A Method for Detecting Selenium Speciation in Groundwater Katta

To better understand the potential toxicity of Se, it is necessary to know the concentration of different Se ionic species (e.g., Se032-and Se042-). The hydride generation atomic absorption spectrophotometry (HGAAS) method of Se analysis cannot separate Se into individual ionic species. Ion chromatography (IC) can determine Se032-and Se042-concentrations simultaneously; however, common anions, such as sulfate (S042-)f in groundwater interferes with Se0$ and Se042-speciation. The purpose of this study was to measure the concentration of ionic Se032-and Se042-species in groundwater, thereby determining the chemical speciation of dissolved Se. Three groundwater samples with high concentrations of Mg2-and S042-were used in this study. The ionic Se032-and Se042-species in groundwater samples were selectively adsorbed onto copper oxide (CuO) particles by lowering the pH to 5.5. These ionic species were desorbed from the surface of CuO particles by increasing the pH to 12.5. Subsequently, the concentrations of Se032-and Se042-ionic species in solutions were determined with HGAAS and IC. The effect of divalent cations (e.g., Mg2+) on the concentration of Se042-in aqueous solutions was also evaluated. The dissolved Se concentration in three groundwater samples ranged from 22 to 151 pg/ L. The CuO particles extracted 97% of Se032-from groundwater samples, suggesting that Se(IV) concentrations were dominated by the SeO3*-ion. However, CuO particles extracted 80% of Se042-from groundwater samples. These results suggest that Se(VI) concentrations consisted of Se042-and metal Se042-solution species. The dissolved Mg2+ in groundwater samples formed a strong neutral ion pair with Se042-(MgSe04O), which was not adsorbed by the CuO particles. Overall chemical speciation of dissolved Se, extracted with CuO particles, suggests that groundwater samples consisted of Se032-(6-36%), the proposed method is that CuO can be used in the field to extract both Se032-and Se042-ionic species from groundwater samples, and these species could be desorbed from CuO and measured using HGAAS or IC methods, depending upon the concentrations of these species.