上海春季近地面大气CO_2浓度空间分布特征及其影响因素分析

SPATIAL CHARACTERISTICS OF NEAR SURFACE CO_2 CONCENTRATION AND ANALYSIS ON ITS INFLUENCING FACTORS IN SPRING IN SHANGHAI CITY

基于移动监测手段获取上海春季典型样带近地面CO2浓度监测数据,在明确近地面CO2浓度空间分布格局的基础上,分析了城市化水平以及土地利用类型对近地面CO2浓度的影响。结果表明上海市春季近地面CO2浓度空间分布呈现西高东低、北高南低的特征,空间异质性较为明显,市中心比郊区高出55.1μmol/mol(13.3%),存在着明显的城市"CO2"岛现象。城市化水平对于上海市近地面CO2浓度影响较为显著,总体上呈现随城市化水平上升而下降的趋势,距市中心距离每增加1km,CO2浓度下降1.56μmol/mol。上海市近地面CO2浓度与5km范围内下垫面土地利用类型相关性显著,其中近地面CO2浓度与林地以及建设用地覆盖率相关性最高,依次为-0.64和0.63。进一步分析表明近地面CO2浓度与土地利用类型的相关性在高度城市化以及城郊区域较高,在中低城市化水平区域较低。

The rapid process of urbanization worldwide has a profound effect on global carbon cycle.It＇s important to have an explicit understanding of the spatial distribution of CO2 to recognize and control Green-house gases（GHGs）emission,which is helpful to reduce human-induced contribution to global climate change.The study area of this project is set in the metropolitan city of Shanghai with the background of high-intensity of human activities and rapid urbanization.Mobile measuring methodology was used to determine near surface CO2 concentration along typical transects in spring,2014 by means of near infrared gas analyzer LI-840 A,combined with classification of urbanization levels and types of land use information derived from remote sensing data.Qualitative and quantitative analysis of CO2concentration＇s response mechanisms to urbanization levels and types of land use are represented in this paper.Data suggested a well-shaped carbon dioxide dome with mean concentration of 445.8±40.5μmol/mol in the city center,55.1μmol/mol（13.3%）higher than that in suburban areas.CO2 concentration exhibited a significant spatial heterogeneity and descended in a sequence with three directions which were northwest,southwest and southeast,respectively.Near surface CO2 has a negative relationship with distance to the city center with a decline of 1.56μmol/mol per kilometer.In general,Near surface CO2 concentrations dropped rapidly within the range of 20 km from the urban core（DUC）while rather slowly out of the same range（approximately 0.7μmol/mol/km）.Urbanization levels within the territory of Shanghai City have significant impacts on concentrations of near surface CO2.According to the classification of urbanization levels,concentrations with high,middle,low urbanization level and suburban areas are 467.6±44.7,451.7±41.1,452.7±34.9and 426.0±24.8μmol/mol,respectively.Coverage rate of forested land has the highest correlation with near surface CO2 concentration following by the construction areas,farmland and grassland with the correlation coefficient of-0.64,0.63,-0.55and-0.52（P0.01）,respectively.Correlation coefficients between near surface CO2 concentrations and types of land use score higher values in high urbanization and suburban areas than in middle and low urbanization areas.