Browsing by Author "Kreisberg, Nathan M."

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    Emissions of organic compounds from western US wildfires and their near-fire transformations
    Liang, Yutong; Stamatis, Christos; Fortner, Edward C.; Wernis, Rebecca A.; Van Rooy, Paul; Majluf, Francesca; Yacovitch, Tara, I; Daube, Conner; Herndon, Scott C.; Kreisberg, Nathan M.; Barsanti, Kelley C.; Goldstein, Allen H. (Copernicus, 2022-08-03)
    The size and frequency of wildfires in the western United States have been increasing, and this trend is projected to continue, with increasing adverse consequences for human health. Gas- and particle-phase organic compounds are the main components of wildfire emissions. Some of the directly emitted compounds are hazardous air pollutants, while others can react with oxidants to form secondary air pollutants such as ozone and secondary organic aerosol (SOA). Further, compounds emitted in the particle phase can volatize during smoke transport and can then serve as precursors for SOA. The extent of pollutant formation from wildfire emissions is dependent in part on the speciation of organic compounds. The most detailed speciation of organic compounds has been achieved in laboratory studies, though recent field campaigns are leading to an increase in such measurements in the field. In this study, we identified and quantified hundreds of gas- and particle-phase organic compounds emitted from conifer-dominated wildfires in the western US, using two two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC x GC ToF-MS) instruments. Observed emission factors (EFs) and emission ratios are reported for four wildfires. As has been demonstrated previously, modified combustion efficiency (MCE) was a good predictor of particle-phase EFs (e.g., R-2=0.78 and 0.84 for sugars and terpenoids, respectively), except for elemental carbon. Higher emissions of diterpenoids, resin acids, and monoterpenes were observed in the field relative to laboratory studies, likely due to distillation from unburned heated vegetation, which may be underrepresented in laboratory studies. These diterpenoids and resin acids accounted for up to 45 % of total quantified organic aerosol, higher than the contribution from sugar and sugar derivatives. The low volatility of resin acids makes them ideal markers for conifer fire smoke. The speciated measurements also show that evaporation of semi-volatile organic compounds took place in smoke plumes, which suggests that the evaporated primary organic aerosol can be a precursor of SOAs in wildfire smoke plumes.
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    A new approach for measuring the carbon and oxygen content of atmospherically relevant compounds and mixtures
    Hurley, James F.; Kreisberg, Nathan M.; Stump, Braden; Bi, Chenyang; Kumar, Purushottam; Hering, Susanne V.; Keady, Pat; Isaacman-VanWertz, Gabriel (2020-09-18)
    Due to its complexity, gas- and particle-phase organic carbon in the atmosphere is often classified by its bulk physicochemical properties. However, there is a dearth of robust, moderate-cost approaches to measure the bulk chemical composition of organic carbon in the atmosphere. This is particularly true for the degree of oxygenation, which critically affects the properties and impacts of organic carbon but for which routine measurement approaches are lacking. This gap has limited the understanding of a wide range of atmospheric components, including particulate matter, the mass of which is monitored worldwide due to its health and environmental effects but the chemical characterization of which requires relatively high capital costs and complex operation by highly trained technical personnel. In this work, we demonstrate a new approach to estimate the mass of carbon and oxygen in analytes and mixtures that relies only on robust, moderate-cost detectors designed for use with gas chromatography. Organic compounds entering a flame ionization detector were found to be converted with approximately complete efficiency to CO2, which was analyzed downstream using an infrared detector to measure the mass of carbon analyzed. The ratio of the flame ionization detector (FID) signal generated to CO2 formed (FID=CO2) was shown to be strongly correlated (R-2 = 0.89) to the oxygen-to-carbon ratio (O=C) of the analyte. Furthermore, simple mixtures of analytes behaved as the weighted average of their components, indicating that this correlation extends to mixtures. These properties were also observed to correlate well with the sensitivity of the FID estimated by structure activity relationships (quantified as the relative effective carbon number). The relationships between measured FID=CO2, analyte O=C, and FID sensitivity allow the estimation of one property from another with < 15% error for mixtures and < 20% error for most individual analytes. The approach opens the possibility of field-deployable, autonomous measurement of the carbon and oxygen content of particulate matter using time-tested, low-maintenance detectors, though such an application would require some additional testing on complex mixtures. With some instrumental modifications, similar measurements on gas-phase species may be feasible. Moreover, the potential expansion to additional gas chromatography detectors may provide concurrent measurement of other elements (e.g., sulfur, nitrogen).
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    Observations of sesquiterpenes and their oxidation products in central Amazonia during the wet and dry seasons
    Yee, Lindsay D.; Isaacman-VanWertz, Gabriel; Wernis, Rebecca A.; Meng, Meng; Rivera, Ventura; Kreisberg, Nathan M.; Hering, Susanne V.; Bering, Mads S.; Glasius, Marianne; Upshur, Mary Alice; Be, Ariana Gray; Thomson, Regan J.; Geiger, Franz M.; Offenberg, John H.; Lewandowski, Michael; Kourtchev, Ivan; Kalberer, Markus; de Sa, Suzane S.; Martin, Scot T.; Alexander, M. Lizabeth; Palm, Brett B.; Hu, Weiwei; Campuzano-Jost, Pedro; Day, Douglas A.; Jimenez, Jose L.; Liu, Yingjun; McKinney, Karena A.; Artaxo, Paulo; Viegas, Juarez; Manzi, Antonio; Oliveira, Maria B.; de Souza, Rodrigo; Machado, Luiz A. T.; Longo, Karla; Goldstein, Allen H. (European Geophysical Union, 2018-07-23)
    Biogenic volatile organic compounds (BVOCs) from the Amazon forest region represent the largest source of organic carbon emissions to the atmosphere globally. These BVOC emissions dominantly consist of volatile and intermediate-volatility terpenoid compounds that undergo chemical transformations in the atmosphere to form oxygenated condensable gases and secondary organic aerosol (SOA). We collected quartz filter samples with 12 h time resolution and performed hourly in situ measurements with a semi-volatile thermal desorption aerosol gas chromatograph (SV-TAG) at a rural site ("T3") located to the west of the urban center of Manaus, Brazil as part of the Green Ocean Amazon (GoAmazon2014/5) field campaign to measure intermediate-volatility and semi-volatile BVOCs and their oxidation products during the wet and dry seasons. We speciated and quantified 30 sesquiterpenes and 4 diterpenes with mean concentrations in the range 0.01-6.04 ng m(-3) (1670 ppq(v)). We estimate that sesquiterpenes contribute approximately 14 and 12% to the total reactive loss of O-3 via reaction with isoprene or terpenes during the wet and dry seasons, respectively. This is reduced from similar to 50-70% for within-canopy reactive O-3 loss attributed to the ozonolysis of highly reactive sesquiterpenes (e.g., beta-caryophyllene) that are reacted away before reaching our measurement site. We further identify a suite of their oxidation products in the gas and particle phases and explore their role in biogenic SOA formation in the central Amazon region. Synthesized authentic standards were also used to quantify gas-and particle-phase oxidation products derived from beta-caryophyllene. Using tracer-based scaling methods for these products, we roughly estimate that sesquiterpene oxidation contributes at least 0.4-5% (median 1 %) of total submicron OA mass. However, this is likely a low-end estimate, as evidence for additional unaccounted sesquiterpenes and their oxidation products clearly exists. By comparing our field data to laboratory-based sesquiterpene oxidation experiments we confirm that more than 40 additional observed compounds produced through sesquiterpene oxidation are present in Amazonian SOA, warranting further efforts towards more complete quantification.