Effects of microbial activity and coexisting cation on association of selenium with humic substance in deep groundwater

Terashima, Motoki  ; Amano, Yuki   

Effects of microbial activity and coexisting cations on association of selenium (Se) with humic substance (HS) in deep groundwater were investigated by means of incubation experiments, DAX-8 extraction, and size-exclusion chromatography combined with UV-Vis and ICP-MS detections (SEC-ICP-MS). Selenite added into the groundwater was effectively reduced to elemental Se(0) by microbial activity stimulated by a nutrient. The DAX-8 extraction showed the existence of Se fraction that is extracted with HS. The SEC-ICP-MS analysis for alkaline extracts of the DAX-8 showed that the chromatogram of Se, HS and Fe are well corresponded each other, and were obtained regardless of the sterilization of groundwater. These indicate the possibility that Se can associate with HS in deep groundwater via the interaction with Fe.