The ecological status of oil-contaminated soils of Sakhalin and their background analogues has been evaluated with the use of soil invertebrates. The survival rates of Enchytraeus albidus in soils with different textures and the contents of organic carbon and nutrients have been compared. The indicative role of soil mesofauna (Enchytraeus albidus) for the ecological evaluation of oil-contaminated soils with due account for their properties has been shown. The permissible residual concentration of oil hydrocarbons in some soils of Sakhalin—acid brown forest soils (Umbrisols), high-moor peat soils (Histosols), acid meadow alluvial soils (Fluvisols), cultivated meadow soddy soils (Anthrosols), and mucky-podzolic surface-gleyed soils (Gleysols)— has been determined from data on the response of Enchytraeus albidus to different levels of the soil contamination with oil hydrocarbons.

The model of ecological rationing of oil-polluted soils is substantiated according to the function of providing the soil with conditions for biological activity according to separate biological indicators sensitive to oil products, in particular, catalase activity and survival of pot worms. Petroleum products were rationed in different types of soils of the Sakhalin region: high-moor peat bog; humus podzolic surface-glue; alluvial meadow acidic; brown forest acid podzolic in model series with different levels of pollution. The establishment of a standard value at which the functioning of the studied soils changes, was carried out according to the criterion of changing the values of selected biological parameters corresponding to the change in the rate of soil functioning with increasing oil concentration according to the dose-effect model. For the standard of soil quality for petroleum products in the regions of oil production, the value of petroleum products was used, leading to a significant deviation of the values of biological indicators from background values determined by the same biological indicators. For the permissible residual content of oil products in soils, in which the soil maintains stable functioning, performs environmental functions, a 30% change in the functioning of the soil from the background analogue according to the studied biological indicators was taken. Calculations on the rationing of oil content in soils can be performed using the non-linear regression model described by the logistic curve.

In Russia, the area of oil-contaminated soils exceeds tens of thousands of hectares. However, to date, there are no unified approaches for evaluation soil