Peroxy radical isomerization in the oxidation of isoprene

Crounse, J. D.; Paulot, Fabien; Kjaergaard, Henrik G.; Wennberg, P. O.

doi:10.1039/c1cp21330j

Cited by 331 publications

(493 citation statements)

References 44 publications

Supporting

Mentioning

455

Contrasting

Order By: Relevance

“…Using isomerization rates derived from first principles, Peeters and Mu¨ller 16 predict C 5 -HPALD yields of as much as 70% from summertime isoprene oxidation. More recently, a laboratory investigation by Crounse et al 18 has provided experimental evidence that the C 5 -HPALD production rate is 25 to 75 times slower than previously predicted. Despite the slower rate, C 5 -HPALD production is still predicted to make up as much as 20% of the annual average reactive flux in high-isoprene, low-NO regions; thus, its chemistry is, in places, as significant as that of methyl vinyl ketone and methacrolein and therefore should be incorporated into chemical models.…”

Section: Introductionmentioning

confidence: 92%

“…18 All experiments were performed at room temperature (296 AE 2 K) and atmospheric pressure (745 Torr, 99.3 kPa). UV lights along one wall of the chamber enclosure provide radiation with a peak emission at 340 nm as measured by a Licor spectroradiometer (LI-1800, 300-850 nm).…”

Section: Methodsmentioning

confidence: 99%

“…[5][6][7][8][9][10][11][12] Modelmeasurement discrepancies tend to be most severe in high-VOC regions dominated by isoprene (2-methyl-1,3-butadiene), a biogenic hydrocarbon with an annual global emission rate of B500 Tg per year. 13 In attempts to better understand these issues, renewed theoretical [14][15][16][17] and experimental 5,6,9,18,19 work on isoprene oxidation have revealed a rich chemistry previously unknown, including several mechanisms which effectively recycle HO x (= OH + HO 2 + RO 2 ). One such mechanism, originally proposed by Peeters et al, 17 involves the isomerization and decomposition of isoprene hydroxyperoxy radicals (ISO 2 ) to release HO 2 and a new class of products known as C 5 -hydroperoxyenals (C 5 -HPALDs).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Photolysis, OH reactivity and ozone reactivity of a proxy for isoprene-derived hydroperoxyenals (HPALDs)

Wolfe

Crounse

Parrish

et al. 2012

Phys. Chem. Chem. Phys.

Self Cite

103

View full text Add to dashboard Cite

The C 5 -hydroperoxyenals (C 5 -HPALDs) are a newly-recognized class of multi-functional hydrocarbons produced during the hydroxyl radical (OH)-initiated oxidation of isoprene. Recent theoretical calculations suggest that fast photolysis of these compounds may be an important OH source in high-isoprene, low-NO regions. We report experimental constraints for key parameters of photolysis, OH reaction and ozone reaction of these compounds as derived from a closelyrelated, custom-synthesized C 6 -HPALD. The photolysis quantum yield is 1.0 AE 0.4 over the range 300-400 nm, assuming an absorption cross section equal to the average of those measured for several analogous enals. The yield of OH from photolysis was determined as 1.0 AE 0.8. The OH reaction rate constant is (5.1 AE 1.8) Â 10 À11 cm 3 molecule À1 s À1 at 296 K. The ozone reaction rate constant is (1.2 AE 0.2) Â 10 À18 cm 3 molecule À1 s À1 at 296 K. These results are consistent with previous first-principles estimates, though the nature and fate of secondary oxidation products remains uncertain. Incorporation of C 5 -HPALD chemistry with the above parameters in a 0-D box model, along with experimentally-constrained rates for C 5 -HPALD production from isomerization of first-generation isoprene hydroxyperoxy radicals, is found to enhance modeled OH concentrations by 5-16% relative to the traditional isoprene oxidation mechanism for the chemical regimes of recent observational studies in rural and remote regions. This enhancement in OH will increase if C 5 -HPALD photo-oxidation products also photolyze to yield additional OH or if the C 5 -HPALD production rate is faster than has been observed.

show abstract

Section: Introductionmentioning

confidence: 92%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Photolysis, OH reactivity and ozone reactivity of a proxy for isoprene-derived hydroperoxyenals (HPALDs)

Wolfe

Crounse

Parrish

et al. 2012

Phys. Chem. Chem. Phys.

Self Cite

103

View full text Add to dashboard Cite

show abstract

“…Transport schemes (advection, convection, and turbulent mixing) are implemented by following previous work (50)(51)(52). SI Appendix, The chemical mechanism is adopted from GEOS-Chem v9.1 with updates on chemistry of aromatics (47), isoprene (54,55), and isoprene nitrates (56)(57)(58). It is noteworthy that recent studies (58) found that field measurements are consistent with relatively low NO x recycling efficiency (∼25%), resulting mainly from aerosol uptake, indicating that the impact of isoprene nitrate chemistry on surface ozone is much smaller than previously thought (56).…”

Section: Methodsmentioning

confidence: 99%

Climate-driven ground-level ozone extreme in the fall over the Southeast United States

Zhang

Wang

2016

Proc. Natl. Acad. Sci. U.S.A.

