Quantifying the composition-dependent hygroscopicity of aerosol particles is essential for advancing our understanding of atmospheric processes. Existing methods do not integrate chemical composition with hygroscopicity. We developed a novel method to assess the water uptake of particles sampled on aerosol filters at relative humidity levels up to 97 % and link it with their composition. This approach allows for the separation of total water uptake into inorganic and organic components.

In the US, routine particulate matter composition is measured on samples collected on three types of filter media and analyzed using several techniques. We propose an alternate approach that uses one analytical technique, Fourier transform-infrared spectroscopy (FT-IR), and one filter type to measure the chemical composition of particulate matter in a major US monitoring network. This method could be used to add low-cost sites to the network, fill-in missing data, or for quality control.

Measuring emissions from stacks requires techniques to address a broad range of conditions and measurement challenges. Here we describe an instrument package held by a crane above a stack to characterize both wet droplet and dried aerosol emissions from cooling tower spray drift in situ. The instrument package characterizes the velocity, size distribution, and concentration of the wet droplet emissions and the mass concentration and elemental composition of the dried PM_2.5 and PM₁₀ emissions.