TY - JOUR
T1 - Changes in lead and zinc lability during weathering-induced acidification of desert mine tailings
T2 - Coupling chemical and micro-scale analyses
AU - Hayes, Sarah M.
AU - White, Scott A.
AU - Thompson, Thomas L.
AU - Maier, Raina M.
AU - Chorover, Jon
N1 - Funding Information:
This research was supported by Grant 2 P42 ES04940-11 from the National Institute of Environmental Health Sciences Superfund Basic Research Program, NIH . 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, and at the Advanced Photon Source, Argonne National Laboratory, Geo-Soil-Enviro-CARS, Beamline 13-BM-D, which is supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. We are grateful to John Bargar, Sam Webb, Matt Newville, Robert Downs, and Mary Kay Amistadi for assistance with sample analyses.
PY - 2009/12
Y1 - 2009/12
N2 - Desert mine tailings may accumulate toxic metals in the near surface centimeters because of low water through-flux rates. Along with other constraints, metal toxicity precludes natural plant colonization even over decadal time scales. Since unconsolidated particles can be subjected to transport by wind and water erosion, potentially resulting in direct human and ecosystem exposure, there is a need to know how the lability and form of metals change in the tailings weathering environment. A combination of chemical extractions, X-ray diffraction, micro-X-ray fluorescence spectroscopy, and micro-Raman spectroscopy were employed to study Pb and Zn contamination in surficial arid mine tailings from the Arizona Klondyke State Superfund Site. Initial site characterization indicated a wide range in pH (2.5-8.0) in the surficial tailings pile. Ligand-promoted (DTPA) extractions, used to assess plant-available metal pools, showed decreasing available Zn and Mn with progressive tailings acidification. Aluminum shows the inverse trend, and Pb and Fe show more complex pH dependence. Since the tailings derive from a common source and parent mineralogy, it is presumed that variations in pH and "bio-available" metal concentrations result from associated variation in particle-scale geochemistry. Four sub-samples, ranging in pH from 2.6 to 5.4, were subjected to further characterization to elucidate micro-scale controls on metal mobility. With acidification, total Pb (ranging from 5 to 13 g kg-1) was increasingly associated with Fe and S in plumbojarosite aggregates. For Zn, both total (0.4-6 g kg-1) and labile fractions decreased with decreasing pH. Zinc was found to be primarily associated with the secondary Mn phases manjiroite and chalcophanite. The results suggest that progressive tailings acidification diminishes the overall lability of the total Pb and Zn pools.
AB - Desert mine tailings may accumulate toxic metals in the near surface centimeters because of low water through-flux rates. Along with other constraints, metal toxicity precludes natural plant colonization even over decadal time scales. Since unconsolidated particles can be subjected to transport by wind and water erosion, potentially resulting in direct human and ecosystem exposure, there is a need to know how the lability and form of metals change in the tailings weathering environment. A combination of chemical extractions, X-ray diffraction, micro-X-ray fluorescence spectroscopy, and micro-Raman spectroscopy were employed to study Pb and Zn contamination in surficial arid mine tailings from the Arizona Klondyke State Superfund Site. Initial site characterization indicated a wide range in pH (2.5-8.0) in the surficial tailings pile. Ligand-promoted (DTPA) extractions, used to assess plant-available metal pools, showed decreasing available Zn and Mn with progressive tailings acidification. Aluminum shows the inverse trend, and Pb and Fe show more complex pH dependence. Since the tailings derive from a common source and parent mineralogy, it is presumed that variations in pH and "bio-available" metal concentrations result from associated variation in particle-scale geochemistry. Four sub-samples, ranging in pH from 2.6 to 5.4, were subjected to further characterization to elucidate micro-scale controls on metal mobility. With acidification, total Pb (ranging from 5 to 13 g kg-1) was increasingly associated with Fe and S in plumbojarosite aggregates. For Zn, both total (0.4-6 g kg-1) and labile fractions decreased with decreasing pH. Zinc was found to be primarily associated with the secondary Mn phases manjiroite and chalcophanite. The results suggest that progressive tailings acidification diminishes the overall lability of the total Pb and Zn pools.
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U2 - 10.1016/j.apgeochem.2009.09.010
DO - 10.1016/j.apgeochem.2009.09.010
M3 - Article
AN - SCOPUS:70350618762
SN - 0883-2927
VL - 24
SP - 2234
EP - 2245
JO - Applied Geochemistry
JF - Applied Geochemistry
IS - 12
ER -