粤港澳大湾区城镇化河流氮素来源解析及迁移转化研究：基于多相多形态氮同位素示踪的探索

课题以粤港澳大湾区为研究区，以河流溶解相、悬浮颗粒相及沉积相氮库为研究对象，针对城市河流氮素高污染负荷、污染源众多和复杂迁移转化过程等特点，在传统氮同位素示踪基础上引入多相态多形态氮同位素联合示踪技术开展城市河流氮循环研究。研究旨在：1）明确城市河流氮素多相态及多形态的含量水平及时空变化特征，揭示其对环境因子的响应规律；2）结合大湾区典型城市产业发展特色，建立适用于大湾区典型氮源的多同位素动态谱线特征，基于多端元混合模型开展多相态多形态氮素定量源解析研究；3）以同位素分馏原理为理论基础，考察城市河流复杂水动力、温度及氧化还原条件等环境因子限制下，多形态氮素的相间转化规律。主要创新点：重点挖掘氮循环中间产物亚硝态氮和氧化亚氮氮氧同位素的应用潜力，探讨城市河流在高污染负荷条件下的源汇过程及生化反应的作用机制，该研究为深入揭示城市河流氮循环过程及开展精细化水环境管理提供了技术支撑和科学依据。

This research takes the Guangdong-Hong Kong-Macao Greater Bay Area as the research area, taking the dissolved nitrogen, suspended particulates, and sedimentary nitrogen reservoirs of the river as the research objects. In view of the characteristics of urban rivers such as high nitrogen pollution load, multiple pollution sources, and complex migration and transformation processes, based on the traditional nitrogen isotope tracing technique, the multi-phase and multi-phase nitrogen isotope tracing technology is introduced to clarify the spatial and temporal variations of the nitrogen in urban rivers, and to reveal their response to environmental factors. The multi-isotopic characteristics of the typical pollution sources is established based on the filed work in the GBA. And then the multi-phase multi-form nitrogen quantitative source apportionment is carried out based on the SIAR model. Based on the principle of isotope fractionation, we investigate the transformation of nitrogen among different phases under the constraints of environmental factors such as complex hydrodynamics, temperature, and redox conditions in urban rivers. Further, we focus on the application of nitrogen and oxygen isotopes of nitrite and nitrous oxide to reveal the source and sink process and the mechanism of biochemical processes in urban rivers with high pollution loads. This research provides a scientific basis to nitrogen cycle of urban rivers and meticulous water environment management.