Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States.
Environ Sci Technol. 2012 Sep 4;46(17):9464-72. doi: 10.1021/es301883y. Epub 2012 Aug 23.
We have conducted laboratory experiments to investigate the impacts of secondary organic aerosol formation on soot properties from OH-initiated oxidation of toluene. Monodisperse soot particles are exposed to the oxidation products of the OH-toluene reaction in an environmental chamber, and variations in particle size, mass, organic mass faction, morphology, effective density, hygroscopicity, and optical properties are simultaneously determined by an integrated aerosol analytical system. The thickness of the organic coating, correlated to reaction time and initial reactant concentrations, is shown to largely govern the particle properties. With the development of organic coating, the soot core is changed from a highly fractal to compact form, evident from the measured effective density and dynamic shape factor. The organic coating increases the particle hygroscopicity, and further exposure of coated soot to elevated relative humidity results in a more spherical particle. The single scattering albedo and scattering and absorption cross sections are also enhanced with the organic coating. Our results suggest that the oxidation products of anthropogenic pollutants alter the composition and properties of soot particles and lead to increased particle density, hygroscopicity, and optical properties, considerably enhancing their impacts on air quality, climate forcing, and human health.
我们进行了实验室实验，以研究二次有机气溶胶形成对甲苯 OH 引发氧化生成的烟尘性质的影响。单分散烟尘颗粒在环境室内暴露于 OH-甲苯反应的氧化产物中，通过集成气溶胶分析系统同时测定粒径、质量、有机质量分数、形态、有效密度、吸湿性和光学性质的变化。有机涂层的厚度（与反应时间和初始反应物浓度相关）显示对颗粒性质有很大的影响。随着有机涂层的发展，烟尘核心从高度分形变为紧凑的形态，这可以从测量的有效密度和动态形状因子中明显看出。有机涂层增加了颗粒的吸湿性，进一步将涂覆的烟尘暴露于升高的相对湿度下会导致颗粒更球形化。随着有机涂层的增加，单散射反照率和散射和吸收截面也得到了增强。我们的结果表明，人为污染物的氧化产物改变了烟尘颗粒的组成和性质，导致颗粒密度、吸湿性和光学性质增加，极大地增强了它们对空气质量、气候强迫和人类健康的影响。
