Assessment of metal contamination in the sediments of Vembanad wetland system, from the urban city of southwest India

Abstract

Surface sediments in the Vembanad wetland system, southwest India were analyzed for metals. Assessing the extent of metal contamination in Vembanad wetland surface sediments using individual and combined metal pollution indices shows high heterogeneity of sediment characteristics, sources, sedimentary dynamics and geochemical processes and deciphering natural to anthropogenic contribution. The metal distributions varied greatly in the northern and southern stations suggesting sediment heterogeneity. Sediment concentrations of Cd, As, Pb and Zn were high and exceeded the standard value. Enrichment factor, geoaccumulation index, modified degree of contamination and pollution load index showed that the sediments are moderate to extremely polluted in most of the northern sites. It suggests that Cd and As fell under the extreme amount of metal contamination followed by Pb and Zn which comes under strongly contaminated level. The close relationship of sedimentological and geochemical parameters could be due to the intrinsic relationship of the physico-chemical condition and provenance to the Vembanad wetland system. The main contaminated metal contribution appears to be the anthropogenic input and a small amount from the weathered rocks and sediments present in the course of the rivers. The extent of metal pollution in the Vembanad wetland system implies that the condition may impact the biota and also human health in the vicinity of the wetland.