生物滞留措施被广泛应用于城市地表径流水量削减与污染控制，但是对地表径流氮污染去除作用变化范围大、不稳定。这与氮素复杂的生物地球化学转化与循环有关。本项目拟采用水文、水质监测与多种定量微生物反硝化过程和速率的综合方法，选择不同设计配置的生物滞留设施，连续监测研究城市地表径流不同形态氮素（PON、DON、NH4+、NO3-）在生物滞留中的截留转化与去除过程。通过N2O排放通量、反硝化潜势与反硝化功能基因丰度组成的动态监测研究，定量微生物反硝化对氮素的去除作用，揭示生物滞留设计配置与水文、水质变化对反硝化除氮的耦合影响机制。该项目的成功实施，不仅可为生物滞留除氮的设计配置提供理论依据，而且可增加城市这种特殊生境中氮循环的认知。

Bioretention measures have been widely employed to detain urban stormwater and control its pollution. However, nitrogen removal performance is often highly variable, which may be related to complex biogeochemical transformation and cycling of nitrogen. In this project we propose to continuously monitor the retention, transformation and removal process of nitrogen multiple chemical forms (e.g., total nitrogen, particulate organic nitrogen, dissolved organic nitrogen, ammonium and nitrate) in bioretention facilities with different design configurations. An integrated method including hydrology, water quality monitoring and quantitative microbial denitrification process and rate will be employed. We will quantitatively characterize nitrogen removal through microbial denitrification by using dynamic monitoring of N2O emission flux, denitrification potential, and functional gene composition and abundance of denitrifying bacteria, and further disclose the influence mechanisms of the bioretention design configurations, hydrogeology and water quality change on nitrogen removal through denitrification. The successful implementation of this project will (1) fill the knowledge gap regarding the importance of denitrification as a nitrogen removal pathway , and (2) provide preliminary understanding of microbial nitrogen cycling functions and drivers in these ecosystems.