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Measurement of glyoxal using an incoherent broadband cavity enhanced absorption spectrometer (2008)

Washenfelder, R. A. ; Langford, A. O. ; Fuchs, H. ; [et al.]

Copernicus

In: Atmospheric Chemistry and Physics. 2008; 8(24): 7779-7793. Published 2008 Dec 23. doi: 10.5194/acp-8-7779-2008.

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Publication Date: 2008-12-23

Description: We describe an instrument for simultaneous measurements of glyoxal (CHOCHO) and nitrogen dioxide (NO2) using cavity enhanced absorption spectroscopy with a broadband light source. The output of a Xenon arc lamp is coupled into a 1 m optical cavity, and the spectrum of light exiting the cavity is recorded by a grating spectrometer with a charge-coupled device (CCD) array detector. The mirror reflectivity and effective path lengths are determined from the known Rayleigh scattering of He and dry zero air (N2+O2). Least-squares fitting, using published reference spectra, allow the simultaneous retrieval of CHOCHO, NO2, O4, and H2O in the 441 to 469 nm spectral range. For a 1-min sampling time, the precision (±1σ) on signal for measurements of CHOCHO and NO2 is 29 pptv and 20 pptv, respectively. We directly compare measurements made with the incoherent broadband cavity enhanced absorption spectrometer with those from cavity ringdown instruments detecting CHOCHO and NO2 at 404 and 532 nm, respectively, and find linear agreement over a wide range of concentrations. The instrument has been tested in the laboratory with both synthetic and real air samples, and the demonstrated sensitivity and specificity suggest a strong potential for field measurements of both CHOCHO and NO2.

Print ISSN: 1680-7316

Electronic ISSN: 1680-7324

Topics: Geosciences

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High resolution vertical distributions of NO3 and N2O5 through the nocturnal boundary layer (2007)

Brown, S. S. ; Dubé, W. P. ; Osthoff, H. D. ; [et al.]

Copernicus

In: Atmospheric Chemistry and Physics. 2007; 7(1): 139-149. Published 2007 Jan 11. doi: 10.5194/acp-7-139-2007.

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Publication Date: 2007-01-11

Description: The shallow mixing depth and vertical stratification of the lowest levels of the atmosphere at night has implications for the chemistry of nitrogen oxides emitted from the surface. Here we report vertical profiles of NO3, N2O5 and O3 measured from in-situ instruments on a movable carriage on a 300 m tower. The study offers high-resolution (

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Radicals in the marine boundary layer during NEAQS 2004: a model study of day-time and night-time sources and sinks (2009)

Sommariva, R. ; Osthoff, H. D. ; Brown, S. S. ; [et al.]

Copernicus

In: Atmospheric Chemistry and Physics. 2009; 9(9): 3075-3093. Published 2009 May 13. doi: 10.5194/acp-9-3075-2009.

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Publication Date: 2009-05-13

Description: This paper describes a modelling study of several HOx and NOx species (OH, HO2, organic peroxy radicals, NO3 and N2O5) in the marine boundary layer. A model based upon the Master Chemical Mechanism (MCM) was constrained to observations of chemical and physical parameters made onboard the NOAA ship R/V Brown as part of the New England Air Quality Study (NEAQS) in the summer of 2004. The model was used to calculate [OH] and to determine the composition of the peroxy radical pool. Modelled [NO3] and [N2O5] were compared to in-situ measurements by Cavity Ring-Down Spectroscopy. The comparison showed that the model generally overestimated the measurements by 30–50%, on average. The model results were analyzed with respect to several chemical and physical parameters, including uptake of NO3 and N2O5 on fog droplets and on aerosol, dry deposition of NO3 and N2O5, gas-phase hydrolysis of N2O5 and reactions of NO3 with NMHCs and peroxy radicals. The results suggest that fog, when present, is an important sink for N2O5 via rapid heterogeneous uptake. The comparison between the model and the measurements were consistent with values of the heterogeneous uptake coefficient of N2O5 (γN2O5)〉1×10−2, independent of aerosol composition in this marine environment. The analysis of the different loss processes of the nitrate radical showed the important role of the organic peroxy radicals, which accounted for a significant fraction (median: 15%) of NO3 gas-phase removal, particularly in the presence of high concentrations of dimethyl sulphide (DMS).

