Identification of chemical states of acidic atmospheric aerosols and sensitivity analysis of rainwater acidification by microscopic model

为了检测单个气溶胶颗粒中硫酸盐和硝酸盐的混合状态，在核孔滤光片上采用双真空镀膜的方法制备了混合薄膜。使用喷雾器产生的硫酸盐和/或硝酸盐颗粒检查其适用性。应用混合薄膜方法对安徒生采样器采集的乌日夏季和冬季大气气溶胶的混合状态进行了探测。冬季，未检测到硫酸盐-硝酸盐内部混合颗粒物，而夏季，内部混合颗粒物在各级采样器上采集的总颗粒物中，数量浓度仅占总颗粒物的几个百分点。我们应用深度选择性XAFS光谱技术，利用SR测定了在乌吉和樱岛采集的大气气溶胶中硫和硅的化学状态。同时测定X射线荧光产额(XFY)和总电子产额(Tey)。大多数气溶胶样品只有S的a…峰。除了在樱岛采集的一个样品外，没有检测到其他峰，表明该颗粒由S硫原子(硫酸盐)组成，其表面既含有S硫原子，也含有S硫原子。在樱岛采集的大气气溶胶的X射线吸收光谱显示出两个峰。一种是Si^-lt；4+-gt；，另一种是位于SiO和SiO之间，前者来自SiO_2，后者被认为是由于硅酸盐矿物的SiK边的化学位移所致。该模型包括雨滴的尺寸分布、气体吸收、颗粒捕获和雨水中的水相化学反应。定量分析了云下酸化对地面降水化学的影响。在我们的计算条件下，气溶胶对雨水中硫酸盐和硝酸盐浓度的贡献非常小。对S(VI)和降水中Ca~(2+)浓度(C)的模拟结果表明，长时间降水后，C/r关系(C与雨滴半径的关系)不同。这可能是由于雨水中的Ca~(2+)主要来源于对粗钙颗粒的清除，而SO_2的水相氧化是对雨水中的S(VI)的主要贡献。较少

Mixing thin film was prepared on a Nuclepore filter by dual vacuum deposition of barium chloride and nitron in order to detect the mixing states of sulfate and nitrate in individual aerosol particles. Applicability was examined using sulfate and/or nitrate particles generated by a nebulizer. The mixing thin film method was applied to detect the mixing states of atmospheric aerosols collected by Andersen samplers at Uji in summer and winter seasons. In winter, internally mixed sulfate-nitrate particles were not detected, while internally mixed particles were found to be a few percent in number concentration to the total particles collected on each stages of the sampler in summer.We have applied the depth selective XAFS spectrometry using SR to determine the chemical states of sulfur and silicon in atmospheric aerosols sampled at Uji and Sakurajima. X-ray fluorescence yield (XFY) and total electron yield (TEY) was measured simultaneously. Most of aerosol samples showed only S^<6+> peak a … More nd no other peaks were detected except one sample collected at Sakurajima, which indicated that the particles consist of S^<6+> sulfur atoms (sulfate) and their surfaces contain both S^<6+> and S^<2-> chemical species. X-ray absorption spectra of atmospheric aerosols sampled at Sakurajima showed two peaks. One is for Si^<4+> and the other lies between Si^<4+> and SiO.The former peak comes from SiO_2 and the latter one is considered to be attributable to chemical shift in the Si K-edge of silicate minerals.One-dimensional and time-variant model was presented for simulating below-cloud scavenging of gaseous and particulate matters. The model includes size distribution of raindrops, gas absorption, particle capture and aqueous chemical reactions in rainwater. We analyzed quantitatively the effects of below-cloud acidification on precipitation chemistry at ground level. Contribution of aerosols to sulfate and nitrate concentrations in rainwater was extremely small in our calculation conditions. Simulation results of S(VI) and Ca_2^+ concentrations (C) in rain at ground level indicated that C/r-dependence (relation between C and raindrop radius) was different after long precipitation times. The difference can be explained by the fact that Ca_2^+ in rain attributes from the scavenging of coarse calcium particles, while aqueous-phase oxidation of SO_2 is the major contribution to S(VI) in rainwater. Less