沉积物不同还原性条件下石油烃的降解及重金属的转化

The co-occurrence of petroleum hydrocarbons and heavy metals are commonly existed in sediments. So far, the biodegradation behaviors of petroleum hydrocarbons during sediment bioremediations have not yet well understood due to the complexity of hundreds to thousands fractions of petroleum hydrocarbons, the anaerobic conditions of sediment environments, as well as the heterogeneity of sediments. Besides, investigations on the effects of bioremediations under various reducing conditions on the heavy metals are still very limited. The proposed study attempts to investigate the biodegradation behaviors of petroleum hydrocarbons under denitrifying condition, Fe(III)-reducing and sulfate-reducing conditions, as well as methanogenic condition. The biodegradation efficiencies, preferential degradation patterns and degradation kinetics of different petroleum hydrocarbon fractions will be analyzed. The microbial community structure and diversity, and the activation pathways of different petroleum hydrocarbon fractions will also be determined in order to explore the involved mechanisms of different biodegradation behaviors of petroleum hydrocarbons under various reducing conditions. Meanwhile, the transformation of heavy metal speciation distribution, the changes of heavy metal mobility and bioavailability under various reducing conditions will be systematically investigated, and the effects of such heavy metal transformation on the aquatic/sediment environments will be studied in a long run. Based on the above results, the interactions between petroleum hydrocarbon degradation and heavy metal transformation under various reducing conditions will be explored. The outcomes obtained from the proposed research will assist in revealing underlying mechanisms of the degradation and transformation behaviors of various contaminants in a combined polluted environment. And in real practice, this study may provide useful technical data for determining suitable bioremediation strategies to effectively decontaminate petroleum hydrocarbons from sediments with simultaneously minimizing the potential adverse influence of the co-presented heavy metal on the environment.

石油烃和重金属所造成的复合污染普遍存在于水体沉积物当中。由于石油烃的复杂性、沉积物的厌氧环境及本身较复杂的非匀质体系，目前对于沉积物中石油烃的降解行为仍然缺乏系统的认识。而不同还原性条件下的生物修复过程对沉积物中重金属的影响也鲜有报道。本项目拟通过对反硝化、三价铁还原、硫酸盐还原以及产甲烷等条件下不同组分石油烃的降解效率、优先降解模式及降解动力学特征等研究揭示石油烃在沉积物中的厌氧降解行为，并结合微生物种群结构及多样性和石油烃降解初始活化方式的分析探讨石油烃不同还原性条件下降解行为的产生机制。同时还将系统分析不同还原性条件下重金属形态、迁移性及生物可利用性的转化及其对环境的长期效应，并探讨这一过程中石油烃降解与重金属转化的交互作用。其研究结果将有助于更好地理解复合污染条件下各类污染物的降解和转化规律；在工程实践中也能够更加有效地对污染场地开展生物修复并全面评估修复过程对环境造成的潜在影响。

随着人口的快速增长和经济社会发展，越来越多的石油烃类有机污染物被不断地释放到周围的环境中，给生态系统及人类健康带来了严峻的威胁。河道沉积物是石油烃类有机污染物进入环境中后的主要“储存库”和“二次污染源”。在沉积物环境中，微生物降解是有机污染物去除的主要途径。然而由于有机污染物组分及沉积物环境条件的复杂多样，导致对沉积物环境中有机污染物的降解行为、关键微生物等降解机制的认识仍然不够充分，制约了沉积物环境中有机污染的微生物修复技术发展与应用。因而，本研究首先利用室内培养实验从有机污染物的降解行为和关键微生物两个角度系统地研究了沉积物环境中有机污染物微生物降解机制。进一步地，基于沉积物环境中有机污染物降解行为的微生物调控机制，探索了针对复合污染沉积物的多项生物修复技术，主要结果和结论如下：反硝化和三价铁还原条件下有利于短链正构烷烃和低分子量多环芳烃的降解；产甲烷条件下有利于长链正构烷烃和高分子量多环芳烃的降解。进一步发现羧化作用是正构烷烃在反硝化条件下主要的初始活化方式；加延胡索酸作用是正构烷烃在硫酸盐还原条件下主要的初始活化方式；此外还发现不同还原性条件对重金属的形态转化起到显著影响。利用稳定性同位素标记技术鉴定了菲的主要降解菌。共鉴定出9株降解菌参与了反硝化和三价铁还原条件下菲的降解，其中反硝化条件为Sphingobium属、Desulfitobacterium属和Azoarcus属；三价铁还原条件下为Desulfatiglans属和Deltaproteobacteria纲。反硝化强化微生物燃料电池技术在高效同步降解多种多环芳烃的同时，可以有效去除沉积物中还原性硫化物并产生电能。添加硝酸根的处理组中还原性硫化物的含量的去除率高达94%。反硝化强化微生物燃料电池技术对菲、芘、苯并芘等多环芳烃组分的去除率最高，分别为93%、80%、69%。反硝化强化微生物燃料产生的电压最高，达到341 mV。论文研究结果可为进一步认识沉积物环境中有机污染物的环境行为、环境风险以及制定相关修复措施提供理论依据和数据支撑。