Dynamics of polycyclic aromatic hydrocarbons (PAHs) in surface sediments of Cochin estuary, India.

Polycyclic aromatic hydrocarbons (PAHs) showed significant seasonal dynamics in surface sediments of a tropical ecosystem (Cochin estuary, south west coast of India). Concentrations ranged from 304 to 5874ngg-1 in pre-monsoon, 493 to 14,149ngg-1 in monsoon, and 194 to 10,691ngg-1 in post-monsoon. The estuary was moderately contaminated with low molecular weight PAH fractions, which increased rapidly during the monsoon season indicating land/river runoff as the major transport pathway. The dominance of 2-3 ring fractions in the PAH indicated petrogenic and low temperature combustion processes as major sources, while the very low levels of 5-6 ring components indicated low contribution from pyrolytic sources. Low molecular weight fractions were higher in concentration than the Effective Range-Median (ERM) levels, whereas high molecular weight PAHs were lower than the Effective Range-Low values (ERL). Calculated carcinogenic toxicity equivalents (TEQ) values ranged from 1 to 971ngg-1 in the surface sediments.