Tao Jun, Zhang Zhisheng, Zhang Leiming, Wu Yunfei, Wu Zhijun, Nie Fuli, Chen Laiguo, Wang Boguang
Institute for Environmental and Climate Research, Jinan University, Guangzhou, China.
South China Institute of Environmental Sciences, Ministry of Ecology and Environmental, Guangzhou, China.
Sci Total Environ. 2024 Jan 10;907:167980. doi: 10.1016/j.scitotenv.2023.167980. Epub 2023 Oct 21.
Uncertainties in estimating the hygroscopicity of bulk aerosols under conditions of low relative humidity (RH) or below the deliquescent RH (DRH) of aerosols remain to be significant, mainly due to the presence of water-soluble organic matter (WSOM). To quantify the contributions of WSOM to aerosol hygroscopicity and associated uncertainties, a field campaign was conducted to measure the hygroscopic growth curve (f(RH)) of bulk aerosols online, dominant chemical compositions in PM online and offline, and size distributions of the dominant chemical compositions offline during the dry and wet seasons of 2019-2020 in urban Guangzhou of south China. Based on the measured f(RH), the hygroscopicity parameter (κ) of bulk aerosols (κ) exhibits a logarithmic increase with increasing RH until RH reaches 69 %. Beyond this threshold, κ increases very slowly with further increase of RH, reaching 0.32 ± 0.04 during the dry season and 0.31 ± 0.05 during the wet season. The κ of WSOM (κ) was further estimated to be 0.22 ± 0.03 and 0.13 ± 0.04 in the dry and wet seasons, respectively, when RH > 69 %. WSOM significantly affects κ by retarding the deliquescence process of aerosols and altering the mass ratio of water-soluble inorganic salts (WSIS) to WSOM within the size range of 0.4-0.9 μm, especially under low RH conditions (<60 %). The κ under low RH conditions was revised based on the logarithmic regression equation between RH and the ratio of measured κ to estimated κ. f(RH) of WSIS and WSOM were then corrected using the revised κ under low RH conditions, which showed 22-31 % lower values than those produced by the IMPROVE formulas.
在低相对湿度（RH）条件下或低于气溶胶潮解相对湿度（DRH）时，估算大气气溶胶吸湿性的不确定性仍然很大，主要原因是存在水溶性有机物（WSOM）。为了量化WSOM对气溶胶吸湿性的贡献及相关不确定性，在中国南方广州市区于2019 - 2020年的干湿季开展了一项实地考察，以在线测量大气气溶胶的吸湿增长曲线（f(RH)）、在线和离线测量PM中的主要化学成分以及离线测量主要化学成分的粒径分布。基于测得的f(RH)，大气气溶胶的吸湿参数（κ）随RH增加呈对数增长，直至RH达到69%。超过此阈值后，κ随RH进一步增加而增长非常缓慢，在干季达到0.32±0.04，在湿季达到0.31±0.05。当RH > 69%时，WSOM的κ在干季和湿季分别进一步估算为0.22±0.03和0.13±0.04。WSOM通过延缓气溶胶的潮解过程并改变0.4 - 0.9μm粒径范围内水溶性无机盐（WSIS）与WSOM的质量比，对κ有显著影响，尤其是在低RH条件下（<60%）。基于RH与测得的κ与估算的κ之比之间的对数回归方程，对低RH条件下的κ进行了修正。然后使用低RH条件下修正后的κ对WSIS和WSOM的f(RH)进行校正，校正后的值比IMPROVE公式计算的值低22 - 31%。
