Enzymatic Activity of Chernozem and Sod-Podzolic Soils under Pollution by Oil

An assessment of the enzymatic activity of chernozem and sod-podzolic soils contaminated with oil was carried out across a wide range of activity of 20 enzymes. The objects of the study are ordinary chernozem and sod-podzolic soil. To simulate hydrocarbon contamination, oil was added to the soil (1, 5 and 10%). To assess the enzymatic activity of soils, the activity of 20 enzymes of the oxidoreductase and hydrolase classes participating in the biogeochemical cycles of C, N, O, P and S was determined. Cellulase and cysteine reductase were the most sensitive to oil pollution of ordinary chernozem, and adenosine triphosphatase and nitrate reductase were the most sensitive to oil pollution of sod-podzolic soil. All the studied enzymes (except for protease and β-glucosidase in ordinary chernozem) showed high information content – a close correlation with the oil content in the soil (r > 0.65). The integral index of enzymatic activity (IIEA), geometric mean (GMEА) and integral pollution index (AР) were calculated. Of the integrated indicators, IIEA (r = –0.97…–0.98) and GMEA (r = –0.98…–0.99) showed high information content, while indicator AР showed low information content in sod-podzolic soil (r = –0.46). It is recommended to use IIEA and GMEA for enzymatic diagnostics of the ecological state of soil after oil pollution. When soils are contaminated with oil, the N, P and C cycles are disrupted to a greater extent, and S and O cycles to a lesser extent. When contaminated with oil, the enzymes of the C cycle (invertase, polyphenoloxidase, dehydrogenases), N cycle (urease), P cycle (acid and alkaline phosphatases) and O cycle (catalase and peroxidases) have the highest average score of enzyme applicability for soil health diagnostics. The use of enzymatic diagnostics is very effective and appropriate for assessing the ecological state of soils contaminated with petroleum hydrocarbons.