INTRODUCTIONIndustrial, agricultural and domestic wastes are continuouslydischarged into water-bodies. Such pollutants, particularlyheavy metals, can endanger public health by being incorpor-ated into the food chain. Heavy metals are not biologicallydegraded like many organic pollutants; thus, heavy metalstend to accumulate, particularly in sediments in associationwith organic and inorganic matter, and involves adsorption,complex formation and chemical combination.

This paper documents and discusses the results of aninvestigation of heavy metal concentrations in various com-ponents of a man-made tropical lake, Shahpura Lake, whichis located 23°18� N, 77° 27� E, and 488 m above mean sealevel. The lake covers an area of 2.6 km2 , has a mean depthof 3.0 m, and a catchment area of 8.3 km2. The lake originatedfrom stone quarrying activity adjacent to the village ofShahpura. The basin later filled with rainwater and surfacerun-off. In 1947, the capacity of the water-body was increasedby the construction of an embankment. Sewage from a

part of the new Bhopal township is discharged into the lake, and the level of pollution has increased in recent years.

Approximately 110 tons/day solid waste is generatedwithin the catchment and 9.6 million litres per day of sewageenters the lake from residential areas in the catchment.

MATERIALS AND METHODSThe five sampling stations that were selected took intoaccount topography and other significant features, and fourwere positioned in lakes while one was in a sewage inletdrain.

Water samples were collected monthly for 24 months.Fish, sediment and plankton samples were collected annu-ally. Samples were digested and preserved according to stan-dard methods and an atomic absorption spectrophotometer(Perkin Elmer 2380; Perkin Elmer Corporation, Norwalk,U.S.A.) was used to determine the concentration of heavymetals.

RESULTS AND DISCUSSIONMean concentrations of metals in the lake water are shownin Table 1, which reveals that the concentrations of cobalt,

Lakes & Reservoirs: Research and Management 2003 8: 1–4

Heavy metal pollution in a sewage-fed lake of Bhopal,(M. P.) India

Pradeep Shrivastava,1* Alok Saxena1 and Abha Swarup2

1Department of Limnology, Barkatullah University, Bhopal 462 003, India, and 2Council of Science and Technology, Bhopal 462 003, India.

AbstractShahpura Lake receives untreated domestic sewage from residential areas in Bhopal city. Analysis of water, plankton, fishand sediment reveals that the lake is contaminated by certain heavy metals. The concentrations of some of these metals including iron and manganese were within acceptable limits, whereas others including chromium, nickel, zinc and lead werenot within acceptable water quality limits. Metal concentrations in the sewage inlet drain and lake sediment were comparedwith published criteria. The comparison revealed that the metals in the sediment ranged from the ‘non-polluted’ to the ‘heavypollution’ categories. The reference dose was calculated by the adoption of the United States Environmental Protection Agencyreference dose factor, and the result reveals that the local population is not exposed to undue health risks. Concentrations ofheavy metals in the water increased during the second year of the study, indicating an increase in the pollution load on thesystem. This might increase the bioaccumulation levels in fish and increase the actual dose of metals to which the local population will be exposed.

Key wordshealth risk, metal accumulation, metal contamination.

*Corresponding author. Email: hodlt@bom3.vsnl.net.in

Accepted for publication 13 July 2001.

copper, iron, manganese, nickel, zinc and lead increased during the second year of the study in both the sewage inletdrain and the lake water. The concentrations of chromium,nickel, zinc and lead were beyond the limits set for aquaticlife by the United States Environmental Protection AgencyUSEPA (1976), United States National Academy ofSciences/National Academy of Engineering (1973),Anonymous (1974), International Joint Commission GreatLakes (1974–1976) and Canada (1972). The mean concen-trations of iron and manganese, although higher than those of other metals, were within the prescribed limits of surface-water quality for aquatic life.

The accumulation of metals in the sediment is mainly aresult of biogenous and lithogenous formations (Forstner &Wittman 1979). Enrichment of zinc in the sediment mightbe the result of the input of domestic sewage (Facetti et al.1998). Lead, mostly from lead compounds used in gasolineas additives, can be transported by the atmosphere andappear in basin sediment (Nriagu 1979), and comes fromurban run-off after having been emitted by vehicles, which

is then deposited on the streets and washed off by rainfall(Laxen & Harrison 1997). The lake is surrounded on threesides by major roads with high vehicular traffic. A motorvehicle workshop is also situated in its immediate catchment.Occurrence of lead in the lake might therefore be attributedto this. Bottom sediment cannot be considered as a per-manent sink of pollutants. Metal mobilization in the sedimentenvironment is dependent on physico-chemical changes inthe water at the sediment–water interface. The precipitationof lead, copper, iron, chromium and zinc might be the resultof alkaline pH in the form of insoluble hydroxides, oxidesand carbonates. Metals such as chromium, copper and nickelhave interacted with organic matter in the aqueous phaseand settled, resulting in a high concentration of these metalsin the sediment, a situation also observed by Pande andSharma (1999). Iron and manganese hydroxides are goodsites for metal binding in sediment and soil. These com-pounds are unstable and reduced to lower oxidation statesin low dissolved oxygen concentration in water at the bottom of the lake, resulting in the metals being released

2 P. Shrivastava et al.

Table 2. Heavy metal concentration in the sediment, plankton and fish flesh samples collected from the lake (1995–1996 and 1996–1997)

Sample number Metal Soil of nearby Sewage inlet Lake sediment Plankton Fish flesh

study area drain sediment (mg/kg) (mg/g) (mg/kg) wet

(mg/kg) (mg/kg) n = 2 n = 2 weight

n = 2 n = 2 A B

1. Chromium 15.0 21.000 18.000 BDL 0.66 BDL

2. Cobalt 3.7 9.000 7.000 0.024 BDL 4.12

3. Copper 90.3 83.640 87.300 BDL 2.64 1.28

4. Iron 2680.0 5044.000 5264.600 5.388 81.20 1.24

5. Manganese 248.9 277.000 386.000 4.109 2.98 BDL

6. Nickel 17.0 27.000 38.000 BDL 0.12 5.72

7. Zinc 50.4 0.122 0.028 0.188 8.60 10.72

8. Lead BDL 0.020 0.019 0.185 4.40 7.60

BDL, below detection limit; n, frequency of sampling.

