The Role Formation of Methylglyoxal, Carbonyl Compound, Hydrogen
Glyoxal and Methylglyoxal; Chemistry and Their Effects on Secondary Organic Aerosol
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Transcript of Glyoxal and Methylglyoxal; Chemistry and Their Effects on Secondary Organic Aerosol
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Glyoxal and Methylglyoxal; Glyoxal and Methylglyoxal; Chemistry and Their Effects Chemistry and Their Effects
on Secondary Organic on Secondary Organic AerosolAerosol
Dasa GuSungyeon Choi
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Glyoxal and MethylglyoxalGlyoxal and Methylglyoxal• Glyoxal
• Simplest alpha dicarbonyl organic compounds• Average life-time: ~1.3 hrs
• Methylglyoxal
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MotivationMotivation• Glyoxal can be an indicator for fast VOC chemistry in urban air,
since it’s mainly formed from the oxidation of numerous VOCs and minor tailpipe emissions. (SCIENCE, 2005)
• Glyoxal uptake accounts either forseveral 10 μg/m3 or several 10 μg/m3 of equivalent SOA mass in urban air. (Kroll et al, 2005; Liggio et al, 2005)
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Sources of GlyoxalSources of Glyoxal• Glyoxal is identified as
a major primary product from the BTX-OH reaction.
• Alkenes and acetylene are also precursors of glyoxal.
(Volkamer et al, 2001)
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Sinks of GlyoxalSinks of Glyoxal
• Rapid photolysis and OH-reactions are main loss processes. (Wittrock et al, 2006)
• Dry deposition and dilution in a rising planetary boundary layer are used in some models. (Volkamer et al, 2007)
• Formation into Secondary Organic Aerosols is widely concerned. (Kroll et all, 2005; Liggio et al, 2005)
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Monitoring (1)Monitoring (1)
Chemical Derivatization• DNPH(2,4-dinitrophenylhydrazine) – HPLC (Munger et al,1995; Lee et al,1998)
• PFPH – GCMS
F F
NHNH2
FF
F + O C
F F
NH
FF
F
R2
R1
+ H2O
PFPH aldehyde orketone
hydrazone
F F
NH
FF
F NH Ck1
k-1
R1
OH
R2k2(s) (g) (s)
(s)N C
F F
NH
FF
FN C
R1
R2
R1
R2
(s)
(Ho et al, 2002)
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Monitoring (2)Monitoring (2)DOAS (Differential Optical Absorption Spectroscopy)
CHO-CHO hour-by-hour: CHO-CHO hour-by-hour: peaks peaks between 1030h and 1300hbetween 1030h and 1300h
CHO-CHOCHO-CHO, , HCHOHCHO diurnal variation; diurnal variation;CHOCHO/NO2 (%)CHOCHO/NO2 (%) ratioratio
(Volkamer Volkamer et al,2005et al,2005)
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Monitoring (3)Monitoring (3)
Satellites• SCIMACHY• OMI
(Kurosu et al, AGU 2006Kurosu et al, AGU 2006)
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Glyoxal and Secondary Glyoxal and Secondary Organic AerosolOrganic Aerosol
• Oxidation products from VOCs contribute to SOA formation
• Growing evidence for glyoxal uptake to particles and cloud droplets despite its high volatility
• Chemical reactions lead to formation of low-volatility products like oxalic acid
VOCsoxidation
Semivolatile products
Inorganic/organic waterinteraction
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Glyoxal and SOA formationGlyoxal and SOA formation
• Aerosol growth vs. glyoxal concentration is plotted
• Highly dependent to RH value(water content in inorganic seed)
• Dry seed, no growth
Seinfeld, 2005, ASP Science Team Meeting
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Gas-Phase GlyoxalGas-Phase GlyoxalConcentration in Mexico CityConcentration in Mexico City
• High-time resolution glyoxal measurement by long-path Differential Optical Absorption Spectroscopy were conducted as part of the Mexico City Metropolitan Area Field Campaign
• Direct measurements of gas-phase glyoxal in Mexico City are compared to model prediction
Volkamer et al, 2007
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Gas-Phase Glyoxal Gas-Phase Glyoxal Concentration in Mexico CityConcentration in Mexico City
