Isomerization of Simple Alkoxyl Radicals:  New Temperature-Dependent Rate Data and Structure Activity Relationship

Johnson, David C.; Cassanelli, Paola; Cox, R. A.

doi:10.1021/jp037196k

Cited by 19 publications

(35 citation statements)

References 14 publications

(27 reference statements)

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“…Among anthropogenic hydrocarbons, aromatic compounds have been traditionally considered to be the most important SOA precursors. It has recently been established that the SOA yields (aerosol yield is defined as the ratio of the mass of organic aerosol produced to the mass of parent hydrocarbon reacted) from aromatics, as well as those from a variety of other hydrocarbons, depend critically on the prevailing level of nitrogen oxides (NO x ) (Hurley et al, 2001;Martin-Reviejo and Wirtz, 2005;Presto et al, 2005;Song et al, 2005;Johnson et al, 2004Johnson et al, , 2005Ng et al, 2007;Song et al, 2007). This discovery led to a systematic re-evaluation of aromatic SOA yields (Ng et al, 2007) from the historical yields of Odum et al (1996Odum et al ( , 1997) that were measured under high-NO x conditions.…”

Section: Introductionmentioning

confidence: 99%

Global modeling of secondary organic aerosol formation from aromatic hydrocarbons: high- vs low-yield pathways

Henze¹,

Seinfeld²,

Ng³

et al. 2007

Preprint

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Abstract. Formation of SOA from the aromatic species toluene, xylene, and, for the first time, benzene, is added to a global chemical transport model. A simple mechanism is presented that accounts for competition between low and high-yield pathways of SOA formation, wherein secondary gas-phase products react further with either nitrogen oxide (NO) or hydroperoxy radical (HO2) to yield semi- or non-volatile products, respectively. Aromatic species yield more SOA when they react with OH in regions where the [NO]/[HO2] ratios are lower. The SOA yield thus depends upon the distribution of aromatic emissions, with biomass burning emissions being in areas with lower [NO]/[HO2] ratios, and the reactivity of the aromatic with respect to OH, as a lower initial reactivity allows transport away from industrial source regions, where [NO]/[HO2] ratios are higher, to more remote regions, where this ratio is lower and, hence, the ultimate yield of SOA is higher. As a result, benzene is estimated to be the most important aromatic species with regards to formation of SOA, with a total production nearly equal that of toluene and xylene combined. In total, while only 39% percent of the aromatic species react via the low-NOx pathway, 72% of the aromatic SOA is formed via this mechanism. Predicted SOA concentrations from aromatics in the Eastern United States and Eastern Europe are actually largest during the summer, when the [NO]/[HO2] ratio is lower. Global production of SOA from aromatic sources is estimated at 3.5 Tg/yr, resulting in a global burden of 0.08 Tg, twice as large as previous estimates. The contribution of these largely anthropogenic sources to global SOA is still small relative to biogenic sources, which are estimated to comprise 90% of the global SOA burden, about half of which comes from isoprene. Compared to recent observations, it would appear there are additional pathways beyond those accounted for here for production of anthropogenic SOA. However, owing to differences in spatial distributions of sources and seasons of peak production, there are still regions in which aromatic SOA produced via the mechanisms identified here are predicted to contribute substantially to, and even dominate, the local SOA concentrations, such as outflow regions from North America and South East Asia during the wintertime, though total SOA concentrations there are small (~0.1 μg/m³).

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Section: Introductionmentioning

confidence: 99%

Global modeling of secondary organic aerosol formation from aromatic hydrocarbons: high- vs low-yield pathways

Henze¹,

Seinfeld²,

Ng³

et al. 2007

Preprint

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show abstract

“…As pointed out by Aumont et al [2000], Derwent et al [2003], and Bonn et al [2004], successive generations of oxidation products would add to the condensable pool. Product yields could also be different at the cold temperatures of the FT; for example, oxy radicals RO could add O 2 instead of thermolyze [ Johnson et al , 2004], promoting subsequent OC aerosol formation. SOA yields at ambient low nitrogen oxides concentrations may also be underestimated by smog chamber data [ Song et al , 2005].…”

mentioning

confidence: 99%

A large organic aerosol source in the free troposphere missing from current models

