城市生物滞留系统中的反硝化和厌氧氨氧化脱氮作用

Excess nitrogen in urban runoff is becoming one of the major sources of eutrophication of the receiving water bodies. Although bioretention, as part of the emerging concept “Sponge City”, has been proved effective in controlling runoff quantity and quality, its nitrogen removal performance has fluctuated significantly under different conditions in various systems. This proposed project is designed to use the 15N tracer technology to explore the fates of nitrogen in bioretention systems, focusing on evaluating the contribution of the gaseous nitrogen loss pathway to nitrogen removal over multi-timescales; apply the 16S rRNA gene sequencing technology to determine whether there are anammox bacteria taking part in nitrogen removal; use the natural abundances of soil nitrate 15N and 18O isotopes and 15N tracers to constrain the rates of denitrification and anammox simultaneously; study the influence mechanism of several environmental and design factors on the microbial community structure and rates of denitrification and anammox, which will provide insights into the optimization of bioretention engineering practices.

城市地表径流中过量的氮是导致水体富营养化的主要原因之一。生物滞留系统是构建海绵城市的基本单元，在调控径流水量水质方面发挥着重要作用，但目前对氮的去除不稳定。本申请项目拟应用稳定性同位素15N标记技术示踪生物滞留系统内氮的归趋，重点评价气态氮损失在多时间尺度上对脱氮的贡献；应用16S rRNA基因高通量测序技术和15N标记技术考察是否存在厌氧氨氧化细菌和厌氧氨氧化脱氮途径；通过测定硝酸盐15N和18O同位素自然丰度以及室内培养实验中示踪15N标记同时表征系统中的反硝化和厌氧氨氧化作用速率；探讨生物滞留系统的主要环境和设计因素对反硝化和厌氧氨氧化的细菌分布和作用速率的影响机理，为生物滞留系统的工程实践优化提供科学依据。

本项目应用稳定性15N同位素标记技术示踪了生物滞留系统内氮的归趋，重点评价了气态氮损失对脱氮的贡献；应用稳定性15N同位素标记控制实验完整解析了生物滞留系统“黑箱”中的主要氮转化过程；结合16S rRNA基因和功能基因分析，广泛调研了深圳和珠海市生物滞留系统中的微生物群落结构特征，未能检测到厌氧氨氧化微生物（anammox）的存在，说明生物滞留系统中厌氧氨氧化途径贡献较小，但意外验证了具有单独将氨氧化为硝酸盐能力的全程氨氧化微生物（简称comammox）的存在；耦合稳定性同位素技术和功能基因分析，探讨了主要环境和设计因素对硝化和反硝化作用的影响，揭示了生物滞留系统中脱氮机理。该项目有望为生物滞留系统的脱氮能力提供诊断和改良建议，为模拟生物滞留系统去除径流氮污染的过程提供理论指导和数据支持。