Distribution, sources and forms of mercury occurrence in the street dust of Mezhdurechensk (Kemerovo Region)

Abstract

The aim of this study was to investigate mercury concentration and forms of its occurrence in the dust component of the atmospheric air (street dust) to assess the geo-ecological condition of the area where coal is mined, processed and transported. The mean mercury concentration of 29 street dust samples collected along a uniform network throughout the city was 36.4 ± 4.7 ng/g, with a minimum (4.6 ng/g) and a maximum (104.6 ng/g) value, respectively. This value was much lower than the mean concentration in soil samples taken previously at the same sites (58.4 ng/g) but higher than the mean concentration in snow solids (29.8 ng/g), which was likely due to precipitation that washed out mercury from the street dust and to the wind blowing. The method of successive chemical extraction revealed a weakly bonded water-soluble form, inorganic poorly sorbed mercury compounds, an organic form of mercury, and mercury associated with minerals. The proportion of each fraction accounted for on average 10.94%, 10.32%, 44.76%, and 33.97%, respectively. Water-soluble and acid-soluble mercury forms were less common. The bulk of mercury had metal-organic and sulfide forms. The study of mercury distribution based on particle size indicated that the mercury concentration increased as the diameter of the grains of dust material decreased. The fine fraction with a diameter of 20 to 50 μm contained the bulk of mercury, which stayed in suspension form for a long time before settling on the surface.