Extraction and distribution of soil organic and inorganic selenium in coal mine environments of Wyoming, USA |
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| Authors: | S. Sharmasarkar G. F. Vance |
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| Affiliation: | (1) Department of Plant, Soil and Insect Sciences, University of Wyoming, Laramie, WY 82071-3354, USA, US |
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| Abstract: | Selenium (Se), an animal toxicant and aquifer contaminant, occurs in coal mine environments of Wyoming. There is a paucity of information on solution-phase Se speciation in mine soils. The objectives of this study were to compare Se extraction efficiencies of various reagents and to characterize SeO2– 3 (selenite), SeO2– 4 (selenate) and organic Se components in these extracts. Forty coal mine soils were extracted using DI (deionized) water, hot water (0.1% CaCl2), AB-DTPA, NaOH, and KH2PO4. Each solution was analyzed for total dissolved Se, and inorganic and organic Se fractions. Both inorganic and organic Se fractions were detected in the soil extracts. The order of Se (total, inorganic, and organic) extraction efficiency for different reagents was DI water < hot water < AB-DTPA < NaOH < KH2PO4. The inorganic–organic Se ratios in DI water, hot water, AB-DTPA, NaOH, and KH2PO4 extracts were 60 : 40, 26 : 74, 61 : 39, 87 : 13, and 52 : 48, respectively, indicating predominance of inorganic Se in all but the hot water extract. Selenite was the dominant inorganic species in AB-DTPA and KH2PO4 extracts, while SeO2– 4 was the major Se species in the DI water, hot water, and NaOH extracts. Significant correlations (P<0.01) were observed among extractable inorganic Se [NaOH and KH2PO4 (r=0.95); hot water and AB-DTPA (r=0.89)], total soluble Se [DI water with hot water (r=0.98) and AB-DTPA (r=0.95)], and Se species [SeO2– 3 in AB-DTPA with SeO2– 4 in NaOH (r=0.94) and SeO2– 3 in KH2PO4 (r=0.88)]. These correlations are indicative of Se extraction efficiency, thermodynamically predicted chemical transformations (such as oxidation of SeO2– 3 to SeO2– 4), and probable interconversions between the organic and inorganic Se fractions (r=0.70 in KH2PO4 extracts); as a whole the correlations can be used as statistical validations of possible geochemical processes. Received: 21 August 1995 · Accepted: 16 October 1995 |
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| Keywords: | Selenite Selenate Organic selenium Extraction Speciation Distribution |
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