中文摘要：

城市是碳排放的重要空间,低碳减排是通过调控进入到城市系统内部的物质代谢路径来降低碳通量。从城市经济-环境的复合系统均衡的视角,将碳排放嵌入到城市系统的代谢分析体系之内,以天津市为例,动态测度碳排放的通量代谢特征与碳平衡的变化规律。研究表明：近十年来天津市碳储量总体呈现逐年递增趋势,自然碳库增长速度低于人为碳库增长速度;城市系统碳输出总体高于碳输入,通量水平变化明显,且总体处于不平衡状态、碳补偿能力较差。其中,化石能源消费是影响碳通量变化的主要因素。在此基础上,提出城市系统碳减排的关键环节。

英文摘要：

Urban system is an important space for carbon emissions. Low carbon is to reduce the carbon flux through the regulation of material metabolism path in urban system. From an academic perspective of maintaining the equilibrium and function of the eco-economic system,combined with the carbon emission and regional substance flow,we analyzed the characteristics of carbon flux metabolic and the law of carbon balance in urban system of Tianjin. The result showed that urban carbon storage showed an overall trend of increasing in recent ten years,and the natural carbon storage growth rate was lower than anthropogenic carbon storage. The carbon output was higher than that of carbon input for the urban system,and the whole was in a state of imbalance; at the same time,the fossil energy consumption played an essential role in the process of increasing carbon flux. On this basis,the suggestions for the urban low carbon were proposed.