Assessment of metal enrichment and bioavailability in mangrove and mudflat sediments of the tropical (Zuari) estuary, west coast of India

Mangrove and mudflat sediment cores at the confluence point of the Cumbarjua Canal and the Zuari River were collected and analyzed to assess metal enrichment and bioavailability, with the background of significant bioaccumulation reported in earlier studies within the Zuari Estuary, a recipient of open-cast mining waste containing Fe and Mn. Metals were enriched in mangrove and mudflat sediments due to additions from natural and anthropogenic sources. Contamination factor showed moderate degree of contamination of Fe, Mn, Cu, and Co in mangroves while of Fe, Mn, and Co in mudflats. Pollution load index suggested metal pollution in the sediments of the Zuari Estuary. Metal speciation study indicated largely lithogenic source of Fe (in mudflats), Cu, Zn, and Co, whereas abundant bioavailable Fe (in mangroves) and Mn (in both mangroves and mudflats) suggest their possible mobilization, preferential accumulation, and bioavailability. Further, sediment quality values indicated toxicity of bioavailable Mn and Co, and risk assessment code revealed medium risk of Mn to sediment associated organisms.