Global budgets of atmospheric glyoxal and methylglyoxal, and implications for formation of secondary organic aerosols

Abstract

[1] We construct global budgets of atmospheric glyoxal and methylglyoxal with the goal of quantifying their potential for global secondary organic aerosol (SOA) formation via irreversible uptake by aqueous aerosols and clouds. We conduct a detailed simulation of glyoxal and methylglyoxal in the GEOS-Chem global 3-D chemical transport model including our best knowledge of source and sink processes. Our resulting best estimates of the global sources of glyoxal and methylglyoxal are 45 Tg a À1 and 140 Tg a À1 , respectively. Oxidation of biogenic isoprene contributes globally 47% of glyoxal and 79% of methylglyoxal. The second most important precursors are acetylene (mostly anthropogenic) for glyoxal and acetone (mostly biogenic) for methylglyoxal. Both acetylene and acetone have long lifetimes and provide a source of dicarbonyls in the free troposphere. Atmospheric lifetimes of glyoxal and methylglyoxal in the model are 2.9 h and 1.6 h, respectively, mostly determined by photolysis. Simulated dicarbonyl concentrations in continental surface air at northern midlatitudes are in the range 10-100 ppt, consistent with in situ measurements. On a global scale, the highest concentrations are over biomass burning regions, in agreement with glyoxal column observations from the SCIAMACHY satellite instrument. SCIAMACHY and a few ship cruises also suggest a large marine source of dicarbonyls missing from our model. The global source of SOA from the irreversible uptake of dicarbonyls in GEOS-Chem is 11 Tg C a À1 , including 2.6 Tg C a À1 from glyoxal and 8 Tg C a À1 from methylglyoxal; 90% of this source takes place in clouds. The magnitude of the global SOA source from dicarbonyls is comparable to that computed in GEOS-Chem from the standard mechanism involving reversible partitioning of semivolatile products from the oxidation of monoterpenes, sesquiterpenes, isoprene, and aromatics.

An evaluation of real‐time air quality forecasts and their urban emissions over eastern Texas during the summer of 2006 Second Texas Air Quality Study field study

“…Comparing model and observed source apportionment from the sparse surface network over the United States is complicated by regional and seasonal SOA forcing from biomass burning and wildfires and uncertainties in biogenic emissions [Yu et al, 2007b]. Recent model estimates have North American biogenic SOA sources dominating over anthropogenic sources for the larger continental scale [Heald et al, 2008;Fu et al, 2008], while precursor volatility and emission-based estimates argue for a dominant anthropogenic contribution [Donahue et al, 2009]. The fresh, urban emissions results presented here show that urban and industrial SOA sources are clearly missing in the AQFMs.…”

Mechanism of the Reaction of OH with Alkynes in the Presence of Oxygen

“…11,12 In addition, (HCO) 2 photochemistry is a recognised source of HOx (OH and HO 2 ) radicals in the troposphere. [13][14][15] (HCO) 2 is removed from the troposphere within a few hours, during daylight its atmospheric lifetime is largely determined by the rates of photolysis and reaction with OH: 13, [16][17][18] (HCO) 2 + hv  2HCO or HCHO + CO (R1) (HCO) 2 + OH  HC(O)CO + H 2 O (R2)…”

On-road vehicle emissions of glyoxal and methylglyoxal from tunnel tests in urban Guangzhou, China

“…Some carbonyls such as formaldehyde and acetaldehyde have been identified as toxic air contaminants with adverse health effects (Partridge et al, 1987). However, less attention had been paid to dicarbonyls until recently glyoxal (CHOCHO) and methylglyoxal (CH 3 C(O)CHO) were identified as important precursors of SOA through homogeneous and heterogeneous reactions (Liggio et al, 2005;Fu et al, 2008). Very recently data are accumulating about dicarbonyls in the ambient air (Dai et al, 2012;Ho et al, 2014;Li et al, 2013Li et al, , 2014.…”

“…Glyoxal and methylglyoxal can both formed from the oxidation of VOCs (Calvert et al, 2000(Calvert et al, , 2002Volkamer et al, 2001) and emitted directly from tailpipes and biomass burning Kean et al, 2001;Hays et al, 2002;Ban-Weiss et al, 2008), yet direct emissions were viewed as being minor when compared to the secondary formation (Volkamer et al, 2005;Fu et al, 2008). As for speciated carbonyls emitted by gasoline and diesel vehicles, data were mostly obtained from tunnel studies carried out in the United States more than a decade ago Kean et al, 2001;Hays et al, 2002), and the trends in carbonyl emissions from vehicles were thereafter reviewed by Ban-Weiss et al (2008).…”

“…Glyoxal and methylglyoxal, the two smallest dicarbonyl organic compounds, are the most prevalent dicarbonyls in the atmosphere with the global sources of 45 Tg/yr and 140 Tg/yr, respectively, as estimated by Fu et al (2008). Glyoxal and methylglyoxal can both formed from the oxidation of VOCs (Calvert et al, 2000(Calvert et al, , 2002Volkamer et al, 2001) and emitted directly from tailpipes and biomass burning Kean et al, 2001;Hays et al, 2002;Ban-Weiss et al, 2008), yet direct emissions were viewed as being minor when compared to the secondary formation (Volkamer et al, 2005;Fu et al, 2008).…”