Vertical stratification of bacteria and the chemical compounds in crude oil-contaminated soil layers of the semi-deserted Dzungharian Basin

The largely semi-deserted and deserted Dzungharian Basin sites in the northwest of China geologically represent an extension of the Paleozoic Kazakhstan Block and were once part of an independent continent. For reasons of overdevelopment and unreasonable operations during the process of exploitation and transportation, oil pollutants that were discharged into the soil environment caused serious pollution in this weak ecosystem. To explore the bacterial community composition in detail and their possible origination and potential during the natural attenuation of petroleum contaminants in this type of ecologic niche, GC-MS and high-throughput sequencing techniques were used to resolve the organic compounds and bacterial communities in vertical soil layers. The degradation of petroleum contaminants in semi-deserted and deserted soils mainly occurred in the layer at a depth of 45–55 cm. During this process, aromatic and heterocyclic compounds were significantly enriched in soils. The bacterial communities in this basin exhibited a distinct vertical stratification from the surface layer down to the bottom soil layer. Considering the interaction between the community composition and the geochemical properties, we speculate that the degradation of petroleum contaminants in this semi-deserted and deserted soil might represent a microorganism-mediated process and mainly occur in the deeper soil layer.