石油污染土壤自然衰减过程多环芳烃降解基因动态特征

Dynamic characteristics of genes involved in degradation of polycyclic aromatic hydrocarbons during natural attenuation of crude oil-contaminated soils in Xinjiang, China

摘要:

新疆石油污染土壤中微生物多环芳烃(polycyclic aromatic hydrocarbons, PAHs)降解功能基因研究甚少，且环境因子和功能基因之间相关性仍不清楚。【目的】揭示新疆石油污染砂质土壤自然衰减过程中多环芳烃降解关键基因结构和变化规律。【方法】以新疆准东油田为研究区，分析同一采油区不同石油污染年限土壤理化因子和多环芳烃含量变化，采用扩增子测序研究石油自然衰减过程中多环芳烃降解酶基因结构变化规律，利用Mental检验探讨其环境驱动因子。【结果】石油污染时间1年和3年的土壤中有多项理化指标与背景土存在显著性差异，而污染5年土壤与背景土之间仅2项指标具有显著性差异，随石油自然衰减逐渐恢复至正常。石油污染1年的土壤中16种多环芳烃除苊烯和䓛以外，其余14种多环芳烃均高于石油污染3年和5年土壤，多环芳烃总量和含油率污染1年土壤均显著高于污染3年和5年的土壤，多环芳烃会在污染后短时间内迅速被降解。扩增子测序结果显示，萘双加氧酶基因分类操作单元(operational taxonomic units, OTUs)序列随污染年限延长逐渐增多；芳环羟化双加氧酶基因OTUs序列BLAST(basic local alignment search tool)比对注释为6类多环芳烃降解基因，随着污染年限延长呈现先升高后降低趋势，污染5年土壤后OTUs急剧减少。Mental检验结果显示，土壤可溶性有机碳和含水量会显著影响功能基因结构，多环芳烃并不能显著影响功能基因结构。【结论】新疆准东油田石油污染砂质土壤自然衰减过程中多环芳烃降解基因结构主要受土壤可溶性有机碳和含水量影响。

Abstract:

There are few studies about the functional genes involved in the microbial degradation of polycyclic aromatic hydrocarbons (PAHs) in crude oil-contaminated soils in Xinjiang, and the correlations between environmental factors and functional genes remain unclear. [Objective] To reveal the structures and dynamic characteristics of key PAH-degrading genes during the natural attenuation of crude oil-contaminated sandy soils in Xinjiang. [Methods] We studied the variations in the physicochemical properties and the content of PAHs in the soils contaminated by crude oil for different years in the same oil production area in Zhundong Oilfield in Xinjiang. Amplicon sequencing was employed to study the dynamic characteristics of genes involved in the degradation of PAHs during the natural attenuation of crude oil-contaminated soils. Mental test was performed to explore the environmental driving factors. [Results] The soils contaminated by crude oil for 1 and 3 years had several physicochemical properties significantly different from the background soils, while that contaminated for 5 years had only 2 physicochemical properties significantly different, which gradually returned to normal levels with the natural attenuation of crude oil. Among the 16 PAHs studied, the remaining 14 PAHs except acenaphthylene and chrysene in the soils contaminated by crude oil for 1 year had higher content than those in the soil contaminated by crude oil for 3 and 5 years. The total PAHs and crude oil content in the 1-year contaminated soils were significantly higher than those in the 3-year and 5-year contaminated soils, which indicated that PAHs could be rapidly degraded in a short time after contamination. The amplicon sequencing results showed that the operational taxonomic units (OTUs) of naphthalene dioxygenase gene gradually increased with the extension of pollution years. The OTUs of aromatic ring-hydroxylating dioxygenase gene were annotated by BLAST alignment into 6 types of PAH-degrading genes, which first increased and then decreased with the extension of contamination time. The OTUs of aromatic ring-hydroxylating dioxygenase gene presented dramatically decreased diversity within 5 years of contamination. The Mental test results showed that the functional gene structures were significantly affected by soil soluble organic carbon and water content and not by PAHs. [Conclusion] The structures of PAH-degrading genes are mainly affected by soil soluble organic carbon and water content during the natural attenuation of crude oil-contaminated sandy soil in the Zhundong Oilfield of Xinjiang.