Perchlorate mobilization of metals in serpentine soils |
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| Institution: | 1. CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China;2. School of Chemistry and Materials Science, University of Science and Technology of China, Hefei 230026, China;3. Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China;4. CAS Center for Excellence in Comparative Planetology, University of Science and Technology of China, Hefei, 230026, China;1. Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, CA 90095, USA;2. Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, Japan;3. Department of Geography, Dawson College, Montreal, H3Z 1A4, Canada;4. IRAP, University of Tolouse, Tolouse, France;5. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA;6. Planetary Science Institute, Tucson, AZ 85719, USA;7. Department of Planetology and Habitability, Centro de Astrobiología (CSIC-INTA), Madrid, Spain;8. Department of Astronomy, Cornell University, Ithaca, New York, USA;9. Center of Astronomy and Astrophysics, Technical University Berlin, Berlin, Germany;10. School of the Environment, Washington State University, Pullman, Washington, USA;11. Applied Physics Laboratory, Johns Hopkins University, Laurel MD 20723, USA |
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| Abstract: | Natural processes and anthropogenic activities may result in the formation and/or introduction of perchlorate (ClO4?) at elevated levels into the environment. Perchlorate in soil environments on Earth and potentially in Mars may modify the dynamics of metal release and their mobilization. Serpentine soils, known for their elevated metal concentrations, provide an opportunity to assess the extent that perchlorate may enhance metal release and availability in natural soil and regolith systems. Here, we assess the release rates and extractability of Ni, Mn, Co and Cr in processed Sri Lankan serpentine soils using a range of perchlorate concentrations (0.10–2.50 w/v ClO4?) via kinetic and incubation experiments. Kinetic experiments revealed an increase of Ni, Mn, Co and Cr dissolution rates (1.33 × 10?11, 2.74 × 10?11, 3.05 × 10?12 and 5.35 × 10?13 mol m?2 s?1, respectively) with increasing perchlorate concentrations. Similarly, sequential and single extractions demonstrated that Ni, Mn, Co and Cr increased with increasing perchlorate concentrations compared to the control soil (i.e., considering all extractions: 1.3–6.2 (Ni), 1.2–126 (Mn), 1.4–34.6 (Co) and 1.2–6.4 (Cr) times greater than the control in all soils). Despite the oxidizing capability of perchlorate and the accelerated release of Cr, the dominant oxidation state of Cr in solution was Cr(III), potentially due to low pH (<2) and Cr(VI) instability. This implies that environmental remediation of perchlorate enriched sites must not only treat the direct hazard of perchlorate, but also the potential indirect hazard of related metal contamination. |
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| Keywords: | Perchlorate Heavy metals Serpentine soils Dissolution rate Bioavailability |
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