 12.89 a 25.98±3.88 10.90±1.09 9.96 ± 0.98 15.61±8.99

b 2.20±0.04 0.98 ±0.04 1.02 ±0.09 1.40 ±0.69

c 0.62±0.04 0.56 ±0.04 0.46 ± 0.02 0.55 ±0.08

Post-monsoon 640.28 ± 33.09 a 60.86±6.10 38.68 ±4.21 44.78 ±3.28 48.11 ± 11.46

b 6.98±0.96 5.21 ±1.02 3.98 ±0.88 5.39 ±1.51

c 0.71±0.08 0.71 ±0.09 0.62 ±0.04 0.68 ±0.05

MERCURY POLLUTION AROUND CHLOR - ALKALI INDUSTRY

358

Table 6: Levels of mercury in the soil and root, stem, leaf and fruit of

the plants (fresh wt. basis) at different sites (Conc. of Hg in mg kg-1

dry wt.). Data presented, Means of five samples ± standard

deviation. (Shaw et al., 1986 a, b and Sahu, 1987)

Name of the Plant Conc. of mercury in mg / kg fresh wt.

(For soil, it is kg dry wt.)

Soil Root Stem Leaf Fruit

Croton sparsiflorus 1 610.00 2.62 3.05 6.63 1.04

2 576.67 1.98 2.80 4.98 0.71

3 660.00 4.17 6.36 7.7 1.15

4 613.33 1.40 2.08 4.26 0.39

5 2.13 0.87 1.79 0.64 0.13

Jatropha gossypifolia 1 82.67 2.17 3.33 3.98 -

2 12.17 0.21 0.28 0.51 -

3 503.33 1.91 2.52 3.13 -

4 9.20 0.38 0.26 0.63 -

Ipomoea digitata 1 288.67 1.77 0.72 2.28 -

2 202.00 5.79 1.56 6.42 -

3 212.28 5.07 1.22 5.51 -

Argemone mexicana 1 5.20 0.94 0.75 1.24 1.04

2 3.87 0.74 0.60 1.01 0.76

3 4.60 0.87 0.64 1.20 0.83

Calotropis procera 1 893.33 4.93 1.95 4.95 -

2 130.00 1.09 0.44 1.88 -

3 210.00 2.51 0.70 2.96 -

Root Stem Leaf Fruit

Croton sparsiflorus

Soil 0.649NS 0.514NS 0.900 0.754NS

(p ∠ 0.050)

Root - 0.967 0.895 0.929

(p∠0.010) (p∠0.050) (p∠0.010)

Stem - - 0.771NS 0.806NS

Leaf - - - 0.960

(p∠0.010)

Jatropha gossypifolia

Soil 0.606NS 0.521NS 0.533NS -

Root - 0.992 0.995 -

(p∠0.001) (p∠0.001)

Stem - - 0.999 -

(p∠0.001)

Ipomoea digitata

Soil -0.998 -0.875NS -0.995 -

(p∠0.010) (p∠0.010)

Root - 0.904NS 0.999 -

(p∠0.001)

Stem - - 0.921NS -

Root Stem Leaf Fruit

Argemone mexicana

Soil 0.993 0.956 0.947NS 0.949NS

(p∠0.010) (p∠0.050)

Root - 0.984 0.901NS 0.980

(p∠0.050) (p∠0.050)

Stem - - 0.811NS 1.000

(p∠0.001)

Leaf - - - 0.790NS

Calotropis procera

Soil 0.961 0.998 0.966 -

(p∠0.050) (p∠0.010) (p∠0.050)

Root - 0.977 1.000 -

(p∠0.050) (p∠0.001)

Stem - - 0.981 -

(p∠0.050)

Table 7: Matrices showing correlation coefficients (r) between mercury

concentration in soil and different plant tissues (dry wt. Basis). P =

Level of significance, NS= Not significant. (Shaw et al., 1986 a, b

and Sahu, 1987)January. The mean mercury value was 929.39 ± 405.23 (Table

1). Out of the four stations of the estuary, station II was the site

of maximum mercury contamination similar to that of water

(Table 1). Here also the concentration of mercury fluctuated

much. Mean value was 369.25 mg kg-1 dry wt (Table 1). No

particular trend of increase or decrease was marked. However,

lower concentrations of mercury were observed in the

monsoon and the post monsoon seasons, i.e., from June to

December. No relationship could be noticed between the

concentration of mercury in sediment of this site and that of

the effluent channel. Unlike water samples, levels of mercury

were slightly higher at station I than at station III. When

compared to 1986 mercury levels, in 1996 in station-I,18.37%

increase; in station-II, 21.89% decrease; in station-III,135.42%

increase; in station-IV,34.62% increase and in the effluent

channel, station-E, 29.17% decrease in mercury concentration

was recorded. Within 10 years time (1986-1996), significant

increase in mercury level was recorded in station- II and III

and sediment mercury level in station-I, III and IV (Table 1).

