CAS Key Laboratory of Regional Climate-Environment for Temperate East Asia, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China.
CAS Key Laboratory of Regional Climate-Environment for Temperate East Asia, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China.
Sci Total Environ. 2017 Dec 1;599-600:76-84. doi: 10.1016/j.scitotenv.2017.04.194. Epub 2017 Apr 29.
Aerosol optical properties and the effect of hygroscopic growth on the scattering coefficients at a rural site in the southern North China Plain were investigated based on a two-month observation conducted in the summer of 2014. The scattering coefficient of dry aerosols was high, with a mean (±standard deviation) of 338.8±209.9Mm (520nm) during the observation period. A noticeable enhancement in aerosol scattering due to hygroscopic growth was observed, e.g., by a factor of 2.28±0.69 at RH of 80% (referred to as f(RH=80%)) and 3.39±1.14 at RH of 85% (f(RH=85%)). The high content of water-soluble secondary inorganic aerosols (SIAs), accounting for 53.1% of fine particulate matter (i.e., PM) on average, was mainly responsible for the high hygroscopicity. f(RH=80%) increased with increasing SIA mass fraction in PM. This was especially the case when SIAs were mainly in finer particulate matter, i.e., PM. A number of considerably low f(RH=80%) values was observed due to relatively low mass fraction of SIAs in PM despite high fraction in PM. Particle size distributions, especially those of SIAs, also played a remarkable role in the hygroscopicity of ambient aerosols. No significant difference in hygroscopicity was found between different pollution episodes due to the dominance of SIAs in all the cases. Slightly higher hygroscopic growth factors were observed during the clean episode, which were attributed to the smaller particle sizes.
基于 2014 年夏季两个月的观测，研究了中国华北平原南部农村地区气溶胶的光学特性和吸湿增长对散射系数的影响。在观测期间，干燥气溶胶的散射系数较高，平均值（±标准偏差）为 338.8±209.9Mm（520nm）。观察到由于吸湿增长导致气溶胶散射明显增强，例如，在相对湿度为 80%（记为 f（RH=80%））时，散射系数增加了 2.28±0.69 倍，在相对湿度为 85%（f（RH=85%））时，散射系数增加了 3.39±1.14 倍。水溶性二次无机气溶胶（SIAs）含量高，占细颗粒物（即 PM）的平均含量的 53.1%，是高吸湿性的主要原因。f（RH=80%）随着 PM 中 SIA 质量分数的增加而增加。当 SIAs 主要存在于细颗粒物质中，即 PM 中时，这种情况尤其明显。尽管 PM 中的 SIAs 分数较高，但由于 PM 中的 SIAs 分数相对较低，观察到相当多的 f（RH=80%）值较低。颗粒物粒径分布，特别是 SIAs 的粒径分布，对环境气溶胶的吸湿性也起着显著的作用。由于在所有情况下 SIAs 都占主导地位，因此不同污染事件之间的吸湿性没有明显差异。在清洁事件中观察到稍微更高的吸湿增长因子，这归因于较小的颗粒物尺寸。
