碱蓬-生物炭固定化嗜盐菌联合修复盐碱土壤多环芳烃污染的机制研究

Polycyclic aromatic hydrocarbons (PAHs) are widespread in oil field contaminated soil. This oil field contaminated soil usually has a high salt content, high pH, as well as a high concentration of PAHs. The efficiency for bioremediation of PAHs in saline-alkali soil is often unsatisfactory to remove PAHs by bioaugmentation using only halophilic bacteria in saline-alkali soil. In order to enhance the efficiency of bioremediation of PAHs, methods that use Suaeda heteroptera, and biochar immobilized moderately halophilic bacteria are suggested as a feasible strategy. This work clarifies molecular mechanisms of degradation of PAHs in a saline-alkali environment by moderately halophilic bacteria. Additionally, the objectives of this study are to focus on the interaction between Suaeda heteroptera and meat and bonemeal biochar immobilized moderately halophilic bacteria by metagenomics and metatranscriptomics, promote the growth of Suaeda heteroptera and its roots absorption of soil salts. The competitive advantage of moderately halophilic bacteria in rhizosphere soil and PAHs activity can be maintained effectively, so as to achieve high efficiency of PAHs degradation and improve soil saline and alkaline environment. The results of the research have successfully achieved efficient, stable and safe bioremediation and provide the theoretical basis for future real-world implementation.

针对采油区污染土壤中PAHs组分复杂且浓度高，同时污染土壤呈现盐碱化、板结化，造成污染土壤暴露的潜在风险高和自净效率低两大突出问题，本研究以盐碱土壤改良的先锋植物翅碱蓬和在盐碱环境中高效降解PAHs的中度嗜盐菌为材料，采用翅碱蓬-生物炭固定化中度嗜盐菌的联合生物强化技术修复盐碱土壤PAHs。基于转录组学、代谢组学等阐明中度嗜盐菌AD-3在高盐碱环境中降解PAHs的分子机制，利用宏组学解析肉骨生物炭固定化中度嗜盐菌AD-3与翅碱蓬联合修复的相互作用机制，并通过优化环境因素，促进翅碱蓬的生长和对根际土壤盐的吸收。通过生物炭固定化维持中度嗜盐菌在根际土壤中的竞争优势和高效降解PAHs活性，为实现PAHs高效降解的同时并改良土壤盐碱环境，以达到降低污染土壤的潜在风险并改良土壤。本研究期望能够为我国油田地区PAHs污染盐碱土壤的生物修复提供理论和技术支撑。

我国部分采油区多环芳烃(Polycyclic Aromatic Hydrocarbons, PAHs)污染土壤面积大、土壤中PAHs浓度高、种类多、盐碱含量高、潜在风险大，亟需解析PAHs高效降解并协同改良土壤盐碱的机制，突破生物强化修复效率不高的技术瓶颈。本研究以翅碱蓬和PAHs高效降解嗜盐菌Martelella sp. AD-3为材料，采用植物-生物炭固定化微生物的联合生物强化修复PAHs污染盐碱土壤。主要研究结果如下：（1）基于多组学阐明了AD-3菌降解多环芳烃的分子机制，该菌基因组存在环羟基化双加氧酶基因等PAHs降解基因簇以及四氢嘧啶等相容性溶质的合成与转运耐盐相关基因；AD-3菌在5%盐度+菲的降解组，环羟基化双加氧酶组分中的铁氧还蛋白上调110倍，甘氨酸甜菜碱转运蛋白上调5.5倍，尤其四氢嘧啶合成酶仅出现在高盐菲降解组。（2）阐明了生物炭固定化AD-3菌强化修复PAHs污染盐碱土壤的机理。经Fe3O4改性的生物炭负载菌量达4.2×1010 CFU/g，24 h对200 mg/L的菲降解率为95.46%，比未改性生物炭负载量和降解率分别提高了53.62%、10.95%，同时能提高土壤16S rDNA含量1.73倍。改性生物炭菌剂在4℃条件下保存21 d后对菲降解率仍达90.0%，高于游离菌的54.03%。（3）生物炭固定化中度嗜盐菌AD-3菌与翅碱蓬联合修复的相互作用机制研究。Fe3O4改性生物炭固定化菌剂与翅碱蓬联合修复42 d 后对菲去除率为 91.67%，同时土壤 pH 和电导率分别下降了 0.15-0.18 和 1.78-2.16 ds/m，生物炭固定化菌剂的添加使翅碱蓬根系土壤中富集了丰富的Halomonas等PAHs降解微生物，PAH-RHDα基因含量较游离菌剂添加提高2.64-19.79倍，有利于增强PAHs的微生物降解。联合修复体系翅碱蓬鲜重较仅种植翅碱蓬增加了0.97-1.25倍，有效缓解了翅碱蓬的生存压力，使翅碱蓬能更高效吸收土壤中的盐分和 PAHs。此外，翅碱蓬根系分泌物富含的草酸、柠檬酸等有机酸类为根系生物的存活提供良好的微环境。二者的协同作用促进了PAHs污染盐碱土壤的修复。本项目研究成果可为微生物修复我国油田地区PAHs污染盐碱土壤及生态恢复中的应用提供理论依据和技术支撑。