Carbon dioxide fluxes from an urban area in Beijing

A better understanding of urban carbon dioxide (CO2) emissions is important for quantifying urban contributions to the global carbon budget. From January to December 2008, CO2 fluxes were measured, by eddy covariance at 47 m above ground on a meteorological tower in a high-density residential area in Beijing. The results showed that the urban surface was a net source of CO2 in the atmosphere. Diurnal flux patterns were similar to those previously observed in other cities and were largely influenced by traffic volume. Carbon uptake by both urban vegetation during the growing season and the reduction of fuel consumption for domestic heating resulted in less-positive daily fluxes in the summer. The average daily flux measured in the summer was 0.48 mg m(-2) s(-1), which was 82%, 35% and 36% lower than those in the winter, spring and autumn, respectively. The reduction of vehicles on the road during the 29th Olympic and Paralympic Games had a significant impact on CO2 flux. The flux of 0.40 mg m(-2) s(-1) for September 2008 was approximately 0.17 mg m(-2) s(-1) lower than the flux for September 2007. Annual CO2 emissions from the study site were estimated at 20.6 kg CO2 m(-2) y(-1), considerably higher than yearly emissions obtained from other urban and suburban landscapes. (C) 2011 Elsevier B.V. All rights reserved.