RAPID: TAG-AMS Measurements of Organic Aerosol during the BEACHON-RoMBAS 2011 Field Campaign

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The objective of this project is to investigate the sources, processing, and feedbacks of secondary organic aerosols (SOAs) that are produced from volatile organic precursors emitted from the Manitou Forest in Colorado during summer 2011. The principal investigator (PI) has developed a novel thermal desorption aerosol gas chromatograph (TAG) coupled to an aerosol mass spectrometer (AMS) that characterizes the organic composition of ambient aerosols. This project supports deployment of TAG-AMS as part of the BEACHON-RoMBAS (Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics, and Nitrogen - Rocky Mountain Biogenic Aerosol Study) intensive field campaign and the interpretation of resulting data. The TAG speciates the organic composition of ambient aerosols hourly while the AMS measures mass spectra of the corresponding total particulate organic matter. Relative to other approaches, the simultaneous quantification of organic speciation and mass loading using the same ion source and high-resolution time-of-flight mass spectrometer provides enhanced resolution in characterizing the associated sources and chemical processing of particulate organic matter in the atmosphere. The prototype TAG-AMS instrument was deployed and operated successfully in Pasadena, CA as part of the CalNex (Nexus of Air Quality and Climate Change) campaign during May and June 2010. Measurements with the TAG-AMS during BEACHON-RoMBAS will contribute to the overall programmatic goal of understanding sources, processing, and feedbacks of secondary biogenic aerosols. Results will also be interpreted in conjunction with prior TAG and AMS measurements in the Blodgett Forest in California during BEARPEX (Biosphere Effects on Aerosols and Photochemistry Experiment). Both the Manitou and Blodgett forests are dominated by ponderosa pine but differ significantly in relative amounts of anthropogenic air pollutants and emission fluxes of biogenic volatile organic carbon (VOC). The combined data sets from these two sites will yield insight regarding production pathways for SOA from biogenic precursors over a broad range in chemical regimes. In addition, experience gained through this field deployment will allow the PI to further evaluate performance of the new TAG-AMS system. Results from this project will substantially improve our understanding of and ability to predict the chemical processing of biogenic gases to form particulate organic matter in the atmosphere, influences of this particulate material on clouds and precipitation fields, and resulting feedbacks on forests. This project will foster new collaborations involving the PI and other participants in the BEACHON-RoMBAS field campaign. Data interpretation will lever additional insight from measurements during the BEARPEX campaign. A postdoctoral researcher will be trained through the project and results will be integrated into classroom instruction by the PI. Knowledge gained by the PI, collaborating scientists, and students will be broadly disseminated through scholarly publications and will thereby contribute substantively to both the atmospheric chemistry and air quality communities.