摘要
氧化亚氮(N_(2)O)是强温室气体和破坏臭氧层的主要物质之一,河湖生态系统是人为活动导致N_(2)O排放的热点区域.含有nosZ功能基因的N_(2)O还原菌(N_(2)ORB)是唯一已知的N_(2)O还原微生物,在减少N_(2)O排放中起着至关重要的作用.先前的研究关注于河湖中N_(2)O的产生和排放过程及其影响因子,缺少对N_(2)O汇过程及其微生物还原作用的系统报道.本研究通过系统梳理发现,寒冷的北方地区和河湖局部位点,如底泥、水库深水层和水草区,广泛表现为N_(2)O的汇.非反硝化N_(2)ORB是N_(2)O的净汇,新发现的nosZⅡ型N_(2)ORB更加多样,其N_(2)O还原酶转位能量需求更低.相比于nosZⅠ型N_(2)ORB,nosZⅡ型N_(2)ORB还原N_(2)O的半饱和常数更低,对N_(2)O的亲和力更高,在利用环境中低浓度的N_(2)O时具有优势.内源电子供体对N_(2)O还原过程的影响受微生物自身代谢特性的影响,内源电子供给不足会减弱N_(2)O还原过程,然而部分完全反硝化菌株会优先进行N_(2)O还原.河湖系统中的胞外呼吸细菌和腐殖质等电子穿梭体,可以增加外源电子供给,从而促进N_(2)O还原.河湖系统中竞争性电子受体对N_(2)O的影响复杂,可以通过影响电子分配减弱反硝化细菌尤其是nosZⅡ型N_(2)ORB的N_(2)O还原性能,但也有发现并不会影响水体N_(2)O/NO_(3)-和纯菌培养系统稳定阶段的最低N_(2)O浓度.最后,温度、溶解氧浓度、pH和河流水力停留时间会通过改变N_(2)O还原酶活性和N_(2)O还原反应时间来影响河湖系统N_(2)O还原过程.未来应当加强对河湖系统中原位N_(2)ORB的生物动力学特征及其环境影响机制的探索,提高对环境中N_(2)O减排机制的理解,这对正确估算全球N_(2)O温室气体排放总量及其受全球变化的影响具有重要意义.
Nitrous oxide(N_(2)O)is a potent greenhouse gas and a major contributor to ozone layer depletion.River and lake ecosystems are hotspots for anthropogenic N_(2)O emissions.N_(2)O emissions from river and lake ecosystems are the end result of N_(2)O production and consumption processes.N_(2)O-reducing bacteria(N_(2)ORB)containing functional nosZ gene are currently the only known biological N_(2)O reduction process and play a vital role in reducing global N_(2)O emissions.However,there is currently a lack of systematic research on N_(2)O sinks in rivers and lakes,microbial N_(2)O reduction,and factors affecting N_(2)O production and emission.Through systematic investigation,this study found that northern cold areas and specific locations such as sediments,deep water layers in reservoirs,and aquatic vegetation zones are significant sinks of N_(2)O.The various reduction steps of denitrification occur mostly in an environmental setting in a modular manner.Non-denitrifying N_(2)ORB acts as a net N_(2)O sink.The newly discovered nosZⅡ-type N_(2)ORB exhibits greater diversity and belongs to different phyla,including Proteobacteria,Firmicutes,Bacteroidetes,and Chloroflexi,among others.In addition,nosZⅡ-type N_(2)ORB contains a greater number of non-denitrifying N_(2)ORB and exhibits lower translocation energy requirements for N_(2)O reductase.There is no significant difference in the maximum N_(2)O reduction rate between nosZ I-type and nosZⅡ-type N_(2)ORB.However,the N_(2)O reduction half-saturation constant of nosZⅡ-type N_(2)ORB is significantly lower than that of nosZⅠ-type N_(2)ORB.Furthermore,nosZⅡ-type N_(2)ORB exhibits significantly higher N_(2)O affinity compared with nosZⅠ-type N_(2)ORB.Therefore,nosZⅡ-type N_(2)ORB has advantages in utilizing low concentrations of N_(2)O in river and lake ecosystems.Finally,endogenous electron donors,exogenous electron donors,competitive electron acceptors and other environmental factors significantly affect the N_(2)O reduction process by affecting the activitie
作者
宋康
邓闵
森巴提·叶尔肯
王昱人
李露
SONG Kang;DENG Min;SENBATI Yeerken;WANG Yuren;LI Lu(State Key Laboratory of Freshwater Ecology and Biotechnology,Institute of Hydrobiology,Chinese Academy of Sciences,Wuhan 430072,China;University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《环境科学研究》
CAS
CSCD
北大核心
2024年第5期929-938,共10页
Research of Environmental Sciences
基金
国家自然科学基金项目(No.42222709,42307505)
湖北省自然科学基金计划项目(No.2022CFA109)。
关键词
氧化亚氮还原
河湖系统
基因型
动力学
电子供体
腐殖质
酶活性
电子穿梭体
nitrous oxide reduction
river and lake systems
gene-type
biokinetic
electron donor
humic substances
enzymatic activity
electron shuttle
