Determination and chemical speciation of selenium in farmlands from southeastern Spain: Relation to levels found in sugar cane

The concentration and the oxidation state of selenium in farmland soils, sewage sludges, and sands was determined by using hydride generation atomic absorption spectrometry. Total Se concentrations ranged from 0.071 to 0.390 mu g/g, whereas Se-IV concentrations varied from not detectable to 0.050 mu g/g. Selenium is predominantly present as Se-VI; a minor fraction was found as Se-IV. We also studied the influence of pH, its values varied between 7.03 and 8.33, on the oxidation state and the content in Se and its possible correlation with the selenium uptake and accumulation in the sugar cane plants. Significant differences were observed between the levels of total Se (p < 0.01) and Se-IV (p < 0.05) in farmland soils, whether they are located in the industrialized or nonindustrialized areas. Total Se is found in higher concentrations and mainly as Se-IV (selenite) in industrialized area. The content of total Se in the samples of sugar cane taken from the zone is independant of the concentration of total Se and Se-IV in farmland soils of the zone (p < 0.05).