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Rainer Volkamer - One of the best experts on this subject based on the ideXlab platform.
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Glyoxal and methylGlyoxal setschenow salting constants in sulfate nitrate and chloride solutions measurements and gibbs energies
Environmental Science & Technology, 2015Co-Authors: Eleanor M Waxman, Theo Kurten, Jonas Elm, Kurt V Mikkelsen, P Ziemann, Rainer VolkamerAbstract:Knowledge about Setschenow salting constants, KS, the exponential dependence of Henry’s Law coefficients on salt concentration, is of particular importance to predict secondary organic aerosol (SOA) formation from soluble species in atmospheric waters with high salt concentrations, such as aerosols. We have measured KS of Glyoxal and methylGlyoxal for the atmospherically relevant salts (NH4)2SO4, NH4NO3, NaNO3, and NaCl and find that Glyoxal consistently “salts-in” (KS of −0.16, −0.06, −0.065, −0.1 molality–1, respectively) while methylGlyoxal “salts-out” (KS of +0.16, +0.075, +0.02, +0.06 molality–1). We show that KS values for different salts are additive and present an equation for use in atmospheric models. Additionally, we have performed a series of quantum chemical calculations to determine the interactions between Glyoxal/methylGlyoxal monohydrate with Cl–, NO3–, SO42–, Na+, and NH4+ and find Gibbs free energies of water displacement of −10.9, −22.0, −22.9, 2.09, and 1.2 kJ/mol for Glyoxal monohydr...
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aircraft measurements of bro io Glyoxal no 2 h 2 o o 2 o 2 and aerosol extinction profiles in the tropics comparison with aircraft ship based in situ and lidar measurements
Atmospheric Measurement Techniques, 2015Co-Authors: S Coburn, Rainer Volkamer, S Baidar, J P Digangi, T Campos, Barbara DixAbstract:Abstract. Tropospheric chemistry of halogens and organic carbon over tropical oceans modifies ozone and atmospheric aerosols, yet atmospheric models remain largely untested for lack of vertically resolved measurements of bromine monoxide (BrO), iodine monoxide (IO) and small oxygenated hydrocarbons like Glyoxal (CHOCHO) in the tropical troposphere. BrO, IO, Glyoxal, nitrogen dioxide (NO2), water vapor (H2O) and O2–O2 collision complexes (O4) were measured by the University of Colorado Airborne Multi-AXis Differential Optical Absorption Spectroscopy (CU AMAX-DOAS) instrument, aerosol extinction by high spectral resolution lidar (HSRL), in situ aerosol size distributions by an ultra high sensitivity aerosol spectrometer (UHSAS) and in situ H2O by vertical-cavity surface-emitting laser (VCSEL) hygrometer. Data are presented from two research flights (RF12, RF17) aboard the National Science Foundation/National Center for Atmospheric Research Gulfstream V aircraft over the tropical Eastern Pacific Ocean (tEPO) as part of the "Tropical Ocean tRoposphere Exchange of Reactive halogens and Oxygenated hydrocarbons" (TORERO) project (January/February 2012). We assess the accuracy of O4 slant column density (SCD) measurements in the presence and absence of aerosols. Our O4-inferred aerosol extinction profiles at 477 nm agree within 6% with HSRL in the boundary layer and closely resemble the renormalized profile shape of Mie calculations constrained by UHSAS at low (sub-Rayleigh) aerosol extinction in the free troposphere. CU AMAX-DOAS provides a flexible choice of geometry, which we exploit to minimize the SCD in the reference spectrum (SCDREF, maximize signal-to-noise ratio) and to test the robustness of BrO, IO and Glyoxal differential SCDs. The RF12 case study was conducted in pristine marine and free tropospheric air. The RF17 case study was conducted above the NOAA RV Ka'imimoana (TORERO cruise, KA-12-01) and provides independent validation data from ship-based in situ cavity-enhanced DOAS and MAX-DOAS. Inside the marine boundary layer (MBL) no BrO was detected (smaller than 0.5 pptv), and 0.2–0.55 pptv IO and 32–36 pptv Glyoxal were observed. The near-surface concentrations agree within 30% (IO) and 10% (Glyoxal) between ship and aircraft. The BrO concentration strongly increased with altitude to 3.0 pptv at 14.5 km (RF12, 9.1 to 8.6° N; 101.2 to 97.4° W). At 14.5 km, 5–10 pptv NO2 agree with model predictions and demonstrate good control over separating tropospheric from stratospheric absorbers (NO2 and BrO). Our profile retrievals have 12–20 degrees of freedom (DoF) and up to 500 m vertical resolution. The tropospheric BrO vertical column density (VCD) was 1.5 × 1013 molec cm−2 (RF12) and at least 0.5 × 1013 molec cm−2 (RF17, 0–10 km, lower limit). Tropospheric IO VCDs correspond to 2.1 × 1012 molec cm−2 (RF12) and 2.5 × 1012 molec cm−2 (RF17) and Glyoxal VCDs of 2.6 × 1014 molec cm−2 (RF12) and 2.7 × 1014 molec cm−2 (RF17). Surprisingly, essentially all BrO as well as the dominant IO and Glyoxal VCD fraction was located above 2 km (IO: 58 ± 5%, 0.1–0.2 pptv; Glyoxal: 52 ± 5%, 3–20 pptv). To our knowledge there are no previous vertically resolved measurements of BrO and Glyoxal from aircraft in the tropical free troposphere. The atmospheric implications are briefly discussed. Future studies are necessary to better understand the sources and impacts of free tropospheric halogens and oxygenated hydrocarbons on tropospheric ozone, aerosols, mercury oxidation and the oxidation capacity of the atmosphere.
