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 multi- component aerosol types. 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 photo-acoustic spectrometers, and a condensation particle counter. This suite of instruments enables measurement of aerosol particle mass, extinction coefficients, absorption coefficients and aerosol number density, respectively. Taken together, these observables yield the mass extinction coefficient and mass absorption coefficient 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.
Citation: Analytical Chemistry
Pub Type: Journals
particle, optical properties, cavity ring-down spectroscopy, photoacoustic spectroscopy