Possible application of elementary geochemical landscapes map for mapping heavy metals and metalloids content in urban soils

Mapping heavy metals and metalloids (HMM) content in urban soils is necessary for the public health risk assessment. The sampling step is usually large in comparison with typical variability intervals due to the complexity and expensiveness of analysis. This paper considers an attempt to map HMM concentration coefficients based on landscape-geochemical positions (LGP). The case study area is Darkhan, Mongolia, a large industrial and transport hub. 126 soil samples were taken for analysis of contaminants As, Cd, Cr, Cu, Pb, Sb, W; the distance between sampling points was 500-700 m. For each point, the concentration coefficient (DF) of each pollutant was calculated. The LGP map was derived from SRTM digital elevation model, with supplement of hydrographic network data. The final maps of the concentration coefficients were created using areal interpolation technique with the Voronoi diagram of sampling points as an input data and the LGP polygons as a target dataset. The relatively low sampling points density, as well as the relatively large DEM cell size limit the possibility to harmonize datasets. This leads to the noticeable difference between the parameter distribution obtained from areal interpolation and the distribution obtained from deterministic method. Besides, some resulting features should be considered as interpolation artifacts. Nevertheless, the potential suitability of LGP maps as a basis for mapping pollution of urban areas is shown.