Evaluation of a New Aerosol Chemical Speciation Monitor (ACSM) System at an Urban Site in Atlanta, GA: The Use of Capture Vaporizer and PM_(2.5) Inlet

Abstract

Aerosol mass spectrometers (AMSs) and aerosol chemical speciation monitors (ACSMs) have been deployed at numerous locations to quantify nonrefractory aerosol composition. Recent instrumentation advancement includes the development of a new capture vaporizer (CV) to improve collection efficiency and a PM_(2.5) aerodynamic lens to measure aerosol up to 2.5 μm in diameter. To validate these new instrument capabilities and investigate differences in composition of atmospheric PM₁ and PM_(2.5), a PM₁-SV-AMS, and a PM_(2.5)-CV-ACSM were deployed in urban Atlanta, GA in winter 2018 with other instruments. Nonrefractory species measured by the two instruments agree well and are dominated by organic aerosol (OA). About 85% of the nonrefractory species in PM_(2.5) are in the PM₁. Positive matrix factorization (PMF) analysis was performed and the same number and OA subtypes were resolved for both instruments. While the relative contribution of each factor to OA was different, more-oxidized oxygenated organic aerosol (MO-OOA) is determined to be the major type of OA in both instruments. The biomass burning organic aerosol (BBOA) resolved from CV-ACSM significantly contributes to signals at m/z 26, 42, 68, and 96. Cross-comparison with other instruments demonstrates that ∼80% of PM₁ and ∼90% of PM_(2.5) is nonrefractory species. The mass concentrations of PM₁ and PM_(2.5) are comparable in general. During time periods when PM_(2.5)/PM₁ is enhanced, the PM_(1–2.5) composition is dominated by OA and corresponds to higher less-oxidized-OOA (LO-OOA)/OA and organic nitrate/total nitrate ratios. Results from this study demonstrate the capability of PM_(2.5)-CV-ACSM and provide new insights into PM_(2.5) composition and sources in the southeastern US.

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