Biodegradation and phytotoxicity of crude oil hydrocarbons in an agricultural soil

Land treatment of crude oil is used by the oil industry, since it has been recognized that hydrocarbons (HC) can be metabolized by the indigenous microbial community of soil. The crude oil biodegradation in agricultural soil was studied for 12-mo to determine the HC biodegradation and leaching, the effect of HC on barley productivity and soil properties, and the potential for HC uptake in the plant. Concentration and composition of HC in the soil were periodically determined at a depth of 0 to 75 cm. The HC concentration decreased over time due mainly to the microbial degradation. At the end, 12% of the primary crude oil amount remained constant in the soil. A vertical migration, leaching and metabolic products of HC into subsoil occurred. The HC have changed soil fertility. Barley has been successfully cultivated in soil but the HC reduced some plant growth parameters. However, HC were not detected in plant seeds. Many of oil-utilizing bacteria and fungi were isolated from soil. The HC biodegradation potential of oil polluted soil (6% to 66%) were higher than of unpolluted one (4% to 53%). The bacteria (22% to 66%) were more active than fungi (4% to 46%) in HC biodegradation. The study demonstrated that agricultural lands with low rates of oil contamination allows the growth of plants. They ensure high efficiency of HC biodegradation. Vertical infiltration plays an important role in HC removing from soil. Alkanes were completely assimilated by microorganisms and polar compounds were more resistant to microbial attack.