Heavy metal accumulation in marine sediments - An assessment in ONGC’s platforms in Mumbai High Region, Arabian Sea

Abstract

Heavy metal pollution, in the aquatic ecosystem, especially sediments, has become an area of concern garnering increasing attention since the past few decades. Some metals like manganese (Mn), copper (Cu), iron (Fe) and zinc (Zn) are biologically important for marine life, others like lead (Pb), cadmium (Cd), and Arsenic (As) are non-essential and become toxic at higher concentrations. These metals introduced into the marine ecosystem mainly due to anthropogenic activities. These heavy metals when discharged into the marine ecosystem may be absorbed in suspended solids, remain in seawater, etc., but ultimately end up in the sediments which act as a “sink” and later the “source”, due to their restricted mobility. Hence, monitoring the heavy metal concentrations in these marine sediments over a period of time is of great help in checking the pollution level and identifying the trend, which in turn will be instrumental in formulating sustainable practices. The paper mainly focuses on the study of the concentration of non-essential heavy metals in sea sediment around the operational areas of ONGC in western offshore area. The distribution of heavy metals in the sediments of ONGC’s exploratory blocks in Mumbai High Region, Arabian Sea was investigated. Surface sediment samples collected from 5 platforms (R-12A, BLQ, NBP, ICP and NQ) of Mumbai High Region, Arabian Sea and digested samples were analyzed by ICP-MS for 75As, 111Cd and 208Pb. Comparison of results in studied 5 platforms with various sediment quality guidelines is discussed to assess the present contamination. It reveals that sediments in study area are not contaminated with respect to perceived heavy metals. Generated data will assist in future for proactive measures and minimize the impact of anthropogenic sources.