Air Pollution, the Automobile, and Public Health (1988) / Chapter Skim
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Atmospheric Transformations of Automotive Emissions
Atmospheric Transformations of Automotive Emissions
Pages 99-132
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From page 99... ...
Atmospheric Transformations of Automotive Emissions ROGER ATKINSON University of California, Riverside Components of Atmospheric Pollution / 100 Physical and Chemical Transformations Under Atmospheric Conditions / 101 Physical Removal Processes / 101 Chemical Removal Processes / 102 Atmospheric Lifetimes, Fates, and Products of the Atmospheric Transformations of Automotive Emissions / 105 Atmospheric Lifetimes / 105 Atmospheric Transformations / 109 Analytical Techniques / 125 Summary / 126 Summary of Research Recommendations / 126 Air Pollution, the Automobile' and Public Health.
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From page 100... ...
The possible chemical transformations and physical loss processes that occur in the atmosphere during transport of these primary automotive emissions from source to receptor are the main subjects of this chapter. The time scales of these atmospheric transformations and physical loss processes vary widely, with chemical life times ranging from '1 min for some highly reactive organic compounds to months or even years for other much more inert emissions (Atkinson 1986~.
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From page 101... ...
A list of research recommendations to obtain the necessary data base about these atmospheric transformations is presented. Physical and Chemical Transformations Under Atmospheric Conditions Two decades of laboratory, environmental chamber, and ambient atmospheric measurements have revealed the physical and chemical processes that transform and/or remove chemical compounds emitted into the atmosphere.
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From page 102... ...
Thus, only average wet deposition velocities can be ascribed, and these are strong functions of the climatological conditions at the particular geographic location in question. Chemical Removal Processes Many chemical processes contribute to the removal of compounds emitted into the Atmospheric Transformations of Automotive Emissions troposphere.
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From page 103... ...
Nitrous acid, which is present during nighttime hours in urban atmospheres (Platt et al. 1980a; Harris et al.
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From page 104... ...
Nitric acid is formed in the gas phase from the reaction of OH radicals with NOB OH + NO2 ~ HNO3 (23) and can be formed, probably in the ad with N2O5 being in relatively rapid (< 1 sorbed phase, from the heterogeneous hy min at 298°K and 760 torr total pressure)
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From page 105... ...
. Atmospheric Lifetimes, Fates, and Products of the Atmospheric Transformations of Automotive Omissions This section reviews and summarizes the present status of knowledge concerning the atmospheric loss processes and atmospheric lifetimes of automotive emissions and the products formed from them under atmospheric conditions.
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From page 106... ...
] O3 NO3 HO2 N2Os Emlsslon OH 1.1 x 10-11 6.6 x 10-12 6.6 x 10-'2 1.3 x 10-13 9 x 10-13 1.6 x 10-13 2.2 x 10-" 3 x 10-14 4.7 x 10-12 3.3 x 10-'l 1.7 x 10-12 1.2 x 10-12 2.5 x 10-'2 8.7 x 10-'2 2.2 x 10-13 2.5 x 10-13 8.5 x 10-12 2.6 x 10-11 3.1 x 10-" 6.4 x 10-" 7.8 x 10-13 6.1 x 10-'2 2 x 10-11 9.0 x 10-12 1.6 x 10 1.3 x 10-11 2.0 x 10-" 3.6 x 10 1.9 x jo-" 2.3 x 10-13 1.0 x 10-'2 3.0 x 10-'2 9 x 10-13 2.9 x 10-12 4.6 x 10-13 ~ 1.8 x 10-13 1.3 x 10-'2 6.2 x 10-12 2.5 x 10-1' 4.0 x 10-' 2.8 x 10-'1 2.2 x 10-" 5.2 x 10-" 7.7 x 10-" 3.2 x 10-1' 1.3 x 10-'° NO2a NO HNO2a HNO3b SO2 NH3C CH3NH2C HCN H2S CH3SH H2O2a Propane e-Butane e-Octane 1,2-Dichloroethane 1,2-Dibromoethane Ethene Propene 1-Butene trans-2-Butene Acetylene Propyne Butadiyne Formaldehydea Acetaldehydea Benzaldehydea Acrolein Crotonaldehyde Methyl vinyl ketone Acetonea 2-Butanone`' Dimethyl ether Methanol Ethanol Formic acid Methyl nitritea Benzene Toluene m-Xylene 1 ,2,4-Trimethylbenzene Phenol Naphthalene 2-Methylnaphthalene 2,3-Dimethylnaphthalene Phenanthrene Anthracene 3.2 x 10-17 1.8 x 10-'4 < 5 x 10-19 <2 x 10-22 2.1 x 10-2° < 2 x 10-2° < 6 x 10-24 < 1 X 10-23 1.8 x 10-'8 1.1 X 10-17 1.1 X 10-~7 2.0 x 10-16 8 x 10-21 1.4 x 10-2° 6 x 10-2° 2 x 10-24 6 x 10-2~ 2.8 x 10-~9 9.0 x 10-~9 4.8 x 10-'8 1.3 x 10-2° 7 x 10-23 1.5 x 10-22 6 x 10-22 1.3 x 10-21 2 x 10-19 4 x 10-~9 4 x 10- i9 1.2 x 10-'2 3.0 x 10-" < 7 x 10-2' <3 x 10-'4 1 X 10-12 < 2 x 10- 15 3.6 x 10-17 9.9 x 10-~7 1.1 X 10-'6 7.5 x 10-~5 9.7 x 10-~5 3.8 x 10-'3 s 2.3 x 10-~7 9.4 x 10-~7 5.8 x 10-'6 2.4 x 10-~5 2.0 x 10-~5 < 3 x 10- ~s < 6 x 10- 16 <9 x 10-'6 <2 x 10-~7 3.6 x 10-~7 1.3 x 10-'6 9.7 x 10-'6 3.8 x 10-'2 1.4 x 1()
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From page 107... ...
