Column leaching of arsenic in coal ashimpacted soils using citric acid (Zemianske Kosto?any, Slovakia)

摘要

This paper describes the mobilization of arsenic (As) in technosols (soils with high content of coal ashes) using 35–d experimental soil column studies. The two soil samples with high total concentrations of As (1100–1139 mg·kg-1) were collected from an environmental burden near the village of Zemianske Kosto?any, which is one of the most As-contaminated areas in Slovakia. Amorphous solid phases, mainly glasses of variable chemical compositions, Fe oxy-hydroxides and unburned coal residues, are the major components of the soil-ash samples. In this study, two different leaching agents (deionized water and 1 mM citric acid aqueous solution) were pumped through soil columns to assess the solubility of As. The results showed that citric acid was more efficient in the mobilization of As (> 14.5% of the total As content) than deionized water, confirming the assumption that organic acids produced by plants and soil microorganisms increase As leaching in soils. Soil column experiments with deionized water indicated lower extractabilities of As that ranged from 9.74% to 11.4%. In addition, water extractable As concentrations increased with increasing pH values of the leachates (R2 = 0.70 at p < 0.01). It was also observed that extraction time was an important factor, affecting the release of As from the soil-ash samples.