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 μg/g, whereas SeIV concentrations varied from not detectable to 0.050 μg/g. Selenium is predominantly present as SeVI; a minor fraction was found as SeIV. 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 SeIV (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 SeIV (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 SeIV in farmland soils of the zone (p < 0.05). Keywords: Se speciation; pH; farmlands and sewage sludges; uptake by sugar cane; influence of human and industrial activities