When compared to 1996 mercury levels, in 2006 in station-I-

36.21% decrease; in station-II- 53.94% decrease; in station-

III-52.21% decrease; in station-IV-28.57% increase and in the

effluent channel, station-E- 26.09% decrease in mercury

concentration was recorded. The significant decrease in the

sediment mercury concentration was mostly due to periodic

removal of sediments from the effluent channel and dumping

them in the Rushikulya river estuary and due to the change in

technology by the industry, where mercury was no more used.

The decrease in mercury concentration in the effluent channel

was due to periodic removal of sediments from the channel

and dumping the wastes in a nearby site. No particular trend

of increase or decrease in the mercury concentration was

noticed at any station during the entire period. However, the

levels of mercury were lower in the monsoon and the post

monsoon season at all the three stations. While studying the

total mercury distribution in the Rushikulya River and estuarine

bed and estuary, the highest level (1043.33 mg kg-1 dry wt) of

mercury was marked in the sediment from the effluent channel.

This was followed by the sediment zone, the lowest samples

from the junction zone. The lowest concentration of mercury

at upstream was 0.03 mg kg-1 dry wt in 1986, 0.02 mg kg-1 dry

wt in 1996 and 0.01 mg kg-1 dry wt in 2006, whereas at down

stream, at a similar distance from the junction concentration

was 0.28 mg kg-1 dry wt in 1996 and 0.12 mg kg-1 dry wt in

2006. The observations in 2006 were significantly less than

1996 and 1986 values. The depletion in mercury level was

probably due to recycling technology adopted by the industry

by way of effluent treatment by chemical and biological

methods and by change in technology. Concentrations of

mercury in the samples collected from the middle region of

the estuary were always higher in comparison to the samples

collected from the bank regions at the same distance from the

junction.

The plant species collected from the contaminated area during

1986 and 2010 were analyzed for residual mercury

accumulation. Table 2 shows the comparative account of

residual mercury retention/ accumulation. The data revealed

AJIT K. MISRA et al.,

359

Table 8: Matrices showing correlation coefficients (r) between mercury

concentration in soil and different plant tissues (fresh wt. Basis) P =

Level of significance, NS= Not significant. (Shaw et al., 1986 a, b

and Sahu, 1987)

Root Stem Leaf Fruit

Croton sparsiflorus

Soil 0.652NS 0.513NS 0.900 0.756NS

(p∠0.050)

Root - 0.965 0.897 0.928

(p∠0.010) (p∠0.050) (p∠0.010)

Stem - - 0.770NS 0.801NS

Leaf - - - 0.960

(p∠0.010)

Jatropha gossypifolia

Soil 0.607NS 0.520NS 0.531NS -

Root - 0.992 0.995 -

(p∠0.001) (p∠0.001)

Stem - - 0.999 -

(p∠0.001)

Ipomoea digitata

Soil -0.998 -0.954 -0.975 -

(p∠0.010) (p∠0.050) (p∠0.050)

Root - 0.970 0.999 -

(p∠0.050) (p∠0.001)

Stem - - 0.979 -

(p∠0.050)

Argemone mexicana

Soil 0.991 0.949NS 0.954 0.944NS

(p∠0.01) (p∠0.050)

Root - 0.899 0.986 0.891NS

(p∠0.050)

Stem - - 0.812NS 1.00

(p∠0.001)

Leaf - - - 0.801NS

Calotropis procera

Soil 0.961 0.998 0.967 -

(p∠0.050) (p∠0.010) (p∠0.050)

Root - 0.977 1.000 -

(p∠0.050) (p∠0.001)

Stem - - 0.982 -

(p∠0.050)

Name of the Plant Conc. of Hg in mg kg-1 dry wt., 1987

Croton sparsiflorus 0.012

Jatropha gossypifolia 0.014

Ipomoea digitata 0.011

Argemone mexicana 0.004

Calotropis procera 0.004

Table 9: Natural background levels of mercury in some plant species

under study

Data presented are the mean of three samples

Name of the species Sample size Concentration of mercury in mg kg-1 wet wt

Blood Liver Muscle Brain

Domestic Goat (Capra hircus) 7 9.15 4.16 34.25± 11.35 2.86± 0.96 2.81 ± 0.44

Red sheep (Ovis orientalis) 7 8.24 ± 3.26 26.14 ± 8.52 2.91±0.86 3.11 ± 0.91

Table 10: Residual mercury level in some animal samples collected from the contaminated area. (Shaw et al., 1986 a, b and Sahu, 1987)

Table 11: Analysis of variance for total mercury content of the water at different stations along the Rushikulya River estuary (Shaw et al., 1986

a, b and Sahu, 1987)

Source of variation degree of Freedom Mean Squares F ratio LSD at p ≤p ≤ 0.001 0.010 0.050

Stations 3 0.06 6.00 0.010 - 0.11 0.08

Months 11 0.01 1.00 NS - - -

Residual 33 0.01 - - - - -

Total 47 - - - - - -

significant amount of mercury in their body. It was observed

that the plants collected from the solid waste dumping site

and in and around the effluent channel showed highest amount

of mercury accumulation. The values of 2010 were much

higher than 1986 values. This increase indicated that with

time, growth and age of the plant, residual mercury significantly

increased pointing at biomagnification of mercury in the plant

system (Table 2). It was alarming to note that significant amount

residual mercury was available in plants grazed by herbivores.

