Abstract
The current study aimed to evaluate the distribution and status of heavy metal contamination of surface water in the Nijhum Dweep, northern Bay of Bengal. Ten surface water samples were collected to determine the heavy metals and the associated human health risk. The mean concentrations of the selected heavy metals were ranked in descending order of Fe (3.412 mg/L) > Mn (0.3911 mg/L) > Pb (0.3 mg/L) > Co (0.2918 mg/L) > Zn (0.230 mg/L) > Ni (0.1943 mg/L) > Cu (0.167 mg/L) > Cd (0.11 mg/L) > Cr (0.077 mg/L). All the metals except Cd, Pb, and Ni were found uncontaminated, and these three metals influenced the values of heavy metal pollution indices. Heavy metal evaluation index (HEI), heavy metal pollution index (HPI), and Nemerow pollution index (NI) revealed that the surface water of the study area is low to moderately contaminated by these selected heavy metals. Hazard quotient (HQ) and hazard index (HI) for adults and children showed no non-carcinogenic risk of heavy metals from dermal exposure pathways except station number 4 at the south of the Nijhum Dweep due to high Mn concentration. No possible carcinogenic risk was found from the analyzed metals. Several local sources of heavy metals were found during the field investigation, such as domestic effluents, small-scale metallurgical activities, oil spills from ships, and fishing trawlers. Again, industrial effluents and agrochemicals from upstream regions also contribute to heavy metal pollutions in downstream coastal regions of Bangladesh. Even though the surface water pollution level is low in the study area, the authority should take proper management and monitoring strategy for sustainability.
Heavy metals distribution and contamination in surface water of the Bay of Bengal coast
