Nadezhda Borisovna Sadovnikova

The main components of the CO2 balance - emission from the surface, removal with lysimetric runoff, and dynamics of reserves in a 1.5 m soil layer, taking into account interphase equilibria, were quantitatively assessed in a 2-year soil-lysimetric experiment. A significant (up to 20-90%) contribution of lysimetric runoff to the total gas exchange in cold weather (autumn-winter) against the background of a small (0.3-3.7%) share during the growing season (spring-summer) is shown. Due to the unsteadiness and inertia of gas accumulation / unloading processes inside the soil, emission from the surface does not adequately reflect the gross CO2 production by the soil volume, underestimating in the spring-summer period and overestimating in autumn. The obtained 2-year correlation between emission and gross-production indicates the possibility of a 1.3-1.4-fold underestimation of the dissimilation component of the carbon cycle in the traditional emission assessment of soil respiration.

Methodological problems of the quantitative assessment of pollution of urban soils by benzo(a)pyrene and their bioremediation are considered by the example of the Moscow metropolis. Available materials of scientific publications and official reports of the «Mosecomonitoring» municipal system about pollution of urban soils by benzo(a)pyrene and the patterns of its dynamics were used. The methodological basis of the study was mathematical modeling, including both non-linear regression analysis in the S-Plot-11 program and numerical computer simulation in the Matlab-7 software. Analysis of published materials reveals at least a double excess of the maximum permissible level of pollution of urban soils by benzo(a)pyrene at 70% of the territory of the Moscow metropolis, with a high probability of an extremely high degree of pollution in several dozen MPCs at 10% of the city's area. Unlike known works in this field, the study links such a negative situation not with the resistance of benzo(a)pyrene in soils, but with its high technogenic load. A simple kinetic model, verified for experimental information on biodegradation of benzo(a)pyrene in soils, makes it possible to assess the permissible limits of technogenic load, guaranteeing the self-cleaning of urban soils from this dangerous pollutant in the conditions of Moscow.

The high water retention and water capacity functions of detritus determine its potential hydrological significance in the formation of the water regime of soils and phytoproductivity of forest landscapes. Using computer modeling of water exchange in the “soil-plant-atmosphere” HYDRUS-1D system, we preliminary studied the hydrological func- tion of detritus for water retention of precipitation and root water consumption at different amounts and variants of the arrangement of detritus layers in the soil profile. The soil structures designed on the basis of this information for sustainable afforestation with increased carbon sequestration demonstrated in field experiments with water balance monitoring high efficiency in optimizing the water retention capacity of the soil and roots water consumption of the test crop (Glauca spruce) with a 2-3-fold reduction in unproductive water losses and a 1.5–2-fold increase in the current plant growth relative to untreated control. The physical mechanism of the detritus hydrological function is the formation of capillary barriers blocking evaporation and capillary resorption of soil water due to due to surface accumulation (forest litter) or placement in layers inside the soil (peat layers in constructosems).

The adsorption properties of dispersed systems are determined by their surface energy, therefore the indicators of hygroscopy (adsorbed water content) and dispersity (specific surface area of the solid phase) of soils and sediments are in close mutual correlation. This well-known empirical fact received a new fundamental interpretation based on the theory of disjoining water pressure according to Deryagin in the form of a thermodynamic equation connecting the specific surface area, hygroscopic water content of soil samples and the relative humidity of the air in the laboratory room. The theoretical equation allowed us to substantiate the methodology for quantifying the hydrophilic specific surface area of soil samples based on widespread data on their hygroscopy. A comparison of the new method with the standard BET-analysis of the specific surface area, as well as with the previously proposed physically based method for its determining by the slope of thermodynamic water retention curves, showed their statistically reliable agreement in a wide range of estimated specific surface area values from 5 to 340 m²×g^-1 for soil samples of different genesis and texture.