¹⁴C Isotopes and microbial community structures as evidence for biodegradation in a petroleum hydrocarbon-contaminated aquifer

Petroleum hydrocarbon contamination of groundwater and soil constitutes a serious threat to human health and the natural environment. In situ biodegradation is a low-cost, low-risk and effective technique to remove petroleum hydrocarbon contaminants. The concentrations of total petroleum hydrocarbons (TPH), dissolved inorganic carbon (DIC) and \(^{14} {\text{C}}_{{{\text{HCO}}_{3} }}\) were analyzed, and polymerase chain reaction–denaturing gradient gel electrophoresis was used to investigate bacterial community structures. Downgradient from the contaminated source along the groundwater flow, the concentrations of TPH and DIC decreased and the ¹⁴C content increased from 44.3 to 64.3 pmc, which confirmed petroleum hydrocarbon biodegradation in the contaminated aquifers. The sequence analysis of the DGGE bands revealed that some species of known bacterial biodegrading strains, such as Dechloromonas aromatica RCB, Pseudomonas putida and Pseudomonas protegens, were the dominant bacterial groups in the field. Hydrogeochemical and stable isotope measurements, combined with analysis of bacterial community structures, could be useful tools to prove the occurrence of biodegradation processes in contaminated aquifers.