Our system has two inlets, allowing collection of paired samples simultaneously. In addition, several of the particle-associated ions are tracers of sources of gas and aerosol pollutants (e.g., SO4 2- from industrial emissions of SO2, enhancements of C2O4 2-, K +, and NH4 + indicate encounters with biomass burning plumes, Na +, and Cl - are tracers of seasalt, Mg 2+ and Ca 2+ are tracers of dust). Our measurements help to validate and extend retrievals of aerosol distributions and properties by MODIS, MISR and CALIPSO. Aerosols participate in heterogeneous chemistry, impact radiative transfer, and can be detected from space. Below 3 km exposure times are 5 minutes or less, increasing at higher altitudes to a maximum sample time of 15 minutes. Filters are exposed on all level flight legs. We use ion chromatography on aqueous extracts of the bulk aerosol samples collected on Teflon filters to quantify soluble ions (Cl -, Br -, NO3 -, SO4 2-, C2O4 2-, Na +, NH4 +, K +, Ca +, and Mg +). As part of the measurement team on the NASA DC-8 we operate two related installations: a mist chamber/ion chromatograph (MC/IC) sampling/analysis system providing near real time results for selected species, and a bulk aerosol system that collects particulates onto filters for subsequent analysis.
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