多生态类型湖泊N2O跨界面生成与排放特征及其关键影响因素

Formation and emission of nitrous oxide in eutrophic lakes are attracting increasing attention of researchers. This project aims to begin to solve the difficult problems of nitrous oxide formation, dissolution and transfer across the interfaces in water environments, Taihu Lake, an typical eutrophic lake with multi ecosystem types is selected as research object. We use both microcosm tests in laboratory and in situ observation tests in lake, and also utilize various experimental techniques such as continuous flow incubation, high resolution determination of multi parameters at the sediment-water micro-interface, N-15 tracer, membrane-inlet mass spectrometry and isotope mass spectrometry analysis and Rhizon and peeper pore-water passive sampling, to study the characteristics of N2O production, accumulation, dissolution and transfer in sediment and water column of different region dominated by different ecosystem tapes in Taihu Lake and the key influencing factors. Additionally, we apply microbial and molecular biology techniques such as quantitative analysis of PCR, assessment of fluorescein diacetate hydrolysis activity (FDA), Biolog microplates and PCR-DGGE analyses to study the microbiological mechanism of affecting N2O production and transfer. The purpose of this project is to reveal the mechanism and the effect of different environmental conditions on N2O production and transfer in different lake region dominated by different ecosystem types, the research results of this project has important realistic meanings for the estimation of N2O flux and assessment of the importance of N2O emission from lakes in China and the whole world.

富营养化湖泊中温室气体氧化亚氮（N2O）生成和排放问题正日益受到研究者的关注。针对N2O在水环境中生成、溶存和跨界面迁移相对复杂的问题，以典型的多生态类型湖泊-太湖为研究对象，采用室内微环境试验和湖泊原位观测试验方法，应用连续流动培养、高精度微界面多参数测定、N-15同位素示踪、膜接口质谱和同位素质谱分析与间隙水Rhizon和Peeper法获取等技术，研究太湖不同生态类型湖区N2O在沉积物、沉积物-水界面、水柱和水-气界面等多介质间产生、积累、溶存和跨界面迁移特征及其关键影响因素。并用定量PCR、FDA水解、BIOLOG和PCR-DGGE等微生物和分子生物学技术研究影响N2O生成和迁移的微生物学机制。着重揭示浅水富营养化湖泊不同生态类型湖区环境条件的差异对N2O生成和排放的影响及其内在机制，研究成果对于我国和全球进行湖泊N2O通量估算及评估湖泊N2O排放的重要性都具有重要的现实意义。

多生态类型湖泊N2O生成与排放的时空差异给全球湖泊N2O生成与排放带来了很大的不确定因素，关于N2O在湖泊生态系统中生成与排放机制的研究仍然有限。本研究以典型的多生态类型湖泊-太湖为研究对象，采用室内微环境试验和湖泊原位观测试验方法，应用连续流动培养、高精度微界面多参数测定、N-15同位素示踪、膜接口质谱和同位素质谱分析与间隙水Rhizon和 Peeper法获取等技术，研究太湖不同生态类型湖区N2O在沉积物、沉积物-水界面、水柱和水-气界面等多介质间产生、积累、溶存和跨界面迁移特征及其关键影响因素。并用定量PCR、高通量测序等微生物和分子生物学技术研究影响N2O生成和迁移的微生物学机制。.研究结果表明：沉积物-水界面硝化反硝化速率及N2O交换通量最大值均出现在6月份的藻型湖区，水体氮水平与硝化反硝化速率及N2O交换通量显著相关，而与沉积物氮水平无明显相关关系；N2O交换通量与沉积物-水界面硝化速率关系更为密切，太湖沉积物-水界面硝化反硝化以及N2O交换通量可能仅受水体氮水平影响，硝化和反硝化过程均对N2O的产生有重要影响，但主要受硝化过程控制，太湖沉积物-水界面较低的N2O通量，主要与硝化速率较低有关；水－气界面N2O排放通量全年变幅较小(-0.05~1.16µmol N m−2 h−1)，年均值0.25±0.77µmol N m−2 h−1，现在太湖较低的水柱氮水平是太湖N2O排放各样点间无差异和减少的主要原因。太湖各样点沉积物各反硝化功能基因丰度均表现为夏秋季高冬春季低，具明显的季节变化特征。沉积物TN和NO2--N是影响反硝化功能基因丰度的重要环境因子。各样点沉积物中AOB的多样性指数均无显著差异，NOB的 Shannon指数夏季显著高于冬季。沉积物有机碳可能是影响底泥中硝化细菌多样性的关键因子。亚硝化螺菌属（Nitrosopira）是太湖沉积物硝化细菌中的优势属。藻型湖区与其他湖区底泥样品中硝化细菌物种存在较大差异，沉积物总氮是影响硝化细菌空间分布差异的主要环境因子。该项目的研究成果对于我国和全球进行湖泊N2O通量估算及评估湖泊N2O 排放的重要性都具有重要的现实意义。