The herbivores accumulated significant amount of mercury

in their body which ultimately comes from the grazed plants

available in the contaminated sites. Insignificant amount of

residual mercury was recorded in the plants collected from

the nearby populated localities of the industry. The amount

may be insignificant but the very presence of mercury in those

plants is interesting and draws the attention of ecologists.

Cynodon dactylon was collected from three different directions

from the industry (I, II, III) and from ½ (a), 1(b), 2(c) km distance

from the factory. Station-a showed the highest concentration

of residual mercury, when compared to station-b and c. Station-

c situated at a distance of 2km showed the lowest amount of

residual mercury in Cynodon dactylon. The values clearly

indicated that the industry is the origin of mercury and with

increase in distance the amount of residual mercury decreases

significantly (Table 3). The availability of mercury in direction-

I, II and III (a, b, c) was probably due to the mercury volatilized

in the Cell house of the industry carried by wind and dispersed

in all the three directions. The residual mercury availability in

Cynodon dactylon was also strongly seasonal (Table 3). This

particular grass was of interest only because the grass was

available in all the stations and in all the directions.

Data presented, Mean of five samples ± standard deviation. a,

b and c are stations at ½ km, 1 km and 2 km respectively.

The table also indicated the fluctuation of residual mercury

concentration in the solid waste in different monsoon periods

(Table 3). The values presented in Table 3 were significant, as

this grass is generally grazed by all the grazers. Table 4 showed

the mercury level in the soil samples (mg kg-1 dry wt) collected

along different directions and in different seasons from the

area within 2km radius of the factory. The Table 4 indicated

the mercury concentration in the solid waste deposit in different

monsoon periods. This table was important as the select grass

was collected from these sites, where solid waste was

deposited. The residual accumulation of mercury in different

plants was only due to the mercury absorbed from the solid

MERCURY POLLUTION AROUND CHLOR - ALKALI INDUSTRY

360

waste deposit area. As the soil is rich in mercury concentration,

we may practically expect high mercury values in plants

growing in these sites.

All the plants collected showed the presence of an

objectionable amount of mercury in their tissues (Table 2).

Maximum amount of mercury was found in the plants

collected from the areas of solid waste deposits. A significant

amount of mercury, 19.07 mg kg-1 dry wt. was found in Jatropha

gossypifolia. A minimum tissue concentration of 1.23 mg kg-1

dry wt. was found in Boerhaavia repens. Plants collected from

the nearby populated localities showed decreasing

concentrations of mercury. The levels of mercury ranged from

2.12 mg kg-1 dry wt. as in Amaranthus spinosus to 0.38 mg kg-

1 dry wt. as in Croton sparsiflorus. Some economically

important plants used as daily food, such as L. cylindrica,

Dolichos lablab, Oryza sativa etc. also showed a remarkable

accumulation of mercury in their tissues.

Geographical distribution of mercury

Tables 3 and 4 represent the levels of mercury in Cynodon

and soil samples collected in and around the factory.

Concentrations of mercury in both the soil and the Cynodon

samples were remarkably high. Samples of the soil collected

from the area of solid waste deposit showed mercury

concentration as high as 640.28 mg kg-1 dry wt, where as the

Cynodon samples showed a maximum value of 90.12 mg kg-

1 dry wt. Concentrations of mercury in both the cases declined,

rather abruptly, with increase in distance from the factory.

Deposition of mercury was higher in direction I then the other

directions. Levels of mercury declined in the monsoon season,

particularly the stations located closer to the industry were

affected. Decline in the mercury levels at Station ‘c’ was not

pronounced during the monsoon season, rather Cynodon

samples showed higher accumulation during the monsoon

and post-monsoon seasons.

Absorption and tissue distribution

Results obtained in this study are presented in Tables 5 - 8.

Table 5 represents the residual Hg levels in mg kg-1 dry wt,

whereas Table 6 represents the values in fresh wt. Tables 7

and 8 represent the correlation coefficient values for the soil

vs root, stem and leaf mercury concentrations and for the inter

tissue mercury concentrations, separately for each plant species

analysed on the basis of dry wt and fresh wt., respectively. No

definite relationship between the concentration of mercury in

the soil and the amount of mercury in different tissues of the

plant was marked. Even negative correlation between soil and

different tissues were observed in case of Ipomoea digitata

(Table 7 and 8). However, in some cases highly significant

correlation values were obtained as in C. procera. The values

were r = 0.961 (p ∠ 0.050) for soil vs root, r = 0.998 (p ∠

0.010) for soil vs stem and r = 0.966 (p ∠ 0.50) for all vs leaf

(Table 2.6). Correlation values were also similar for fresh weight

conversion except for soil vs leaf where it was r = 0.967

(Table 8).

