Depositional environment and metal distribution in mangrove sediments within middle region of tropical estuaries, Karnataka, west coast of India

Abstract

Two mangrove sediment cores representing middle region of the Panchagangavali Estuary (one each at Chakra Estuary and Halady Estuary) were analysed for sedimentological and geochemical parameters. The data revealed prevalence of uniform violent hydrodynamic energy condition in the Chakra Estuary (core G3), whereas, varying and relatively calm hydrodynamic energy conditions in the Halady Estuary (core G4). All the studied metals (Al, Fe, Mn, Ni, Zn, Cu and Cr) were of mainly lithogenic origin in both the estuaries, except Co which may be derived from a different source. The Enrichment Factor (EF) indicated deficiency to minimal enrichment of Fe, Mn, Ni, Zn, Cu and Co whereas, Cr showed a moderate enrichment in sediments. However, metals Fe, Ni, Zn, Cr and Cu were relatively enriched in the top section 3 of Halady Estuary indicating their enhanced release in recent years possibly due to increased human activities and high rain fall in the catchment area.