Abstract Details
| Characterization of Mine Tailings Using Complimentary Synchrotron Techniques | |
|---|---|
| Abstract ID | ENV-06 |
| Presenter | Sarah Hayes |
| Presentation Type | Poster |
| Full Author List | Sarah Hayes (1) , Jon Chorover (1) |
| Affiliations | (1) University of Arizona |
| Category | Environmental Science |
| Abstract | Mining sites with high residual heavy metal(loid) concentrations remain unvegetated throughout the arid southwestern US even decades after mining cessation. This represents a significant human health risk because metal laden particles can be transported off site by wind and water erosion. Phytostabilization, establishing plant growth to prevent erosion, is a potential first step to mitigating the landscape-scale risk to human health and minimizing effects of the mine tailings on surrounding ecosystems. The objective of this project is to understand the effects of plant growth on the speciation of Pb and Zn metal contaminants in remediated mine tailings, to better assess the implications for bioavailability. A first step in this process has been to characterize the initial (pre-plant growth) mineralogy and contaminant speciation of the target mine tailings.
We used several synchrotron methods at various scales (from bulk to molecular) in combination with wet chemistry. We made conjunctive use of XRD (BL11-3), sulfur NEXAFS (BL6-2), bulk Pb and Zn XAS (BL11-2), and micro-focused-XRF and XAS (BL2-3) to used to characterize the tailings prior to treatment. XRD, Pb XAS and sulfur NEXAFS confirm that the tailings are predominated by sulfates, although micro-focused XAS identified a small number of residual sulfide particles. The tailings contain soluble and oxalate extractable sulfate phases, iron and manganese oxides, and a backbone of primary and secondary aluminosilicate phases. Using linear combination fitting to analyze the XANES and EXAFS data, we have found that the lead speciation is predominated by plumbojarosite (Pb(Fe3(SO4)2(OH)6)2) and anglesite (PbSO4) with more anglesite in the surficial tailings than those collected at depth. Zinc speciation demonstrates a strong dependence on pH and at high pH is dominated by a zinc talc and at low pH by recalcitrant species. Micro-focused data demonstrates that surficial tailings have more well defined particles and subsurface tailings contaminants occur mainly as coatings on silicate particles or as parts of aggregates that are physically occluded from weathering. |
| Footnotes | |
| Funding Acknowledgement | |