Arsenic containing phases in soils from São Domingod mining area and in non-contaminated soils from Pomarão and Serra do Caldeirão

São Domingos mining area is located in the Iberian Pyrite Belt, in south-east Portugal. Intensive gossan gold, copper and silver mining was done in roman times. More recently, mining activities were concentrated in the copper, zinc, arsenic and lead rich sulfide orebodies. To evaluate arsenic hazard, soils developed on the gossan mine waste piles were analysed, using as reference non- contaminated soils from Pomarão (south east Portugal) and Serra do Caldeirão (south of Portugal). Soils were characterized by the classical methodologies for pH (H2O), particle size distribution, cation exchange capacity, Fe and Mn oxides, and mineralogy. The soils (fraction <2 mm) were analysed, for total concentrations of As, Cu, Fe, Mn, Pb and Zn by instrumental neutron activation analysis after acid digestion and, for the concentration of As associated with the different soil phases (exchangeable complex, organic matter, total and non-crystalline Fe oxides and Mn oxides), by hydride generation atomic absorption spectrometric after selective chemical extractions with appropriate reagents using the parallel method. São Domingos soils contain high levels of total As (1940-3030 mg kg-1) but the available fraction is very low (