Geochemical evidence of anthropogenic impacts in sediment cores from mudflats of a tropical estuary, central west coast of India

Abstract

The concentration of trace metals (Co, Cr, Zn, Cu, and Pb), major elements (Al, Mn, Fe, Ca, Mg, and K), along with the percentage of sediment components (sand, silt, clay, and organic carbon), was determined in three sediment cores, collected from intertidal regions of the Zuari estuary (ZA and ZR) and Cumbharjua canal (CB). The Cores CB and ZR, collected from the upper middle estuarine environment, showed higher values of finer fractions and total organic carbon as well as metals (except of Ca) than Core ZA, which was sampled from the lower estuarine environment. The concentration of trace metals including Mn and Fe was found to be largely dependent on the proximity to mining areas, with Core ZR and Core CB representing the highest metal concentrations (Mn, Fe, Cr, and Zn). Absence of a significant early diagenetic remobilization might have preserved the metal loadings due to mining and industrial activities in Cores ZR and CB. In Core ZA, all the elements except Cu showed significant enrichment in the upper portion. Enrichment factor computed in all the cores was found to be above 2 for all the studied metals except Zn, which suggests a high degree of metal contamination. All these observations indicate that the present study area is under the strong influence of anthropogenic activities, especially in recent years.