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Title: Polysulfide speciation and reactivity in chromate-contaminated soil

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Journal Article: Publisher's Accepted Manuscript
Journal Name:
Journal of Hazardous Materials
Additional Journal Information:
Journal Volume: 281; Journal Issue: C; Related Information: CHORUS Timestamp: 2016-09-04 16:31:24; Journal ID: ISSN 0304-3894
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Citation Formats

Chrysochoou, Maria, and Johnston, Chad P. Polysulfide speciation and reactivity in chromate-contaminated soil. Netherlands: N. p., 2015. Web. doi:10.1016/j.jhazmat.2014.07.022.
Chrysochoou, Maria, & Johnston, Chad P. Polysulfide speciation and reactivity in chromate-contaminated soil. Netherlands. doi:10.1016/j.jhazmat.2014.07.022.
Chrysochoou, Maria, and Johnston, Chad P. 2015. "Polysulfide speciation and reactivity in chromate-contaminated soil". Netherlands. doi:10.1016/j.jhazmat.2014.07.022.
title = {Polysulfide speciation and reactivity in chromate-contaminated soil},
author = {Chrysochoou, Maria and Johnston, Chad P.},
abstractNote = {},
doi = {10.1016/j.jhazmat.2014.07.022},
journal = {Journal of Hazardous Materials},
number = C,
volume = 281,
place = {Netherlands},
year = 2015,
month = 1

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.jhazmat.2014.07.022

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Cited by: 7works
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  • Laboratory testing activities indicate that hexavalent chromium, a vadose zone contaminant at many waste sites owing to its mobility and toxicity, can be immobilized in place through chemical reduction to the nontoxic trivalent oxidation state using diluted hydrogen sulfide gas. Treating vadose zone contamination by in situ gaseous reduction thus may be potentially applied as part of an overall strategy for groundwater protection and remediation. A proof-of-concept field test has been undertaken by the U.S. Department of Energy and U.S. Department of Defense in a joint demonstration conducted at White Sands Missile Range, New Mexico, to evaluate this remedial approach.more » This test involved injecting hydrogen sulfide diluted in air into contaminated vadose zone sediments via a centrally located borehole over a 76-day period. The gas mixture was then directed through the sediments using a vacuum applied to six extraction boreholes at the site periphery. Comparison of soil samples taken before and after the test indicated that 70% of the total mass of hexavalent chromium originally present at the site was reduced and immobilized. The zone of highest Cr(VI) contamination was nearly completely treated, with Cr(VI) concentrations of soil samples decreasing from an average of 8.1 mg/kg before treatment to 1.14 mg/kg after treatment and a mass reduction of 88% achieved. Treatment was generally better in zones of higher permeability sand containing less silt and clay. However, all Cr(VI) concentrations measured in post-test samples were well below the EPA Region 9 Residential Preliminary Remediation Goal of 30 mg/kg, compared to a maximum pre-test concentration as high as 85 mg/kg, thus indicating the viability of the technology as a remediation approach.« less
  • Methylated forms of arsenic (As), monomethylarsenate (MMA) and dimethylarsenate (DMA), have historically been used as herbicides and pesticides. Because of their large application to agriculture fields and the toxicity of MMA and DMA, the distribution, speciation, and sorption of methylated As to soils requires investigation. Monomethylarsenate and DMA were reacted with a soil up to one year under aerobic and anaerobic conditions. Microsynchrotron based X-ray fluorescence ({mu}-SXRF) mapping studies showed that MMA and DMA were heterogeneously distributed in the soil and were mainly associated with iron oxyhydroxides, e.g., goethite, in the soil. Micro-X-ray absorption near edge structure (XANES) spectra collectedmore » from As hotspots showed MMA and DMA were demethylated to arsenate over one year incubation under aerobic conditions. Monomethylarsenate was methylated to DMA, and DMA was maintained as DMA over a 3 month incubation under anaerobic conditions. Arsenic-iron precipitation, such as the formation of scorodite (FeAsO{sub 4} {center_dot} 2H{sub 2}O), was not observed, indicating that MMA and DMA were mainly associated with Fe-oxyhydroxides as sorption complexes.« less
  • The nature and proportion of Zn species present in an agricultural soil overlaid by a dredged contaminated sediment have been untangled by the novel combination of three non-invasive synchrotron-based x-ray techniques: x-ray microfluorescence ({mu}SXRF), microdiffraction ({mu}XRD), and absorption spectroscopy (EXAFS). One primary (franklinite) and two secondary (phyllomanganate and phyllosilicate) Zn-containing minerals were identified in the initial soil, and another primary (ZnS) and a new secondary (Fe-(oxyhydr)oxide) Zn species in the covered soil. The quantitative analysis of EXAFS spectra recorded on bulk samples indicated that ZnS and Zn-Fe (oxyhydr)oxides amounted to 71+-10 percent and 27+-10 percent, respectively, and the other Znmore » species to less than 10 percent. The two new Zn species found in the covered soil result from the gravitational migration of ZnS particles initially present in the sediment, and from their further oxidative dissolution and fixation of leached Zn on F e (oxyhydr) oxides.« less