人类活动对氮循环的扰动日益加剧，氮循环失衡导致的环境污染日趋严重。在此背景下，厘清人类社会-经济-生态系统中的活性氮流动过程，定量识别活性氮的时空分布特征和排放结构特征，探讨活性氮减排与优化控制措施，对于促进经济和环境协调发展具有重要的现实意义。本研究以京津冀地区为案例，运用物质流分析法构建区域尺度活性氮循环模型，应用模型对2005年、2010年和2014年京津冀社会-经济-生态系统中的氮通量进行估算，总结活性氮的时空变化特征和结构特征等，识别其对土壤、大气和水环境的影响。结果表明，从2005年到2014年，京津冀地区活性氮累积总量不断增长，从345万吨/年增长到460万吨/年。土地子系统活性氮累积量由233万吨/年增长为309万吨/年，同比增长33%；大气子系统活性氮累积量由45万吨/年增长为81万吨/年，同比增长80%；而水体子系统活性氮累积量变化不明显，但是活性氮输入源的结构有很大差别。土地子系统是区域尺度氮循环的关键调控部门，而且受人为干扰的直接影响最为显著。2005年、2010年和2014年的氮素保有率分别为42%、44%和40%，十年间陆地系统的活性氮保有率基本稳定。通过与相关研究的对比发现，京津冀陆地系统保有新增活性氮的这项至关重要的能力正在衰退。 本研究进一步收集不同技术条件下全行业活性氮排放因子，结合研究区域特点和数据可得性等因素，建立京津冀地区大气、土地和水体活性氮排放清单，量化活性氮排放总量、强度和结构，识别影响活性氮循环的关键部门和重点行业。结果表明，2014年京津冀全行业NH3排放总量为125.3万吨/年，农业部门是NH3排放的最主要人为源，其中来自畜禽养殖和氮肥施用的NH3排放分别占总排放的55.0%和34.8%。2014年京津冀地区大气环境接收活性氮排放总量215.3万吨/年，其中农业部门占比最高（47%），其次是交通运输部门（22%）和工业部门（21%）；土壤环境接收活性氮排放总量为353万吨/年，其中种植部门的活性氮排放量为270万吨/年，占总排放的76.5%；水体环境接收活性氮排放总量为82.5万吨/年，其中畜禽养殖部门和污水处理部门的活性氮排放量为31.1万吨/年和23.7万吨/年，分别占总排放的38%和29%。本研究识别出影响活性氮循环的关键部门包括农业种植和养殖行业，污水处理部门和道路移动源，建议从农业生产方式转变、流域综合管控、机动车强化治理等方面进行区域活性氮减排与调控。

The disturbance of human activities to the nitrogen cycle is increasingly aggravated, and the environmental pollution caused by the imbalance of the nitrogen cycle is becoming increasingly serious. Clarifying the pathway of nitrogen throughout the social-economic-ecological system, identifying the spatio-temporal distribution characteristics and emission structure characteristics of nitrogen quantitatively, and discussing the measures for regulating reactive nitrogen emissions have important practical significance for promoting the coordinated development of economy and environment. .With a framework of substance flow analysis, a regional scale reactive nitrogen cycling model was constructed, and a case study for the Beijing-Tianjin-Hebei region was brought out to estimate the nitrogen fluxes and identify the effects on regional environment. The results showed that Nr accumulation in the Beijing-Tianjin-Hebei region increased from 345 million tons to 4.6 million tons from 2005 to 2014. Nr accumulation in the land subsystem increased from 2.33 million tons to 3.09 million tons, with an accumulation rate of 33%. Nr accumulation in the land subsystem increased from 0.45 million tons to 0.81 million tons, with an accumulation rate of 80%. Nr accumulation in the water subsystem did not change significantly, but the structure of the Nr input varied greatly. Land subsystem is the key regulatory agencies in the regional-scale nitrogen cycle, directly affected by human disturbances. According to our assessment, the retention rate of Nr in the landscape had remained stable over the past 10 years. These results suggested that the critically important ability of regional landscapes to retain new Nr seemed to decline and that the potential for the landscapes to retain annual new added N is limited.This study established a list of Nr emissions from the atmosphere, soil, and water in the Beijing-Tianjin-Hebei region by further collecting active nitrogen emission factors for different industries under different technical conditions, combining the characteristics of the study area, and data availability and other factors. The results showed that in 2014, the total amount of NH3 emissions in Beijing, Tianjin and Hebei was 1.253 million tons, of which the NH3 emissions from the agricultural sector was 1.126 million tons, and the NH3 emissions from livestock and poultry farming and nitrogen application accounted for 55.0% and 34.8% of the total emissions, respectively. The agricultural sector was the most important anthropogenic source of NH3 emissions. In 2014, the total amount of Nr released from the land subsystem was 3.53 million tons, of which the planting sector had 2.7 million tons of Nr. The total amount of Nr released from the water subsystem was 0.825 million tons, of which the livestock and poultry breeding departments and the sewage treatment departments had 0.311 million tons of Nr and 0.237 million tons of Nr respectively. This paper proposed targeted reductions and adjustments of Nr from key aspects such as the transformation of agricultural production methods, comprehensive watershed management, and enhanced vehicle management.