Paleo-Reconstruction of Heavy Metal Accumulation during the Holocene in Coastal Odisha, India

Abstract

This study evaluates spatial trend and distribution history of selected metals in the complex coastal environment of Odisha, India. The main objective is to analyse metal enrichment and level of contamination in sediment deposits. It is also attempted to evaluate the past depositional environment and prevailing process leading to metal enrichment and contamination. Three sediment cores up to a depth of 10 m were collected from older beach deposit of Chandbali (CB) and paleochannels of Agiviligan (AG) and Kasturikaran (KK) villages located along River Baitarani, coastal Odisha. The study area, to a large extent, is a transition zone of terrestrial and marine sediments. The assessment of metal contamination is based on spatial and down-core variability of selected metals- Al₂O₃, MnO, Cr, Co, Cu, Zn, and Pb against their background values. Contamination is examined using enrichment factor (EF), contamination factor (CF) and geo-accumulation index (I_geo). The study exhibits a complex pattern of metal distribution over space and time. The sediments are enriched and contaminated with MnO, Cr, and Pb not only in the surface layers but also in the deeper layers such as CBL4 (–7.3 m), CBL5 (–7.9 m), CBL6 (–10 m), AGL3 (–6 m), AGL5 (–10 m) and KKL3 (–8 m). Metal enrichment in deeper layers can be associated with the past depositional environment, prevailing processes, geology and geomorphology of the region. In the surface layers, metal contamination can result from recent anthropogenic activities like untreated industrial waste from Ferro-alloys Corporation Ltd. (FACCOR) and domestic waste. There is a decline in contamination levels as we move from inland (CB) to coast (KK). The samples are also analysed for grain size and geochemistry to differentiate between sedimentary layers deposited under distinct depositional environments in the past. The results reveal the existence of humid and dry climatic phases along with oscillating sea levels in the past, influencing metal enrichment and contamination.