Compositional-geochemical characterization and multi-element pollution and risk assessment of potentially toxic elements in the urban landfill soil.

Urban areas are characterized by the presence of various pollution sources including landfills. During the recent decade, urban landfills were investigated as a source of pollution by potentially toxic elements and potential deposits for landfill mining. The contents of Cr, V, Ti, Ca, K, Mo, Zr, Sr, Rb, As, Zn, Cu, Co, Fe, Mn, Pb, Ba in soils of Vanadzor city landfill site (VL) were determined using the X-ray fluorescence spectrometer to assess multi-element pollution and ecological risk and to identify potentially toxic elements geochemical associations through the application of compositional data analysis. The results showed that Cr, Mo, Zn, Cu, and Pb displayed significant values (>100%) of coefficient of variation suggesting their anthropogenic origin. Moreover, these elements, except Cr, displayed outliers and extreme values in the same sampling sites located directly on the reclaimed part of the landfill. The median contents of Zn, Pb, Cu, Cr, Cd, and As exceeded the global median values by 8.2, 9.8, 19.0, 4.6, 6.1, and 4.5 times, respectively. The multi-element pollution assessment showed that an extremely hazardous level of pollution was observed on the reclaimed part of the VL. From this site, a trend of decrease in the pollution level was observed in the eastern and western directions. In contrast, an allowable level of pollution was observed in the northern part - toward the direction of the above-located hill. The VL was found to be in an inferior ecological condition (a very high level of potential ecological risk was observed), which might also have a negative impact on the ecosystems located in its vicinity. The hierarchical clustering has revealed that the studied elements are grouped in two geochemical associations: a naturally formed - Co, Fe, V, Ti, Mn, Sr, Zr, Rb, K, Ba, As; and an anthropogenic one - Zn, Pb, Cu, Ca.