Depth profiles of lithogenic and anthropogenic mercury in the sediments from Thane Creek, Mumbai, India

Abstract

Mercury (Hg) is well known as one of the most toxic elements to man. The coastal environments adjacent to industrial areas are reported to often be contaminated with mercury. Mercury becomes more toxic in the form of methylmercury (Me-Hg) which is converted from inorganic mercury in aqueous systems by microbial activity and can bio-magnify through the food chain. A simple method for the determination of total mercury and methylmercury in sediments was optimized by slightly modifying an old method using the direct mercury analyzer technique. Core sediment samples from Thane Creek, Mumbai, India were collected and analysed for total mercury and methylmercury. The Hg concentration in the creek varied between 0.54 to 16.03 μg g−1 while Me-Hg concentrations ranged between 0.04 to 1.07 μg g−1. In surface sediment, mercury concentrations ranged from 4.33 μg g−1 to 12.16μg g−1. Total organic carbon content was found to be around 2 percent in different layers of the sediments. The enrichment factors, which indicate the extent of pollution in sediments, were estimated to range from 26 to 50 at different locations in the creek. Lithogenic and anthropogenic concentrations of mercury in the creek were also determined to compare the impact of anthropogenic and natural sources. Anthropogenic inventories were about 5-70 times more in concentration than the lithogenic in the different core sediments.