Crop growth, culturable bacteria, and degradation of petrol hydrocarbons (PHCs) in a long-term contaminated field soil

A greenhouse pot experiment was conducted for investigating the capability of a grass (annual ryegrass), a legume (summer vetch), and a crucifer (white mustard) to grow in a soil with portions from a former coal gasification site, influence the soil bacterial community, and promote the biodegradation of petrol hydrocarbons (PHCs). Soil concentrations of 1517 mg kg−1 of total petrol hydrocarbons (TPHs), including 71.4 mg kg−1 of total US EPA priority polycyclic aromatic hydrocarbons (TPAHs) have caused a significant (P < 0.05) reduction in shoot and root dry matter yields by more than 50%. Culturable bacteria and actinomycetes in soil were as much as 18-fold more abundant and the species composition was largely altered because of PHC contaminants and depending on crop species and age. After 95 days, 68.7% of initial TPH amounts and 59% of the TPAHs had disappeared from unplanted soil. Mustard and vetch fostered the removal of PHCs from soil reaching final TPH concentrations that were 15.6% and 12% lower than in unplanted soil. Both crops elicited the greatest degradative root activities and sustained particularly great populations of rhizosphere bacteria that are known hydrocarbon degraders. None of the crops aided the reduction of TPAHs in soil.