Residual pesticides in water from agricultural plots recently converted to organic farming

The widespread use of plant protection products in agriculture has led to the contamination of surface water and groundwater, which are the resources used for human consumption. The European Framework Directive 91/474 imposes an obligation to achieve results: a return to good ecological status by 2015. Complex interactions within the soil immobilise pesticides and thus influence their transfer to surface waters, which can lead to long-term contamination. The persistence of pesticides appears to vary considerably. Whilst there are numerous studies on the degradation and persistence of pesticides, few assess them over the long term. The experimental site (240 ha) at the INRA ASTER research unit in Mirecourt was converted in 2004 and certified as compliant with the regulatory framework for organic farming in September 2006. The study of pesticide persistence in water from agricultural plots following conversion will enable an assessment of the duration of this persistence and the resilience of the environments.