Heavy metal accumulation in a flow restricted, tropical estuary

Levels of heavy metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn), organic carbon content and textural characteristics in the surficial sediments of Cochin estuary (SW coast of India) and adjacent coast are presented. Anthropogenic inputs from industries have given rise to a gradient in concentration of metals in estuarine sediments. Metal accumulation initiated by precipitation of iron complexes is probably responsible for the enrichment of Cd, Cu, Pb and Zn in the estuary, whereas the coastal sediments did not accumulate them to the same degree. Statistical analyses of the coastal and estuarine geochemical data indicated a different association of elements in the two provinces. The present enrichment factors for Zn (!25) and Cd (!10) place the region among the impacted estuaries in the world. Accumulation of metals in this estuarine system is aggravated by the weak flushing. These pressures are deemed inevitable with growth initiated in the harbour and associated with mega city development in the offing.