105

View full text Add to dashboard Cite

Ground-level ozone is adverse to human and vegetation health. High ground-level ozone concentrations usually occur over the United States in the summer, often referred to as the ozone season. However, observed monthly mean ozone concentrations in the southeastern United States were higher in October than July in 2010. The October ozone average in 2010 reached that of July in the past three decades . Our analysis shows that this extreme October ozone in 2010 over the Southeast is due in part to a dry and warm weather condition, which enhances photochemical production, air stagnation, and fire emissions. Observational evidence and modeling analysis also indicate that another significant contributor is enhanced emissions of biogenic isoprene, a major ozone precursor, from water-stressed plants under a dry and warm condition. The latter finding is corroborated by recent laboratory and field studies. This climate-induced biogenic control also explains the puzzling fact that the two extremes of high October ozone both occurred in the 2000s when anthropogenic emissions were lower than the 1980s and 1990s, in contrast to the observed decreasing trend of July ozone in the region. The occurrences of a drying and warming fall, projected by climate models, will likely lead to more active photochemistry, enhanced biogenic isoprene and fire emissions, an extension of the ozone season from summer to fall, and an increase of secondary organic aerosols in the Southeast, posing challenges to regional air quality management.ground-level ozone | ozone season | regional climate change | isoprene | air quality G round-level ozone is a pollutant harmful to human and vegetation health (1, 2). High ground-level ozone events are typically found in the summer when the formation of ozone is active through photochemical reactions involving nitrogen oxides (NO x = NO + NO 2 ) and volatile organic compounds (VOCs). However, ozone concentrations are sensitive to weather and climate (3-8), and the high-ozone season could extend beyond summer in the future (9-13). Previous climate-chemistry model studies have estimated the change of ground-level ozone (ΔO 3 ) in the United States resulting only from meteorological changes. Their results show large variation in the sign and magnitude of ΔO 3 in the fall, especially over forested regions such as the southeastern United States (SE) (10, 13). The lack of consensus reflects the uncertainties in modeling regional climate change and the consequent response of ground-level ozone.In this study, we focus on analyzing the historical ozone records. Fig. 1A Fig. S1). The number increases to 324 exceedances at 112 stations if the new US ambient ozone standard threshold value, 70 ppbv, is used (SI Appendix, Fig. S1). The regional average reached 65 ppbv during October 8-10, 2010 ( Fig. 2A). ppbv, considerably lower than that in the summer ozone season (∼50 ppbv in July). However, in the two extreme years, 2000 and 2010, regional monthly mean [O 3 ] MDA8 are 52 and 49 ppbv, respectively, two interannual standa...

show abstract

“…Phys. H-shift from C-H to an R-O-O bond and subsequent O2 additions (Crounse et al, 2011;Jokinen et al, 2014;Ehn et al, 2014;Berndt et al, 2016). Mass spectrometric signals relating to these highly oxidised RO2 species have also been observed during field measurements .…”

Section: Uncertainties In the Model Chemistry Under Low No Conditionsmentioning

confidence: 99%

Understanding in situ ozone production in the summertime through radical observations and modelling studies during the Clean air for London project (ClearfLo)

Whalley¹,

Stone²,

Dunmore³

et al. 2017

Preprint

View full text Add to dashboard Cite

Abstract. Measurements of OH, HO2, RO2i (alkene and aromatic related RO2) and total RO2 radicals taken during the ClearfLo campaign in central London in the summer of 2012 are presented. A photostationary steady-state calculation of OH which considered measured OH reactivity as the OH sink term and the measured OH sources (of which HO2+NO reaction and HONO photolysis dominated) compared well with the observed levels of OH. Comparison with calculations from a detailed box model utilising the Master Chemical Mechanism v3.2, however, highlighted a substantial discrepancy between radical 20 observations under lower NOx conditions ([NO] < 1 ppbv) typically experienced during the afternoon hours, and indicated that the model was missing a significant peroxy radical sink; the model over-predicted HO2 by up to a factor of 10 at these times.Known radical termination steps, such as HO2 uptake on aerosols, were not sufficient to reconcile the model measurement discrepancies alone suggesting other missing termination processes. This missing sink was most evident when the air reaching the site had previously passed over central London to the east and when elevated temperatures were experienced and, hence, 25 contained higher concentrations of VOC. Uncertainties in the degradation mechanism at low NOx of complex biogenic and diesel related VOC species which were particularly elevated and dominated OH reactivity under these easterly flows, may account for some of the model measurement disagreement. Under higher [NO] (>3 ppbv) the box model increasingly underpredicted total [RO2]. The modelled and observed HO2 were in agreement, however, under elevated NO concentrations ranging from 7 -15 ppbv. 30The model uncertainty under low NO conditions leads to more ozone production predicted using modelled peroxy radical concentrations (~3 ppbv hr -1 ) versus ozone production from peroxy radicals measured (~1 ppbv hr -1 ). Conversely, ozone 2 production derived from the predicted peroxy radicals is up to an order of magnitude lower than from the observed peroxy radicals as [NO] increases beyond 7 ppbv due to the model under-prediction of RO2 under these conditions.

show abstract

Peroxy radical isomerization in the oxidation of isoprene

Cited by 331 publications

References 44 publications

Photolysis, OH reactivity and ozone reactivity of a proxy for isoprene-derived hydroperoxyenals (HPALDs)

Photolysis, OH reactivity and ozone reactivity of a proxy for isoprene-derived hydroperoxyenals (HPALDs)

Climate-driven ground-level ozone extreme in the fall over the Southeast United States

Understanding in situ ozone production in the summertime through radical observations and modelling studies during the Clean air for London project (ClearfLo)

Contact Info

Product

Resources

About