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Changes in zinc speciation with mine tailings acidification in a semiarid weathering environment
Sarah M Hayes1, Peggy A O'Day, Sam M Webb
1Department of Soil, Water and Environmental Science, University of Arizona, Tucson, Arizona 85721, United States.
Environmental Science & Technology
|July 19, 2011
Summary
Mine tailings contain metal contaminants that spread easily. This study reveals how zinc speciation changes with acidification, crucial for managing environmental risks and revegetation efforts.
Area of Science:
- Environmental Science
- Geochemistry
- Soil Science
Background:
- Unvegetated mine tailings pose risks due to mobile metal contaminants.
- Acidification in semiarid mine tailings alters metal speciation and mobility.
- Understanding zinc (Zn) speciation is key for phytotoxicity control and site revegetation.
Purpose of the Study:
- To determine the solid-phase zinc speciation in weathered mine tailings.
- To investigate the relationship between tailings acidification and zinc speciation.
- To assess the mobility and bioavailability of zinc in mine tailings.
Main Methods:
- Utilized bulk and microfocused Zn K-edge X-ray absorption spectroscopy (XAS).
- Employed a six-step sequential extraction procedure for chemical analysis.
- Applied linear combination fitting with reference spectra for bulk XAS data.
Main Results:
- Zinc sorbed to Fe/Mn (oxyhydr)oxides decreased with acidification.
- Octahedral zinc in sulfate minerals and crystalline Fe oxides relatively accumulated.
- Identified minor Zn phases including hetaerolite, hemimorphite, and sphalerite.
Conclusions:
- Zinc speciation shifts from sorbed forms to sulfate and crystalline Fe oxide associations during tailings weathering and acidification.
- A multi-method approach combining spectroscopy and chemical extraction is vital for understanding complex tailings systems.
- Findings provide critical insights for managing metal contaminant mobility and supporting revegetation of impacted mine sites.
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