Particle hygroscopicity and its link to chemical composition in the urban atmosphere of Beijing, China, during summertime

作者：Zhijun Wu, Jingyun Zheng, Dongjie Shang, Zhuofei Du, Yusheng Wu, Liming Zeng, Alfred Wiedensohler, Min Hu · 发表于：Atmospheric chemistry and physics · 年份：2016 · DOI：10.5194/acp-16-1123-2016 · 被引用次数：210 · 研究领域：Atmospheric chemistry and aerosols、Air Quality and Health Impacts、Atmospheric aerosols and clouds

Simultaneous measurements of particle number size distribution, particle hygroscopic properties, and size-resolved chemical composition were made during the summer of 2014 in Beijing, China. During the measurement period, the mean hygroscopicity parameters ( κ s) of 50, 100, 150, 200, and 250 nm particles were respectively 0.16 ± 0.07, 0.19 ± 0.06, 0.22 ± 0.06, 0.26 ± 0.07, and 0.28 ± 0.10, showing an increasing trend with increasing particle size. Such size dependency of particle hygroscopicity was similar to that of the inorganic mass fraction in PM 1 . The hydrophilic mode (hygroscopic growth factor, HGF > 1.2) was more prominent in growth factor probability density distributions and its dominance of hydrophilic mode became more pronounced with increasing particle size. When PM 2.5 mass concentration was greater than 50 μg m −3 , the fractions of the hydrophilic mode for 150, 250, and 350 nm particles increased towards 1 as PM 2.5 mass concentration increased. This indicates that aged particles dominated during severe pollution periods in the atmosphere of Beijing. Particle hygroscopic growth can be well predicted using high-time-resolution size-resolved chemical composition derived from aerosol mass spectrometer (AMS) measurements using the Zdanovskii–Stokes–Robinson (ZSR) mixing rule. The organic hygroscopicity parameter ( κ org ) showed a positive correlation with the oxygen to carbon ratio. During the new particle formation event associated with strongly active photoch...