Table 1. Concentration of metals in water samples during the study period

Sample number Metal Sewage inlet drain Lake water*

1995–1996 1996–1997 1995–1996 1991–1997

1. Chromium 0.109 0.034 0.0480 0.011

2. Cobalt 0.024 0.091 0.0110 0.087

3. Copper 0.001 0.016 0.0005 0.012

4. Iron 0.140 0.306 0.1140 0.413

5. Manganese 0.110 0.223 0.0690 0.156

6. Nickel 0.020 0.060 0.0070 0.070

7. Zinc 0.011 0.039 0.0080 0.030

8. Lead 0.010 0.027 0.0060 0.041

*Mean concentration of four sampling stations.

into the overlying water, thereby becoming available for utilization by phytoplankton biomass. Mobilization of zinc and lead is also affected by higher concentrations of manganese in the sediment (Fernandes et al. 1994).Concentrations of metals in the sediment are shown in Table 2. Chromium, lead and zinc in the sediment were categorized as ‘non-pollution’, nickel was categorized as‘moderate pollution’ and copper was categorized as ‘heavypollution’, as per the criteria for sediment concentration ofmetals established by the USEPA (Nichlos et al. 1991).Mineralogical studies of polluted sediments indicate thatheavy metals are found to be associated with fine particlesof silt clay that have large surface areas and the tendencyto adsorb and accumulate metal ions due to their inter-molecular forces.

Phytoplankton might be a bioindicator of the presence of metals in an aquatic ecosystem because it eliminates metals from the water, accumulates and stores them over a long period, even when the concentrations of metals in the water is low. High water temperature, oxygen concentration, basic pH and hardness of lake water increase heavy metal toxicity (Forstner & Wittman 1979).The observed concentrations of metals in the plankton

are depicted in Table 2. The occurrence of higher concen-trations of iron and manganese in phytoplankton is attributed to their higher concentrations in the lake water and sediment.

Study of fish muscle is one of the means to investigate theamount of heavy metals entering the human body in food.Concentrations of metals in fish muscles that were observedduring the present study are shown in Table 3. Comparisonwith metal concentrations were observed by some authors,as shown in Table 3, were found to be higher than thosereported by Ayyadurai et al. (1994) and Fernandes et al.(1994).

The reference dose was calculated by the adoption of the USEPA reference dose factor, which is an estimate inmg/kg of fish muscles per day of an exposure level that would not be expected to cause adverse effects whenexposure occurs during a life-time period. The fish consump-tion rate was estimated to be 50 g per day for the hypotheticalcritical population, but the actual dose has been calculatedand depicted in Table 4. It is evident from the result that the local population is not exposed to unacceptable doses of metals with respect to zinc, nickel, manganese andchromium. The calculation of metal doses does not, however,

Heavy metal pollution in India 3

Table 4. Metal dose exposure by local population

Sample number Metal Rfd*† Acceptable* Actual dose exposed to local population on

(mg/kg per day) dose fish consumption basis during present

(mg/kg per day) study (mg/day)

1. Zn 2.0 � 101 14.00 0.480

2. Ni 2.0 � 102 1.40 0.146

3. Mn 2.0 � 101 14.00 0.074

4. Cr(cl) 5.0 � 103 0.35 0.016

*Fernandes et al. (1994). †Rfd, reference dose factor.

Table 3. Comparison of metal content in fish muscle observed by different authors

Sample no. Description Metal (mg/kg) Author

fresh weight

Cda Crb Coc Cud Fee Mnf Nig Znh Pbi

1. River Cauvery (India) – – – 1.26 7.79 1.00 – 7.61 – Ayyadurai

et al. (1994)

2. Jacare Pagua

Lagoon (Brazil) 0.01 0.08 – 0.40 2.40 0.40 0.02 4.60 0.02* Fernandes

et al. (1994)

3. Shahpura Lake

Bhopal (India) BDLj 0.33 2.06 1.96 41.20 1.49 2.92 9.67 6.0* Present study

1995–1997

aCd, cadmium; bCr, chromium; cCo, cobalt; dCu, copper; eFe, iron; fMn, manganese; gNi, nickel; hZn, zinc; iPb, lead; jBDL, below detection

limit. *Results are the mean concentrations in fish muscle of the species of varied food habit.

take into account metals entering the local population byother pathways (Fernandes et al. 1994).

The study revealed that Shahpura Lake is contaminatedwith heavy metals. Although the metals are accumulated in the food chain, the observed concentrations in are safe for human consumption, and bioconcentration requires theuptake of metals mainly from water (Forstner & Prosi 1978;Manson 1996). Concentration in sewage from the inlet drainand lake water increased during the second year of the studyas a result of the 78.42% increase in rainfall during this periodof the study, which resulted in an increased run-off volumeof waste water from the catchment area.

ACKNOWLEDGEMENTSThe authors would like to thank the staff members of the Research Centre at the Madhya Pradesh PollutionControl Board in Bhopal for their cooperation and assistance.

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4 P. Shrivastava et al.