Distribution of nondetrital trace metals in sediment cores from Ennore Creek, Southeast Coast of India

Two sediment cores collected from the Ennore Creek, southeast coast of India, were studied for sand-silt-clay contents, CaCO₃, organic matter and nondetrital trace metals in order to understand the geochemical processes controlling the distribution of metals including anthropogenic factors, if any. Core 1 from the intertidal region with sandy sediments shows lower metal contents, except for the top oxic layer, when compared to core 2, consisting mostly of silty sand with significant percentage of clay and showing higher concentration of metals. The sediments of core 1 show an oxidized upper layer where metals are mobilized and diffused from less oxidized deeper layers due to early diagenetic processes. While Mn, Fe, Ni, Co, Zn and Cr are diagenetically modified, anthropogenic processes seem to influence Pb, Cd and, to some extent, Cr and Zn. Discharge of wastes from the nearby located thermal power plant, fertilizer (phosphate) industry, electroplating industries, and sewage are identified as additional possible sources for these metals. Detrital elements (Si and A1) do not show any relation with the metals studied, except Fe and A1 in core 1. Textural changes at three subsurface depths represented by silty sand (15, 40 and 50 cm) in core 1 and clayey sand (10, 32.5 and 55 cm) in core 2 are probably correlatable with the low rainfall intensity suggesting past drought conditions in the study area. A distinct increase in concentrations of nondetrital trace metals Pb, Cr, Zn and Cd at a depth of 37.5 cm in core 2 is probably related to the beginning of intense industrialization around 1970s in the area under investigation.