Environmental and geochemical assessment of sealed soils in the Eastern Moscow

Abstract

Sealed with road coverings soils in the Eastern Administrative District (EAD) of Moscow were studied, their morphological and physico-chemical properties have been established in various landuse zones, their ecological and geochemical state and level of readily soluble salts and priority organic pollutants - petroleum products (PP) and benzo(a)pyrene (BaP) as compared with background and open urban soils. The article is based on the results of soil-geochemical survey of ekranozems in September 2016 and previously obtained analytical data from an unsealed territory in the southern part of the EAD. A mapping technique was developed and a map of degree of soil sealing in the EAD was compiled. The morphological features and the basic properties of ekranozem’s horizons in different land-use zones of the EAD were determined. They have a low content of organic matter (2,24%), an alkaline pH (8,0), light loamy texture. Despite the use of de-icing salts and mineral fertilizers, the upper part of the profile of the sealed soils is not saline, salts accumulate mainly in the middle and lower parts of the profile, forming maxima in the RAT horizon. Screening of soils with asphalt concrete is not an obstacle to the penetration of technogenic flows of polluting substances - salts, PP, BaP, capable of accumulating in increased concentrations and forming pronounced technogenic anomalies. The average BaP content in the sealed soils exceeds the background level by 56 times, and the MPC - by 9,6 times. The permissible content of PP in ekranozems is exceeded by 9,5 times. However, in comparison with unsealed soils, the content of BaP and PP in ekranozems is 3,5 times less. The vertical distribution of the BaP is, as a rule, uniform, with the exception in the industrial zone, and for the PP it is accumulative with several well-defined maxima in different parts of the profile. As a result of lateral migration, BaP and PP accumulate in the sealed soils of the lower parts of the slopes, where they form accumulations on organomineral and sorption-sedimentative geochemical barriers. High-level man-made accumulations of hydrocarbons are formed mainly in the sealed soils of industrial and transport zones. When opening the asphalt, risks associated with the migration of hydrocarbons to other components of the landscape, including them in the biological cycle and food chains may appear.