藻型水体不同水层生物脱氮排放N2和N2O的垂向空间异质性及驱动机制

Denitrification is the main process responsible for permanent removal of nitrogen (N) from aquatic ecosystem to the atmosphere, leading to the reduction of eutrophication. Although the process of denitrification in aquatic ecosystem plays a significant role in reducing excess nitrogen (N), it is still unclear the characteristic patterns of denitrification process in eutrophic waters. Based on the phenomena of the vertical N2 and N2O distribution at different water layers in eutrophic waters, this project will use a self-developed gas collecting apparatus to collect in situ nitrogen gas (N2 and N2O) released from different layers of waters under the different hydraulics. The concentrations, ratios and flux of N2 and N2O will be studied in the two eutrophic waters with significantly different alga types. At the same time, the vertical distribution of the environmental factors (such as DO, pH, ORP, temperature, light intensity and chlorella-a et al.) will be monitored at the different water layers in eutrophic waters. The interactions between nitrogen gas (N2 and N2O) emission and the environmental factors will be statistically analyzed to elucidate the mechanisms involved in the mediating the vertical distribution of N2 and N2O in eutrophic waters. Through these studies, it is expected to find the main environmental factor influencing the vertical distribution of denitrification, achieve the comprehensive understanding of denitrification process in eutrophic waters, and provide the principles in increasing capacity of self-purification in eutrophic waters.

水体生态系统中反硝化脱氮过程对减缓过量氮引发的水体富营养化意义重大，然而目前为止还未能真正掌握水体的反硝化脱氮规律。本申请根据创新发现的藻型水体不同深度水层气态脱氮垂向空间上存在分层效应的现象，拟借助新型的可原位、连续收集不同深度水层断面释放脱氮气态产物的装置，研究水动力条件具有明显差异的两类藻型水体不同深度水层断面排放N2/N2O的浓度、比例及通量的规律，并同步原位、实时监测与反硝化脱氮过程密切相关的环境参数变化规律。进一步利用地统计学手段，评价两类藻型水体气态脱氮过程在垂向空间上的变异程度，并分析不同深度水层断面中各环境因素变化规律与相应水层中反硝化气态脱氮特征指标变化的耦合关系及主控驱动因子。通过研究期望阐明富营养化水体生物脱氮垂向空间异质性规律及主要驱动机制，为全面掌握富营养化水体的反硝化脱氮规律，把握水体生态系统脱氮过程的调控机制及提高水体生态系统自净能力提供理论依据。

水体生态系统中反硝化脱氮过程对减缓过量氮引发的水体富营养化意义重大，然而目前为止还未能真正掌握水体的反硝化脱氮规律。本项目借助自主研发的新型的可原位、连续收集不同深度水层断面释放脱氮气态产物的装置，对两类不同藻型水体（湖泊、河塘）不同深度水层断面气体释放的特征、环境因素变化规律和不同深度水层断面微生物群落分布规律及主要驱动环境因子进行了研究。发现太湖和农用富营养化水体在水体环境特征、气体释放特征方面具有较大差异，富营养化河塘水体不同深度水层气态脱氮垂向空间上存在分层效应的现象，呈现表层与底层水体气体释放通量高、中层水体气体释放通量低的情况，而太湖水体该分层效应不明显；不同深度水层富营养化水体释放气体的量及生物脱氮气体N2、N2O 的通量主要受到温度、溶解氧DO、光照强度、藻类浓度及分布的影响；富营养化河流细菌群落丰度、结构在不同深度水层（0.1m、0.6m、底泥以上0.05m）及上游-下游之间均存在着明显的时空分布差异；分析表明叶绿素Chlo-a浓度、养分化学计量比（TDP/TDP, NH4+/TDP, NO3-/PO43-）、pH是驱动细菌群落结构空间分布形成差异的主要环境因子。本项目的研究结果有助于更加全面、系统地掌握富营养化水体的脱氮规律，充分了解不同深度水层反硝化生物脱氮速率、脱氮程度、释放N2/N2O 比例的驱动机制，在此基础上能够把握水体生态系统脱氮过程的调控机制，提高水体生态系统自净能力，调节N2/N2O 的释放比例，控制温室气体的排放，为优化水生态系统管理策略提供理论依据和决策参考。