Vertically resolved chemical characteristics and sources of submicron aerosols measured on a Tall Tower in a suburban area near Denver, Colorado in winter

Öztürk, Fatma; Bahreini, R.; Wagner, Nick; Dubé, W. P.; Young, Cora J.; Brown, Steven S.; Brock, C. A.; Ulbrich, I. M.; Jimenez, José L.; Cooper, O. R.; Middlebrook, A. M.

doi:10.1002/2013jd019923

Cited by 19 publications

(12 citation statements)

References 86 publications

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“…For most of the NACHTT study, fine particle volume and organic aerosol mass were not correlated with these BB tracers and were attributed to other sources [ Öztürk et al ., ]. However, the correlation of HNCO with fine particle volume was quite strong during the AB plume in Figure a when the carriage was at the surface ( R 2 = 0.916), and in the plume observed at the top of the tower, it had a smaller slope and was not quite as well correlated ( R 2 = 0.687).…”

Section: Resultsmentioning

confidence: 92%

New insights into atmospheric sources and sinks of isocyanic acid, HNCO, from recent urban and regional observations

et al. 2014

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Isocyanic acid (HNCO) has only recently been measured in the ambient atmosphere, and many aspects of its atmospheric chemistry are still uncertain. HNCO was measured during three diverse field campaigns: California Nexus-Research at the Nexus of Air Quality and Climate Change (CalNex 2010) at the Pasadena ground site, Nitrogen, Aerosol Composition, and Halogens on a Tall Tower (NACHTT 2011) at the Boulder Atmospheric Observatory (BAO) in Weld County, CO, and Biofuel Crops emission of Ozone precursors intensive (BioCORN 2011), in a cornfield NW of Fort Collins, CO. Mixing ratios varied from below detection limit (~0.003 ppbv) to over 1.2 ppbv during a period when agricultural burning impacted the BAO Tower site. Urban areas, such as the CalNex 2010 Pasadena site, appear to have both primary (combustion) and secondary (photochemical) sources of HNCO, 50 ± 9%, and 33 ± 12%, respectively, while primary sources were responsible for the large mixing ratios of HNCO observed during the wintertime NACHTT study in suburban Colorado. Isocyanic acid during the BioCORN study in rural NE Colorado was closely correlated to ozone and therefore likely photochemically produced as a secondary product from amines or formamide. The removal of HNCO from the lower atmosphere is thought to be due to deposition, as common gas phase loss processes of photolysis and reactions with hydroxyl radicals, are slow. These ambient measurements are consistent with some HNCO deposition, which was evident at night at these surface sites.

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Section: Resultsmentioning

confidence: 92%

New insights into atmospheric sources and sinks of isocyanic acid, HNCO, from recent urban and regional observations

et al. 2014

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“…This procedure ensures that the fraction of the carboxylic acid in the gas-phase was greater than 10%, assuming that the classroom organic aerosol concentration was ~1 µg m -3 , which is typical of outdoor concentrations in this region. 31,32 This procedure excluded 25 of the 180 ions, leaving 155 for further analysis. The remaining ions accounted for 87% and 62% of the total signals (above background) for indoor and outdoor measurements, respectively.…”

Section: Methodsmentioning

confidence: 99%

Gas-Phase Carboxylic Acids in a University Classroom: Abundance, Variability, and Sources

Liu

Thompson

Stark

et al. 2017

Environ. Sci. Technol.

100

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Gas-phase carboxylic acids are ubiquitous in ambient air, yet their indoor occurrence and abundance are poorly characterized. To fill this gap, we measured gas-phase carboxylic acids in real-time inside and outside of a university classroom using a high-resolution time-of-flight chemical ionization mass spectrometer (HRToF-CIMS) equipped with an acetate ion source. A wide variety of carboxylic acids were identified indoors and outdoors, including monoacids, diacids, hydroxy acids, carbonyl acids, and aromatic acids. An empirical parametrization was derived to estimate the sensitivity (ion counts per ppt of the analytes) of the HRToF-CIMS to the acids. The campaign-average concentration of carboxylic acids measured outdoors was 1.0 ppb, with the peak concentration occurring in daytime. The average indoor concentration of carboxylic acids was 6.8 ppb, of which 87% was contributed by formic and lactic acid. While carboxylic acids measured outdoors displayed a single daytime peak, those measured indoors displayed a daytime and a nighttime peak. Besides indoor sources such as off-gassing of building materials, evidence for acid production from indoor chemical reactions with ozone was found. In addition, some carboxylic acids measured indoors correlated to CO in daytime, suggesting that human occupants may contribute to their abundance either through direct emissions or surface reactions.

