Mercury distribution and mobility in contaminated soils from vicinity of waste incineration plant

The potential bioavailability of Hg from soil might be estimated by a variety of chemical extraction procedures, differing in the extraction agent, its concentration, the sample weight, and the time of extraction. In this study, a comparative analysis of several extraction methods, commonly used for obtaining the mobile and potentially mobilizable phase of the mercury was carried out. Concentrated HNO3, 0.01 mol/L Na2S2O3, 0.05 mol/L EDTA and 0.11 mol/L CH3COOH were used as the single extraction agents. Moreover, the sequential extraction was performed. This procedure involved the following fractions: water soluble Hg, Hg extracted in acidic conditions, Hg bound to humic substances, elemental Hg and mercury bound to complexes, and residual Hg. The results showed that even strong acid HNO3 is unable to release the mercury tightly bound to the soil matrix. This particular method with microwave digestion is commonly used for the estimation of anthropogenic pollution. Conversely, the lowest mercury yield was obtained using the acetic acid as the single extraction agent. In this case, the concentrations were below 0.15% of the total Hg content, which is a proportion generally defined as bioavailable to plants.