Heavy metal pollution and ecological risk assessment in the surface water from a marine protected area, Swatch of No Ground, north-western part of the Bay of Bengal

The primary intends of the study was to ascertain the degree of pollution, spatial distribution, and prime sources of heavy metals in a marine protected area, Swatch of No Ground, north-western part of the Bay of Bengal. Six heavy metals were considered, and their concentrations were found in the decreasing order of Fe > Pb > Cu > Zn > Ni > Cd. Several indices namely Heavy metal pollution index (HPI), Heavy metal evaluation index (HEI) and Nemerow pollution index (NPI), Potential ecological risk index (PER), Hazard quotient (HQ), and Hazard index (HI) were measured to portray the degree of pollution and risk assessment, respectively. HPI, HEI, and NPI suggested that the surface water of North-western Bay of Bengal is under moderate to high degree of pollution due to the higher concentration of Pb, Cu, and Cd. In addition, heavy metal pollution is moderate according to PER, and human health hazards are comparatively low according to HQ and HI. Principal component analysis, hierarchical cluster analysis, and correlation analysis result further reveal that anthropogenic activities are primly influencing the heavy metal accumulation in the study area. Moreover, all of the heavy metals had surpassed the background value of natural surface water in their concentrations. Three of the six heavy metals exceed the lowest biological chronic safety limit, except for Zn, Cd, and Ni recommended by the National Oceanographic and Atmospheric Administration. Hence, to conserve the balance of marine ecology, the local authorities must implement proper treatment of domestic and industrial waste management policies before causing excessive risk.