Role of natural organic solutes on the sorption of selenium by coal mine backfill-core samples from the Powder River Basin, Wyoming
Conference
·
OSTI ID:98662
- Univ. of Wyoming, Laramie, WY (United States); and others
Concentrations of dissolved selenium (Se) as large as 330 {mu}gL{sup -1} have been detected in water samples from backfill aquifers in the southern Powder River Basin (PRB) of northeastern Wyoming. During surface coal mining, rock material overlying the coal is redistributed in relation to its original stratigraphic position; exposure of the previously buried material to surface oxidizing conditions decreases the stability of sulfides and organic matter containing Se, increasing Se concentrations in associated ground waters. Ground-water and backfill-core samples were collected from three sites located at two active mines in the PRB. Dissolved organic carbon (DOC) in the ground-water samples was dominated by the acid fraction (sum of hydrophobic and hydrophilic acids) at 38 to 84% of the DOC; the neutral fraction (sum of hydrophobic and hydrophilic neutrals) ranged from 10 to 55% and the base fraction (sum of hydrophobic and hydrophilic bases) was generally less than 10%. Three sorption experiments were conducted to investigate selenite sorption on backfill-core samples. Selenite concentration in these experiments ranged from 0 to 11 mg kg{sup -1} in backfill-core samples. The first experiment determined the selenite sorption capacity of the backfill-core samples with selenite in distilled-deionized water as a background solution. In the third experiment, hydrophobic and hydrophilic acid fractions, isolated and concentrated from ground-water samples, were added to the selenite background solutions. Results of the three experiments indicated that backfill-core samples have a high sorption capacity for Se (generally, greater than 90% of the added Se) and can sorb as much as 99% of Se added as selenite. A substantial decrease in selenite sorption rates occurred in the presence of individual organic-solute fractions. Hydrophilic acids caused the largest decrease in Se sorption by the backfill-core samples.
- OSTI ID:
- 98662
- Report Number(s):
- CONF-9506226--
- Country of Publication:
- United States
- Language:
- English
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