Seasonal distributions of fungicides in soils and sediments of a small river basin partially devoted to vineyards.

The acid soils of Ourense province riverland (Galicia, NW Spain) produce about 50,000 tons of grapes for winemaking. As part of ongoing investigations into fungicide transport in Ourense vineyard soils, the occurrence of several fungicides in such soils was investigated. Soil samples were collected from the inter-row topsoil of a vineyard adjacent to the River Alongos, approximately 15 km SW of the main city of Ourense. The vines were grown in sandy loam with moderate organic carbon (OC) content (1-2%). Fungicide residues were measured in vineyard soils and river sediments by solid-liquid extraction followed by gas chromatography with mass spectrometric detection (GC-MSD). Procymidone and cyprodinil occurred at higher levels in river sediments than in the case of fludioxonil, metalaxyl and penconazole. The highest concentrations of procymidone in sediments were still low (29-57 microg/kg or ppb) suggesting that no accumulation of these compounds occur. All of them were found at higher concentrations in soil; maxima concentrations were about 1000 microg/kg for procymidone and metalaxyl, and about 400 microg/kg for cyprodinil, fludioxonil and penconazole. Folpet was never detected (detection limit lower than 2 microg/kg) in soil and sediments, suggesting that this fungicide was unstable in such samples. The frequency of fungicide detections in soils can be related to their applications in vineyards and the effect of washing off through vineyard canopy by rainfalls. The results found suggest that the vineyard soils of this region are unlikely to be prone to transport of fungicides, and therefore water supplies in this area are unlikely to be at any significant risk of contamination through viticultural use of these compounds.