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computational study of the effect of Glyoxal sulfate clustering on the henry s law coefficient of Glyoxal
Journal of Physical Chemistry A, 2015Co-Authors: Theo Kurten, Jonas Elm, Nonne L Prisle, Kurt V Mikkelsen, Christopher J Kampf, Eleanor M Waxman, Rainer VolkamerAbstract:We have used quantum chemical methods to investigate the molecular mechanism behind the recently reported (Kampf, C. J.; Environ. Sci. Technol. 2013, 47, 4236−4244) strong dependence of the Henry’s law coefficient of Glyoxal (C2O2H2) on the sulfate concentration of the aqueous phase. Although the Glyoxal molecule interacts only weakly with sulfate, its hydrated forms (C2O3H4 and C2O4H6) form strong complexes with sulfate, displacing water molecules from the solvation shell and increasing the uptake of Glyoxal into sulfate-containing aqueous solutions, including sulfate-containing aerosol particles. This promotes the participation of Glyoxal in reactions leading to secondary organic aerosol formation, especially in regions with high sulfate concentrations. We used our computed equilibrium constants for the complexation reactions to assess the magnitude of the Henry’s law coefficient enhancement and found it to be in reasonable agreement with experimental results. This indicates that the complexation of gly...
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measurements of diurnal variations and eddy covariance ec fluxes of Glyoxal in the tropical marine boundary layer description of the fast led ce doas instrument
Atmospheric Measurement Techniques, 2014Co-Authors: Ryan Thalman, S Coburn, Ivan Ortega, Byron Blomquist, C W Fairall, Rainer VolkamerAbstract:Abstract. Here we present first eddy covariance (EC) measurements of fluxes of Glyoxal, the smallest α-dicarbonyl product of hydrocarbon oxidation, and a precursor for secondary organic aerosol (SOA). The unique physical and chemical properties of Glyoxal – i.e., high solubility in water (effective Henry's law constant, KH = 4.2 × 105 M atm−1) and short atmospheric lifetime (~2 h at solar noon) – make it a unique indicator species for organic carbon oxidation in the marine atmosphere. Previous reports of elevated Glyoxal over oceans remain unexplained by atmospheric models. Here we describe a Fast Light-Emitting Diode Cavity-Enhanced Differential Optical Absorption Spectroscopy (Fast LED-CE-DOAS) instrument to measure diurnal variations and EC fluxes of Glyoxal and inform about its unknown sources. The fast in situ sensor is described, and first results are presented from a cruise deployment over the eastern tropical Pacific Ocean (20° N to 10° S; 133 to 85° W) as part of the Tropical Ocean tRoposphere Exchange of Reactive halogens and Oxygenated VOCs (TORERO) field experiment (January to March 2012). The Fast LED-CE-DOAS is a multispectral sensor that selectively and simultaneously measures Glyoxal (CHOCHO), nitrogen dioxide (NO2), oxygen dimers (O4), and water vapor (H2O) with ~2 Hz time resolution (Nyquist frequency ~1 Hz) and a precision of ~40 pptv Hz−0.5 for Glyoxal. The instrument is demonstrated to be a "white-noise" sensor suitable for EC flux measurements. Fluxes of Glyoxal are calculated, along with fluxes of NO2, H2O, and O4, which are used to aid the interpretation of the Glyoxal fluxes. Further, highly sensitive and inherently calibrated Glyoxal measurements are obtained from temporal averaging of data (e.g., detection limit smaller than 2.5 pptv in an hour). The campaign average mixing ratio in the Southern Hemisphere (SH) is found to be 43 ± 9 pptv Glyoxal, which is higher than the Northern Hemisphere (NH) average of 32 ± 6 pptv (error reflects variability over multiple days). The diurnal variation of Glyoxal in the marine boundary layer (MBL) is measured for the first time, and mixing ratios vary by ~8 pptv (NH) and ~12 pptv (SH) over the course of 24 h. Consistently, maxima are observed at sunrise (NH: 35 ± 5 pptv; SH: 47 ± 7 pptv), and minima at dusk (NH: 27 ± 5 pptv; SH: 35 ± 8 pptv). In both hemispheres, the daytime flux was directed from the atmosphere into the ocean, indicating that the ocean is a net sink for Glyoxal during the day. After sunset the ocean was a source for Glyoxal to the atmosphere (positive flux) in the SH; this primary ocean source was operative throughout the night. In the NH, the nighttime flux was positive only shortly after sunset and negative during most of the night. Positive EC fluxes of soluble Glyoxal over oceans indicate the presence of an ocean surface organic microlayer (SML) and locate a Glyoxal source within the SML. The origin of most atmospheric Glyoxal, and possibly other oxygenated hydrocarbons over tropical oceans, remains unexplained and warrants further investigation.
