Assessment of the ecological state of haplic chernozem contaminated by oil, fuel oil and gasoline after remediation

Abstract

The intensive use of petroleum hydrocarbon products has made them priority environmental pollutants. When petroleum hydrocarbons enter the soil, a change in physical, chemical, and biological properties is observed. The natural restoration of oil-contaminated soils is a lengthy process; therefore, remediation is often required. The aim of this study is to assess the change in the ecological state of haplic chernozem soil contaminated with oil, fuel oil, and gasoline after remediation. The indicators of soil biological activity, such as phytotoxicity (germination, length of shoots and roots), the activity of oxidoreductase enzymes (catalase and dehydrogenases), and the total number of bacteria were studied. The effects of nitroammophoska fertilizer, sodium humate, biochar, and the biofertilizer “Baikal EM-1” on the ecological state of soils contaminated with oil, fuel oil, and gasoline were studied. Pollution with oil, fuel oil, and gasoline decreased the values of all biological indicators. The most sensitive indicator was the length of radish roots in soils polluted with oil, gasoline, and fuel oil after remediation with nitroammophoska and Baikal EM-1 addition. The length of roots was the most sensitive indicator when remediation was performed with biochar and sodium humate added to soil contaminated with oil and gasoline, and with contamination of haplic chernozem soil with fuel oil, the total number of bacteria was the most sensitive indicator. The most effective ameliorant to phytotoxicity indicators for oil pollution was a 1 D dose of biochar, for fuel oil it was 1 D biochar and 2 D sodium humate, and for gasoline it was a 2 D dose of biochar and Baikal EM-1. All ameliorants at most of the studied doses increased dehydrogenase activity, but increased catalase activity only in some cases. An increase in the total number of bacteria in oil-contaminated soils was promoted by biochar and nitroammophoska at a dose of 2 D. Nitroammophoska was the most effective in ameliorant in soils contaminated with fuel oil; in soils polluted with gasoline, all doses of ameliorant increased the number of bacteria equally. The stimulating effect of ameliorants on biological activity of oil-contaminated haplic chernozem were in the following sequence: nitroammophoska > biochar > sodium humate > Baikal EM-1. The 2 D biochar dose was most effective. The stimulation of biological indicators by ameliorants when soil was contaminated with fuel oil were in the following sequence: biochar > Baikal EM-1 > sodium humate > nitroammophoska. The same sequence of ameliorant stimulation was observed in soil polluted with gasoline. The results of this study can be used to biodiagnose the ecological state of oil-contaminated soils after remediation.