Abstract's Details

Characterizing the Speciation, Distribution, and Correlations of Heavy Metals in Mine Wastes
Abstract ID	UMTG:7-2
Presenter	Christopher Kim
Presentation Type	SSRL/LCLS
Full Author List	C. S. Kim (1), J. J. Rytuba (2)
Affiliations	(1) Chapman University (2) U.S. Geological Survey
Category	Environmental Science
Abstract	Centuries of mining have left a legacy of metal-contaminated mine wastes across the world’s mineralized regions. Characterizing trends in metal concentrations, metal speciation, and correlations between metals as a function of particle size can provide insight into the mechanical and chemical processes that distribute metals in the environment and impact their availability to living organisms. Bulk and microspectroscopic methods were applied to selected size fractions of mine wastes, utilizing uXRF and EXAFS spectroscopy to assess the speciation, distribution, and correlation of metals of interest. The microspectroscopic methods in particular can allow the analysis of samples previously inaccessible by bulk spectroscopic techniques due to sample concentration limitations. Results from bulk concentration analyses demonstrate that many heavy metals are concentrated in the finer grain size fractions, sometimes by over an order of magnitude, increasing their mobility and potential availability by ingestion or inhalation. However, changes in metal speciation corresponding to preferential weathering of more soluble phases may offset the potential toxicity of such metals in fine-grained fractions; this is tested through selective leach extractions. Consistent correlations between certain metals, such as iron and arsenic, were identified and further investigated with uXRF, where specific As:Fe ratios could be associated with discrete As phases identified through EXAFS spectroscopy. The trends identified in these selected mine wastes are expected to be transferable to a wider range of samples, improving the potential to better predict the mobilization and transport of metals from mining regions.
Footnotes
Funding Acknowledgement	Portions of this research were carried out at the Stanford Synchrotron Radiation Laboratory, a national user facility operated by Stanford University on behalf of the U.S. Department of Energy, Office of Basic Energy Sciences. This study was supported by a grant from the USGS-Mineral Resources External Research Program, and beamtime was provided through SSRL beamtime proposal #3113.