Concentration of mercury in the root tissue of Croton was

found to be 1.55 mg kg-1 dry wt (0.67 mg kg-1 fresh wt) when

the soil mercury concentration was 2.13 mg kg-1, however, in

the same species the root tissue mercury concentration of

only 7.4 mg kg-1, dry wt (4.17 mg kg-1 fresh wt) was noted even

though the mercury level in the soil was many times more

(660 mg kg-1 dry wt). Besides, in some cases a negative trend

was marked, i.e. when the soil mercury concentration was

more, concentration of mercury in root and other tissues were

less or vice-versa as in Jatropha and Ipomoea. In Jatropha

when the soil mercury concentration was 9.2 and 12.17 mg

kg-1 dry wt, the root tissue mercury concentration were 1.78

and 0.97 mg kg-1 dry wt. (0.38 and 0.21 mg kg-1 fresh wt),

respectively. Similarly, when the soil mercury concentrations

were 82.67 and 503.33 mg kg-1 dry wt, the root tissue mercury

concentration recorded were 10.07 and 8.85 mg kg-1 dry wt.

Ipomoea showed highly significant negative correlation value

(r = -0.998) on dry wt. as well as on fresh wt. basis. In Argemone

correlation between the soil mercury concentrations and

concentrations of mercury in different tissues were highly

significant. Though concentrations of mercury in the soil were

very low the absorption and accumulation were very high,

comparatively. This is evident from the fact that when the soilmercury concentration were 5.2, 4.6 and 3.87 mg kg -1 drywt., the root mercury concentrations were 3.92, 3.42 and3.02 mg kg-1 dry wt (or 0.94, 0.87 and 0.74 mg kg-1 fresh wt),respectively. In general, relationship between the concentrationof mercury in soil and its accumulation in plant tissue appearto be much fluctuating. Relationship between the mercuryconcentrations of root and stem as well of other tissues, suchas leaf and fruit, were high significant. In Calotropis therelationship was remarkably significant (r =1.000, p∠ 0.001).One thing of importance to note is that the concentrations ofmercury in the root were always less in comparison to leaf,but when compared to stem the concentration were less inCroton and Jatropha whereas more in Ipomoea, Argemoneand Calotropis. Relationship between stem and leaf as well asbetween stem and fruit with respect to mercury concentrationswere found to be appreciably high with significant correlationvalue (p∠ 0.050) in majority of the cases. No correlation existedfor stem vs. leaf mercury concentration in Croton and inArgemone. From the results it can be said that stem tends toaccumulate less mercury than leaf. However, the amount ofmercury was always higher in stem than in fruit. Theaccumulation of mercury in leaf was much more significant

than in other tissues. A highly significant correlation was noted

between leaf and fruit in Croton (p∠ 0.010) with respect to

AJIT K. MISRA et al.,

Table 12: Analysis of variance for total mercury content of the sediment at different stations along the Rushikulya river estuary (Shaw et al.,

1986 a, b and Sahu, 1987)

p = Level of significance; LSD = Least significant difference; NS= Not significant

Source of variation Degree of Freedom Mean Squares F ratio p< LSD at p<

0.001 0.010 0.050

Stations 3 99133.33 10.85 0.001 138.55 105.38 78.84

Months 11 9136.36 1.00 NS - - -

Residual 33 9139.39 - - - - -

Total 47 - - - - - -

361

accumulation of mercury, both on fresh and dry wt. basis,

however, similar result was not marked in Argemone. The

level of accumulation in fruit was appreciable in comparison

to root and stem accumulation.

The effluent which when released from the factory finds its

way into the Rushikulya river estuary, was found to contain

very high amount of mercury (Table 11). Out of twelve analyses

carried out in twelve months, only once, in the month of

March, a lower concentration of mercury (0.0268 mg 1-1) was

observed. Though the concentration in march was low, the

value was in itself much higher than the permissible limit of

0.01 mg 1-1. maximum concentration of mercury, as recorded

in the month of January, was to the tune of 1.5487 mg 1-1.

Concentration of mercury in the effluent was found to be much

fluctuating having a mean value of 0.4474 ± 0.4466 mg 1-1.

Out of the four stations selected for studying mercury dynamics

in the estuary, station II, which is the junction point was found

to be having the highest amount of mercury in comparison to

other stations. The range was 0.0176 mg 1-1 in the month of

March to 0.4838 mg 1-1 in the month of February with a mean

value of 0.1690 ± 0.1536 mg 1-1. Mercury levels at this station

were found to be dependent on the levels of mercury in the

effluent to some extent except in the month of January. Levels

of mercury at other stations were lower in comparison to station

II. Out of the three stations, station IV was found to contain the

lowest amounts of mercury. Levels of mercury at station I and

III were nearly identical with a tendency of little higher levels at

station I than at station III, except in the month of April when

the value was less than at station III. No particular trend of

increase or decrease in the levels of mercury was noted at any

of the station. However, all the three stations showed their

minimum and maximum levels in the monsoon and pre-

monsoon seasons, respectively. The levels of mercury during

monsoon season at these stations were much less and very

similar to each other. The trend of decrease or increase in the

levels of mercury was also similar. Sediment analysis showed

the presence of a remarkable quantity of mercury. Maximum

amount of mercury was found in the sediment from the effluent

channel. The levels of mercury fluctuated much, the maximum

being 2053.3 mg kg-1 dry wt in the month of July and the

minimum 456.67 mg kg-1 dry wt in the month of January. The

mean mercury value was 929.39 ± 405.23 (Table 8).