Roger Atkinson 107 Table 3. Calculated Atmospheric Lifetimesa for the Gas-Phase Reactions of the Selected Automotive Emissions with Atmospherically Important Intermediate Speciesb Atmospheric Lifetime Due to Reaction with EmissionOHO3NO3HO2 ho' NO22 days12 hr1 hr2 hr 2 min NO4 days1 min3 min20 min HNO24 days> 33 days ~ 10 min ANON180 days SO2e26 days> 200 yr> 4.5 x 104 yr> 600 yr NH3f140 days CH3NH2f12 hr2 yr HCN2 yr HIS5 days> 2 yr> 4 days CH3SH8 hr 1 hr H20214 days > 60 days 36 hr Propane19 days> 7,000 yr e-Butane9 days> 4,500 yr9 yr e-Octane3 days 3 yr 1,2-Dichloroethane100 days 1,2-Dibromoethane90 days Ethene3 days9 days3 yr Propene11 hr1.5 days15 days 1-Butene9 hr1.5 days12 days trans-2-Butene4 hr2 hr4 hr> 150 yr Acetylene30 days6 yr-14 yr Propyne4 days3 yr3.4 yr Butadiyne1 day~ 270 days Formaldehyde3 days> 2 x 104 yr210 days23 days 4 hr Acetaldehyde1 day> 7 yr50 days 60 hr Benzaldehyde2 days 60 days Acrolein1 day60 days Crotonaldehyde8 hr18 days Methyl vinyl ketone1 day3 days Acetone100 days 15 days 2-Butanone23 days Dimethyl ether7 days > 40 days Methanol26 days > 190 days Ethanol8 days > 130 days Formic acid50 days Methyl nitrite~ 120 days3 yr 8 min Benzene18 days600 yr> 16 yr Toluene4 days300 yr9 yr m-Xylene11 hr75 yr2 yr 1,2,~Trimethylbenzene7 hr35 yr120 days Phenol10 hr 20 min Naphthalenee1 day> 80 days 2-Methylnaphthalenee5 hr> 40 days 2,3-Dimethylnaphthalenee4 hr> 40 days Phenanthrene9 hr Anthracene2 hr a The time for the compound to decay to 37 percent of its original concentration.
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From page 108... ...
However, for certain chemicals that have relatively slow gas-phase chemical loss rates, such as HNO3 and SO2, dry deposition can be the major loss process under typical atmospheric conditions. Because of the potential importance of the dry deposition atmospheric removal process, measurements of the deposition velocities of gaseous and particulate species need to be carried out for a variety of terrains.
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From page 109... ...
These data will then allow the importance of this wet deposition process to be better evaluated, both as a loss process for primary automotive emissions as well as for the formation and deposition of acid species resulting from aqueous-phase reactions. The major atmospheric loss process for most of the automotive emissions present in the gas phase is by daytime reaction with the OH radical.
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From page 110... ...
, and are important as nighttime loss processes for NOX as well as for acid deposition. If N2O5 is hydrolyzed in the gas phase, presently viewed as unlikely (Atkinson et al.
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From page 111... ...
In summary, these various nitrogen oxide species are readily interconverted in the lower atmosphere, but the major tropospheric loss process of NOX occurs by the formation of gas-phase HNO3 from the daytime reaction of OH radicals with NO2 (the gas-phase HNO3 being removed from the troposphere mainly by dry and wet deposition) and by wet and/or dry deposition of N2O5 during nighttime hours.
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From page 112... ...
Reactions of amines with O3 have been shown to be slow, and are of minor significance under atmospheric conditions (Atkinson and Carter 1984~. The major atmospheric removal processes involve gas-phase reactions with the OH radical OH + NH3 ~ H2O + NH2 (34' OH + CH3NH2 ~ H2O + CH3NH `35' Atmospheric Transformations of Automotive Emissions NRR'R" + HNO3 ~ [NRR'R''Hl4-NO3- (39)
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From page 113... ...
