Copper pollution in Italian vineyard soils

SILPA, Italian Association between Public Agrochemical Laboratories, started in 1994 to collect soils samples in vineyard cultivations to verify if copper, heavily used for protection against fungal disease, is linked by superficial layers or is partially leached through deeper horizons. Five or six soils were investigated by each seven participating region and five layers (0-10, 10-20, 20-40, 40-60 and 60-100 cm) were sampled for each soil. Every sample was analyzed for pH water, pH KCl, texture, organic carbon, CEC, and copper (Cu) extracted by aqua regia, DTPA and CaCl2. A decreasing gradient of Cu was found passing from superficial to deeper layers. Average Cu concentration in the topmost layer is about four (aqua regia), five (DTPA) and two and a half (CaCl2) times the one in deepest, respectively. Climatic, pedological and agronomical conditions effect this gradient. In southern regions there is no significative enrichment in Cu concentration even in superficial layers, while in the northern region there is little difference between Cu concentration in different layers only if soils are non-calcareous. High correlation was found between aqua regia and DTPA Cu (R = 0.981, p < 0.001), while very low was found between CaCl2 Cu and both aqua regia and DTPA Cu. There was no correlation between Cu fractions concentration and other soil characteristics.