• Production– From oxidation of 26 VOCs
listed– Including second and higher
generation oxidation products• Loss
– Photolysis– Reaction with OH-radicals– Dry deposition– Dilution in a rising planetary
layer
Model - based on Master Chemican Mechanism(MCM)
Volkamer et al, 2007
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Gas-Phase Glyoxal Gas-Phase Glyoxal Concentration in Mexico CityConcentration in Mexico City
• Observed glyoxal levels are significantly below those predicted
• The difference is resolved by parameterization either of– Irreversible uptake to aerosol
surface area– Reversible partitioning to
aerosol liquid water– Reversible partitioning to
oxygenated organic aerosol– A combination of above
Volkamer et al, 2007
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• Chamber study: Effective Henry’s law solubility coefficient(H*) is determined from measured uptake of methylglyoxal in sulfuric acid
Zhao et al, 2006
(t)4kwVA
1/a bt1/ 2
bw
4H*RT(Dl / )1/ 2where
Uptake of Methylglyoxal on Uptake of Methylglyoxal on Acidic MediaAcidic Media
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Uptake of Methylglyoxal on Uptake of Methylglyoxal on Acidic MediaAcidic Media
• Henry’s law solubility coefficient depends on acidity and temperature
• H* increases at lower acidity & lower temperature• Implies that aqueous reaction in hydrate form is dominant
Zhao et al, 2006
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Aqueous Phase Reactions of Aqueous Phase Reactions of MethylglyoxalMethylglyoxal
• Possible aqueous reaction pathway in acidic condition is provided
• Hydration reaction and formation of various oligomers are shown
• 2 and 3 are major forms in pure water solution, consisting of 56-62% and 38-44% respectively
Zhao et al, 2006
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Aqueous Phase Reactions of Aqueous Phase Reactions of MethylglyoxalMethylglyoxal
(Continued Mechanism)
Zhao et al, 2006
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Aqueous Photooxidation of Aqueous Photooxidation of Glyoxal to Form Oxalic AcidGlyoxal to Form Oxalic Acid
• Current aqueous-phase model assumes glyoxal is oxidized to glyoxylic acid and subsequently to oxalic acid (b)
• Carlton et al. suggested more complex pathway (a), (c)
Carlton el at., 2007
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• Aqueous-phase photooxidation of glyoxal is conducted at pH 4-5
• Oxalic acid formed from photooxidation of glyoxal
• Involves rapid formation of formic acid followed by large multifunctional compounds
• Glyoxalic acid is below the detection limit
Aqueous Photooxidation of Aqueous Photooxidation of Glyoxal to Form Oxalic AcidGlyoxal to Form Oxalic Acid
Carlton el at., 2007
GLY + UV + H2O2 --> Oxalic acid
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ReferenceReference• Carlton et al. (2007), Atmospheric oxalic acid and SOA production from glyoxal:
Results of aqueous photooxidation experiments, Atmos. Environ., 41, 7500-7602• Kroll, J. H. et al. (2005), Chamber studies of secondary organic aerosol growth
by reactive uptake of simple carbonyl compounds, J. Geophys. Res., 110, D23207, doi: 10.1029/2005JD006004.
• Liggio, J. et al.(2005a), Reactive uptake of glyoxal by particulate matter, J. Geophys. Res., 110, D10304, doi:10.1029/2004JD005113.
• SCIENCE, June 3 2005, VOL 308, 1379• Volkamer, R., et al. (2001), Primary and secondary glyoxal formation from
aromatics: Experimental evidence for the bicycloalkyl-radical pathway from benzene, toluene, and p-xylene, J. Phys. Chem. A, 105, 7865– 7874.
• Volkamer et al. (2007), A missing sink for gas-phase glyoxal in Mexico City: Formation of secondary organic aerosol, Geophys. Res. Lett., 45, L19807, doi:10.1029/2007GL030752
• Zhao et al. (2006), Heterogeneous Reactions of Methylglyoxal in Acidic Media: Implication for Secondary Organic Aerosol Formation, Environ. Sci. Technol., 40, 7682-7687