Seasonal variations in mercury concentrations in the coastal waters of Kalpakkam, southeast coast of India

Studies were carried out in the coastal waters of Kalpakkam to monitor the seasonal variation in mercury (Hg) concentration. The Hg level (dissolved + acid leachable) ranged from 3 to 50 ppb for surface and 1.5 to 47.9 ppb for bottom-water samples, yielding an annual average concentration of 20.42 ± 11.44 and 23.11 ± 13.06 ppb for surface and bottom waters respectively. Strong positive correlation of Hg with salinity and its relatively low concentrations during monsoon and post-monsoon showed that concentration of Hg in this coastal water was mainly of marine origin, indicating absence of any other external source of input. Relatively high Hg concentrations were encountered in bottom samples compared to the surface. Madras Atomic Power Station (MAPS) outfall discharge water did not show elevated Hg level compared to ambient surroundings. The present observed values are significantly lower (30 times) than the earlier reported values from this coast.