Phytoremediation of alkylated polycyclic aromatic hydrocarbons in a crude oil-contaminated soil

Phytoremediation uses plants and their associated microorganisms in conjunction with agronomic techniques to remove or degrade environmental contaminants. The objective of the field study was to evaluate the effect of vegetation establishment plus fertilizer addition on the biodegradation of alkylated polycyclic aromatic hydrocarbons in a crude oil-contaminated soil. Four replications of the following treatments were used: non-vegetated non-fertilized control; fescue (Lolium arundinaceum Schreb.) - ryegrass (Lolium multiflorum L.) mixture + fertilizer; or bermudagrass (Cynodon dactylon (L.) Pers.) - fescue mixture + fertilizer. Vegetation was successfully established at the site that had an initial total petroleum hydrocarbon (TPH) concentration of 9,175 mg/kg. While alkylated two-ring naphthalenes were degraded in all treatments equally, there was greater degradation of the larger three-ring alkylated phenanthrenes-anthracenes and dibenzothiophenes in the vegetated fertilized plots compared to the non-vegetated non-fertilized plots. In this field study, an increase in rhizosphere soil volume associated with increased root length along with nutrient additions resulted in increased total bacterial, fungal, and polycyclic aromatic hydrocarbon (PAH) degrader numbers that most likely resulted in increased biodegradation of the more recalcitrant alkylated polycyclic aromatic hydrocarbon compounds in the crude oil-contaminated soil.