Estimation of carbon dioxide flux and source partitioning over Beijing, China

The magnitude and partitioning of carbon dioxide emission from the urban area in Beijing, China was estimated based on a statistical approach. Results showed that the urban surface is a net source of CO₂ to atmosphere. The main sources of CO₂ are vehicles, which accounted for 75.5% and 38.9% of CO₂ emission in summer and winter, respectively. At midday in summer, the CO₂ uptake of -0.034 mg/(m².sec) indicated that vegetation is an important sink of CO₂ in summer. Comparison between the annual emission rates of CO₂ from the statistical approach and that directly measured by the eddy covariance technique implies that a bottom-up emission approach is a viable means to estimate CO₂ emission in an urban area.