Mudflats in lower middle estuary as a favorable location for concentration of metals, west coast of India

Abstract

Present study was an attempt to understand hydrodynamic conditions and the main factors regulating the distribution of metals in mudflats in the recent past along Mandovi Estuary. Sediment cores of 20 cm length were collected from three mudflats viz. near the mouth, lower middle and upper middle regions representing monsoon season from Mandovi Estuary. Cores were sub sampled at every 2 cm interval and analyzed for sand, silt, clay, organic carbon and selected metals. Sand percentage is the highest in the mudflat situated near the mouth (Betim) and finer sediments are higher in the lower (Karyabhat) and upper (Ribander) middle regions of the estuary. Organic matter associated more with finer sediment fractions at Karyabhat and Ribander (2.19% to 2.37%) mudflat cores as compared to Betim (0.13%). The sediments of Betim fall in the class I to IV, whereas sediments of two cores collected from middle estuarine region fall largely in class III. Sediment samples were analyzed for selected metals. Fe is highest in Ribander mudflat as compared to other cores. Cr, Co, Cu and Pb distribution agrees largely with the pattern of Fe in all the cores. Distribution of Cu and Pb also agrees with that of Mn. Zn and Ni follow the pattern of Co agreeing Fe distribution pattern. Concentration of Fe and Mn along with Ni, Zn, Cr, Pb and Cu are higher in Karyabhat.