Determination and aquatic risk assessment of pesticide residues in riparian drainage canals in northeastern Greece.

An approach combining monitoring and ecotoxicological data has been undertaken to assess pesticide loading in the drainage canals of two transboundary rivers of northeastern Greece near the Greek/Bulgarian/Turkish borders as well as the subsequent risk to non-target aquatic organisms. Aquatic risk assessment was based on the Risk Quotient (RQ=MEC/PNEC) regarding three trophic levels, algae, aquatic invertebrates and fish. Alachlor, atrazine, carbaryl, carbofuran, cypermethrin, DEA, DIA, diazinon, dimethoate, endosulfan, metolachlor, monilate, prometryn and trifluralin were the compounds detected at the highest concentrations on a regular basis. Extreme concentrations were observed just after high rainfall events during the month of pesticide application. Aquatic risk assessment revealed non-acceptable risk for 10 compounds when median concentrations were used as ΜEC values. However, should extreme concentrations be taken into account, 15 compounds were considered as likely to pose a threat to aquatic organisms. Conformity to EC environmental quality standards is also discussed.