Assessment of selected organic pollutants in sediments from a highly urbanized environment along the southeast coast of India.

As part of the Marine Spatial Planning (MSP) for the Puducherry coast-a highly urbanized coastal area along India's southeast coast-an extensive assessment of organic pollutants was conducted in the sediments of the Thengaithittu Estuary, one of the major urban confluences in the region. Surface sediment samples were collected during both the dry season (June) and the wet season (September) in 2023 from six stations to measure polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and organochlorine pesticides (OCPs), including DDTs. The results indicated that high molecular weight (HMW) PAHs predominated in both seasons, primarily from pyrogenic sources with concentrations ranging from 0.26 to 369.16 ng g dw. Carcinogenic PAHs (C-PAHs) accounted for 51-98 % of the total PAHs, although the overall PAH levels remained below the Effect Range Low (ERL) threshold, reflecting a low ecological risk. PCBs were detected only at the fishing harbour region at the estuary's mouth, with concentrations varying from 17.16 to 130.04 ng g dw, where 5Cl and 6Cl biphenyls comprised 80 % of the total composition. DDT levels, ranging from below detection limit (BDL) to 2.30 ng g dw, suggested minimal recent inputs. The mean sediment quality guideline quotient (mSQGq) indicated low overall biological adverse effects across all stations. These findings offer essential baseline data regarding organic pollutant levels and ecological risks, emphasizing the need for enhanced management strategies to mitigate contaminant inputs and protect both the estuarine ecosystem and public health.