Md. Saiful Islam
Faculty and Graduate School of Environment and Information Sciences, Yokohama National University, Yokohama, Kanagawa, Japan
Md. Kawser Ahmed
Department of Oceanography,University of Dhaka, Dhaka, Bangladesh
Md. Habibullah-Al-Mamun
Department of Fisheries, University of Dhaka, Dhaka, Bangladesh
Bangladesh; Bioaccumulation; Fish; Health risk; Metal pollution; Sediment
Korotoa River located at the northern part of Bangladesh
Risk Management in Agriculture
Heavy metal, Fish
Description of the study area: This study focused on the Korotoa River located at the northern part of Bangladesh. The study river originated from the Himalayas, the mother of numerous rivers.Originating from the northern frontier of Bhutan, the Korotoa enters Bangladesh territory through the Darjeeling and Jalpaiguri districts of West Bengal, India, and forms the boundary between Dinajpur and Rangpur districts in Bangladesh. For the present study, we selected sites of the Korotoa River that flow through the Bogra District urbanized area with an area of about 71.56 km2. The total population of this district is about 350,397, and it is situated between 2484091.8200N and 8937029.5700E. Thousands of villages, towns, and commercial places such as Shibganj, Mohasthangarh, Bogra, and Sherpur have been built on both sides of the Korotoa River. Mohasthangarh, the capital of ancient Pundranagar, is still there beside the Korotoa as a witness of history in Bangladesh. Sample collection and preparation: The sampling was conducted in August and September of 2013. A total of 30 composite sediment samples were collected from 10 different locations of the Korotoa River situated in the northern part of Bangladesh. At each point, 3 composite sediment samples were collected using a standard protocol.34The riverbed sediment samples were taken at a depth of 0–5 cm using a portable Ekmangrab sampler. Three composite samples of mass approximately 200 g were collected at each station. The upper 2 cm of each sample was taken from the center of the catcher with an acid-washed plastic spatula to avoid any contamination from the metallic parts of the sampler. We collected about 110 samples of eleven different fish species: Channa punctata, Awaous grammepomus, Anabastestudineus, Heteropneus tesfossilis, Neotropius atherinoides, Colisa fasciata, Channa striata, Notopterus notopterus, Batasio batasio, Coricaso borna, and Puntius chola. Fish species were collected using nylon net with the help of fishermen at almost the same locations where the sediments were collected. After collection, fish samples were carefully washed immediately with distilled water, and the edible parts of the fish (muscle tissue) were cut into small pieces and oven-dried at 70–80 C to attain constant weight. The moisture content of the fish was calculated by recording the difference between fresh and dry weights.The dried fish samples were crumbled with a porcelain mortar and pestle and sieved through a 2-mm nylon sieve and stored in airtight, clear zip-lock bags in freezer condition until chemical analysis was performed. Analytical procedure for heavy metals: All reagents used were Merck analytical grade (AR). Deionized water was used for solution preparation. For metal analysis, about 0.3 g of sediment and 0.5 g of the dried fish samples were digested with 15 mL of concentrated HNO3, H2SO4, and HCIO4 in a 5:1:1 ratio at 80C until a transparent solution was obtained.35The digested samples of sediment and fish species were filtered through Whatman no. 42 filter paper, and the filtrates were diluted to 50 mL for sediment and 25 mL for fish with deionized water. All samples were stored at ambient temperature before analysis. For heavy metals, samples were analyzed using an atomic absorption spectrometer (Perkin Elmer Analyst 300). Blank samples were analyzed after 8 samples. Concentrations were calculated on a dry weight (dw) basis for sediment and a wet weight basis for fish samples. All analyses were replicated 3 times. The precision and analytical accuracy were checked by analysis of standard reference material NMIJCRM 7303 (lake sediment) and DORM-2 (dogfish muscle) from the National Research Council, Canada. Comparison is made with the certified values, which in both cases confirmed that the sample preparation and operating condition of the instrument provided good levels of accuracy and precision. Analysis of physicochemical properties of sediment: The pH of sediments was measured in a 1:2.5 sediment-to-water ratio. The suspension was allowed to stand overnight prior to pH determination. The pH was measured using a pH meter with the calibration of pH 4.0, pH 7.0, and pH 9.0 standards. For electrical conductivity (EC) determination, 5.0 g of sediment was taken in50 mL polypropylene tubes. Then, 30 mL of distilled water was added to the tube and was shaken for 5 minutes. After that, EC was measured using a portable EC meter (Horiba D-52). Percent nitrogen (%N) and organic carbon (%C) of sediment were measured using an elemental analyzer (vario EL III, Elenemtar, Germany). For total nitrogen (TN) and total organic carbon(TOC) determination, sediment samples were weighed in tin or silver vessels and loaded in the integrated carousel. In a fully automatic process, the transfer of the sample through the ball valve into the combustion tube was performed. Each sample was individually flushed with carrier gas to remove atmospheric nitrogen, resulting in a zero blank sampling process. The catalytic combustion was carried out at a permanent temperature of up to1200C. The element concentration from the detector signal and the sample weight on the basis of stored calibration curves were measured. Metal bioaccumulation in fish species: Metal concentrations in fish species and sediments from the studied river were used for calculating the biota-sediment accumulation factor (BSAF). The BSAF is an index of the ability of fish species to accumulate a particular metal with respect to its concentration in sediment. It was calculated by the following equation.
ARCHIVES OF ENVIRONMENTAL & OCCUPATIONAL HEALTH 2017, VOL. 72, NO. 1, 26–38
Journal