Out of the four stations of the estuary, station II was the site of

maximum mercury contamination similar to that of water. Here

also the concentration of mercury fluctuated much. Maximum

value was recorded in February (665.00 mg kg-1 dry wt) and

minimum value in July (44.33 mg kg-1 dry wt). Mean value was

181.69 mg kg-1 dry wt (Table 11). No particular trend of increase

or decrease was marked. However, lower concentrations of

mercury were observed in the monsoon and the post monsoon

seasons, i.e., from June to December. No relationship could

be noticed between the concentration of mercury in sediment

of this site and that of the effluent channel. Unlike water

samples, levels of mercury were slightly higher at station III

than at station I with exception of May and October.

Concentrations at station IV were found to be the lowest when

compared to the other stations except in September and

November. No particular trend of increase or decrease in the

mercury concentration was noticed at any station. However

the levels of mercury were lower in the monsoon and the post

monsoon season at all the three stations. Analysis of variance

revealed no significant difference in the mercury levels in water

(Table 12) and sediment (Table 13) between different seasons.

However, different stations did differ from each other with

respect to the mercury levels. From correlation analysis (Table

11) it appears that significant correlation existed between the

concentration of mercury in water and sediment at station I, III

and IV, but not at station II and E. However, at all the stations

many examples were marked relating to increase in

concentration of mercury in water with concomitant decrease

of the same in the sediment.

All the plants collected from the industrial area and from nearby

field/ locality showed the pressure of an objectionable amount

of mercury in their tissues. Maximum amount of mercury was

recorded in plants, collected from the solid waste deposit areas.

Alarming level of mercury was found in plant s used for human

consumption. The plants collected within 1km radius showed

higher level of mercury. Cyperus rotendus showed 27.9 ± 6.8

mg of Hg kg-1 dry weight. Whereas, Cynodon dactylon showed

22.8 ± 3.6 mg of Hg kg-1 dry weight. Lippia nodiflora showed

24.2 ± 9.5 mg of Hg kg-1 dry weight. Pandanus odaratissimus

showed 18.5 ± 1.6 mg of Hg kg-1 dry weight, which has

ecological significance. Ipomea digitata showed the least

amount of residual mercury accumulation among the plants

collected from 1km radius area of the industry. The plants

collected from solid waste deposit area, showed higher

accumulation of mercury. Jatropha gossypifolia accumulated

23.8 ± 9.2 mg of Hg kg-1 dry weight and Justicia simplex showed

19.2 ± 4.4 mg of Hg kg-1 dry weight. Colotropis procera showed

15.6 ± 1.8 mg of Hg kg-1 dry weight. Ageratum conyzoids

showed 9.6 ± 3.1 mg of Hg accumulated in kg-1 dry weight of

the sample. Croton and Desmodium showed the least amount

of mercury accumulation. Amaranthus viridis showed 5.9 ±2.2mg of Hg kg-1 dry weight, where as Azadirachta indica

showed 5.6 ± 0.9 mg of Hg kg-1 dry weight of the sample.

Table C showed the residual mercury accumulation in plants

collected from the populated localities of the Ganjam areaand also the cultivated plants available in the contaminatedareas. Amaranthus spinosus showed 4.12 ± 1.08 mg of HgKg-1 dry weight. Solanum melongena showed 3.04 ± 0.8 mgof Hg kg-1 dry weight and Zizyphus jujuba showed 2.14 ± 0.7mg of Hg kg-1 dry weight. Ocimum basillcum showed 1.14 ±0.5 mg of Hg kg-1 dry weight. Among cultivated plants,Phaseolus vulgaris showed 0.54 ± 0.3mg of Hg Kg-1 dry weight,Phaseolus mungo showed 0.86 ± 0.7 mg of Hg kg-1 dry weight.Psiduim guayava accumulated 2.88 ± 0.9 mg of Hg kg-1 dryweight. Oryza sativa interestingly showed 2.11 ± 0.7 mg ofHg kg-1 dry weight, which is highly significant, as rice is regularlyneeded as food by the local people. Cucurbita showed 1.36 ±0.5 mg of Hg kg-1 dry weight, Hibiscus esculentus showed0.88 ± 0.4mg of Hg kg-1 dry weight. Momordica charantiashowed 1.32 ± 0.8mg of Hg kg-1 dry weight. The values

presented for domesticated plants may look very small but

these values were highly significant, when we consider it long

run effect and future bio-magnification of mercury in the food

chain. Table showed the natural background level of mercury

in the plants collected from the area. Croton showed 0.014 ±0.003 mg of Hg Kg-1 dry weight. Jatropha showed 0.029 ±0.006 mg of Hg Kg-1 dry weight. Ipomoea digitata showed

MERCURY POLLUTION AROUND CHLOR - ALKALI INDUSTRY

362

0.011 ± 0.002 mg of Hg kg-1 dry weight Argemone showed

0.008 ± 0.001 mg of Hg kg-1 dry weight. Calotropis procera

showed 0.012 ± 0.003 mg of background Hg kg-1 dry weight

of the sample (Table 3).

