First evaluation of pesticides occurrence in groundwater of Tidone Valley, an area with intensive viticulture.

Agricultural practice often involves an intensive and incorrect use of pesticides and fertilizers. These chemicals can leach through the soil profile and contaminate groundwater, including drinking water. For this reason, an effective groundwater monitoring is strongly advisable. The aim of this study was to investigate the groundwater contamination by plant protection products (PPPs) on a hilly area situated in the Tidone Valley, North-West of Italy, a region characterized by an intensive viticulture production. This area is not included in the national groundwater monitoring plan and therefore scarce information is available regarding the quality of groundwater, even though the local Environmental Agency previously revealed the occurrence of PPPs at values higher than the Environmental Quality Standard downstream this area. Hence, a monitoring wells network was developed following an upstream-downstream criterion, a list of pesticides to be monitored, based on a multi-actor approach, and an analytical method for PPPs detection and quantification. The analytical approach involved solid phase extraction followed by High-Performance Liquid Chromatography tandem mass spectrometry. The results of three monitoring campaigns revealed the occurrence of seven PPPs at a level higher than EQS for groundwater (0.1 µg/L) in 30% of the wells. The main pesticides detected were Chlorantraniliprole, Dimethomorph, Fluopicolide, Metalaxyl-M, Penconazole, and Tetraconazole, all commonly used in viticulture, together with S-metolachlor, authorized for cereal cropping. Statistical analysis revealed a significant influence of the sampling time, slope of the soil surrounding the wells, wells depth and wells location on the concentration of five PPPs. Therefore, the results obtained show that the improper use of PPPs for grapevine cultivation may cause groundwater contamination and suggest the need for a deeper analysis of territorial reality, including hydrology studies and farmer behavior and for an urgent introduction of best management practices and mitigation measures to promote a sustainable use of PPPs in viticulture.