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simulation of semi explicit mechanisms of soa formation from Glyoxal in aerosol in a 3 d model
Atmospheric Chemistry and Physics, 2014Co-Authors: Christoph Knote, Jose L Jimenez, Rainer Volkamer, Alma Hodzic, John J Orlando, S Baidar, J Brioude, Jerome D Fast, Drew R GentnerAbstract:Abstract. New pathways to form secondary organic aerosol (SOA) have been postulated recently. Glyoxal, the smallest dicarbonyl, is one of the proposed precursors. It has both anthropogenic and biogenic sources, and readily partitions into the aqueous phase of cloud droplets and deliquesced particles where it undergoes both reversible and irreversible chemistry. In this work we extend the regional scale chemistry transport model WRF-Chem to include detailed gas-phase chemistry of Glyoxal formation as well as a state-of-the-science module describing its partitioning and reactions in the aerosol aqueous-phase. A comparison of several proposed mechanisms is performed to quantify the relative importance of different formation pathways and their regional variability. The CARES/CalNex campaigns over California in summer 2010 are used as case studies to evaluate the model against observations. A month-long simulation over the continental United States (US) enables us to extend our results to the continental scale. In all simulations over California, the Los Angeles (LA) basin was found to be the hot spot for SOA formation from Glyoxal, which contributes between 1% and 15% of the model SOA depending on the mechanism used. Our results indicate that a mechanism based only on a reactive (surface limited) uptake coefficient leads to higher SOA yields from Glyoxal compared to a more detailed description that considers aerosol phase state and chemical composition. In the more detailed simulations, surface uptake is found to give the highest SOA mass yields compared to a volume process and reversible formation. We find that the yields of the latter are limited by the availability of Glyoxal in aerosol water, which is in turn controlled by an increase in the Henry's law constant depending on salt concentrations ("salting-in"). A time dependence in this increase prevents substantial partitioning of Glyoxal into aerosol water at high salt concentrations. If this limitation is removed, volume pathways contribute > 20% of Glyoxal-SOA mass, and the total mass formed (5.8% of total SOA in the LA basin) is about a third of the simple uptake coefficient formulation without consideration of aerosol phase state and composition. Results from the continental US simulation reveal the much larger potential to form Glyoxal-SOA over the eastern continental US. Interestingly, the low concentrations of Glyoxal-SOA over the western continental US are not due to the lack of a potential to form Glyoxal-SOA here. Rather these small Glyoxal-SOA concentrations reflect dry conditions and high salt concentrations, and the potential to form SOA mass here will strongly depend on the water associated with particles.
Frank N Keutsch - One of the best experts on this subject based on the ideXlab platform.
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yields of oxidized volatile organic compounds during the oh radical initiated oxidation of isoprene methyl vinyl ketone and methacrolein under high no x conditions
Atmospheric Chemistry and Physics, 2011Co-Authors: Arthur W. H. Chan, John H. Seinfeld, Melissa M Galloway, C L Loza, Andrew J Huisman, Lindsay D Yee, Frank N KeutschAbstract:We present first-generation and total production yields of Glyoxal, methylGlyoxal, glycolaldehyde, and hydroxyacetone from the oxidation of isoprene, methyl vinyl ketone (MVK), and methacrolein (MACR) with OH under high NO_x conditions. Several of these first-generation yields are not included in commonly used chemical mechanisms, such as the Leeds Master Chemical Mechanism (MCM) v. 3.2. The first-generation yield of Glyoxal from isoprene was determined to be 2.1 (±0.6)%. Inclusion of first-generation production of Glyoxal, glycolaldehyde and hydroxyacetone from isoprene greatly improves performance of an MCM based model during the initial part of the experiments. In order to further improve performance of the MCM based model, higher generation Glyoxal production was reduced by lowering the first-generation yield of Glyoxal from C5 hydroxycarbonyls. The results suggest that Glyoxal production from reaction of OH with isoprene under high NO_x conditions can be approximated by inclusion of a first-generation production term together with secondary production only via glycolaldehyde. Analogously, methylGlyoxal production can be approximated by a first-generation production term from isoprene, and secondary production via MVK, MACR and hydroxyacetone. The first-generation yields reported here correspond to less than 5% of the total oxidized yield from isoprene and thus only have a small effect on the fate of isoprene. However, due to the abundance of isoprene, the combination of first-generation yields and reduced higher generation production of Glyoxal from C5 hydroxycarbonyls is important for models that include the production of the small organic molecules from isoprene.
