Hydrological distribution of physicochemical parameters and heavy metals in surface water and their ecotoxicological implications in the Bay of Bengal coast of Bangladesh.

Accumulation of heavy metals in the coastal ecosystem has become a prodigious problem in any developing countries like Bangladesh. The impact of human activities on some physicochemical parameters and heavy metals was studied in surface water of the Bengal coast, Bangladesh. For ease of description, the fourteen study stations were categorized into four regions of the coastal sites of Bangladesh to determine physicochemical parameters and nine heavy metals like chromium (Cr), nickel (Ni), copper (Cu), arsenic (As), cadmium (Cd), lead (Pb), iron (Fe), manganese (Mn), and zinc (Zn) in water samples. The mean concentrations for water physico-chemistry are temperature (27.7±1.2 °C), pH (7.4±0.27), electrical conductivity (EC) (41.8±6.6 mS/cm), dissolved oxygen (DO) (6.7±0.69 mg/L), turbidity (58.5±12.0 NTU), fluoride (1.4±1.2 mg/L), chloride (126±66.3 mg/L), sulfate (120±90.5 mg/L), nitrate (4.7±2.5 mg/L), and phosphate (4.7±2.5 mg/L). While the mean concentrations of Cr, Ni, Cu, As, Cd, Pb, Fe, Mn, and Zn were 150±58.3, 40.2±10.1, 186±114, 77.3±31.3, 32.7±20.7, 66.7±32.5, 871±268, 178±41.4, and 222±100 μg/L, respectively. As a whole, average concentration of studied metals in surface water followed the decreasing order of Fe > Zn > Cu > Mn > Cr > Pb > As > Ni > Cd. Heavy metals in water samples were much higher than the water quality guidelines for freshwater quality criteria for protection of aquatic life and drinking, indicated that the water of the study areas may create health hazard. The outcomes of the contamination factor (CF), pollution load index (PLI), Nemerow's pollution index (NPI), degree of contamination (Cd), and modified degree of contamination (mCd) varied spatially and most of the water samples were moderately to heavily polluted.