Arsenic fractionation in agricultural acid soils from NW Spain using a sequential extraction procedure

Arsenic fractionation has been studied in nine vineyard soils from a wine-producing area in Galicia (NW Spain) characterized by an unusually high As content. Total As concentrations are 7 to 10 times higher the maximum values allowed by the legislation, reaching maximum value of 200 mg kg− 1. The study of As fractionation revealed that those fractions showing strong correlations to crystalline Fe and Al hydrous oxides (r > 0.69, p < 0.01 and r > 0.71, p < 0.01 respectively) represented, on average, higher than the 80% of total As. The low levels of mobile and potentially toxic As fractions (< 4% of total As) suggest that its toxicity is partially minimized in these soils, although the modifications induced by soil management could promote an increase of As availability.