Differences in atmospheric CO2 concentration and δ13C value between green spaces and its adjacent roads as well as the influencing factors in Beijing, China.

Abstract

Near-surface atmospheric CO2 concentration and δ13C value in four greenspaces and on their adjacent roads in Beijing were measured by off-axis integrated cavity output spectroscopy to analyze the influence of urban greenspace on spatial distribution of near-surface atmospheric CO2. The results showed that atmospheric CO2 concentration and δ13C value varied substantially both temporally and spatially. The highest CO2 concentration was found in the urban area, followed by the suburbs, and the lowest CO2 concentration was in the outer suburbs. There was a clear near-surface atmospheric CO2 dome, but a reverse pattern for δ13C value. During the non-growing season, the ΔCO2 and Δ13C between greenspace and adjacent roads were low. The differences among the four experimental sites were not significant. In the growing season, the ΔCO2 and Δ13C at the BLA4th RR (Beijing Institute of Landscape Architecture and 4th Ring Road) and BOP5th RR (Beijing Olympic Forest Park and 5th Ring Road) in urban areas were significantly higher than those at DPSR (Daoxianghu Park and Sujiatuo Road) and MTGMR (Mentougou forest experimental station and an adjacent road) in the suburbs. During the growing and non-growing seasons, CO2 concentration of all examined sites was significantly positively related with the traffic volume, indicating that traffic volume was an important factor affecting the spatial distribution of CO2. The δ13C value was significantly negatively related with traffic volume during non-growing season, but no significant relationship was found during the growing season. The ΔCO2 concentration between the four green-spaces and their adjacent roads were significantly negatively related with leaf area index (LAI). The Δ13C value were significantly logarithmically related to LAI. Results from stepwise regression showed that solar radiation, temperature, and LAI significantly affected ΔCO2 in urban areas and suburbs during the growing season, and that temperature and solar radiation were the major driving factors for Δ13C. During the growing season, plants in the greenspaces assimilated CO2 via photosynthesis and thus reduced the near-surface atmospheric CO2 concentration. Our results indicate that green-spaces play a positive role in improving ecological environment in urban areas.