北京城市绿地与周边道路空气CO2浓度和δ13C值的差异及影响因素

采用离轴积分腔输出光谱技术测定了北京市4组绿地及其相邻道路上CO₂浓度和δ¹³C值的变化,分析城市绿地对近地层CO₂浓度空间分布的影响.结果表明:北京城市CO₂浓度和δ¹³C值存在时空差异,城区CO₂浓度最高,近郊次之,远郊最低,CO₂存在明显的穹顶式分布,但δ¹³C值变化分布恰好相反.在非生长季节中,绿地与相邻道路之间的ΔCO₂和Δ¹³C值较小,4个试验点之间差异不显著.然而,在生长季节中,城区的北京园林科学研究院绿地与4环路(BLA&4^th RR)、北京奥林匹克森林公园与5环路(BOP&5^th RR)的ΔCO₂和Δ¹³C值显著高于郊区的稻香园公园与苏家屯东路(DP&SR)、北京门头沟城郊森林站与站外道路(MTG&MR).在生长季节和非生长季节中,4个试验点的CO₂浓度与车流量呈显著正相关,表明车流量是影响市区CO₂浓度空间分布的重要因素之一.非生长季节中δ¹³C值与车流量呈显著负相关,但在生长季节,δ¹³C值与车流量相关性不显著.4块绿地内外的ΔCO₂浓度值均与叶面积指数(LAI)呈显著负相关,Δ¹³C值与LAI呈极显著的对数函数关系.逐步回归分析表明,生长季节中太阳辐射、温度和LAI对市区和近郊绿地内外ΔCO₂浓度具有显著影响,温度和太阳辐射是影响Δ¹³C值的主要因子.生长季节中,植物通过光合作用降低了绿地系统近地层的CO₂浓度,表明绿地系统在改善城市生态环境方面发挥积极作用.

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

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 BLA&4^th RR (Beijing Institute of Landscape Architecture and 4^th Ring Road) and BOP&5^th RR (Beijing Olympic Forest Park and 5^th Ring Road) in urban areas were significantly higher than those at DP&SR (Daoxianghu Park and Sujiatuo Road) and MTG&MR (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.