Project Title: Trace Metal Sequestration and Release from Secondary Hydroxysulfate Minerals: Implications for Contamination in Mining Environments
Mendenhall Fellow: Bryn E. Kimball, (703) 648-6148, email@example.com
Duty Station: Reston, VA
Start Date: October 1, 2010
Education: Ph.D. (Geosciences and Biogeochemistry), Pennsylvania State University, 2009
Research Advisors: Bob Seal, (703) 648-6290, firstname.lastname@example.org; Mary Voytek, (703) 648-6894, email@example.com; I-Ming Chou, (703) 648-6169, firstname.lastname@example.org
Project Description: Metal-rich, acidic drainage, known as acid rock drainage (ARD), occurs anywhere that sulfide minerals are exposed to atmospheric oxygen, most commonly at locations where sulfide-bearing metalliferous ore deposits and sulfide-rich coal are exploited (Blowes and others, 2003). Metals released in ARD can be naturally attenuated through precipitation (for example, Hammarstrom and others, 2005; Sidenko and Sherriff, 2005; Kumpulainen and others, 2007), sorption of metals onto (oxyhydr)oxide minerals (for example, Smith, 1999; Schemel and others, 2000; Nimick and others, 2003; Parker and others, 2007), and dilution by mixing with water at circumneutral pH (for example, Paulson and Balistrieri, 1999; Balistrieri and others, 2007). While sorption of metals to abundant (oxyhydr)oxide minerals can be significant, partial desorption of metals can re-release metals with decreasing pH (Schultz and others, 1987; Backes and others, 1995; Nimick and others, 2003). Co-precipitation of metals as solid-solution substitutions into secondary hydroxysulfate minerals that are stable under acidic conditions, such as crystalline jarosite [(K+,H3O+)Fe3(SO4)2(OH)6] or poorly-crystalline schwertmannite [Fe16O16(OH)12(SO4)2], causes metals to be less bioavailable, and might be considered a more permanent sink for metals than sorption.
Understanding the long-term stability of hydroxysulfate minerals is critical for predicting the fate of co-precipitated trace metals. Over time, hydroxysulfate minerals are likely to transform to other minerals or to dissolve. Few studies have investigated dissolution of hydroxysulfates under anoxic conditions, where microbially-mediated dissolution of minerals becomes important. Microbially mediated dissolution of Fe(III) hydroxysulfate minerals by Fe-reducing microorganisms (Jones and others, 2006; Weisener and others, 2008) and sulfate-reducing microorganisms (Gramp and others, 2009) has received little attention compared to abiotic hydroxysulfate dissolution. Because microoganisms are ubiquitous in the environment, this process is likely an important contributor to metal release from secondary hydroxysulfates.
This interdisciplinary project stems from ongoing U.S. Geological Survey work relating to cycling of trace metals and acidity via secondary hydroxysulfate minerals in mining environments. It aims to identify the variables that increase dissolution of the secondary hydroxysulfates jarosite schwertmannite, brochantite [Cu4(SO4)(OH)6], and anterlite [Cu3(SO4)(OH)4], and to characterize trace metal (Cu, Cr, Zn, and Pb) release from these minerals during dissolution. Specifically, the research objectives are:
The experimental design entails synthesizing and characterizing pure and trace metal-substituted hydroxysulfates, then subjecting them to dissolution experiments under controlled temperature and atmospheric conditions either in the absence or presence of Fe- or SO4-reducing microorganisms. Mineralogy and dissolved elemental compositions will be monitored over time using standard techniques. Additionally, the metal, S, and O isotopic compositions of solids and solubilized elements will be measured over time. Such measurements will ultimately be used to improve modeling and prediction of the transport of trace metals in contaminated environments.
- to investigate the kinetics of abiotic and biotic dissolution of hydroxysulfates;
- to characterize the effect that trace metal substitution in hydroxysulfates has on dissolution of these minerals; and
- to measure how metal, S, and O isotopes might be fractionated during hydroxysulfate mineral dissolution, and whether isotopic fractionation, if any, provides insight into the dissolution mechanism.
