Assessment of the Impact of Industry-Related Air Emission of Arsenic in the Soils of Forest Ecosystems

Abstract

The soils of forest ecosystems are often affected by the industrial activity of mining and metallurgical enterprises, and insufficiently investigated for the content of pollutants due to enterprise emissions. Some pollutants, such as arsenic, are transported over long distances by these emissions. To analyze this connection, the present study was conducted on the eastern slope of Mount Yurma, the Southern Urals, Russia, to determine the content of arsenic in the soils of mountain forest areas in the impact zone of the copper smelter (Karabash). The physical and chemical parameters, total content of arsenic, mineralogical composition of silt, and concentration of arsenic in the silty fraction in soils located at different altitudes were determined using atomic absorption spectroscopy (AAS) and X-ray diffraction (XRD) techniques. The soils under study are physico-chemically and chemically acidic in the upper horizons with a pH of 3.26 to 4.05. The carbon of organic matter decreases with depth from 7.98 to 0.06%. Exchangeable Ca and Mg cations in the range of 2.6–8.6 mg-eq per 100 g of soil were determined. The mineralogical composition of the silty fraction consists mainly of quartz and aluminosilicates. Following an analysis of the arsenic content in the above-ground leaf litter, the bioconcentration factor (BCF) was calculated. Arsenic exceeding Clarke concentrations was recorded. In all upper soil horizons, concentrations of total arsenic exceeded background values by 3.7–5.2 times, with maximum values in the horizons A—25.3 mg/kg, in the horizons O—64.4 mg/kg. The obtained BCF > 1 data points to the biological arsenic accumulation by plants and, as a result, its input into the soil via industrial emissions from the smelter. It was found that the silty fraction plays a special role in the accumulation of arsenic in the studied soils. Accumulation of arsenic occurred mainly due to the secondary minerals of Ca and Mg. Differences in the accumulation of arsenic in the forest litter depending on the plant association were noted. The obtained results could serve as a guideline for monitoring the areas around the enterprise and enhancing the understanding of pollutants’ distribution in the soils of remote areas and mountain landscapes.