The samples collected from the solid waste deposit area

indicated significantly high level of mercury contamination.

During pre monsoon period the solid waste contained 585.60

± 38.34 mg of Hg kg-1 dry weight which is very high. During

monsoon period, the mercury level declined to 498.65 ± 18.50

mg of Hg Kg-1 dry weight and in post monsoon period, the

mercury level was 476.12 ± 29.65 mg of Hg kg-1 dry weight. In

station ‘a’ the mercury level in the soil decreased with the

increase in distance from station ‘a’ to station ‘c’ at all the three

seasons and all the three directions. Significantly low level of

mercury was recorded in station ‘c’ in direction I, direction II

and direction III (Table 4). Table clearly indicated that station

‘a’ in all the three direction, showed higher amount of mercury.

Hence, zone ‘a’ i.e. 1/2 km radius from the factory is the hot

zone, where significant amount of soil mercury is available.

The geographical distribution indicated that the mercury is

available within 2kms radius from the factory. Beyond 2kms

distance, mercury was not recorded in all the three directions.

Hence, the available mercury’s source is the chlor-alkali industry

situated at Ganjam area (Table 4). Results of the investigations

represent the gross primary productivity values at station I, II,

III and IV. Station II was noted as the least productive zone, the

minimum and maximum GPP values being 0 and 0.075 g Cm-

2d-1. The most productive zone was station IV, the values ofGPP ranged from 0.853 to 1.331 g Cm-2d-1. The productivityvalues were more or less constant with a slight increase in thepre-monsoon period, probably due to increase inconcentration of the nutrients (Sahu, 1987; Shaw, 1987).Unfortunately no standard GPP values are available from anyregion of the world for comparison. Presence of mercury inthe environment has received considerable attention. Studiesby Jensen and Jernelov, (1969a, b) Jernelov and Wallin (1973),Wallin (1976), Panigrahi and Mishra (1978a and b, 1980),Powell (1983) and Huckabee et al., (1983) pertaining toresidual mercury level in water bodies, soil vegetation aroundchlor-alkali industries and mercury mines, and aquatic andterrestrial animals from the contaminated system stress uponthe importance of the problem of environmental mercurypollution. Reports were also available pertaining to thegeographical distribution (Wallin, 1976; Huckabee et al.,1983) of mercury and the intensity of mercury pollution.

Plants collected from the area showed heavy accumulation ofmercury in their tissue (Table 2) the residual levels recordedwere much more than the natural background levels thatranged from 0.04 to 0.08 mg kg-l dry weight. Soil analysis fromthe area also revealed heavy contamination. These resultssuggest an unnaturally high deposition of mercury in thevicinity of the industry. Decrease in the level of mercury in

both plant and soil with increase in distance from the industry

is indicative of the fact that the industry was the source of

mercury. In a similar work Wallin (1976) and Lodenius and

Tulisalo (1984) reported a gradual reduction of mercury

contamination in mosses with increase in distance from the

factory confirming the source of mercury to be a caustic

chlorine industry. The accumulation in moss bags and the

concentration in mosses and lichens were significantly higher

near the chlor-alkali plant than at a distance of 20-100 km or

in the background are (Lodenius and Tulisalo, 1984).

Difference in the levels of mercury in the tissues of the different

plants species may be assigned to difference in availability of

mercury to them as well as their capacity of absorption,

accumulation and retention inside their tissue system.

Geographical distribution of mercury was more pronounced

in direction I as revealed from its level in Cynodon and the soil

samples, probably due to the prevalent south east wind.

