Forms of mercury in soils and its accumulation by herbs in the zone of influence of the sludge storage of a chlor-alkali plant (Southern Baikal region)

Abstract

Total concentrations of Hg in soils and the narrow-leaved fireweed Chamaenerion angustifolium L., as well as the forms of Hg presence in soils by the method of sequential extractions were examined to study the processes of mobilization-immobilization of Hg in the soils of the territory of the chlor-alkali plant sludge storage and the features of the bioaccumulation of this element in herbs. The determination of Hg in all samples was carried out by the atomic absorption method. High concentrations of Hg in soils near the sludge storage have been established. In almost all soil samples the amount of Hg is above the regional background. Fractionation showed that Hg in soils is found mainly in organic, strongly bound and sulfide fractions. Due to the low concentrations of Hg mobile fractions, water- and acid-soluble, a relatively low accumulation of Hg in Chamaenerion angustifolium L. was found, which was also facilitated by the barrier properties of the herb roots. Nevertheless, the accumulation of predominantly organic and strongly bound forms of Hg in soils indicates a high potential for Hg mobilization from these fractions due to changes in various physicochemical and biogeochemical properties of soils.