Filters will be placed inside a regulated flow apparatus. The prototype design calls for 4 Lpm over a 25 mm diameter filter. The filter is going to be teflon or nucleopore. The former is good because it's easy to clean, the latter is good because volatile nitrates escape less easily. There is no obvious choice, but likely we will end up with teflon.
The steps in the above chart aren't individually complex, but extreme care is needed in order to ensure quality data. If anything goes wrong at any stage (weighing, ion dissolution in water, etc), you can bet the whole goal of the network might be compromised.
Last month I was focused on comparing total PM2.5 aerosol mass with nephelometer bscat measurements. It was important to know as much about what affects the light scattering of aerosols as possible, since the ultimate goal of the network is quantitative PM2.5 mass data (measured in micrograms per cubic meter). One should back spectroscopy data if at all possible (astrophysicists are, for example, limited to spectral data). Even ground nephelometer measurements must be supported by actual weighed filters. Somehow this gives me satisfaction known that practical chemistry has a place among all this modern satellite equipment.
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