武汉市黑碳气溶胶质量浓度空间分布的主导因素分析

Leading Factor Analysis of Horizontal and Vertical Distribution of Black Carbon Aerosol in Wuhan

基于中国东部地区黑碳气溶胶(BC)减排的严峻形势,开展武汉市黑碳气溶胶的水平方向观测和垂直方向模拟工作,了解武汉市黑碳气溶胶的含量和沉降通量的时空变化规律及其主要影响因素,明确黑碳气溶胶释放、输送和沉降规律,对深入地认识黑碳气溶胶的气候和生物地球化学效应具有理论意义。运用Meteoinfolab软件、轨迹分析、相关分析及多种模型拟合等方法,实测武汉市2015年7月—2016年6月黑碳气溶胶水平向分布数据,以WRF-CMAQ模型运行的模拟数据作为垂直向分布的基础数据,分析其空间分布规律;选择气象因子、污染物构成、环流因子、下垫面因子等主导因子,分析它们对武汉市黑碳气溶胶质量浓度空间分布规律的影响。结果表明,(1)BC质量浓度受温度、能见度、气压影响较大,相关系数分别为-0.637、-0.549、0.574。当风速小于2 m?s^(-1)、风向为东北或者东北偏北时,BC质量浓度达到最高值;当风速大于2 pH、风向为西南偏南时,BC质量浓度出现最低值。垂直方向上,低层和高层黑碳浓度主要受风速影响,而中层黑碳浓度则主要受温度影响。(2)BC质量浓度与PM_(2.5)、PM_(10)、CO相关系数为0.863、0.657、0.647,同源性强,采用三次曲线模型对BC与三者之间的关系分别进行拟合,效果最佳。(3)后向轨迹分析表明:武汉市高空气流来自于远源及海洋地区;中低空夏秋季节主要受较短距离的运输气流影响。(4)武汉市黑碳质量浓度受与主干道距离、植被覆盖率、水体分布等下垫面因素影响较大,空间分布差异明显。

Black carbon aerosol has become a hotspot in scientific research in recent years because of its environmental effects such as reducing visibility, harming human health, and also affecting the progress of atmospheric chemical reactions, as well as climate effects and biogeochemical effects that change climate characteristics. Based on the severe situation of black carbon aerosol emission reduction in the eastern part of China, this paper attempts to understand the temporal and spatial variations of black carbon aerosol content and deposition flux in Wuhan City and its main influencing factors, and to clarify the laws of black carbon aerosol release, transport, and settlement, which is of theoretical significance for understanding the climate and biogeochemical effects of black carbon aerosols. This paper used Meteoinfolab software, trajectory analysis, correlation analysis, and various model fitting methods to measure the horizontal distribution data of black carbon aerosols from July 2015 to June 2016 in Wuhan, the simulation data ran by WRF-CMAQ model was used as the basic data of vertical distribution, and the spatial distribution law was analyzed. Secondly, the dominant factors such as meteorological factors, circulation factors, underlying surface factors, pollutant composition, etc. were selected to analyze their influence on the spatial distribution of black carbon aerosols in Wuhan. The results showed that the mass concentration of black carbon aerosol had a positive correlation with temperature, visibility, and atmospheric pressure, and had a strong correlation with PM2.5, PM10, and CO; In the horizontal direction, the maximum value of mass concentration occurred when the wind speed was less than 2 m？s-1 and the wind direction was northeast or northeast; the minimum value occurred when the wind speed was less than 2 m？s-1 and the wind direction was south-southwest; In the vertical direction, the simulated values of black carbon aerosols in the lower and upper layers were mainly affected by the wind speed. In the middle layer, the simulated values of black carbon aerosols were mainly affected by temperature. Finally, using the HYSPLIT4 model to analyze the backward trajectory of the Wuhan air mass, the results showed that the high air flow in Wuhan came from the far source and the ocean area; the mid-low altitude summer and autumn seasons were mainly affected by the air flow with short transportation distance.