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“…The meteorological tower is a unique platform to study the vertical characteristics of air pollutants in the lower levels of the boundary layer. For example, the vertical profiles of trace gases and aerosol species from 3 to 270 m were comprehensively characterized using a 300 m tower at the Boulder Atmospheric Observatory (BAO) during late winter 2011 (Brown et al, 2013), which provides many new insights into the sources of chemical species (e.g., local emissions, regional transport, and point sources) and aerosol processing at different heights (Kim et al, 2014;Öztürk et al, 2013b). Because the BAO tower is located at a suburban area with low aerosol mass loadings, the vertical profiles of aerosol and gas species (VandenBoer et al, 2013;Riedel et al, 2013;Öztürk et al, 2013a) could be substantially different from those in megacities in China.…”

Section: Introductionmentioning

confidence: 99%

“…To reduce the uncertainties in vertical comparisons, the ACSM measurements were further corrected using the regression slopes determined from the intercomparisons. Positive matrix factorization (PMF) (Paatero and Tapper, 1994) was first performed to the unit mass resolution spectra of organic aerosol (OA) at ground level that were measured with HR-ToF-AMS during the same period as that of ACSM, and five factors including three primary OA (POA) factors -i.e., fossil-fuelrelated OA (FFOA) predominantly from coal combustion emissions, cooking OA (COA), and biomass burning OA (BBOA) -and two secondary OA (SOA) factors -i.e., lessoxidized oxygenated OA (LO-OOA) and more-oxidized oxygenated OA (MO-OOA) -were identified. To better compare the OA factors between ground level and 260 m, the multilinear engine 2 (ME-2) (Canonaco et al, 2013;Crippa et al, 2014) using the mass spectral profiles of three POA factors at ground level as constrains was performed to the ACSM OA spectra.…”

Section: Introductionmentioning

confidence: 99%

Vertically resolved characteristics of air pollution during two severe winter haze episodes in urban Beijing, China

Wang

Sun

et al. 2018

Atmos. Chem. Phys.

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Abstract. We conducted the first real-time continuous vertical measurements of particle extinction (bext), gaseous NO2, and black carbon (BC) from ground level to 260 m during two severe winter haze episodes at an urban site in Beijing, China. Our results illustrated four distinct types of vertical profiles: (1) uniform vertical distributions (37 % of the time) with vertical differences less than 5 %, (2) higher values at lower altitudes (29 %), (3) higher values at higher altitudes (16 %), and (4) significant decreases at the heights of ∼ 100–150 m (14 %). Further analysis demonstrated that vertical convection as indicated by mixing layer height, temperature inversion, and local emissions are three major factors affecting the changes in vertical profiles. Particularly, the formation of type 4 was strongly associated with the stratified layer that was formed due to the interactions of different air masses and temperature inversions. Aerosol composition was substantially different below and above the transition heights with ∼ 20–30 % higher contributions of local sources (e.g., biomass burning and cooking) at lower altitudes. A more detailed evolution of vertical profiles and their relationship with the changes in source emissions, mixing layer height, and aerosol chemistry was illustrated by a case study. BC showed overall similar vertical profiles as those of bext (R2=0.92 and 0.69 in November and January, respectively). While NO2 was correlated with bext for most of the time, the vertical profiles of bext ∕ NO2 varied differently for different profiles, indicating the impact of chemical transformation on vertical profiles. Our results also showed that more comprehensive vertical measurements (e.g., more aerosol and gaseous species) at higher altitudes in the megacities are needed for a better understanding of the formation mechanisms and evolution of severe haze episodes in China.

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Vertically resolved chemical characteristics and sources of submicron aerosols measured on a Tall Tower in a suburban area near Denver, Colorado in winter

Cited by 19 publications

References 86 publications

New insights into atmospheric sources and sinks of isocyanic acid, HNCO, from recent urban and regional observations

New insights into atmospheric sources and sinks of isocyanic acid, HNCO, from recent urban and regional observations

Gas-Phase Carboxylic Acids in a University Classroom: Abundance, Variability, and Sources

Vertically resolved characteristics of air pollution during two severe winter haze episodes in urban Beijing, China

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