Vertical migration in the soil of Cr(VI) and chromite ore processing residue: Field sampling and benchtop simulation

Xizhi Wang; Yuanyuan Liu; Bin Liu

doi:10.1016/j.jhazmat.2023.132052

Vertical migration in the soil of Cr(VI) and chromite ore processing residue: Field sampling and benchtop simulation

J Hazard Mater. 2023 Sep 15:458:132052. doi: 10.1016/j.jhazmat.2023.132052. Epub 2023 Jul 11.

Authors

Xizhi Wang¹, Yuanyuan Liu², Bin Liu¹

Affiliations

¹ Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, Chongqing 400044, China; State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China.
² Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, Chongqing 400044, China; State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China. Electronic address: Liuyuanyuan@cqu.edu.cn.

PMID: 37454486
DOI: 10.1016/j.jhazmat.2023.132052

Abstract

Chromite ore processing residue (COPR) keeps releasing Cr(VI) over time, and the mixing of residual COPR into soil makes the remediation of COPR-contaminated sites challenging. In this study, a sample of COPR and two soil profiles were collected from a typical historical COPR-contaminated site, and the vertical migration of Cr(VI) and COPR particles in contaminated soil was simulated in the laboratory. Cr(VI) was detected in the upper layer of the field samples at thousands of milligrams per kilogram even after decades of aging, and it can be leached out and migrate vertically deep into the surrounding soil and groundwater. In the COPR-containing soil, more diverse hydrated minerals of brownmillerite were produced than the COPR in the open air on the site. Minerals with high Cr content in COPR-containing soils have a relatively high proportion of particles smaller than 10 µm. COPR particles smaller than 5 µm were found to have migrated downward into the deep soil. During simulated one-year of precipitation, 578.9 mg Cr(VI)/kg was leached from COPR, while 35.5% of the COPR particles smaller than 5 µm had the potential to migrate vertically. The management of COPR particles should be emphasized during risk management or remediation of COPR-contaminated sites.

Keywords: COPR-containing soil; Hexavalent chromium; Hydrated minerals of brownmillerite; Small particles.