Environmental assessment of pesticides in the Mondego River Estuary (Portugal).

The Mondego River estuary, located on the North Atlantic Ocean Ecoregion, is a basin affected by agricultural run-off with increasing signs of eutrophication. We evaluated the amounts and distribution of 56 priority pesticides belonging to distinct categories (insecticides, herbicides and fungicides). Temporal trends were considered and a total of 42 surface water samples were collected between 2010 and 2011. More than 55% of the GC-MS/MS-quantified pesticides were above the maximum amounts established by the European Directives (98/83/EC and 2013/39/EU). Based on the concentration addition (CA) and independent action (IA) models, we used a two-tiered approach to assess the hazard of the pesticide mixture, at the maximum concentration found, reflecting a potential risk. Short-term exposure using Artemia salina indicated a significant toxic effect where the locomotion of the animals was clearly affected.