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analysis of photochemical and dark Glyoxal uptake implications for soa formation
Geophysical Research Letters, 2011Co-Authors: Melissa M Galloway, P S Chhabra, Arthur W. H. Chan, John H. Seinfeld, C L Loza, L Yee, Frank N KeutschAbstract:The dependence of Glyoxal uptake onto deliquesced ammonium sulfate seed aerosol was studied under photochemical (light + hydroxyl radical (OH)) and dark conditions. In this study, the chemical composition of aerosol formed from Glyoxal is identical in the presence or absence of OH. In addition, there was no observed OH dependence on either Glyoxal uptake or Glyoxal-driven aerosol growth for this study. These findings demonstrate that, for the system used here, Glyoxal uptake is not affected by the presence of OH. In combination with previous studies, this shows that the exact nature of the type of seed aerosol, in particular the presence of a coating, has a large influence on fast photochemical uptake of Glyoxal. Due to the challenge of relating this seed aerosol dependence to ambient conditions, this work highlights the resulting difficulty in quantitatively including SOA formation from Glyoxal in models.
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Glyoxal in aqueous ammonium sulfate solutions products kinetics and hydration effects
Environmental Science & Technology, 2011Co-Authors: Amanda R Bayer, Melissa M Galloway, Kyle J Korshavn, Charles G Fry, Frank N KeutschAbstract:Reactions and interactions between Glyoxal and salts in aqueous solution were studied. Glyoxal was found to react with ammonium to form imidazole, imidazole-2-carboxaldehyde, formic acid, N-Glyoxal substituted imidazole, and minor products at very low concentrations. Overall reaction orders and rates for each major product were measured. Sulfate ions have a strong and specific interaction with Glyoxal in aqueous solution, which shifts the hydration equilibria of Glyoxal from the unhydrated carbonyl form to the hydrated form. This ion-specific effect contributes to the observed enhancement of the effective Henry's law coefficient for Glyoxal in sulfate-containing solutions. The results of UV-vis absorption and NMR spectroscopy studies of solutions of Glyoxal with ammonium, methylamine, and dimethylamine salts reveal that light absorbing compounds require the formation of nitrogen containing molecules. These findings have implications on the role of Glyoxal in the atmosphere, both in models of the contribution of Glyoxal to form secondary organic aerosol (SOA), the role of nitrogen containing species for aerosol optical properties and in predictions of the behavior of other carbonyls or dicarbonyls in the atmosphere.
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Glyoxal in aqueous ammonium sulfate solutions products kinetics and hydration effects
Environmental Science & Technology, 2011Co-Authors: Amanda R Bayer, Melissa M Galloway, Kyle J Korshavn, Charles G Fry, Frank N KeutschAbstract:Reactions and interactions between Glyoxal and salts in aqueous solution were studied. Glyoxal was found to react with ammonium to form imidazole, imidazole-2-carboxaldehyde, formic acid, N-Glyoxal substituted imidazole, and minor products at very low concentrations. Overall reaction orders and rates for each major product were measured. Sulfate ions have a strong and specific interaction with Glyoxal in aqueous solution, which shifts the hydration equilibria of Glyoxal from the unhydrated carbonyl form to the hydrated form. This ion-specific effect contributes to the observed enhancement of the effective Henry’s law coefficient for Glyoxal in sulfate-containing solutions. The results of UV–vis absorption and NMR spectroscopy studies of solutions of Glyoxal with ammonium, methylamine, and dimethylamine salts reveal that light absorbing compounds require the formation of nitrogen containing molecules. These findings have implications on the role of Glyoxal in the atmosphere, both in models of the contribut...
