Spatial-temporal trends and factors of soil cover pollution in Moscow

The distribution and factors of heavy metal and metalloid (HMM) and benzo(a)pyrene (BaP) accumulation were studied in soils of 9 administrative districts (ADs) of Moscow, according to monitoring data in more than 2200 points for 2007-2016, accomplished by the State environmental institution “Mosekomonitoring”. The main physicochemical properties (pH, organic matter Corg and texture), the total content of Cu, Zn, Cd, Pb, Ni, Hg, As and BaP in soil samples were determined, land-use zoning of sampling sites was carried out and monoelemental geochemical maps were compiled. A twofold increase in the content of Cu, Cd, As in the Central AD (CAD) and Cd in the Eastern AD (EAD) and the North-Eastern (NEAD), as well as As in the CAD, NEAD and EAD was established; in all the ADs the soil pollution with Zn, Pb and Hg has been reduced. Concentration of BaP in almost all the districts decreased by 4-8 times. Anthropogenic and soil-geochemical factors of accumulation and dispersion of pollutants were determined using the regression tree method. Spatial factor is the most significant, because the quantity and geochemical specialization of pollution sources vary greatly in different parts of the city. The spatial geochemical heterogeneity of the urban soils caused by atmospheric fallouts is enhanced due to the influence of physical and chemical properties of soils: a rise in pH and Corg values leads to an increase in the content of Cu, Zn, Pb, Hg and Cd, As, respectively; changes in the texture affect the content of Zn, Ni, Cd, As and BaP. Comparison with MPCs/TPCs showed that the traffic zone is influenced by the greatest anthropogenic press in CAD and EAD, the residential one - in the CAD, EAD, South-Eastern and Western ADs, the recreational - in the CAD, EAD and Nothern AD, the industrial - in the Eastern, South-Eastern, North-Eastern, and Northern ADs. By 2016, the MPCs/TPCs of pollutants in the urban soils were violated less frequently.