Distribution, source and potential biological impacts of polycyclic aromatic hydrocarbons in the core sediments of a networked aquatic system in the northwest coast of India - A special focus on Thane Creek Flamingo Sanctuary (Ramsar site)

Mumbai, one of the most industrialised and inhabited cities in the world, has been confronting an exponential increase in pollution brought about by anthropogenic activities throughout its coastal belt over the years. The historical accumulation of 16 polycyclic aromatic hydrocarbons (PAHs) in the sediments of Thane creek, Panvel creek and the Ulhas estuarine river system was examined in light of these circumstances. The present study has found that the PAHs were distributed vertically in the sediments of Thane Creek as 16.53 - 1317.02 ng/g dw and Ulhas Estuary as 105.44 - 1815.20 ng/g dw. Major sources of PAHs pollution to the system like petroleum spillages, biomass burning and vehicular exhaust was discernible based on molecular diagnostic ratio (MDR) and principal component analysis (PCA) tools, signifying petrogenic and pyrogenic origins. Based on the total toxicity equivalence (TEQ) and sediment quality guidelines (SQGs) indices, high or moderate contamination risks have been identified in the lower and middle regions of the Ulhas estuary, as well as in the lower regions of Thane creek. Specifically, high contamination risk of benzo[a]pyrene which has high cancerous potential, was identified in the above sites.