Heavy metal accumulation in marine water: An assessment of ONGC’s blocks in Krishna-Godavari Basin, Bay of Bengal

Heavy metal pollution, in the aquatic ecosystem, has become an area of concern garnering increasing attention since the past few decades. These metals are introduced into the marine ecosystem mainly due to anthropogenic activities including offshore Oil and Gas exploration and production activities Though rich in aliphatic and aromatic hydrocarbons, crude oil also contains some trace element like vanadium, nickel, iron, aluminium, copper and some heavy metals like lead and cadmium. Poisonous or hazardous components of crude oil are mainly benzene and heavy metals which vary depending on the source of the crude oil. Elements like copper, mercury, lead, cadmium, zinc and chromium are very toxic. Except copper and zinc, others are nonessential and toxic. In fact, all metals are toxic at high concentrations. The heavy metal overload has inhibitory effects on the development of aquatic organisms such as phytoplankton, zooplankton, and fish.  The metallic compounds could disturb the oxygen level and mollusc’s development, byssus formation, as well as reproductive processes. Hence, monitoring the heavy metal concentrations in sea water 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 water around the operational areas of ONGC in western offshore area. The distribution of heavy metals in the seawater of ONGC’s exploratory blocks in Krishna-Godavari Basin, Bay of Bengal was investigated.  Fifty four sea water samples collected as per OSPAR guidelines from each blocks (Vasihta G1 PML-65, Yaman PML, Godavari PML-46, DWN M-3, KG OS DW III 62, and KG DWN 98/2-1) of Krishna-Godavari Basin, Bay of Bengal and processed samples were analyzed by ICP-MS for Pb, Cr, As, and Cd. Comparison of average results in studied 6 blocks with various seawater quality guidelines is discussed to assess the present contamination. It reveals that seawater 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.