Distribution of mercury in chemical fractions of contaminated urban soils of Middle Amur, Russia

Abstract

The distribution of mercury (Hg) in fractions of urban soils from two industrial cities in the Russian Far East which are subject to varying degrees of Hg contamination was examined. The speciation scheme applied was based on routine chemical extraction methods used in soil investigations. Such an approach enables the Hg data to be brought into correlation with soil basic fractions and the fate of Hg bound to different soil components to be followed. Humic acids and a non-hydrolysable residue (humin), i.e. the soil fractions most refractory to microbiotic and chemical attack, were found to be principal Hg repositories in the soils studied. This pattern was equally observed for slightly, moderately and heavily contaminated soils. Hymatomelanic acids do not appear to be an efficient Hg concentrator. In heavily contaminated soils, Hg concentrations were evident in mobile fractions of fulvic acids as well as in those fractions extracted by H2O and 0.05 M Na2-EDTA pH 3. A portion of Hg extracted by 1 M HCl increased in lower horizons, reflecting relatively weakly bound Hg.

Mercury in the Urban Topsoil of Athens, Greece

“…In urban soil, Hg concentrations can be higher than the geochemical background values of soil in rural areas [15]. Elevated concentrations of a few to several mg of Hg per kg of soil have been recorded in various cities around the world [16][17][18], typically attributed to anthropogenic sources of enrichment [19,20]. There is a general paucity of information in terms of Hg concentrations in the urban soil environment.…”

Immobilization of soil mercury by colloidal sulphur in the laboratory experiment

“…This concentration jump is indicative of a stage-by-stage process of Hg binding in soils at sites of different binding energy, the phenomenon described earlier [1,11,31]. Zvonarev and Zyrin [31] showed that at low concentrations, almost all Hg is sorbed at sites of high binding energy ( Figure 1, site A).…”

“…The soil subsamples obtained were placed in polyethylene cans which were precleaned by soaking in 2% HNO 3 for 48 hours [1]. Below the soil layer, a drainage layer of washed and burnt sand was spread.…”

“…In the samples of percolating waters, the content of total dissolved Hg was determined after preliminary digestion of the water aliquot by 15 min cautious simmering with a mix of HNO 3 + H 2 SO 4 in Kjeldahl flasks with a reflux condenser [1]. The concentration of reactive dissolved Hg was determined after adding acidic 2.6 mol L −1 HCl 1% SnCl 2 solution to a separate water aliquot, omitting the preliminary oxidation step [25].…”

“…Up to present times, the principal clean-up method of Hg-contaminated areas is their excavation and burial. This method cannot completely solve the problem -atmospheric precipitation and underground waters drain such burials, and Hg is emitted from them as volatile compounds [1].…”