Reading source and processes with time from mangrove sedimentary environment of Vaitarna estuary, west coast of India

Abstract

Two mangrove sediment cores collected from Vaitarna estuary were studied for the distribution of sediment components (sand, silt, clay and organic carbon), major elements (iron, manganese and aluminium) and trace metals (copper, zinc, cobalt, nickel and lead). Both the cores showed a gradual decrease in sand and an increase in clay component from bottom to surface. This change in the type of sediment deposited was attributed to the change in hydrodynamic energy conditions resulting from both natural (decrease in rainfall) as well as anthropogenic activities (construction of dams, freshwater diversion, etc.). Metals were found to be strongly associated with sand, silt and clay, while Fe-Mn oxyhydroxides and organic matter were found to play a minor role. They also showed similarity in their distribution patterns, thus suggesting a common lithogenic source. Enrichment of iron and zinc in core S5 and manganese, copper, cobalt and lead in core S6 towards surface however suggested increase in anthropogenic additions in recent years.