Decrease in the levels of mercury in the monsoon season may

be attributed to the leaching and washing away of the

deposited mercury due to heavy rain. Retention of mercury in

the soil during the monsoon season was in some way related

with its concentration in the pre monsoon season i.e. greater

the concentration, higher was the retention. This indicated

that the mercury particles, to a minimum value depending

upon the original soil concentration, were bound tightly to

the soil particles to be washed away by the rain. Vascular

plants accumulation mercury by three routes of uptakes

through the root from the soil, through the stomata from the

atmosphere and by the retention of particular mercury with

atmospheric uptake predominating in the above ground parts

of herbaceous plant (Lindberg et al., 1979). At the mercury

concentrations prevailing in soils, plants retain mercury almost

exclusively within the root, where it seems to be relatively

tightly bound to acid groups of cell walls, only at exceptionally

high soil mercury contents, there occurred significant

translocation to shoot. Lindberg et al. (1979) reports the

accumulation of more mercury in leaves in comparison to

other tissues of the plants. More mercury concentration in thestem than in the root in Jatropha species and Croton furthersupports the idea. In other plants greater amounts mercurywere observed in the root. The analysis carried out byHuckabee et al. (1983) with Quercus species three samplesfrom Almaden mines areas showed a higher amount of mercuryin the stem than in the leaf. Further same author added thathad there been aerial absorption of mercury, the levels ofmercury in leaves, at least in plants of the same species wouldhave been similar. Moreover, highly significant correlationobserved between the root and the leaf mercury concentrationin all cases, contradicts the possibility of aerial absorption.Higher levels of mercury in the leaves may be attributed to thefact that mercury absorbed from the soil might be gettingtransferred immediately to the leaves. Leaf tissues of the plantssystem may be compared with liver of an animal system withrespect to mercury accumulation where the concentration ofmercury has been found to be the highest in most of the cases(Shaw et al., 1985, 1986a, b; 1988, 1991a, b; Smith andArmstrong, 1975) in comparison to other tissues, primarilybecause both the centers of active metabolic activities. Duringtransportation of the mercury from root to leaf, the stem tissuemight be accumulating mercury resulting in a higher level

than the root, as found in some cases. However, this appears

to be mostly a species dependent phenomenon. The existence

of poor correlations between the concentration of mercury in

soil and different tissues may be explained by the fact that the

soil mercury concentration might not be acting as a limiting

factor. This is evident from the result of Argemone species

where the soil mercury concentration acted as a limiting factor

and the correlation values for the soil vs. Different tissue

AJIT K. MISRA et al.,

363

mercury concentrations were highly significant. Presence of

highly elevated levels of mercury in the plant tissue under this

observation goes against the view of Lorenz (1979) that in

terrestrial ecosystem mercury generally does not enter the food

chain in significant quantities and thus does not play a

significant role because of its chelation by soil organic matter

and its binding to functional groups of cells walls in plants

root. Higher concentration of mercury in leaves than in other

tissues of the plants, as well as in grasses, draw the attention of

ecologists because grazers mostly depend on grasses and

leaves of the plants. Thus, the grazers of the area (Cows, sheep,

goats) must be accumulating a considerable amount of

mercury in their tissues via food chain since they are totally

dependent on the live flora of the area.

Plant systems unlike animals system tend quickly and visibly

to reflect changes in their environment (Naegeta, 1974). This

is because plants lack the complex internally balanced

homeostatic mechanisms that regulate body function and

adaptation that are found in animals. Because of this

homeostasis animal systems tend to ameliorate the adverse

effects of environment. Thus, animals tend to withstand, adjust

and ameliorate the contamination in their external environment

in such a way that only major changes in their environment

become externally detectable. Plants, on the other hand,

respond noticeably to minor, as well as major changes in their

environment. However, the response of a plant to a pollutant

in its environment is an integrated responsibly many other

environmental components. The plant system has a limited

number or finite number of responses to the environment in

which they live. In may ways their responses are generalized

in that they do not have broad varieties of specific behaviorable

responses which animal system have, as a consequence, the

responses of a plant to air pollution is very similar in form.

During samples collections no visible abnormalities in the

plants structure were marked except that the growth was

stunted which might be due to water scarcity. Leaves ofAesculus hipocastanum L. and Quercus petres L from airpolluted areas showed a higher water loss than normal leaves.Trivedi and Dubey (1978) reported even a higher amount ofmercury (15mg) in the effluent of a caustic chlorine industry atBirlagram Nada (M.P) High amount of mercury has beenreported in water receiving industrial discharges contaminatedwith mercury (Zingde et al., 1980; Zindge and Desai, 1981).At the point of discharge in Tyhane creek, the mercuryconcentrations varied from 79 to 320 mg-l (Zingde and Desai,1981). Level of contamination of the Chambai River, whichreceived effluent from Gwalior rayon and caustic chlorineindustries at Birlagram Nagade (M.P), was such that it wasfound to be unfit for fish growth up to 35km downstream(Trivedi and Dubey 1978). Presence of mercury at upstreammay be attribution to the tidal effects of the sea, the water levelswells and carries the contaminated water towards upstream.

Thus during high tide the level of mercury at the upstream

may be higher than at the downstream. Similarly, during low

tide the contaminated water may be carried to a greater distance

towards downstream and thus a higher concentration at site

IV may be resulted. A particular trend of increase or decrease

in the levels of mercury at different stations can’s be expected

since the contamination was related to the effluent discharge

which was periodic but not a continuous one and highly

variable with respect to mercury concentration. Dove et al.

(2011) who analyzed water sampled from the Great Lakes and

connecting channels during 2003-2009 found that mean

concentrations of total mercury in unfiltered waters were less

than 1.0ng/L at most sampling sites within the five great lakes.

Berndt and Bavin (2012) quantified total mercury, methyl

mercury, dissolved organic carbon and sulfate in stream water

from St. Louis River and tributaries draining sub basins in

northeastern Minnesota. Zhang et al. (2012) studied the

seasonal variation in mercury and food web biomagnifications

in Lake Ontario, Canada and reported that highest mercury

concentration in 6 invertebrate species and 8 fish species in

spring and lowest in the summer for most biota.

