Moscow University Soil Studies Bulletin. 2021. 3.

The theoretical equation of the concentration of trace element compounds entering the soil with atmospheric precipitation as a function of depth and time is tested on the example of data on the long-term dynamics (1965, 1995, 2006, and 2013) of Cu, Ni and Mn compounds in the soil profile under artificial phytocenoses of the MSU soil lysimeters. The obtained results indicate the possibility of using an analytical model for predicting the content of heavy metals in the soil profile.

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.

Surface waterlogged soils, drained by ceramic and plastic drainage, are an analogue of large-area lysimetric installations, the drainage runoff in which is represented by gravitational waters like lysimetric waters. The drainage runoff module in the spring and autumn periods at landfills drained with plastic and ceramic drainage, and its dependence on the humidity of the year have been established. It is shown that drainage transforms the type of water regime from stagnant-washing to washing. The long-term and spatial dynamics of the removal of the silty fraction of soils and iron compounds has been studied. The removal of chemical elements with drainage runoff and its influence on the intensity of the loessivage process in agro-gray drained soils have been established.

The migration of the water-soluble fraction of petroleum hydrocarbons in typical soils of Bashkortostan is studied. In a lysimetric model experiment, the possibility of water migration of petroleum hydrocarbons in Fluvic Phaeozems, Haplic Phaeozems and Amphiskeletic Pantocalcic Chernozems was revealed. Among the dissolved organic substances that pass into lysimetric waters from oil-contaminated soils, the components that are not extracted by hexane, but have fluorescence in water at the wavelengths typical for petroleum products are revealed. These substances differ from soluble organic matter of background soils by higher HIX humification indices and presumably represent oxidized products of transformation of petroleum hydrocarbons. Lysimetric waters from all oil-contaminated soils are characterized by biotoxicity, regardless of the presence of non-polar petroleum hydrocarbons. The toxicity T-index positively correlates with the content of dissolved organic carbon and chloride ions that accompany soils oil pollution.

The estimation of the radial migration of petroleum hydrocarbons (TPH) in soil profile and their inflow into lysimetric leachates was done to establish acceptable TPH limits in main soil types of Sakhalin Island. The maximum concentrations of TPH, especially medium and high-boiling fractions of TPH, were accumulated in peat and humus horizons, as well as in soil horizons, characterized by heavy loam or clay granulometric composition, which could be considered as radial geochemical barriers to the migration of pollutants. Benzene and its homologues were detected in filtrates from soil monoliths, after passing a water volume corresponding to three-quarters of the annual precipitation, yet these compounds were not revealed after passing the annual precipitation rate through the soil. The toxicity of the leachates was assessed in bioassay with ceriodaphnia and ciliates. The criteria for establishing the acceptable TPH norms in soils according water migration index can be: concentration of TPH, the content of monoaromatic compounds in leachates and their toxicity for hydrobionts in lysimetric experiments.