与传统的“自下而上”的统计方法以及CO和SF6示踪的方法不同，本项目将14C示踪和WRF-chem模式相结合来“自上而下”地研究我国主要城市大气化石源CO2(CO2ff)的时空分布特征与区域输送。首先通过14C示踪方法评估点源排放数据的不确定性；并获取我国大气14CO2的本底值，来降低因使用国外本底值给14C示踪大气CO2ff的结果带来的误差。进而以14C示踪为手段，将气体样品与植物样品相结合，现代CO2ff观测与历史树轮数据相结合，CO2ff观测与WRF-chem模式相结合，以此来阐明我国不同区域代表性城市大气CO2ff的浓度水平、时空变化特征和输送过程，确定其影响因素，并辨析不同类型城市大气CO2ff的差异及其影响因素。最后通过WRF-chem模式预测未来3~5年CO2ff的排放情景。以此为我国政府制定合理的节能减排政策和履行国际碳减排义务提供科学数据。

Compared with bottom-up as well as CO and SF6 tracer approaches, this proposal will study the spatial-temporal distribution characteristics and transportation of fossil fuel CO2 (CO2ff) in main Chinese cities by top-down approach, i.e., radiocarbon, combined with WRF-chem model. Firstly, the uncertainty of point source CO2ff emissions will be evaluated by 14C tracing method at a fossil-fuel power plant. The background 14CO2 level in China was obtained to reduce the error for CO2ff tracing resulted from the using of abroad background value. Secondly, we clarify the concentration, spatial-temporal variational characteristics, and transportation of CO2ff in typical Chinese cities, discriminate the differences of CO2ff among various types of cities, and then find the factors that controlling these variations. Finally, future CO2ff emissions in recent 3~5 years will be predicted by WRF-chem model. This proposal will provide scientific data to the CO2ff reducing policy for Chinese government to fulfill the international carbon reduction duty.