Limits of resistance of chernozems to petrol pollution: Comparative assessment of different subtypes

Petroleum hydrocarbon (PHs) pollution is a serious environmental hazard owing to the growing concern about oil spills. To predict the possible negative consequences of oil spills and their presence in the environment, it is necessary to identify and develop regional and/or local environmentally safe limits that would take into account the local ecological and geochemical characteristics of soils. Model experiments on PHs pollution were carried out for different subtypes of chernozems: Voronic Chernozems (Pachic, Loamic), Calcic Chernozems (Pachic, Loamic), Haplic Chernozems (Pachic, Clayic), Luvic Chernozems (Pachic, Loamic), Haplic Chernozems (Pachic, Loamic), and Haplic Arenosols (Eutric, Arenic). Petrol was applied as a source of PHs to the pre-moistened soil at weight concentrations of 1 % (low pollution), 5 % (medium pollution), and 10 % (high pollution) of the soil weight. After 30 days, the important soil indicators viz., catalase and dehydrogenase activity, the total number of soil bacteria, and the abundance of Azotobacter along with root length of Raphanus sativus (radish) grown on the sample soils were determined. Based on these findings, the ranking of soil resistance to petrol contamination was compiled as Haplic Chernozems (Pachic, Clayic) ≥ Calcic Chernozems (Pachic, Loamic) = Luvic Chernozems (Pachic, Loamic) ≥ Haplic Chernozems (Pachic, Loamic) = Voronic Chernozems (Pachic, Loamic) ≥ Haplic Arenosols (Eutric, Arenic). The identified environmentally safe petrol limits for different subtypes of chernozems range from 1.5 % to 0,6 %. This finding suggests that Haplic Chernozems (Pachic and Clayic) are more resistant to petrol pollution and also provide a safer limit of up to 1.5 % of petrol pollution. The obtained results can be used to develop regional values of the maximum permissible residual petrol content in different subtypes of chernozems.