Concentration of mercury in sediment is rather more important

in indicating the pollution status of the system than water. This

is because the sediment rapidly binds mercury and also the

sedimentations decrease its availability to aquatic system. As

expected, maximum amount of mercury was found in the

sediment of the effluent channel followed by the sediment

from the junction zone. Contamination of sediment with

mercury has been reported in lake, river and coastal water

(Clifton and Vivian, 1973). The levels of mercury were usually

lower than 10 mg kg-l. Sediment of Minamata bay in Japan in

1963 showed a mercury level varying from 28 to 73 mg kg-l

.dry weight (Fujuki, 1973). Mercury discharged in an aquatic

system is generally lost to sediments (Clifton and Vivian, 1973).

Mercury may be deposited in sediment by precipitation or by

death of contaminated aquatic organisms which finally settle

down at the bottom as human. Arise in the oxygen content

and pH of water in estuarine zone promotes the formation of

metal hydroxides which constitute significant ‘sink’ of heavy

metal by the effect of co precipitation (Lee et al., 1973). When

mercury in first deposited in sediment, it is rapidly and strongly

complexed to various component of the sediment. Mercury is

not strongly bound to Sulfur containing organic and inorganicparticles. Such type of binding is up to 62% (Walters andWolery, 1974). To a lesser extent mercury is also boundstrongly to clays, minerals sediments containing iron andmanganese oxides, and to find sands. Only a small portion ofmercury in sediment is released into the pore water. In thisindustrial water, mercury appears to be associated primarilywith organic acid as fulvates and humates with little or none ofthe mercury in unbounded form. With or without agitation,the rate of release of mercury from sediment is slow and fromsulfur containing sediments is hardly measurable. Mercury insediments can return to water bodies by two processes. Bystirring of bottom sediments, which resulted in the suspensionof the absorbed mercury particles of its compounds in thebottom. However, suspension is only temporary. Moreimportant process of release of mercury from the sediment isthe methylation by microorganism. This is the key reactionleading to mercury contamination of aquatic organisms.Methylation proceeds only at the top layer of the sediment.

Burrowing animals however, expose mercury present in

deeper layers to the methylation processes (Jernelov, 1970

and 1974). Significant correlation between the concentration

of mercury in sediment and water samples at station I, III and

IV in the present study and nearly similar trend of increased or

decrease of mercury levels in water and sediment samples atthose station suggest that the release of mercury from the

MERCURY POLLUTION AROUND CHLOR - ALKALI INDUSTRY

364

sediment into the water was dependent upon theconcentrations of mercury in the sediment and that the bedsediment of the estuary was not completely saturated withmercury. Reasons for the absence of significant correlation atstation II and E may be large fluctuation in the levels of mercuryin the effluent. The industry was forced to change thetechnology as the old technology was discharging hugeamounts of mercury in to the environment through untreateddischarge of effluents. Our publications, inference inconferences and seminars, public agitation regarding mercurypollution both aquatic and terrestrial, probably forced theauthorities at Jayashree Chemicals to change the technologyfrom Mercury cell electrolytic process to membrane systemwhere no mercury is required. At present due to change intechnology in caustic soda production, the intensity of mercurypollution decreased significantly. Now, the data of recentinvestigation indicated that the effluent channel is almost freefrom mercury but the sediments do contain mercury. Theolder plants and perennial plants showed presence of mercurybut the annual plants and fresh plants did not show significantpresence of mercury.

Transport or mercury, released due to the agitation ormethylation or from the site where the mercury is beingdischarged to the other sites may be transport of the alreadysuspended mercury particles in wave action or force of thewater flow in the river to lower site. Higher tidal action inestuary is responsible for the upstream contamination. Mercuryassociated with the bottom sediment acts as a reservoir ofmercury for long after the primary source is removed and mayinfluence the water quality and aquatic life. High amount of

mercury was detected in the bed sediments event after 45

days of the closure of the chlor-alkali factory (Jernelov, 1974).

Return of the immobilised heavy metals in the bottom

sediments of rivers lakes and sea into the water bodies

constitutes a potential hazard to the water quality and the

aquatic life. Polluted sediments are widely accepted as the

primary source of fish contamination in most aquatic systems.

However, there is no unanimously accepted view on the

pathway of Hg from sediment to fish. A pathway of Hg from

sediment to fish via suspended particulate matters and

zooplankton was suggested by Nishimura and Kumagai (1983).

Levels of mercury in the sediments at the mouth region of the

estuary do not seem to present an immediate threat since a

level less than 1mg Kg–l. dry weight has been considered safe

by the Japanese government (Kudo and Miyahara, 1983).However, if discharge of mercury from the factory continuedat this pace then a tragedy similar to Minamata Bay incidencemay not be avoided in near future. After repeated requests,reminders, publications, agitations etc, at present, the industryhas changed the technology from Mercury cell process toMembrane system for producing Caustic soda, where mercuryis no more used. This is a big relief for the area and for us butwe are definitely worried about the fate of the total mercurywhich was released earlier along with effluent in to theenvironment i.e. Rushikulya River, Rushikulya estuary andBay of Bengal.

ACKNOWLEDGEMENT

The authors wish to thank authorities of Berhampur University

for the laboratory and library facilities provided for the work.

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