Spatial analysis, ecological risk assessment, control factors, and sources of heavy metal pollution in the shelf surface sediments of the southwest Bay of Bengal, India

Abstract

Heavy metals such as Mn, Zn, Ni, Cu, Pb, and Co besides Hg were determined to assess the distribution, contamination status, and possible sources in the shelf surface sediment of the southwest Bay of Bengal. Physico-chemical parameters significantly influenced the metals. Higher concentrations of all the metals except Hg were recorded in the Andhra Pradesh and Chennai waters than in waters south of these in Tamil Nadu and Puducherry. Significant differences between areas were found only for Co, Cu, Mn, and Ni. Generally, the pollution indices, namely Contamination factor (CF = <1), Geo-accumulation index (Igeo= <0), Potential contamination index (Cp=<1), and Potential ecological risk factor (Eri=<40) and Risk factor index (RI =<95) revealed the unpolluted nature of marine sediments by Mn, Zn, Ni, Cu, Pb, Co. However, the Cuddalore-SIPCOT transect was moderately and considerably contaminated with Hg (CF = 1.538, Igeo=>0.04, Cp=<1.6, Eri=<80- >40, RI = 95> - <190–190> - <380). The source of Hg was traced to the discharges from the nearby industries. Principal component analysis (factor analysis) suggested the natural input derived from terrigenous detritus materials (lithogenic factor) to influence the distribution of most of the considered metals in the southwest Bay of Bengal. The results are likely to be useful for the coastal zone regulation authorities to develop sustainable management strategies.