南京雾过程对大气气溶胶谱分布及化学组成的影响

为探究南京地区雾过程对气溶胶粒子化学组成和尺度分布的影响,在2017年冬季的雾观测中平行收集了3级分档雾水和分粒径气溶胶样品,并对雾微物理量与气溶胶谱分布、3级分档雾水与雾前、雾中、雾后分粒径气溶胶化学组成对比分析。结果表明,2017年冬季南京第1次雾过程的雾滴液态水含量随粒径分布为不对称“V”型,最低值位于7μm处,第2次雾过程的雾滴液态水含量随粒径分布为3峰型,峰值分别位于5,15,21.5μm处。在雾形成、发展阶段,粒径<0.33μm的气溶胶质量浓度降低,粒径0.38μm气溶胶质量浓度升高,雾成熟阶段,气溶胶粒子质量浓度在全粒径段均达到最低,粒径0.38μm的气溶胶质量浓度大幅降低,与雾前相比,雾后气溶胶质量浓度峰值向大粒径方向移动。雾前,气溶胶水溶性离子组分富集在粒径<0.43μm的小粒子中,随着雾过程进行,成核作用和吸湿增长使得水溶性离子向较大粒径段富集。雾中新生成的气溶胶随着雾滴的蒸发被释放,导致雾后NO₃^-、SO₄^2-和NH₄⁺浓度升高。较小粒径的气溶胶中和率更高,雾形成初期的新生雾滴酸性较强,随着雾过程的进行逐渐中和,雾水pH值逐渐升高。

Effects of Nanjing fog process on the spectral distribution and chemical composition of atmospheric aerosols

In order to explore the effects of fog process on the chemical composition and size distribution of aerosol particles in Nanjing. Three-stage fog samples and particle-size aerosol samples were collected at the same time in the fog observation in winter 2017. The microphysical quantity and aerosol spectral distribution of fog, the chemical composition of three-stage fog samples and particle-size aerosol samples before, in and after fog were compared and analyzed. The results showed that: in the winter of 2017, the fog droplet liquid water content of the first fog process in Nanjing was in the shape of asymmetric "V" with the particle size distribution, and the lowest value was located at 7μm. The fog droplet liquid water content in the second fog process was a 3peak shape with the particle size distribution, and the peaks were located at 5, 15and 21.5μm. The mass concentration of small particle size aerosol decreased while that of large particle size aerosol increased in the stage of fog formation and development. The mass concentration of aerosol particles reached the lowest in the whole particle size in the stage of fog maturity, and the mass concentration of larger particle size aerosol decreased significantly. Compared with that before fog, the peak value of aerosol mass concentration after fog moved to the direction of large particle size. Before fog, the water-soluble ion components in aerosol were enriched in small particles with particle size<0.43μm, with the progress of fog process, nucleation and hygroscopic growth lead to the enrichment of water-soluble ions to larger particle size. The newly generated aerosol in the fog was released with the evaporation of fog droplets, resulted in the increase of NO₃^-, SO₄^2- and NH₄⁺ concentrations after fog. The neutralization rate of aerosol with smaller size was higher, and the new droplets in the early stage of fog formation were more acidic. With the gradual neutralization of fog process, the pH value of fog water increased.