Variability of surface aerosol properties at an urban site in Beijing based on two years of in-situ measurements
Variability of surface aerosol properties at an urban site in Beijing based on two years of in-situ measurements
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DOI：
10.1016/j.atmosres.2021.105562
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发表时间：
2021-07
影响因子：
5.5
通讯作者：
Liang Chang;Jing Li;Yiqi Chu;Yueming Dong;Wangshu Tan;Xianjun Xu;Jing Ren;Xiaoqing Tian;
中科院分区：
文献类型：
--
作者：
Liang Chang;Jing Li;Yiqi Chu;Yueming Dong;Wangshu Tan;Xianjun Xu;Jing Ren;Xiaoqing Tian;
气溶胶光学特性是监测大气气溶胶污染的重要指标。在这项研究中，我们报告了主要气溶胶光学参数的季节和日变化，包括散射系数（σs），吸收系数（σa），单次散射系数（SSA），与PM2.5（空气动力学直径≤ 2.5 μm的颗粒物）和PM10 2017年9月至2019年8月在北京城市站点测量的空气动力学直径≤ 10 μm的颗粒物质量浓度。这些气溶胶特性与气象条件，特别是，混合层高度（MLH），风速和风向之间的关系，进一步研究。结果表明，研究期间PM2. 5和PM10质量浓度、σs和σ的年平均值分别为54 ± 54 μg/m3、100 ± 72 μg/m3、170 ± 180 Mm−1和17 ± 15 Mm− 1，远低于以往报道的数值，表明近年来实施的严格污染控制策略是有效的。SSA用σ和σa计算，其年平均值为0.88 ± 0.07。在季节上，除夏季外，σ a均呈现双峰特征，PM2.5和PM10浓度均以春季最高，而σ a则以夏季最高，春季出现次峰。σ的日变化与MLH的日变化呈高度反相关。对于σs、PM2.5和PM10，其日变化周期在中午前后达到峰值，并与春夏的最大环流相一致，这可能与二次气溶胶的光化学生成有关。σs、σa、PM10和PM2.5浓度与风速呈负相关，但PM10在风速超过4 m/s时开始增加，可能是由沙尘和柳絮引起的。风速的增加也削弱了气溶胶-MLH的关系。后向轨迹分析表明，高气溶胶浓度主要与向南和向西的气团有关。
Aerosol optical properties are important indices for monitoring atmospheric aerosol pollution. In this study, we report the seasonal and diurnal variability of major aerosol optical parameters, including scattering coefficient (σs), absorbing coefficient (σa), single scattering albedo (SSA), together with PM2.5(particulate matter with aerodynamic diameter ≤ 2.5 μm) and PM10(particulate matter with aerodynamic diameter ≤ 10 μm) mass concentrations measured at an urban site in Beijing from September 2017 to August 2019. The relationships between these aerosol properties with meteorological conditions, in particular, the mixing layer height (MLH), wind speed, and wind direction, are further investigated. Results show that the annual average values of PM2.5and PM10mass concentrations, σs, and σaduring the study period are 54 ± 54 μg/m3, 100 ± 72 μg/m3, 170 ± 180 Mm−1, 17 ± 15 Mm−1respectively, which are much lower than those previously reported, indicating the effectiveness of strict pollution control strategies implemented in recent years. SSA is calculated with σsand σa, whose annual average value is 0.88 ± 0.07. Seasonally, σaexhibits dual peaks except in summer, PM2.5and PM10concentrations are the highest value in the spring, whereas σshas the highest value in the summer with a secondary peak in the spring. The diurnal cycle of σais highly anti-correlated with that of the MLH. For σs, PM2.5and PM10, their diurnal cycles often peak around noon and are in phase with the MLH in the spring and summer, which may be associated with the photochemical production of secondary aerosols. σs, σa, PM10, and PM2.5concentrations are inversely related to wind speed, but PM10starts to increase as wind speed exceeds 4 m/s, possibly caused by dust and catkins. The increase in wind speed also weakens the aerosol-MLH relationship. Back trajectory analysis indicates that high aerosol concentrations are mostly associated with southward and westward airmasses.