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Glyoxal uptake on ammonium sulphate seed aerosol: reaction products and reversibility of uptake under dark and irradiated conditions
Atmospheric Chemistry and Physics, 2008Co-Authors: M. M. Galloway, P S Chhabra, Arthur W. H. Chan, John H. Seinfeld, Jason D Surratt, Richard C. Flagan, Frank N KeutschAbstract:Chamber studies of Glyoxal uptake onto ammonium sulphate aerosol were performed under dark and irradiated conditions to gain further insight into processes controlling Glyoxal uptake onto ambient aerosol. Organic fragments from Glyoxal dimers and trimers were observed within the aerosol under dark and irradiated conditions. Glyoxal monomers and oligomers were the dominant organic compounds formed under the conditions of this study; Glyoxal oligomer formation and overall organic growth were found to be reversible under dark conditions. Analysis of high-resolution time-of-flight aerosol mass spectra provides evidence for irreversible formation of carbon-nitrogen (C-N) compounds in the aerosol. We have identified 1H-imidazole-2-carboxaldehyde as one C-N product. To the authors' knowledge, this is the first time C-N compounds resulting from condensed phase reactions with ammonium sulphate seed have been detected in aerosol. Organosulphates were not detected under dark conditions. However, active photochemistry was found to occur within aerosol during irradiated experiments. Carboxylic acids and organic esters were identified within the aerosol. An organosulphate, which had been previously assigned as Glyoxal sulphate in ambient samples and chamber studies of isoprene oxidation, was observed only in the irradiated experiments. Comparison with a laboratory synthesized standard and chemical considerations strongly suggest that this organosulphate is glycolic acid sulphate, an isomer of the previously proposed Glyoxal sulphate. Our study shows that reversibility of Glyoxal uptake should be taken into account in SOA models and also demonstrates the need for further investigation of C-N compound formation and photochemical processes, in particular organosulphate formation.
John H. Seinfeld - One of the best experts on this subject based on the ideXlab platform.
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yields of oxidized volatile organic compounds during the oh radical initiated oxidation of isoprene methyl vinyl ketone and methacrolein under high no x conditions
Atmospheric Chemistry and Physics, 2011Co-Authors: Arthur W. H. Chan, John H. Seinfeld, Melissa M Galloway, C L Loza, Andrew J Huisman, Lindsay D Yee, Frank N KeutschAbstract:We present first-generation and total production yields of Glyoxal, methylGlyoxal, glycolaldehyde, and hydroxyacetone from the oxidation of isoprene, methyl vinyl ketone (MVK), and methacrolein (MACR) with OH under high NO_x conditions. Several of these first-generation yields are not included in commonly used chemical mechanisms, such as the Leeds Master Chemical Mechanism (MCM) v. 3.2. The first-generation yield of Glyoxal from isoprene was determined to be 2.1 (±0.6)%. Inclusion of first-generation production of Glyoxal, glycolaldehyde and hydroxyacetone from isoprene greatly improves performance of an MCM based model during the initial part of the experiments. In order to further improve performance of the MCM based model, higher generation Glyoxal production was reduced by lowering the first-generation yield of Glyoxal from C5 hydroxycarbonyls. The results suggest that Glyoxal production from reaction of OH with isoprene under high NO_x conditions can be approximated by inclusion of a first-generation production term together with secondary production only via glycolaldehyde. Analogously, methylGlyoxal production can be approximated by a first-generation production term from isoprene, and secondary production via MVK, MACR and hydroxyacetone. The first-generation yields reported here correspond to less than 5% of the total oxidized yield from isoprene and thus only have a small effect on the fate of isoprene. However, due to the abundance of isoprene, the combination of first-generation yields and reduced higher generation production of Glyoxal from C5 hydroxycarbonyls is important for models that include the production of the small organic molecules from isoprene.
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analysis of photochemical and dark Glyoxal uptake implications for soa formation
Geophysical Research Letters, 2011Co-Authors: Melissa M Galloway, P S Chhabra, Arthur W. H. Chan, John H. Seinfeld, C L Loza, L Yee, Frank N KeutschAbstract:The dependence of Glyoxal uptake onto deliquesced ammonium sulfate seed aerosol was studied under photochemical (light + hydroxyl radical (OH)) and dark conditions. In this study, the chemical composition of aerosol formed from Glyoxal is identical in the presence or absence of OH. In addition, there was no observed OH dependence on either Glyoxal uptake or Glyoxal-driven aerosol growth for this study. These findings demonstrate that, for the system used here, Glyoxal uptake is not affected by the presence of OH. In combination with previous studies, this shows that the exact nature of the type of seed aerosol, in particular the presence of a coating, has a large influence on fast photochemical uptake of Glyoxal. Due to the challenge of relating this seed aerosol dependence to ambient conditions, this work highlights the resulting difficulty in quantitatively including SOA formation from Glyoxal in models.
