EVALUATION OF THE ENZYMATIC ACTIVITY OF HAPLIC CHERNOZEM CONTAMINATED BY PETROLEUM HYDROCARBONS AFTER BIOREMEDIATION

Abstract

Introduction. The evaluation of the ecological state of soils in terms of enzymatic activity during the remediation of petroleum hydrocarbons contamination is very informative. The activity of enzymes of the oxidoreductases and hydrolases classes in chernozem is most sensitive to contamination by heavy metals, pesticides, and other types of anthropogenic impact. The informativeness and sensitivity of enzymes during the remediation of petroleum hydrocarbons-contaminated soils have not been adequately studied. Materials and methods. The activity of seven enzymes of oxidoreductases and hydrolases classes of petroleum hydrocarbons-contaminated soils after the application of biochar, sodium humate, nitroammophos and Baikal EM-1 was studied. In 90 days from the moment the ameliorants were introduced into the soil, the enzymatic activity of soils was evaluated by changes in the activity of catalase, dehydrogenases, peroxidases, ferrireductases, invertase, urease, and phosphatases. The integral indicator of soil biological activity (IIBA) and the geometric mean enzymatic activity of soils were evaluated for the classes of oxidoreductases (GMea (ОХ)) and hydrolases (GMea (HD)). Results. During the remediation of petroleum hydrocarbons-contaminated chernozem, the concentration of D0.5 of biochar and Baikal EM-1 has a stimulating effect on the activity of oxidoreductases and hydrolases of the soil, and D2 of nitroammophos and sodium humate – D2. At a dose of D0.5 of nitroammophos and biochar, the maximum stimulation of IIBA was established relative to control and petroleum hydrocarbons contamination. The introduction of nitroammophos stimulated the activity of three out of seven enzymes, and biochar stimulated the activity of five out of seven enzymes regarding petroleum hydrocarbons contamination. The highest efficiency of nitroammophos is largely due to excessive stimulation of the urease activity of ordinary chernozem. The values of the geometric mean enzymatic activity (GMea) of oxidoreductases and hydrolases were stimulated relative to the control at a dose of D0.5 of each ameliorant. The sensitivity series of petroleum hydrocarbons-contaminated chernozem enzymes after the introduction of ameliorants from the most sensitive to the least sensitive is the following: ferrireductases > peroxidases > urease > phosphatase > dehydrogenases > invertase > catalase. According to the degree of restoration of the enzymatic activity of soils, the ameliorants can be arranged in the following order (in % of petroleum hydrocarbons contamination): nitroammophos > biochar > sodium humate > Baikal EM-1. Conclusion. During the remediation of petroleum hydrocarbons-contaminated chernozem, the most stimulating effect on the activity of oxidoreductases and soil hydrolases is exerted by the ameliorant at a concentration of D0.5. For biodiagnostics of the ecological state of petroleum hydrocarbons-contaminated black soils, we recommend using the activity of ferrireductases, peroxidases, urease, and phosphatase.