Concentrations of naturally released arsenic in ground water vary with well depth. In the study site near Chiayi County, Taiwan the soil were arsenic contaminated through the irrigation water. The average arsenic concentration of fresh groundwater would in the range between 329±151 ppb. In order to prevent the spatial interferences, five sampling wells set up clustered and near the agricultural land. Except the well depth around 32 to 37 meter, the arsenic concentrations were found increased from absent to 381±8.9 ppb when the sampling depth was increased from 4 to 80 meter. It was believed that reduction condition in groundwater would result to the dissolution of iron oxide and further leading to the release of sorbed arsenic. Arsenite was found the major arsenic species in groundwater while the speciation analysis of rock soil obtained from the sampling well indicated that As(V) were the major dominant in all selected well depths. XANES spectrum results had also indicated the composite of arsenic and iron species in rock soils were different between shallow and deep layers. Therefore, in this study, the arsenic release mechanism and its reduction behavior between shallow and deep layers of groundwater would be discussed.

Arsenic release mechanism in the shallow and deep aquifer in Chiayi County, Taiwan

249th National Meeting (2015)

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