The historical trend in trace metal enrichment in core sediments from Cochin Estuary, Southwest coast of India

•Historical trace metal contamination of Cochin Estuary have studied by analysing the sediment cores.•Age depth relationship of metallic pollution determined using 210Po isotope.•Cores samples deliver information on industrial past and the depositional pattern of trace metal input.•Increase in elemental concentration after 1990's reveals its increment and recent addition.•This study suggests regional specific preindustrial background concentration of Zn, Pb, Cu and Cd.