Metals bioavailability and toxicity in sediments of the main channel and subchannel of a tropical (Mandovi) estuary, Goa, India

Sediment cores collected representing main channel and subchannel mudflats of Mandovi estuary were analyzed for sediment components, total organic carbon (TOC), the bulk metal concentration of Fe, Mn, Zn, Co, and Pb, and their geochemical phases. The sediment of the subchannel was characterized by relatively high average clay and concentration of Mn and Zn whereas Pb along with silt was high in the main channel indicating a difference in hydrodynamic conditions and depositional environment between the two study sites. In the bioavailable phase Mn, Co, and Pb showed higher values indicating that they can be toxic to the environment and also to the sediment associated biota in both subchannel and main channel. Further, Mn and Pb were available more in the exchangeable and carbonate bound fractions and therefore may pose a toxicity risk to the sediment associated biota.