Ecological-geochemical state of soils in Ulaanbaatar (Mongolia)

Abstract

Based on the results of the soil-geochemical survey, the assessment of the soil cover pollution in different Ulaanbaatar functional zones is given. The soils of the industrial and traffic zones concentrating a wide spectrum of pollutants (Zn, Mo, Cr, Cr, Cd, Pb, and Cu) are characterized by the strongest technogenic transformation. The soils of the residential areas accumulate Pb and Zn, while those of the recreation zone, Mo, Ni, and Cr. The geochemical mapping allowed distinguishing four groups of elements with similar distribution patterns determined by the common pollution sources, the specific features of the parent rocks, and the intensity of the migration. Among the natural and technogenic factors responsible for the accumulation of microelements in soils, the basic ones are the soil physical and chemical properties: the contents of organic matter (for As, Cd, Cu, Mo, Zn), physical clay (Ni, Co), sulfates (Pb, Sr), and the pH (Cr). The character of the land use noticeably affects the concentration of many elements. The soils of the city are assessed as weakly polluted (Zc = 11). The contents of As, Zn, Mo, and Pb exceeded their MPC in 100, 34, 20, and 16% of the city’s territory, respectively. As compared to the state of the soil cover in 1990, no significant changes were revealed.