Decreasing arsenic bioaccessibility/bioavailability in soils with iron amendments

• Published in: Journal of environmental science and health. Part A, Toxic/hazardous substances & environmental engineering Vol. 42; no. 9; pp. 1317 - 1329
• Main Authors: Subacz, Jonathan L., Barnett, Mark O., Jardine, Philip M., Stewart, Melanie A.
• Format: Journal Article
• Language: English
• Published: England Taylor & Francis Group 01.01.2007
• Subjects: amendments; Arsenic; Arsenic - analysis; Arsenic - pharmacokinetics; Bioaccessibility; Bioavailability; Biological Availability; Environmental Monitoring - methods; Environmental Restoration and Remediation - methods; Extraction; Humans; Iron; Iron - chemistry; Models, Biological; Moisture; moisture content; Reduction; risk; soil; Soil - analysis; Soil - standards; Soil moisture; Soil Pollutants - analysis; Soil Pollutants - pharmacokinetics; Soils; United States
• ISSN: 1093-4529; 1532-4117
• DOI: 10.1080/10934520701436047

We investigated the use of various iron amendments (metallic Fe and soluble Fe(II)- and Fe(III)-halide salts) to reduce arsenic (As) bioaccessibility (as a surrogate for oral bioavailability) in contaminated soils. Soluble Fe(II)- and Fe(III)-salts were more effective than metallic Fe in reducing As bioaccessibility. Adding soluble Fe(III)-salts to soil reduces As bioaccessibility in two ways, by increasing the Fe(III) (hydr)oxide content and by lowering the soil pH. A detailed investigation into the effect of soil moisture when adding Fe(III) amendments indicated that the reaction can occur in situ if sufficient (≥ 30% moisture) is added. If the amendments are added to the soil without moisture, a reduction in bioaccessibility will occur in the extraction fluid itself (i.e., an experimental artifact not reflecting a true in situ reduction in bioaccessibility). Adding Fe (III)-salts to nine As-contaminated soils at a Fe:As molar ratio of 100:1 reduced the average bioaccessibility in the soils by approximately a factor of two. Greater reductions in As bioaccessibility can be achieved by increasing the Fe:As molar ratio. These results suggest decreasing As bioaccessibility and bioavailability in soil by adding Fe amendments may be an effective strategy to remediate As-contaminated soils.