Abstract
Arsenic contamination of groundwater resulting from natural processes occurs frequently in the midwestern part of Saitama Prefecture. The chemical composition of groundwater is similar throughout the area, and high concentrations of arsenic and iron are detected under reducing conditions. In this study, the mechanism of arsenic release into groundwater was analyzed by selective extraction of iron oxides from sediments. The revised BCR, Tamm, and revised DC methods were used for extraction from two sediment-core samples (Sites A and B) drilled in an area contaminated by arsenic. From the tests of the extraction of arsenic and iron from sediment-core samples, it was recognized that the revised DC method, in which a mixed dithionite - sodium citrate solution is used as the extracting solvent, is the most suitable technique for the analysis of the arsenic release mechanism in this area. The relationship between arsenic and iron extracted from the two core samples by the revised DC method showed a straight line (Site A: R2 = 0.75, n = 19; Site B: R2 = 0.65, n = 32) . This result demonstrates that iron oxides are the principal source of arsenic in this area and the dissolution of iron oxides under reducing conditions is a cause of the release of arsenic into groundwater.
