Petroleum contamination evaluation and bacterial community distribution in a historic oilfield located in loess plateau in China

Abstract

In this study, petroleum contamination and the corresponding distribution of bacterial communities in the Yanchang oilfield, a historic oilfield in north China was evaluated. Surface soil samples and river sediment samples near the oilfield were collected and analyzed for the total petroleum hydrocarbons (TPHs), n-alkanes, polycyclic aromatic hydrocarbons (PAHs), bacterial biodiversity, and environmental factors. Petroleum fingerprinting analysis and redundancy analysis (RDA) were then conducted to evaluate the petroleum contamination and the bacterial community structure. The results of these studies showed that the petroleum contamination in the study area was high in TPHs, present at the levels in the ranges 1678–6748, 1189–2237, and 1089–1728 mg/kg in the wastelands, sediments, and farmlands, respectively. “Chemical fingerprint” indicators (e.g., carbon preference index near 1 and pristane/phytane < 10) indicate that petroleum pollution in the wasteland near the oil wells migrated to the farmlands and rivers, and deep biodegradation occurred in these places. The microbial diversity analysis identified many genus, including Stenotrophomonas, Arenimonas, Sphingomonas, Aquabacterium, Acinetobacter, Comamonas, and Pseudomonas, containing many known petroleum degrading species. The RDA results indicated that moisture was the most significant factor shaping the local bacterial community, followed by the total nitrogen, total organic carbon, and total phosphorus contents, and pH. This study demonstrated an approach for providing comprehensive information to support evaluation and remediation of regional petroleum contamination.