Heald

Jacob

Park

et al. 2005

Geophysical Research Letters

654

632

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[1] Aircraft measurements of organic carbon (OC) aerosol by two independent methods over the NW Pacific during the ACE-Asia campaign reveal unexpectedly high concentrations in the free troposphere (FT). Concentrations average 4 mg sm À3 in the 2 -6.5 km column with little vertical gradient. These values are 10 -100 times higher than computed with a global chemical transport model (CTM) including a standard 2-product simulation of secondary organic aerosol (SOA) formation based on empirical fits to smog chamber data. The same CTM reproduces the observed vertical profiles of sulfate and elemental carbon aerosols, which indicate sharp decreases from the boundary layer to the FT due to wet scavenging. Our results suggest a large, sustained source of SOA in the FT from oxidation of long-lived volatile organic compounds. We find that this SOA is the dominant component of aerosol mass in the FT, with implications for intercontinental pollution transport and radiative forcing of climate.

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“…It has recently been established that the SOA yields (aerosol yield is defined as the ratio of the mass of organic aerosol produced to the mass of parent hydrocarbon reacted) from aromatics, as well as those from a variety of other hydrocarbons, depend critically on the prevailing level of nitrogen oxides (NO x ) (Hurley et al, 2001;Martin-Reviejo and Wirtz, 2005;Presto et al, 2005;Song et al, 2005;Johnson et al, 2004Johnson et al, , 2005Ng et al, 2007;Song et al, 2007). This discovery led to a systematic re-evaluation of aromatic SOA yields from the historical yields of Odum et al (1996Odum et al ( , 1997) that were measured under high-NO x conditions.…”

Section: Introductionmentioning

confidence: 99%

Global modeling of secondary organic aerosol formation from aromatic hydrocarbons: high- vs. low-yield pathways

et al. 2008

View full text Add to dashboard Cite

Abstract. Formation of SOA from the aromatic species toluene, xylene, and, for the first time, benzene, is added to a global chemical transport model. A simple mechanism is presented that accounts for competition between low and high-yield pathways of SOA formation, wherein secondary gas-phase products react further with either nitric oxide (NO) or hydroperoxy radical (HO 2 ) to yield semi-or non-volatile products, respectively. Aromatic species yield more SOA when they react with OH in regions where the [NO]/[HO 2 ] ratios are lower. The SOA yield thus depends upon the distribution of aromatic emissions, with biomass burning emissions being in areas with lower [NO]/[HO 2 ] ratios, and the reactivity of the aromatic with respect to OH, as a lower initial reactivity allows transport away from industrial source regions, where [NO]/[HO 2 ] ratios are higher, to more remote regions, where this ratio is lower and, hence, the ultimate yield of SOA is higher. As a result, benzene is estimated to be the most important aromatic species with regards to global formation of SOA, with a total production nearly equal that of toluene and xylene combined. Global production of SOA from aromatic sources via the mechanisms identified here is estimated at 3.5 Tg/yr, resulting in a global burden of 0.08 Tg, twice as large as previous estimates. The contribution of these largely anthropogenic sources to global SOA is still small relative to biogenic sources, which are estimated to comprise 90% of the global SOA burden, about half of which comes from isoprene. Uncertainty in these esCorrespondence to: D. K. Henze (dkh2114@columbia.edu) timates owing to factors ranging from the atmospheric relevance of chamber conditions to model deficiencies result in an estimated range of SOA production from aromatics of 2-12 Tg/yr. Though this uncertainty range affords a significant anthropogenic contribution to global SOA, it is evident from comparisons to recent observations that additional pathways for production of anthropogenic SOA still exist beyond those accounted for here. Nevertheless, owing to differences in spatial distributions of sources and seasons of peak production, regions exist in which aromatic SOA produced via the mechanisms identified here are predicted to contribute substantially to, and even dominate, the local SOA concentrations, such as outflow regions from North America and South East Asia during the wintertime, though total modeled SOA concentrations there are small (∼0.1 µg/m 3 ).

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Isomerization of Simple Alkoxyl Radicals: New Temperature-Dependent Rate Data and Structure Activity Relationship

Cited by 19 publications

References 14 publications

Global modeling of secondary organic aerosol formation from aromatic hydrocarbons: high- vs low-yield pathways

Global modeling of secondary organic aerosol formation from aromatic hydrocarbons: high- vs low-yield pathways

A large organic aerosol source in the free troposphere missing from current models

Global modeling of secondary organic aerosol formation from aromatic hydrocarbons: high- vs. low-yield pathways

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