TOTAL MERCURY AND SEQUENTIALLY EXTRACTED MERCURY FRACTIONS IN SOIL NEAR A COAL-FIRED POWER PLANT

摘要

Coal-fired power plants are regarded as major anthropogenic pollution sources of Hg. In order to investigate the content of Hg in soil near a coal-fired power plant, soil samples at different depths and distances from the chimney of the power plant were collected. The concentrations of Hg in samples were determined by cold vapor atomic fluorescence spectrometer (CVAFS). The results demonstrated that the total concentrations of Hg in the soil samples were in the range of 0.9-2.4 μg g~(-1). To further understand the mobility and bioavailability of Hg in the soils, one sequential extraction method was performed. Hg in the soil was operationally characterized as five fractions. The distribution of different Hg fractions in soil samples followed the order: elemental fraction (F4) > sulfide fraction (F5) > ion-exchangeable fraction (F1) > organic matter bound fraction (F3) > acid soluble fraction (F2). More than 69% of the total Hg was present in elemental fraction. The proportions of the most labile fractions (Fl and F2) were small. The horizontal and vertical distributions of various fractions of Hg were also investigated and discussed in this paper. The results would benefit us to understand the bioavailability and transportation of Hg in the soils near coal fired power plant.