Metal Fractionation in Surface Sediments of the Brahmaputra River and Implications for Their Mobilization

Assessment of metal bioavailability in sediments and bioaccumulation in edible bivalves, and phyto-remediation potential of mangrove plants in the tropical (Kali) estuary, India

The bioavailability of metals (Fe, Mn, Zn, Cu, Co and Ni) in sediment cores (K-1, K-2, K-3 and K-4) and bioaccumulation in edible bivalves were studied to determine the toxicity of metals in the Kali Estuary, India. Enrichment Factor (EF) construed anthropogenic sources of Zn, Co and Ni, while Geo-accumulation Index (Igeo) revealed pollution of Zn and Ni based on total metal analysis. The Pollution Load Index (PLI >1) supported anthropogenic origin of metals in estuary. Metal speciation study indicated bioavailability of metals in sediments. The bioavailable Mn and Co equalled/exceeded the Apparent Effect Threshold (AET) limit (cores K-1, K-3 and K-4) and indicated toxicity to estuarine biota. The metals in Metetrix casta (Fe, Mn, Zn, Cu, and Ni), Saccostrea cucullata (Fe, Mn, Zn, Cu, Co and Ni) and Villorita cyprinoides (Fe, Mn, Zn, Cu, Co and Ni) exceeded the permissible bioaccumulation limit. Thus, revealed metal toxicity to bivalves and labelled them un-safe for human consumption. Translocation Factor (TF > 1) indicated the use of Kandelia candel in phyto-remediation of Fe, Zn, Cu, Co and Ni at station K-3, and Sonnaretia caseoloris in phyto-remediation of Fe, Zn and Ni at station K-4.