Zinc distribution and acid-base mobilisation in vineyard soils and sediments.

Nineteen vineyard stands located in steep-slope areas of three wine-growing regions in northwest Spain were selected for this study. In each stand, a representative soil sample (19) and one or two sediment samples (24) were collected. In these samples, the Zn distribution in the solid phase was assessed. Moreover, the effect of pH on the release of zinc was determined using a batch-type experiment. The mean zinc concentration (109 mg kg(-1)) of the samples was lower than the maximum concentrations allowed by the European Union. Moreover, most of the zinc that appeared in vineyard soils was residual zinc, suggesting a tendency for zinc in these soils to be irreversibly bound to soil components, reducing its potential environmental impact. In sediments, the mean total Zn concentration (126 mg kg(-1)) was higher than those in the original soils and in the mobile fractions, which could mean a higher risk of liberation. Zinc release was higher under acidic conditions, in which release depends mainly on labile fractions. Under basic conditions, the release of Zn was lower and depended on Zn bound to crystalline oxyhydroxides.