Secondary precipitates rich in copper sulfate found at the Pike Hill Copper Mine, Vermont.
Backes, C.A., McLaren, R.G., Rate, A.W., and Swift, R.S., 1995, Kinetics of cadmium and cobalt desorption from iron and manganese oxides: Soil Science Society of America Journal, v. 59, p. 778–785.
Balistrieri, L.S., Seal, R.R., Piatak, N.M., and Paul, B., 2007, Assessing the concentration, speciation, and toxicity of dissolved metals during mixing of acid-mine drainage and ambient river water dowstream of the Elizabeth Copper Mine, Vermont, USA: Applied Geochemistry, v. 22, p. 930–952.
Blowes, D.W., Ptacek, C.J., Jambor, J.L., and Weisener, C.G., 2003, The geochemistry of acid mine drainage, in Holland, H.D., and Turekian, K.K., eds., Treatise on Geochemistry: Elsevier.
Gramp, J., Wang, H., Bigham, J., Jones, F., and Tuovinen, O., 2009, Biogenic synthesis and reduction of Fe(III)-hydroxysulfates: Geomicrobiology Journal, v. 26, p. 275–280.
Hammarstrom, J.M., Seal, R.R., Meier, A.L., and Kornfeld, J.M., 2005, Secondary sulfate minerals associated with acid drainage in the eastern US: Recycling of metals and acidity in surficial environments: Chemical Geology, v. 215, p. 407–431.
Jones, E.J.P., Nadeau, T.-L., Voytek, M.A., and Landa, E.R., 2006, Role of microbial iron reduction in the dissolution of iron hydroxysulfate mineral: Journal of Geophysical Research, v. 11, G01012.
Kumpulainen, S., Carlson, L., and Räisänen, M.-L., 2007, Seasonal variations of ochreous precipitates in mine effluents in Finland: Applied Geochemistry, v. 22, p. 760–777.
Nimick, D.A., Gammons, C.H., Cleasby, T.E., Madison, J.P., Skaar, D., and Brick, C.M., 2003, Diel cycles in dissolved metal concentrations in streams: Occurrence and possible causes: Water Resources Research, v. 39, p. 1247.
Parker, S.R., Gammons, C.H., Jones, C.A., and Nimick, D.A., 2007, Role of hydrous iron oxide formation in attenuation and diel cycling of dissolved trace metals in a stream affected by acid rock drainage: Water Air and Soil Pollution, v. 181, p. 247–263.
Paulson, A.J., and Balistrieri, L., 1999, Modeling removal of Cd, Cu, Pb, and Zn in acidic groundwater during neutralization by ambient surface waters and groundwaters: Environmental Science and Technology, v. 33, p. 3850–3856.
Schemel, L.E., Kimball, B.A., and Bencala, K.E., 2000, Colloid formation and metal transport through two mixing zones affected by acid mine drainage near Silverton, Colorado: Applied Geochemistry, v. 15, p. 1003–1018.
Schultz, M.F., Benjamin, M.M., and Ferguson, J.F., 1987, Adsorption and desorption of metals on ferrihydrite: reversibility of the reaction and sorption properties of the regenerated solid: Environmental Science and Technology, v. 21, p. 863–869.
Sidenko, N.V., and Sherriff, B.L., 2005, The attenuation of Ni, Zn, and Cu, by secondary Fe phases of different crystallinity from surface and ground water of two sulfide mine tailings in Manitoba, Canada: Applied Geochemistry, v. 20, p. 1180–1194.
Smith, K.S., 1999, Metal sorption on mineral surfaces: an overview with examples relating to mineral deposits, in Plumblee, G.S., and Logsdon, M.J., eds., The environmental geochemistry of mineral deposits: Society of Economic Geologists, Inc. .
Weisener, C.G., Babechuk, M.G., Fryer, B.J., and Maunder, C., 2008, Microbial dissolution of silver jarosite: Examining its trace metal behavior in reduced environments: Geomicrobiology Journal, v. 25, p. 415–424.
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