沼液中DOM和重金属对抗生素光化学行为和微生态效应的影响机制

Biogas slurry discharged from the livestock and poultry breeding is one of the most important source of antibiotics. Biogas slurry not only contains a large amount of antibiotics and heavy metal but also contanis dissolved organic matter (DOM) and inorganic ions. DOM are widely distirbuted in aquatic environment and play an important role in photochemistry because they are the most important natural sunlight absorbing components. DOM can affect the transfer and trasformation of antibiotics in natural water under sunlight irradiation due to their different sources,fraction and complex with metal ion and DOM. The effect of DOM from biogas slurry and heavy metal on the phototransformation behaviors of antibiotics are still unclear. The fluidity of biogas slurry is great and thus antibiotics and the correspoding resistantce genes are proliferation with the utilization of biogas slurry and accordingly will affect the microbial ecology of the environment. Hence, microbiology ecological effect of biogas slurry should be studied under light irradiation. Chloramphenicol, Sulfonamide and fluroquinolones antibiotics are commonly used to treat bacterial infection and promote animal growth and are ubiquitous in biogas slurry. So it is of great significance to investigate their environmental transformation, fate and ecological risk. Hence,the present study selected chloramphenicol, sulfamethazine and Ofloxacin as model compounds and investigated their photodegradation kinetics, quantum yields, photoproducts, pathways and mechanisms. It is important to separate DOM from biogas slurry according to structure and functional group and and characterize the fraction, and study the photodegrdation mechanism of antibiotics in solution containing DOM fractions and metal ion thus elucidated photosensitive fraction of DOM from biogas slurry soruces and structural properties. Reactive oxidative species and microreaction mechanism of photochemical can be performed through 　transient specturm and EPR thchnologies. Traditional and modern molecular biology technology are applied to study the antimicrobial population, anticrobial activity and succession of microbiological community structure of biogas slurry during irridiation.The study is of great helpful for the understanding of photo transformation and microbiology econology effects of antibiotics in actural environment.

畜禽养殖业排放的沼液是抗生素污染物的重要来源之一。DOM对抗生素光解行为的影响因其来源、组分及与其他金属离子络合形态的不同而具有很大差异。沼液中DOM和重金属对抗生素光解行为的影响及微生态效应还有待进一步揭示。本项目拟选取畜禽养殖业常检出的三种抗生素：氯霉素、磺胺二甲嘧啶和氧氟沙星为目标污染物研究其光化学行为，对沼液源DOM进行分离、表征，研究DOM不同组分及DOM与重金属络合物对抗生素的光解作用机理；通过模拟光化学实验确认其光敏作用的级分和结构特征，采用瞬态光谱和EPR等技术分析活性物种及相关微观反应机制；通过传统的微生物学技术与DGGE、荧光定量PCR等分子生物学技术相结合的方式，分析光化学反应对沼液中抗性微生物数量、活性和微生物群落结构的影响。这些问题的揭示，对于更好的理解抗生素在实际环境中的光解行为机制及生态效应具有重要意义。

畜禽养殖业排放的沼液和沼渣是抗生素污染物的重要来源之一。本项目以揭示沼液中典型抗生素及抗性基因的环境光化学行为规律、微生态效应和沼渣堆肥过程中抗生素抗性基因的变化归趋为研究目标，主要进行以下4方面的研究：（1）选定磺胺二甲嘧啶（SM2）为模型污染物，研究SM2在纯水中的光降解行为。研究了光源、pH、初始浓度等对SM2光解速率常数的影响；运用ROS淬灭实验，分析了光致产生的ROS物种，证实SM2的光解反应除了直接光解还有单线态氧（1O2）参与的自敏化光解；研究了添加H2O2对SM2光解速率的影响。（2）研究不同来源DOM及重金属离子对SM2光化学行为的影响。选取腐殖酸标准物质6种，和沼液源DOM进行对比，结果表明沼液源DOM可以有效地促进了抗生素SM2的光化学降解，而其它6种腐殖酸标准物质表现为抑制抗生素的光解；腐殖酸和Cu(II)或Zn(II)共存时，生成的Cu(II)-SRHA或Zn(II)-SRHA络合物，促进了SM2的光解；采用红外光谱及荧光光谱研究了腐殖酸与水中其他溶解性物质(如金属离子Fe3+)的络合效应，并对络合物进行表征，初步揭示影响抗生素光降解的反应机制。（3）采用实时荧光定量PCR，研究了UV-Vis光照对四环素类（tetY，tetC，tetG， tetA，tetH，tetO，tetQ 和tetW）和磺胺类（sul1，sul2和sul3）抗性基因降解的影响，结果表明UV-vis光照射能有效去除沼液中的ARGs。（4）为研究好氧高温堆肥过程对猪粪来源抗生素抗性基因的影响，采用荧光定量PCR法检测了4个大环内酯类抗性基因（ermA、ermB、ermC 和ermF）、3个β-内酰胺抗性基因（blaTEM、blaCTX和blaSHV)和2个喹诺酮类抗性基因（qnrA和qnrS）在堆肥过程中的变化趋势。研究表明高温堆肥过程不能全部去除所有抗生素抗性基因，对于某些抗生素抗性基因，堆肥可能还是良好的生物反应器而导致抗性基因的增殖。这些问题的揭示，对于更好的理解抗生素和抗生素抗性基因在实际环境中的环境行为及生态效应具有重要意义。