Geochemical assessment and fractionation of trace metals in estuarine sedimentary sub-environments, in Mumbai, India

• Sediment cores studied from mudflat and mangrove regions of an estuary.
• Higher sediment contamination seen mudflat core as compared to mangrove core.
• Metals contributed from Geogenic as well as Anthropogenic sources.
• Metal fractionation showed most of the metals in residual fraction except Mn and Zn.
• Potential risk to the estuarine system if the sediment gets disturbed.

The distribution and concentrations of selected metals (Fe, Mn, Cu, Pb, Co, Zn and Cr) in intertidal regions (mudflat and mangrove) of Ulhas estuary, located in Mumbai, India were studied. The sediment metal contamination was assessed by applying Enrichment Factor (EF), Anthropogenic factor (AF), Contamination factor (CF) and Pollution load Index (PLI). Also, Sediment Quality Guidelines (SQGs) by Environmental Protection Agency was used to determine the risk of increased metal levels to biota. Amongst the two sub-environments studied, the mudflat region exhibited higher metal contamination than the mangrove region necessitating fractionation analysis of the core. The geochemical fractionation analysis showed higher metal percentage in the residual fraction, except for Mn and Zn. The fractionation results, in general, indicated that contamination due to the metals- Mn and Zn might pose a potential risk to the estuarine system if the sediment gets disturbed with time.