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

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。

SPATIAL CHARACTERISTICS OF NEAR SURFACE CO2 CONCENTRATION AND ANALYSIS ON ITS INFLUENCING FACTORS IN SPRING IN SHANGHAI CITY

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-840A, combined with classification of urbanization levels and types of land use information derived from remote sensing data. Qualitative and quantitative analysis of CO₂ concentration'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±40.5 μmol/mol in the city center, 55.1 μmol/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 1.56 μmol/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 0.7 μmol/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±34.9 and 426.0±24.8 μmol/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, -0.55 and -0.52(P<0.01), 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.