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elemental analysis of chamber organic aerosol using an aerodyne high resolution aerosol mass spectrometer
Atmospheric Chemistry and Physics, 2010Co-Authors: P S Chhabra, Richard C. Flagan, John H. SeinfeldAbstract:Abstract. The elemental composition of laboratory chamber secondary organic aerosol (SOA) from Glyoxal uptake, α-pinene ozonolysis, isoprene photooxidation, single-ring aromatic photooxidation, and naphthalene photooxidation is evaluated using Aerodyne high-resolution time-of-flight mass spectrometer data. SOA O/C ratios range from 1.13 for Glyoxal uptake experiments to 0.30–0.43 for α-pinene ozonolysis. The elemental composition of α-pinene and naphthalene SOA is also confirmed by offline mass spectrometry. The fraction of organic signal at m/z 44 is generally a good measure of SOA oxygenation for α-pinene/O3, isoprene/high-NOx, and naphthalene SOA systems. The agreement between measured and estimated O/C ratios tends to get closer as the fraction of organic signal at m/z 44 increases. This is in contrast to the Glyoxal uptake system, in which m/z 44 substantially underpredicts O/C. Although chamber SOA has generally been considered less oxygenated than ambient SOA, single-ring aromatic- and naphthalene-derived SOA can reach O/C ratios upward of 0.7, well within the range of ambient PMF component OOA, though still not as high as some ambient measurements. The spectra of aromatic and isoprene-high-NOx SOA resemble that of OOA, but the spectrum of Glyoxal uptake does not resemble that of any ambient organic aerosol PMF component.
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Glyoxal uptake on ammonium sulphate seed aerosol: reaction products and reversibility of uptake under dark and irradiated conditions
Atmospheric Chemistry and Physics, 2008Co-Authors: M. M. Galloway, P S Chhabra, Arthur W. H. Chan, John H. Seinfeld, Jason D Surratt, Richard C. Flagan, Frank N KeutschAbstract:Chamber studies of Glyoxal uptake onto ammonium sulphate aerosol were performed under dark and irradiated conditions to gain further insight into processes controlling Glyoxal uptake onto ambient aerosol. Organic fragments from Glyoxal dimers and trimers were observed within the aerosol under dark and irradiated conditions. Glyoxal monomers and oligomers were the dominant organic compounds formed under the conditions of this study; Glyoxal oligomer formation and overall organic growth were found to be reversible under dark conditions. Analysis of high-resolution time-of-flight aerosol mass spectra provides evidence for irreversible formation of carbon-nitrogen (C-N) compounds in the aerosol. We have identified 1H-imidazole-2-carboxaldehyde as one C-N product. To the authors' knowledge, this is the first time C-N compounds resulting from condensed phase reactions with ammonium sulphate seed have been detected in aerosol. Organosulphates were not detected under dark conditions. However, active photochemistry was found to occur within aerosol during irradiated experiments. Carboxylic acids and organic esters were identified within the aerosol. An organosulphate, which had been previously assigned as Glyoxal sulphate in ambient samples and chamber studies of isoprene oxidation, was observed only in the irradiated experiments. Comparison with a laboratory synthesized standard and chemical considerations strongly suggest that this organosulphate is glycolic acid sulphate, an isomer of the previously proposed Glyoxal sulphate. Our study shows that reversibility of Glyoxal uptake should be taken into account in SOA models and also demonstrates the need for further investigation of C-N compound formation and photochemical processes, in particular organosulphate formation.
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chamber studies of secondary organic aerosol growth by reactive uptake of simple carbonyl compounds
Journal of Geophysical Research, 2005Co-Authors: Jesse H Kroll, Richard C. Flagan, S M Murphy, Varuntida Varutbangkul, John H. SeinfeldAbstract:Recent experimental evidence indicates that heterogeneous chemical reactions play an important role in the gas-particle partitioning of organic compounds, contributing to the formation and growth of secondary organic aerosol in the atmosphere. Here we present laboratory chamber studies of the reactive uptake of simple carbonyl species (formaldehyde, octanal, trans,trans-2,4-hexadienal, Glyoxal, methylGlyoxal, 2,3-butanedione, 2,4-pentanedione, glutaraldehyde, and hydroxyacetone) onto inorganic aerosol. Gas-phase organic compounds and aqueous seed particles (ammonium sulfate or mixed ammonium sulfate/sulfuric acid) are introduced into the chamber, and particle growth and composition are monitored using a differential mobility analyzer and an Aerodyne Aerosol Mass Spectrometer. No growth is observed for most carbonyls studied, even at high concentrations (500 ppb to 5 ppm), in contrast with the results from previous studies. The single exception is Glyoxal (CHOCHO), which partitions into the aqueous aerosol much more efficiently than its Henry's law constant would predict. No major enhancement in particle growth is observed for the acidic seed, suggesting that the large Glyoxal uptake is not a result of particle acidity but rather of ionic strength of the seed. This increased partitioning into the particle phase still cannot explain the high levels of Glyoxal measured in ambient aerosol, indicating that additional (possibly irreversible) pathways of Glyoxal uptake may be important in the atmosphere.
Peter J Obrien - One of the best experts on this subject based on the ideXlab platform.
