Soil and plant selenium at a reclaimed uranium mine

Area of Science:

• Environmental Science
• Soil Science
• Geochemistry

Background:

• Reclaimed uranium mine lands can release selenium (Se), increasing food chain transfer and water contamination risks.
• Understanding selenium bioavailability post-reclamation is crucial for environmental and ecological risk assessment.

Purpose of the Study:

• To assess the post-reclamation bioavailability of selenium at a uranium mine site in Wyoming.
• To investigate soil selenium distribution, dissolution, speciation, and sorption.
• To evaluate plant selenium accumulation.

Main Methods:

• Analyzed soil selenium distribution, extraction (phosphate, AB-DTPA, hot water, saturated paste), and speciation.
• Investigated selenium solid phases and sorption mechanisms using isotherm models.
• Measured plant selenium accumulation in grasses, forbs, and shrubs.

Main Results:

• Phosphate-extractable soil selenium exceeded the critical limit in all samples.
• Selenite was dominant in phosphate and AB-DTPA extracts; selenate in hot water extracts.
• Soil adsorption significantly controlled selenium availability, with a maximum reserve pool of 87% of phosphate-extractable selenium.
• Plant selenium accumulation varied widely (11 to 1800 mg/kg dry weight).

Conclusions:

• High levels of bioavailable selenium exist in reclaimed uranium mine soils.
• Selenium availability is influenced by soil mineralogy, dissolved organic carbon, and adsorption.
• Plants accumulate significant selenium, offering potential for phytoremediation or forage supplements.