The Efficiency of Integrated Bioremediation Techniques in Restoring Oil-Contaminated Soils

Abstract

Contamination of soil ecosystems with oil and petroleum products remains a key environmental problem, requiring the development of effective and environmentally friendly restoration methods. Bioremediation using degradative microorganisms and plants is considered the most promising method for restoring man-made lands. This article examines the effectiveness of the integrated, phased application of chemical, biotechnological, and phytomeliorative techniques for restoring oil-contaminated gray-brown soils (Gypsisols) on the Absheron Peninsula (Azerbaijan), covering approximately 25,000 ha. A laboratory model experiment on the bioremediation of oil-contaminated soils was conducted over 180 days using various ameliorant treatments and native oil-degrading bacteria isolated from these soils and tested for their destructive activity. Microbial counts were determined by plating on nutrient media. The degree of oil biodegradation was monitored using Expand to United States Environmental Protection Agency (EPA) method 3540, and the hydrocarbon-degrading activity of the strains was determined by optical density. Phytotoxicity before and after the experiment was assessed according to ISO 11269-2:2012. The effectiveness of phytoremediation using garden pea (Pisum sativum L.) was assessed based on the total microbial count and hydrocarbon loss in the soil. Laboratory modeling results showed that improving substrate properties with dolomite flour created favorable conditions for the development of an introduced consortium of native bacteria (Arthrobacter sp., Bacillus sp., Pseudomonas sp.), while the final use of phytoremediation (Pisum sativum L.) stimulated microbial community development through the rhizosphere effect. Thus, the integrated approach contributed to a 95–97% reduction in the initial amount of petroleum hydrocarbons within 6 months. These results confirm the high effectiveness of the integrated application of various techniques for the environmentally safe restoration of industrially oriented soils in arid climates, opening up prospects for the reclamation of disturbed lands.