Assessment of Arsenic Stability in Iron Amended Soil by Laboratory and Field Experiments

The aim of this study was to assess the effectiveness of chemical stabilization technique on arsenic (As) contaminated soil amended with metallic or zerovalent iron (Fe0) and combination of Fe0 and peat by laboratory and pilot scale field experiments. The used iron amendments were spent blasting sand (BS), a by-product from a steel industry containing 98.3% of Fe0, and its combination with peat.A pilot scale landfill cover was built at Brännkläppen landfill in Northern Sweden. The untreated and treated As-contaminated soils were used as a 2 m thick vegetation/protection layer of the landfill top cover. The main exposure pathways concerning risks to human health and the environment were studied by analysing leachates from field, soil pore water, As fractionation in soil, phytotoxicity and bioaccessibility. Using the bioaccessibility results, a bioavailability of As to humans was calculated.The results showed that the stabilization of As-contaminated soil with a combination of Fe0 and peat significantly reduced the As concentration in soil pore water, uptake by plants and improved the main morphological parameters of plants. The soil treatment also reduced the bioaccessibility and the bioavailability of As indicating the reduced risks to human health. Nevertheless, the soil treatment using Fe and peat only works under oxidizing soil conditions. Leachates collected in field below the 2 m layer showed an increased As concentration in the water percolating through the treated soil profiles over time, when compared to the leachate collected under the untreated soil.These results point out an importance of maintaining oxidizing conditions in the soil treated with Fe amendments in order to retain the positive impact of the soil treatment on As immobilization in soil. Soil layer containing the stabilized soil should be used only in the very top layer of the landfill cover.Validerat; 20131216 (global_studentproject_submitter