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the cytotoxic mechanism of Glyoxal involves oxidative stress
Biochemical Pharmacology, 2004Co-Authors: Nandita Shangari, Peter J ObrienAbstract:Glyoxal is a reactive α-oxoaldehyde that is a physiological metabolite formed by lipid peroxidation, ascorbate autoxidation, oxidative degradation of glucose and degradation of glycated proteins. Glyoxal is capable of inducing cellular damage, like methylGlyoxal (MG), but may also accelerate the rate of glycation leading to the formation of advanced glycation end-products (AGEs). However, the mechanism of Glyoxal cytotoxicity has not been precisely defined. In this study we have focused on the cytotoxic effects of Glyoxal and its ability to overcome cellular resistance to oxidative stress. Isolated rat hepatocytes were incubated with different concentrations of Glyoxal. Glyoxal by itself was cytotoxic at 5 mM, depleted GSH, formed reactive oxygen species (ROS) and collapsed the mitochondrial membrane potential. Glyoxal also induced lipid peroxidation and formaldehyde formation. Glycolytic substrates, e.g. fructose, sorbitol and xylitol inhibited Glyoxal-induced cytotoxicity and prevented the decrease in mitochondrial membrane potential suggesting that mitochondrial toxicity contributed to the cytotoxic mechanism. Glyoxal cytotoxicity was prevented by the Glyoxal traps d-penicillamine or aminoguanidine or ROS scavengers were also cytoprotective even when added some time after Glyoxal suggesting that oxidative stress contributed to the Glyoxal cytotoxic mechanism.
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toxicity of Glyoxals role of oxidative stress metabolic detoxification and thiamine deficiency
Biochemical Society Transactions, 2003Co-Authors: Nandita Shangari, W R Bruce, R Poon, Peter J ObrienAbstract:: Glyoxals are reactive alpha-oxoaldehydes that are formed endogenously from sugars, the levels of which are increased in various pathological conditions associated with hyperglycaemia and thiamine deficiency. However, the molecular cytotoxic mechanisms of Glyoxal are not known. Results presented here and in the other studies cited provide a glimpse into the cytotoxicity mechanisms involved and their pathological implications. We found that Glyoxal (10 microM) markedly increased the susceptibility of hepatocyte glutathione (GSH) to oxidation by hydrogen peroxide (H(2)O(2)) and markedly increased cytotoxicity by compromising the cellular antioxidant enzyme system. At higher concentrations, Glyoxal was cytotoxic towards hepatocytes, which can be attributed to GSH depletion, oxidative stress and mitochondrial toxicity. Aminoguanidine or penicillamine protected the hepatocytes. Glyoxal cytotoxicity was prevented by increasing Glyoxal metabolism with thiamine or NAD(P)H generators, and was increased in GSH- or thiamine-deficient hepatocytes. It was also found that feeding rats reduced thiamine levels in a diet high in simple sugars increased the number of aberrant crypt foci/colon in the absence of clinical evidence of beriberi. This was associated with decreased plasma thiamine and low erythrocyte transketolase activity. Western diets, which are frequently poor in thiamine and high in sugars, could result in increased levels of endogenous Glyoxals, which in turn may lead to a predisposition to AGE (advanced glycation end-product)-related pathologies and neoplastic conditions.
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toxicity of Glyoxals role of oxidative stress metabolic detoxification and thiamine deficiency
Biochemical Society Transactions, 2003Co-Authors: Nandita Shangari, W R Bruce, R Poon, Peter J ObrienAbstract:: Glyoxals are reactive alpha-oxoaldehydes that are formed endogenously from sugars, the levels of which are increased in various pathological conditions associated with hyperglycaemia and thiamine deficiency. However, the molecular cytotoxic mechanisms of Glyoxal are not known. Results presented here and in the other studies cited provide a glimpse into the cytotoxicity mechanisms involved and their pathological implications. We found that Glyoxal (10 microM) markedly increased the susceptibility of hepatocyte glutathione (GSH) to oxidation by hydrogen peroxide (H(2)O(2)) and markedly increased cytotoxicity by compromising the cellular antioxidant enzyme system. At higher concentrations, Glyoxal was cytotoxic towards hepatocytes, which can be attributed to GSH depletion, oxidative stress and mitochondrial toxicity. Aminoguanidine or penicillamine protected the hepatocytes. Glyoxal cytotoxicity was prevented by increasing Glyoxal metabolism with thiamine or NAD(P)H generators, and was increased in GSH- or thiamine-deficient hepatocytes. It was also found that feeding rats reduced thiamine levels in a diet high in simple sugars increased the number of aberrant crypt foci/colon in the absence of clinical evidence of beriberi. This was associated with decreased plasma thiamine and low erythrocyte transketolase activity. Western diets, which are frequently poor in thiamine and high in sugars, could result in increased levels of endogenous Glyoxals, which in turn may lead to a predisposition to AGE (advanced glycation end-product)-related pathologies and neoplastic conditions.
