Occurrence, Distribution, and Risk Assessment of Organophosphorus Pesticides in the Aquatic Environment of the Sele River Estuary, Southern Italy.

The intensive use of organophosphorus pesticides (OPPs) causes concern among authorities in different countries, as many of them, remaining unchanged for a long time, pose a threat to environmental sustainability. This study assessed the spatio-temporal trends of nine OPPs in the water dissolved phase (WDP), suspended particulate matter (SPM), and sediment samples from the Sele River estuary, Southern Italy. Samples were collected in 10 sampling sites during four seasons. The highest levels were found at the mouth (mean value 28.25 ng L -1 as WDP + SPM) and then decreased moving southwards to the Mediterranean Sea. Moreover, highest concentrations were detected in the warm season (July) with a mean value of 27.52 ng L -1 . The load contribution to the Mediterranean Sea was evaluated in about 61.5 kg year -1 , showing that the river was an important source of OPPs through discharge into the sea. The risk assessment revealed that no high-risk indices for the general-case scenario were observed, but for the worst-case scenario, potential risks were associated with chlorpyrifos, pyrimifos-methyl, and parathion, suggesting that OPP contamination should not be neglected. This study makes up the first record of OPPs in the surface waters of the Sele River and provides helpful data as a starting point for future studies.