Dataset on heavy metal content in background soils of the three gully catchments at Western Siberia

The criteria used include heavy metal (HM) levels in background soils of different countries and territories (Australia, China, Finland, North America, Northern Europe, and Western Siberia) and their threshold concentration values for soils of residential and/or agricultural areas in soil quality standards of Canada (soil quality guidelines), Germany (Trigger Values), the Netherlands (Serious Risk Concentrations), Russia (Maximum Permissible Concentrations), and the USA (Regional Screening Levels). The Retisols, Phaeozems and Chernozems of Western Siberia are characterized by the following range of mean concentrations of heavy metals in topsoil (in mg kg−1): Pb 5–35, Cu 5–100, V 5–180, Cr 5–212, Ni 7–100, Zn 10–135, Mn 50–1800, and Ba 373–1360.

Norway, Poland, Sweden and the USA in terms of the occurrence and distribution of reference soil groups ( Table 1).
The field studies on soils were conducted in Western Siberia, at three sites within small gully catchments ( Table 2, Fig. 1). The study sites were selected on the basis of analysing the maps of vegetation, soils, parent materials and geochemical migration factors within the Ob river basin area [7]. The study sites represented the most typical soil catenas of the central part of Western Siberia [12].
The soil pits were located in sequences from an interfluve down to the slope in order to analyse the redistribution of substances along the soil catenas. In total, there were 142 samples taken from 25 soil pits (Table 3). In soil samples, pHwater, the particle-size distribution, content of total organic carbon (TOC) and HMs were measured (Table 4). Data on HM content were compared to mean concentration within the upper part of the continental earth's crust or a Clark and in soils of the world (Table 5). A Clark of a chemical element and its mean concentration within the UCEC are synonyms.
Total concentration of HMs in the soils were compared to several SQSs (Table 6), because the specified countries have the similar set of soil reference groups, background concentration of HMs (Table 7) and well-developed methodologies for soil quality assessment.
Spearman correlation analyses among the HMs and soil parameters (grain size fractions, TOC and pHwater) were conducted in order to visualize the kind of relationships that exist among the variables (Table 8).
Specifications Table   Subject area Earth Planetary Science More specific subject area Soil Science, Environmental Chemistry Type of data Tables  How data was acquired Data were obtained by means of standard techniques, an 'Analizeter 22' equipment (Germany), an Axios X-Ray fluorescence spectrometer (made by PANalytical, Netherlands) [1]. Data on heavy metal concentration in the upper part of continental earth's crust (UCEC) and background soils of the world were estimated using published materials.

Data format
Raw and analysed Experimental factors Soil samples were taken for heavy metal analysis in the interfluves, slopes and gully bottoms at three gully catchments at Western Siberia Experimental features The eight heavy metals as stated in the abstract were analysed statistically and compared with abundance of elements within the upper part of the continental earth's crust, their levels in background soils of countries and their threshold concentration values for soils of residential and/or agricultural areas in soil quality standards.

Acknowledgments
The work was supported by the Russian Science Foundation (Project 17-77-20072). The authors thank A. Konstantinov and E. Zaitseva for their assistance in field and laboratory work.

Conflict of Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Table 7 Heavy metal concentration (mg kg À1 ) in the upper part of continental earth's crust (UCEC) and background soils of the world.