R Volkamer - One of the best experts on this subject based on the ideXlab platform.
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a missing sink for gas phase Glyoxal in mexico city formation of secondary organic aerosol
Geophysical Research Letters, 2007Co-Authors: Jose L Jimenez, R Volkamer, Luisa T Molina, Federico San Martini, D Salcedo, Mario J MolinaAbstract:[1] The sources of secondary organic aerosol (SOA) are highly uncertain. Direct measurements of gas-phase Glyoxal in Mexico City are compared to experimentally constrained model predictions. Observed Glyoxal concentrations are found significantly below those predicted. Additional Glyoxal sources are likely and would increase these differences; an additional Glyoxal sink must be operative. The model-measurement differences are fully resolved by a sink parameterized from aerosol parameters as either (1) irreversible uptake to aerosol surface area (uptake coefficient γ ≈ 0.0037); reversible partitioning to (2) aerosol liquid water (effective Henry's law coefficient Heff ≈ 4 × 109 M atm−1), or (3) the oxygenated organic aerosol phase (activity coefficient ζ ≈ 6 × 10−9); (4) a combination of the above. The missing sink has the potential to determine 70–95% of the atmospheric lifetime of Glyoxal. The Glyoxal imbalance corresponds to several μg m−3 of equivalent SOA mass, and can explain at least 15% of the SOA formation in Mexico City.
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high resolution absorption cross section of Glyoxal in the uv vis and ir spectral ranges
Journal of Photochemistry and Photobiology A-chemistry, 2005Co-Authors: R Volkamer, J P Burrows, Peter Spietz, U PlattAbstract:Abstract High-resolution absorption cross-sections of Glyoxal have been recorded at 296 K in the ultraviolet and visible (UV–vis: 19000–40000 cm−1, 250–526 nm) and infrared (IR: 1200–8000 cm−1) spectral ranges by means of a Fourier transform spectrometer (FTS). The UV–vis spectra were measured at 1 atm of N2 bath gas. The spectral resolution of the FTS was selected to be 0.06 cm−1 for the richly structured A ˜ 1Au – X ˜ 1Ag and a ˜ 3Au – X ˜ 1Ag band systems, and 1 cm−1 for the diffuse B ˜ − X ˜ transition, which was sufficient to resolve most spectral structures. In addition, low and high-resolution IR spectra (1 and 0.009 cm−1 spectral resolution) of Glyoxal/N2 mixtures were recorded around 2835 cm−1 at 0.2 mbar, 100 mbar, 300 mbar and 1 atm total pressure. UV–vis and IR spectra were recorded quasi-simultaneously by making sequential measurements of identical Glyoxal mixtures in the cell, enabling the direct comparison of UV–vis and IR spectral parameters for the first time. The high-resolution spectra have been used to simulate deviations from Lambert–Beer's law, which occur at lower resolution when spectra are not fully resolved. Special attention has been paid to reduce the uncertainty of the UV–vis spectrum, allowing for an improved determination of the atmospheric photolysis of Glyoxal. Finally, the new UV–vis spectrum has been used to redetermine our previous DOAS measurements of Glyoxal yields from the reactions of OH radicals with benzene, toluene and p-xylene. The high-resolution spectral data can be obtained from http://iup.physik.uni-bremen.de/gruppen/molspec/index.html or email request to the authors.
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doas measurement of Glyoxal as an indicator for fast voc chemistry in urban air
Geophysical Research Letters, 2005Co-Authors: R Volkamer, Luisa T Molina, Mario J Molina, Terry Shirley, William H BruneAbstract:[1] We present the first direct measurements of Glyoxal (CHOCHO) in the atmosphere, and demonstrate that Glyoxal measurements are possible by differential optical absorption spectroscopy (DOAS). Glyoxal was routinely detected during the daytime in Mexico City, where mixing ratios ranged from <0.15 ppbv (detection limit) to 1.82 ppbv. These time-resolved measurements resolve the rapid diurnal variation of Glyoxal, and indicate the onset of volatile organic compound (VOC) oxidation about 1hr after sunrise. The atmospheric lifetime of Glyoxal is determined to be 1.3 hr for overhead sun conditions. Then elevated Glyoxal levels indicate a persistently active VOC chemistry during most of the day. Glyoxal forms from the oxidation of numerous VOCs, which foster the formation of ‘photochemical smog’ including ozone and aerosol particles; atmospheric levels are essentially unaffected by direct vehicle emissions in Mexico City. Satellite measurements of Glyoxal seem feasible, making possible the better identification of photochemical hot spots in the Earth's atmosphere.