Microbial respiration as an indicator of the efficiency of biopreparations for oil-contaminated soil purification

Abstract

This paper presents a comparative study of the efficiency of various oil-degrading preparations used to clean natural soil from old oil contamination, using the integrated indicator of microbial respiration rate. The object of the study was the natural sandy loam soil with an oil pollution lasting about 60 years. A comparative study of the effectiveness of five different biological oil-degrading preparations for cleaning soil from petroleum products was conducted in a laboratory experiment under extreme conditions - low air temperature (14-16°C) and without the addition of fertilizers and lime. The initial petroleum products content in the soil was 3400 mg *kg^-1. The indicators of the effectiveness of the biopreparations used in the experiment were the microbial respiration rate, which was determined by the intensity of the soil CO₂ production using the adsorption method, as well as the content of petroleum products in the soil, which was determined using IR spectrometry. Over a 28-day experiment, depending on the preparation type, 8-16% of the petroleum products were mineralized from their original content. Two biopreparations, “Destroyl” and “Nord”, did not affect the activity of biodegradation, the other studied preparations, “Devoroil”, “Soyleks” and “Aborigen”, intensified the process of petroleum products’ degradation by 1.5, 1.8 and 2.0 times, respectively. The reason for such significant differences in the effectiveness of the studied oil-degrading biopreparations was their specific composition. Microbial respiration has been proven to be a highly informative indicator of the activity of the petroleum hydrocarbons’ mineralization in soil. A strong correlation was established between the rate of microbial respiration and the dynamics of petroleum products in the soil (R > 0.80).