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Heavy Metals Concentration in Water, Sediments and Their Bioaccumulation in Some Freshwater Fishes and Mussel in Dhaleshwari River, Bangladesh

Md. Kawser Ahmed*
Department of Fisheries, University of Dhaka, Dhaka-1000, Bangladesh

Sharif Ahamed
Department of Zoology, Jagannath University, Dhaka, Bangladesh

Safiur Rahman
Bangladesh Atomic Energy Commission, Savar, Dhaka, Bangladesh

Md. Rezaul Haque
Fisheries and Marine Resource Technology Discipline, Khulna University, Khulna, Bangladesh

Md. Monirul Islam
Department of Fisheries, University of Dhaka, Dhaka-1000, Bangladesh

Abstract/ Executive Summary:

The spatial and temporal distribution of heavy metals in water, sediment, fish and mussel of Dhaleswari River, Bangladesh were determined by atomic absorption spectrophotometer. In water, the concentrations of Ni, Pb, Cd, Cr and Cu varied seasonally and spatially from 5.47-9.74, 38.25-63.28, 5.29-8.20, 378.87-501.11 and 98.37-188.08 μg/L, respectively. The sediment also showed a spatial and temporal variation of Ni, Pb, Cd, Cr and Cu ranges from 135.02-231.44, 58.19-70.26, 2.11-4.14, 95.76-141.27 and 31.53-76.52 mg/kg, respectively. These variations are likely to be due to different collection spots with point and non-point sources and seasons. The concentrations of Cd, Cr and Cu were higher, while Ni and Pb were lower in water than those of sediment. In Trypauchen vagina, a bottom-living fish, the concentration of Ni, Pb, Cd, Cr and Cu varied seasonally from 6.35-9.56, 6.14-8.03, 0.51-0.73, 6.92-12.23 and 5.43-9.45 mg/kg, respectively. The concentrations of heavy metals in this fish were much lower than those of water and sediment. In Glossogobius giuris, also a bottom-living fish, the concentration of Ni, Pb, Cd, Cr and Cu varied seasonally from 4.75-10.17, 4.25-8.17, 0.61-0.71, 7.15-11.92, and 5.17-7.48 mg/kg, respectively, which were slightly lower (except Cd) than those of T. vagina. In Lamellidens marginalis, a freshwater bivalve, the concentration of Ni, Pb, Cd, Cr and Cu varied seasonally from 6.07-11.32, 7.03-59.21, 0.56-7.23, 9.38-501.11 and 7.55-183.87 mg/kg, respectively. The concentrations of all the heavy metals studied were much higher in mussel than those of fish that indicate the greater rate of bio-accumulation in mollusc.

Keywords: Aquatic pollution, Glossogobius giuris, Lamellidens marginalis, Trypauchen vagina

Location: Dhaleshwari River, Bangladesh

Start Date:

End Date:

Program Area: Risk Management in Agriculture

Commodity: Heavy metal

Objectives:

The objectives of this study were to determine the concentration of heavy metals: nickel (Ni), copper (Cu), chromium (Cr), cadmium (Cd) and lead (Pb) from water, sediments, fish and mussels from Dhaleshwari River, Bangladesh.

Methodology:

During pre-monsoon, monsoon and post-monsoon of 2001-2002, samples of water, sediment, two species of adult fish, Trypauchen vagina (Bloch and Schneider 1801)locally called cheua and Glos-sogobius giuris (Hamilton 1822) locally called bila and one species of adult bivalve mollusc (freshwater pearl mussel; Lamelli-dens marginalis)were collected from three stations of Dhaleswari River, namely Station 1 (in the Buriganga-Dhaleswari confluence; locally called old launch ghat), Station 2 (in the Shitalakkha-Dhaleswari confluence; locally called launch ghat) and Station 3 (in the Dhaleswari-Meghna confluence; locally called Char-Kishor-gang) . Both T. vagina and G. giuris are under the same family (Gobii-dae) of order Perciformes. Cheua is demersal, occurs along the bottom in tidal rivers and estuaries and stays close to a self-dug burrow, while bila is benthopelagic, found in clear to turbid streams with rock, gravel, or sand bottoms, feeds on small insects, crustaceans and small fish (Shafi and Quddus 1982). The water samples were collected with the help of 1 L plastic bottles, which were previously soaked with a mixture of distilled water (975 ml), 2% HNO3 (20 ml) and H2SO4 (5 ml) for about 24 h. On the next day, these bottles were scrupulously washed several times with distilled water, rinsed with double distilled water and then kept in an oven (60-70°C). The bottles were then ready for sample collection. The sediment samples were collected by a vertical corer and an Ekman grab sampler. The water and sediment samples were acidified immediately with 2 ml of HNO3 per litre of water and preserved in refrigerator at 4°C for laboratory analysis. The fishes which were supplied by the local fishermen collected by netting, were identified according to Shafi and Quddus (1982). All samples were taken in different polythene bags. The mollusc samples were collected with an Ekman grab sampler, stake net (locally called Behundi net) and by hand. After collection mud and other fouling substances were removed and the molluscs were then cut open with the aid of a Teflon-coated stainless steel knife and then dried to room temperature and weighed. The soft flesh was dried in an oven at 90°C to an anhydrous state until a constant weight (dry weight) was obtained. After collection, the sediment and fish samples were washed, weighed and dried in an oven at 105°C until gaining constant weight. After cooling in a dessicator, all the samples were ground by a carbide mortar and pastel to make powder and homogenised. The powdered sediment, fish and mussel samples were finally stored in a pre-cleaned dry plastic bottle and preserved in a dessicator for further analysis. For the quantitative analyses of Ni, Cu, Cr, Cd and Pb, the samples were digested. Dried (0.5 g) powder was placed in a long test tube. Then 1 ml 70% HClO4, 4 ml concentrated HNO3 and 1.5 ml concentrated H2SO4 were added into the test tube. The samples were then heated gently in an oil bath (~100°C) until the solid mass dissolved. If sample was not clear, 4 ml of HNO3 was added into the test tube and repeated until the solution was clear. Finally, the mixture was boiled at about 210°C in a paraffin oil bath in order to drive off the acids except for H2SO4 and then it was cooled down at room temperature. Blank digestion was also performed to quantify possible contamination during sample preparation and analysis. A standard solution of the elements Ni, Cu, Cr, Cd and Pb were prepared by pipetting the required amount of the solution from the stock solution, manufactured by Fisher Scientific Co., USA. The standard solution was prepared before every analysis of the current work. The samples were analyzed by using air acetylene flame with combination, as well as single-element hollow cathode lamps into an atomic absorption spectrophotometer (Shimadzu, AAS-6800). The analytical quality of the work was checked by analysis of standard reference materials: NBS-SRM-1573, tomato leaves and NBS-SRM-1566, oyster tissue, prepared by the National Bureau of Standards, Washington DC, USA. The analytical procedures were also calibrated against the above standard reference materials. The average recovery ranged between 94 to 107%. Statistical software SPSS ver. 12 was used to analyse the data using ANOVA followed by LSD post-hoc for multiple comparisons at a 5% level of significance to determine the significant difference among mean values. In addition, the correlation matrix was carried out by Microsoft Excel.

Source of Information: Terrestrial and Aquatic Environmental Toxicology 3 (1), 33-41

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The results of this study indicate that the concentrations of heavy metals in the river environment of Bangladesh are higher than the permissible levels and the aquatic animals are not safe for human consumption. With the gradual development of industry, intensive use of pesticides and untreated domestic sewage as well as polluted discharge from neighbouring may further deteriorate the situation in the future.

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