Sergey Yakovlevich Trofimov

The process of natural remediation of oil-polluted and salt-polluted raised bogs of KhMAO - Yugra reclaimed 14-16 years ago is analyzed. In general, the revegetation is proceeding successfully, although mesophytic grasses sown during reclamation have almost completely fallen out of the grass stand. In salt-contaminated areas, there is a gradual desalination of peat soil, accompanied by a succession of halophytic (hemigalophytic) plant communities dominated by Calamagrostis epigeios, Eriophorum angustifolium and Phragmites australis with the participation of sphagnum and brown mosses, as well as liverworts. A characteristic feature of these habitats is the settlement of a number of rare protected species ( Heterogemma laxa, Thelypteris palustris, Triglochin maritimum ). In oil-polluted bogs, during the re-vegetation, hydrocarbons often flow from the underlying peat soil horizons to form the surface crust. At the same time, grass stands from Eriophorum angustifolium and some other species with powerful root systems are replacing grass-sedge-cotton grass communities. Sphagnum riparium and Warnstorfia fluitans play also a certain role in the overgrowth of crusted surfaces. Unsuccessful recovery is typical for hollows with difficult runoff in the case of salt-contaminated bogs and the most dry locations in the case of oil - contaminated ones.

The laboratory study of the solid phase of salted peat by X-ray fluorescence analysis revealed the presence of some halogen-organic compounds. Cl-organic compounds were formed in one third of peat samples, while their share is small: 14-15% of the total Cl. On the contrary, Br-organic compounds are formed more often and Br_org proportion is higher: from 12 to 23% of total Br. Relatively weak development of halogenisation of the organic matter in salted peat bog is explained by the recovery conditions that prevent the synthesis of halogen-organic compounds. In X-ray diffraction analysis of peat ash, errors are possible, both due to the growth of minerals, and due to incomplete identification of the number of phases in high-ash peat samples. The second type of error can be corrected using data on the content of chlorine in peat by X-ray fluorescence analysis. In the characteristic of peat bog contamination, in addition to salt profiles in the solution, it is necessary to determine the number and composition of halogen-organic compounds, some of which have herbicide properties.

Mineralization rates of soil organic matter (SOM) decomposition of non-remediated and remediated oil)polluted, as well as background soils from the main types of West Siberian middle taiga’s ecosystems were measured in laboratory experiments. Rates of SOM mineralization were measured by alkali absorption of CO₂ released from wet soil samples at 20°C (basal respiration). Because of linear character of cumulative curves of CO₂ release SOM mi neralization rates were expressed by mineralization index K1 equal to the annual amount of CO₂ released per 1 gramm of soil. K1 values varied in a range 0,123—1,578 mg СО₂/g/day. Highest value was found in background forest soil, lowest — in oil-polluted peat soil with extremely high oil content (544 g/kg). K1 values negatively correlated (K = –0,57) with oil content. SOM mineralization rates in remediated oil)polluted peat soils varied in a range — 0,31—0,85 mg СО₂/g/day

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.

In Russia, the lands with oil contaminated soils exceed tens of thousands hectares. However, to date, there were no unified approaches to the rationing of oil and petroleum hydrocarbons (PH) in soils, a guideline to choose optimal evaluation indicators. The response of plants in the pot experiment could provide significant results for assessing and rationing of PH content in soils and their use in agriculture after land remediation. In this work we assessed the response of higher plants as a marker of the direction and intensity of biological processes in soils in the pot experiment under oil contamination to justify the standards of permissible residual content of PH in soils of agricultural lands. The composition and properties of Luvic Chernozems, Calcic Chernozems, Voronic Chernozems (WRB, 2015) used in the pot experiment, which was carried out in a month after the soil contamination with crude sulfur-containing oil, were investigated. The effect of different oil doses on the bioproductivity of wheat and peas was evaluated. Wheat in terms of dry biomass showed higher sensitivity to PH, containing medium and heavy fractions, than peas. Rationing the PH content in chernozems, a nonlinear regression model described by a logistic curve was applied. The quality standard values found for wheat biomass was 0,9; 0,4; 1,0 g * kg^-1 for Luvic Сhernozems (humus content ~ 9,8%, sandyloam texture); Calcic Chernozems (humus content ~7,6%, clay loam texture), Voronic Chernozems (humus content ~12.8%, loam texture), respectively. The residual PH contents, found as 30% of soil functioning change, which corresponded to the risk level of soil degradation, estimated by the soil fertility parameter — dry wheat biomass were 1,2 g·kg^-1 for Voronic Chernozems; 0,5 g·kg^-1 — Calcic Chernozems; 1,1 g·kg^-1 in Luvic Chernozems.

Milestones in the study of oil-contaminated soils at the Faculty of Soil Science for 50 years of its foundation are dis- cussed from the prospects for the development of environmental regulation and new technologies of soil reclamation. The development of a methodological framework for the determination of oil and petroleum hydrocarbons in soils, studies of soil properties, the chemistry of oil and its components in soil and adjacent media are shown. The devel- opment of legislation on the rationing of petroleum hydrocarbons in soils is given, including the important role of the staff of Faculty of Soil Science of Moscow State University in the work out of a number of regional standards for the permissible residual content of petroleum hydrocarbons in soils is noted. The approaches to ecological rationing of oil and petroleum hydrocarbons in soils are proposed, in the aspects of natural climatic zones and the type of landuse. The importance of improving the regulatory and methodological framework and continuing work in this direction is emphasized. The necessity of research at developing technologies for reclamation of oil-contaminated lands and special use of oil-contaminated waste is indicated.