Study of Bacterization of Medicago sativa L. and Cynodon dactylon (L.) Pers. During the Process of Phytoremediation of Oil-contaminated Soils

Abstract

Recultivation of oil-contaminated soils on the Absheron Peninsula is one of the most important environmental and social problems for this region. One of the promising ways to solve the problem of soil pollution with petroleum hydrocarbons is the development of methods and approaches for their purification and detoxification in situ, and above all, biodetoxification and bioremediation. In a model vegetation experiment using complex systems of a mixture of plants and microorganisms, phytoremediation of soil contaminated with crude oil at a concentration of 15 g/kg was investigated. It has been established that the inoculation of plants with the modified Fermi-Start biological product affects the number of rhizosphere microorganisms that stimulate plant growth, as well as the degree of purification of gray-brown soil from oil. Cynodon dactylon is an effective biosystem for the remediation of oil-contaminated gray-brown soils as it is modified by a culture of an oil-oxidizing microorganism of the Pseudomonas aeruginosa, isolated from oil-contaminated gray-brown soil, the Fermi-Start biological product and belongs to the group of “effective microorganisms”, associated with plants — Medicago sativa. The joint introduction of the Fermi-Start biological product and the culture of P. aeruginosa had the greatest protective effect on seedlings from exposure to crude oil. The height of the shoots increased by 71% compared with the negative control, in parallel, the degree of oil degradation increased to 24%. A significant role of alfalfa in stimulating the number of rhizosphere microorganisms capable of hydrocarbon degradation has been revealed. This is confirmed by data showing that the number of microorganisms in the plant rhizoplane was 1–2 orders of magnitude higher (about 1.1×107 on average) than in the rhizosphere (about 1.4×105 on average), which may be due to secretion of plant root exudates. The results of the research allow us to recommend the use of a plant-microbial biosystem consisting of Medicago sativa and Cynodon dactylon, together with a Fermi-Start modified biological product for phytoremediation of gray-brown soil contaminated with crude oil.