Plant protection products (PPP) have been applied to field crops and permanent cultures in Switzerland regularly for decades now. With increasing knowledge on the effects of long-term exposure to PPP residues on humans, the environment in general and the soil quality in specific the general concern has risen. Consequently, an Action Plan for Risk Minimization and Sustainable Use of Plant Protection Products (AP PPP) was developed with the goal to reduce the risk from use of PPP by 50%. This Action Plan includes a concrete measure to fill knowledge gap concerning PPP residues and their transformation products in the soil. This Measure 6.3.3.7 “Developing a monitoring of PSM-Residues in soil” builds the basis for this project and requests to develop a program to monitor PPP residues in soil. Pesticides have long been monitored in surface- and groundwater. However, so far there has been no comprehensive inventory of PPP residues in soil, let alone any long-term monitoring. Furthermore, it is unknown which impact the combination of PPP residues have on soil quality, which are the risk drivers and how we can reduce the risk by half as demanded by the AP PPP. To fill the knowledge gap concerning PPP residues and their transformation products in soil, we will first define a list of relevant compounds. Under consideration of high-risk substance as defined in the AP PSM, we will select them based on the following criteria: eco- and toxicological relevance, persistence in soil, bioavailability, amount and frequency of usage, analytical determinability and stakeholder interest. Preceding this project, Agroscopes’ Environmental Analytics Group and NABO have already established a multiresidue method to facilitate a cost effective chemical analysis of a number of substances and successfully tested it on NABO sites. This method will now be optimized and extended to cover the above mentioned list of relevant substances. While the NABO already monitors soil properties on a wide selection of sites, we will extend the selection to have a sample set representing the most PPP intensive land-use forms, orchards, vineyards and vegetable growing, with a sample large enough to reach statistical significance. In a core work package, using the NABO site selection we are focusing on evaluating and modelling fate of PPP residues according to management data and developing the analytical multi-residue method. Next to the core work package, we will look into various specific questions in separate thematic work packages designed to provide a comprehensive inventory on spatial and temporal variability of PPP residues in intensively agricultural soils in Switzerland. The goal is to complement the existing collection of sites and the current sampling strategy, to then propose a concept for a long-term exposure monitoring of PPP residues in Swiss agricultural soils. In parallel, we will develop indicators and reference values to determine the impact of PPP residues on soil quality and propose measures to reduce the risk to the soil quality. This concept proposal outlines in more detail which steps we already have taken and which further steps we will take to reach the above outlined goal.
