Influence of particle size distribution, organic carbon, pH and chlorides on washing of mercury contaminated soil

During the present study, the feasibility of soil washing to remediate Hg contaminated soil was evaluated. Dry sieving was performed to evaluate Hg distribution in soil particle size fractions. The influence of dissolved organic matter and chlorides on Hg dissolution was assessed by batch leaching tests. Mercury mobilisation in the pH range of 3-11 was studied by pH-static titration. Results showed infeasibility of physical separation via dry sieving, as the least contaminated fraction exceeded the Swedish generic guideline value for Hg in soils. Soluble Hg did not correlate with dissolved organic carbon in the water leachate. The highest Hg dissolution was achieved at pH 5 and 11, reaching up to 0.3% of the total Hg. The pH adjustment was therefore not sufficient for the Hg removal to acceptable levels. Chlorides did not facilitate Hg mobilisation under acidic pH either. The authors concluded that mercury was firmly bound in the studied soil thus soil washing might be insufficient method to treat the studied soil.

Authors: Xu J, Kleja DB, Biester H, Lagerkvist A, Kumpiene J. ;Full Source: Chemosphere. 2014 Aug;109:99-105. doi: 10.1016/j.chemosphere.2014.02.058. Epub 2014 Apr 22. ;