Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
Anal Chem. 2013 Sep 3;85(17):8319-25. doi: 10.1021/ac401645y. Epub 2013 Aug 13.
The optical properties of atmospheric aerosols vary widely, being dependent upon particle composition, morphology, and mixing state. This diversity and complexity of aerosols motivates measurement techniques that can discriminate and quantify a variety of single- and multicomponent aerosols that are both internally and externally mixed. Here, we present a new combination of techniques to directly measure the mass-specific extinction and absorption cross sections of laboratory-generated aerosols that are relevant to atmospheric studies. Our approach employs a tandem differential mobility analyzer, an aerosol particle mass analyzer, cavity ring-down and photoacoustic spectrometers, and a condensation particle counter. This suite of instruments enables measurement of aerosol particle size, mass, extinction and absorption coefficients, and aerosol number density, respectively. Taken together, these observables yield the mass-specific extinction and absorption cross sections without the need to model particle morphology or account for sample collection artifacts. Here we demonstrate the technique in a set of case studies which involve complete separation of aerosol by charge, separation of an external mixture by mass, and discrimination between particle types by effective density and single-scattering albedo.
大气气溶胶的光学性质变化很大，取决于粒子成分、形态和混合状态。气溶胶的这种多样性和复杂性促使人们采用能够区分和量化各种单组分和多组分气溶胶的测量技术，这些气溶胶既有内混合也有外混合。在这里，我们提出了一种新的技术组合，可直接测量与大气研究相关的实验室生成气溶胶的质量比消光和吸收截面。我们的方法采用串联差分迁移率分析仪、气溶胶颗粒质量分析仪、腔衰荡和光声光谱仪以及凝结核计数器。这些仪器可以分别测量气溶胶粒子的大小、质量、消光和吸收系数以及气溶胶数密度。这些可观测值结合在一起，无需对粒子形态进行建模或考虑样品采集的假象，即可得出质量比消光和吸收截面。在这里，我们通过一系列案例研究展示了该技术，这些案例研究包括通过电荷完全分离气溶胶、通过质量分离外混合以及通过有效密度和单次散射反照率区分粒子类型。
