Pathways of priority pesticides in sediments of coastal lagoons: The case study of Óbidos Lagoon, Portugal

• Lagoon hydrodynamics influenced the dispersion and accumulation of PPs.
• Sediment monitoring is essential to control recent inputs of pesticides.
• Past application of lindane and DDT is still an ecotoxicological threat.

This study reports the concentrations of the priority pesticides (PPs) in 14 surface sediments and 21 layers of a sediment core from Óbidos Lagoon, a shallow Portuguese coastal lagoon. Results show that the PPs are confined to the upper part of the lagoon that receives most of the inputs from surface runoff of the surrounding agricultural fields and from small tributaries. Past and recent applied PPs were registered in sediments, aluminum normalized concentrations varying between 0.05 × 10− 7 and 6.85 × 10− 7. The PP risk assessment based on sediment quality guidelines like the “Probable Effect Level” (PEL) shows no biological effects in either sediments or aquatic organisms of Óbidos Lagoon, except for dieldrin, lindane, DDT, heptachlor epoxide and its parent compound heptachlor.