Fate of arsenic before and after chemical-enhanced washing of an arsenic-containing soil in Hong Kong

Jingzi Beiyuan, Jiang Shan Li, Daniel C.W. Tsang, Lei Wang, Chi Sun Poon, Xiangdong Li, Scott Fendorf

Research output: Journal article publicationJournal articleAcademic researchpeer-review

69 Citations (Scopus)

Abstract

This study evaluated the feasibility of 2-h chemical-enhanced washing of As-containing soil resulting from geogenic sources in Hong Kong and the fate of As before and after remediation. The soil morphology and As speciation in soil was elucidated by scanning electron microscopy with energy dispersive X-ray spectroscopy, X-ray diffractometer, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. Integrated analysis of the results suggests that the As (> 90%) resides predominantly as arsenate bound to ferric iron oxides, with a minor contribution (< 10%) from an AsIII-sulphide phase. This accounts for the marginal leachability, mobility, and bioaccessibility of geogenic As in the untreated soil despite its high concentration. Among the five types of reagents (organic ligands, reductants, alkaline solvents, inorganic acids, and chelants), only dithionite-citrate-bicarbonate method and alkaline solvents (NaOH and Na2CO3) extracted 37–78% and 26–42% of the As by mineral dissolution. However, these extraction methods notably increased the leachability, mobility, and bioaccessibility of remaining As after soil washing, suggesting that a significant proportion of newly released As is prone to re-adsorption onto the soil surface and becomes highly mobile and bioaccessible. While inorganic acids and chelating agents had marginal effects on the fate of remaining As, organic ligands (citrate, oxalate, or pyrophosphate) probably destabilized the bonding of geogenic As and increased its mobility/bioaccessibility despite marginal extraction. The applicability of chemical extraction of geogenic As is questionable regardless of chemical agents, thus proper management of the As-containing soil by containment or physical encapsulation may be considered before land development.
Original languageEnglish
Pages (from-to)679-688
Number of pages10
JournalScience of the Total Environment
Volume599-600
DOIs
Publication statusPublished - 1 Dec 2017

Keywords

  • Arsenic
  • Bioaccessibility
  • Geogenic source
  • Organic ligands
  • Soil washing
  • X-ray absorption spectroscopy

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution

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