Textural and geochemical evaluation of the surface sediments from the continental shelf of Southwestern Bay of Bengal, India

Abstract

An investigation was done to determine the texture, organic matter content, and geochemical characteristics of sediments collected from the continental shelf of the South Western Bay of Bengal. The present study portrays the abundance of sand followed by slightly muddy sand, muddy sand, sandy mud, sandy, and slightly sandy mud in the study area. The mean size of the sediment ranges from 0.40 to 3.57 mm (coarse sand to very fine sand). The sediments are very well to very poorly sorted, coarsely skewed to fine skewed, and platykurtic to very leptokurtic in nature. Trace metals, such as Cu, Co, Fe, Mn, Pb, Zn, Cr, and Ni were analyzed. A relatively high percentage of organic matter is attributed to the predominance of finer sediments entering through the minor and major rivers. The higher trace metal concentration in the study area is closely associated with mud content and Fe is the most abundant trace metal in the study area. Formation of Fe- and Mn-hydroxides in the near-shore regions is responsible for scavenging Pb, Zn, Cu, Ni, and Cr and effectively incorporating them into the inner shelf sediments. Among all the trace metals, the concentration of Co, Pb, Cr, and Ni is found to be higher than the average crustal abundance value marking the role of anthropogenic sources predominantly from industrial, agricultural, scrap metal recycling, sewage, and tourism activities.