Wet and dry deposition of particulate matter lead to its removal from the troposphere. Sulfur dioxide is removed from the troposphere by gas- and aqueous-phase chemical reactions and by dry and wet deposition.
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From page 114... ...
These compounds are readily absorbed into aqueous phases, including Atmospheric Transformations of Automotive Emissions cloud and fog water Jacob and Hoffmann 1983~. In the gas phase, photolysis, ROOH + ha ~ OH + RO where R represents either hydrogen or an alkyl radical, and reaction with OH radicals OH + H2O2 ~ H2O + HO2 (58)
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From page 115... ...
X 108 molecules/cm3. Under polluted urban atmospheric conditions, and possibly for much of the lower troposphere in the eastern United States, reaction with NO is the dominant reaction pathway for RO2- radicals.
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From page 116... ...
The products of these reactions have not been experimentally determined, but a likely reaction sequence is, OH + CH2XCH2X ~ H2O + CHXCH2X Atmospheric Transformations of Automotive Emissions with HO2 and/or other RO2 radicals may occur. The products arising from these radical-radical reactions should be investigated.
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From page 117... ...
Nitrate Radical Reaction. Only for those alkenes more reactive than the 2-butenes does the NO3 radical reaction become important under atmospheric conditions (Atkinson 1986~.
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From page 118... ...
1981b) to ~ 0.18 for trans-2-butene, and to ~ 0.04 for cyclohex Atmospheric Transformations of Automotive Emissions ene.
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From page 119... ...
Data concerning the atmospheric reactions of aromatic aldehydes are available only for benzaldehyde. For benzaldehyde, as for the aliphatic aldehydes, photolysis and OH radical reaction are the major loss processes (Atkinson and Lloyd 1984)
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From page 120... ...
These compounds, exemplified by acrolein, crotonaldehyde, and methyl vinyl ketone, are known to react with 03, OH radicals, NO3 radicals as well as undergo photolysis. Under atmospheric conditions the OH radical reaction is the major loss process (Atkinson and Carter 1984~.
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From page 121... ...
The available data suggest that these carboxylic acids react with the OH radical under atmospheric conditions (Atkinson 1986~. For formic acid, hydrogen-atoms are produced, o 11 OH + HCOH ~ ~ H2O + CO2 + H (104)
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From page 122... ...
Investigations, under atmospheric conditions, of the reaction products for partially oxidized automotive emissions and their health impacts on humans are needed. This area of research includes the atmospheric transformations of methanol and ethanol, formaldehyde and acetaldehyde coemissions, and any other emissions associated with their use as alternative fuels.
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From page 123... ...
Product yields under atmospheric conditions are reliably known for only a few of the many aromatic hydrocarbons emitted from automotive use. Moreover, the health effects of most of these compounds are not known, although methylglyoxal has recently been reported to be mutagenic toward Salmonella typhimurium strain TA100 (Shepson et al.
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From page 124... ...
The available data show that for the PAHs present in the gas phase, reaction with the OH radical predominates, leading to atmospheric lifetimes of a few hours or less (table 3~. The nighttime reaction with N205 is of minor significance as a PAH loss process (table 3)
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From page 125... ...
The atmospheric transformation products of PAHs and their oxygen-, nitrogen-, and sulfur-containing analogues and homologues require study, in the gaseous and the adsorbed phases. In particular, the reaction pathways that lead to nitro-PAHs need to be quantitatively established.
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From page 126... ...
Of prime importance is the development of nondestructive, nonintrusive, in situ analytical techniques that will allow the atmospheric transformations of gaseous and particulate-associated chemical species to be studied. Summary As a result of the last two decades of laboratory, computer modeling, and ambient atmospheric experiments, a large body of data now exists concerning the atmospheric loss processes and transformations of automotive emissions.
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From page 127... ...
This area of research includes the atmospheric transformations of methanol and ethanol, formaldehyde and acetaldehyde co-emissions, and any other emis sions associated with their use as alternative fuels. In addition, the atmospheric transformation products and associated health impli cations of aldehydes, ketones, a,,~unsaturated carbonyl com pounds, carboxylic acids, and other products of incomplete com bustion should be determined.
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From page 128... ...
1986. Kinetics and mechanisms of the gas phase reactions of the hydroxyl radical with organic compounds under atmospheric conditions, Chem.
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From page 129... ...
1984. Toluene 129 degradation products in simulated atmospheric conditions, Nature 311 :248-250.
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From page 130... ...
1985. Tropospheric ozone: seasonal Atmospheric Transformations of Automotive Emissions behavior, trends and anthropogenic influence, J
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From page 131... ...
1986. Factors influencing the reactivity of polycyclic aromatic hydrocarbons adsorbed on filters and ambient POM with ozone, Chemosphere 15:675085.
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From page 132... ...
1984. Determination of vapor pressure of polycyclic aromatic hydrocarbons in the supercooled liquid phase and their adsorption on airborne particulate matter, Nippon Kagaku Kaishi 13201329.
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