Patterns of Arsenic Distribution in Tundra Soils of the European Northeast of Russia

Abstract— Distribution patterns of arsenic (As) were studied in background tundra soils of the European northeast of Russia. Its content, differentiation in the vertical soil profiles, and accumulation factors in soils of different geneses were assessed. The total As content was determined using inductively coupled plasma atomic emission spectrometry, and GIS technologies were used to analyze its spatial distribution. It was found that As distribution in tundra soils is characterized by high spatial heterogeneity and is determined by the complex influence of soil physicochemical properties and landscape-geochemical conditions. Calculation of the geoaccumulation index (Igeo) confirmed that all the studied soils are uncontaminated. The upper 95% confidence limit of As content (UCL95% (As)) was used for environmental purposes. Among sandy and loamy sandy soils, the highest UCL95% (As) values were found in gleyic humus-illuvial peat-podzolic soils (up to 7.2 mg/kg), while for acidic loamy and clayey soils, the highest values of UCL95% (up to 9.2 mg/kg) were found in bog-podzolic and tundra bog soils (Histic Gleysols, Histic Cryosols, and Retisols). This exceeds the current tentative permissible concentration (TPC) for As, thus indicating the need to take natural variability into account when assessing the ecological state of soils. It was shown that organic and mineral horizons function as different geochemical environments: in organic horizons, the As content is controlled by a combination of acidity and organic matter, whereas in mineral horizons, the leading role is played by particle-size distribution, mainly by the content of clay fraction. The obtained results can be used to clarify the regional geochemical background, improve the system of environmental regulation, and increase the reliability of soil monitoring in Arctic territories in the context of climate change and permafrost degradation.