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Organic nitrate and secondary organic aerosol yield from NO3 oxidation of β-pinene evaluated using a gas-phase kinetics/aerosol partitioning model (2009)

Fry, J. L. ; Kiendler-Scharr, A. ; Rollins, A. W. ; [et al.]

Copernicus

In: Atmospheric Chemistry and Physics. 2009; 9(4): 1431-1449. Published 2009 Feb 23. doi: 10.5194/acp-9-1431-2009.

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Publication Date: 2009-02-23

Description: The yields of organic nitrates and of secondary organic aerosol (SOA) particle formation were measured for the reaction NO3+β-pinene under dry and humid conditions in the atmosphere simulation chamber SAPHIR at Research Center Jülich. These experiments were conducted at low concentrations of NO3 (NO3+N2O5

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Isoprene oxidation by nitrate radical: alkyl nitrate and secondary organic aerosol yields (2009)

Rollins, A. W. ; Kiendler-Scharr, A. ; Fry, J. L. ; [et al.]

Copernicus

In: Atmospheric Chemistry and Physics. 2009; 9(18): 6685-6703. Published 2009 Sep 15. doi: 10.5194/acp-9-6685-2009.

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Publication Date: 2009-09-15

Description: Alkyl nitrates and secondary organic aerosol (SOA) produced during the oxidation of isoprene by nitrate radicals has been observed in the SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction Chamber) chamber. A 16 h dark experiment was conducted with temperatures at 289–301 K, and maximum concentrations of 11 ppb isoprene, 62.4 ppb O3 and 31.1 ppb NOx. We find the yield of nitrates is 70±8% from the isoprene + NO3 reaction, and the yield for secondary dinitrates produced in the reaction of primary isoprene nitrates with NO3 is 40±20%. We find an effective rate constant for reaction of NO3 with the group of first generation oxidation products to be 7×10−14 molecule−1 cm3 s−1. At the low total organic aerosol concentration in the chamber (max=0.52 μg m−3) we observed a mass yield (ΔSOA mass/Δisoprene mass) of 2% for the entire 16 h experiment. However a comparison of the timing of the observed SOA production to a box model simulation of first and second generation oxidation products shows that the yield from the first generation products was

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Nocturnal isoprene oxidation over the Northeast United States in summer and its impact on reactive nitrogen partitioning and secondary organic aerosol (2009)

Brown, S. S. ; deGouw, J. A. ; Warneke, C. ; [et al.]

Copernicus

In: Atmospheric Chemistry and Physics. 2009; 9(9): 3027-3042. Published 2009 May 11. doi: 10.5194/acp-9-3027-2009.

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Publication Date: 2009-05-11

Description: Isoprene is the largest single VOC emission to the atmosphere. Although it is primarily oxidized photochemically during daylight hours, late-day emissions that remain in the atmosphere at sunset undergo oxidation by NO3 in regionally polluted areas with large NOx levels. A recent aircraft study examined isoprene and its nocturnal oxidants in a series of night flights across the Northeast US, a region with large emissions of both isoprene and NOx. Substantial amounts of isoprene that were observed after dark were strongly anticorrelated with measured NO3 and were the most important factor determining the lifetime of this radical. The products of photochemical oxidation of isoprene, methyl vinyl ketone and methacrolein, were more uniformly distributed, and served as tracers for the presence of isoprene at sunset, prior to its oxidation by NO3. A determination of the mass of isoprene oxidized in darkness showed it to be a large fraction (〉20%) of emitted isoprene. Organic nitrates produced from the NO3+isoprene reaction, though not directly measured, were estimated to account for 2–9% of total reactive nitrogen. The mass of isoprene oxidized by NO3 was comparable to and correlated with the organic aerosol loading for flights with relatively low organic aerosol background. The contribution of nocturnal isoprene oxidation to secondary organic aerosol was determined in the range 1–17%, and isoprene SOA mass derived from NO3 was calculated to exceed that due to OH by approximately 50%.

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