Copper distribution and acid-base mobilization in vineyard soils and sediments from Galicia (NW Spain)

In northern Spain and elsewhere in the world, many vineyards are located on steep slopes and are susceptible to accelerated soil erosion. Contaminants, notably Cu, originating from repeated application of copper-based fungicides to the vines to prevent mildew, are transported and stored in the sediments deposited close to valley bottoms. In this study, the contents and distribution of Cu in 17 soil samples and 21 sediment samples collected from vineyard stands were determined. In addition, the effect of pH on Cu release from vineyard soils and sediments was quantified. The total Cu content (Cu-T) in the soils varied between 96 and 583 mg kg(-1), and was between 1.2 and 5.6 times greater in sediment samples. The mean concentration of potentially bioavailable Cu (Cu-EDTA) in the sediments was 199 mg kg(-1) (46% of Cu-T), and was 80 mg kg(-1) (36% of Cu-T) in the soils. Copper bound to soil organic matter (Cu-OM) was the dominant fraction in the soils (on average, 53% of the Cu-T), while in sediment samples Cu-OM values varied between 37 and 712 mg kg(-1) and were significantly greater (P < 0.01) than in the soils. Copper associated with non-crystalline inorganic components (Cu-IA) was the second most important fraction in the sediments, in which it was 3.4 times greater than in the soils. Release of Cu due to changes in the pH followed a U-shaped pattern in soils and sediments. The release of Cu increased when the pH decreased below 5.5 due to the increased solubility of the metal at this pH. When the pH increased above 7.5, Cu and organic matter were released simultaneously.