HO<sub><i>x</i></sub> budgets in a deciduous forest: Results from the PROPHET summer 1998 campaign

Tan, D.; Faloona, I. C.; Simpas, James Bernard; Brune, William H.; Shepson, P. B.; Couch, Tara L.; Sumner, Ann Louise; Carroll, Mary Anne; Thornberry, T. D.; Apel, E. C.; Riemer, D. D.; Stockwell, William R.

doi:10.1029/2001jd900016

Cited by 224 publications

(278 citation statements)

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“…Observations of atmospheric OH concentrations indicate that under low NO x conditions isoprene may be involved in a so far unidentified recycling mechanism that converts HO 2 into OH 1022 A. Kiendler-Scharr et al: Effects on new particle formation and OH concentrations without involving ozone formation (Tan et al, 2001;Thornton et al, 2002;Ren et al, 2008;Lelieveld et al, 2008;Hofzumahaus et al, 2009;Whalley et al, 2011;Lu et al, 2011). Contrary, suppression of new particle formation by isoprene was ascribed to its suppression of OH concentrations (Kiendler-Scharr et al, 2009b).…”

Section: Introductionmentioning

confidence: 96%

Isoprene in poplar emissions: effects on new particle formation and OH concentrations

Kiendler‐Scharr¹,

Andres²,

Bachner³

et al. 2012

Atmos. Chem. Phys.

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Abstract. Stress-induced volatile organic compound (VOC) emissions from transgenic Grey poplar modified in isoprene emission potential were used for the investigation of photochemical secondary organic aerosol (SOA) formation. In poplar, acute ozone stress induces the emission of a wide array of VOCs dominated by sesquiterpenes and aromatic VOCs. Constitutive light-dependent emission of isoprene ranged between 66 nmol m −2 s −1 in non-transgenic controls (wild type WT) and nearly zero (<0.5 nmol m −2 s −1 ) in isoprene emission-repressed plants (line RA22), respectively. Nucleation rates of up to 3600 cm −3 s −1 were observed in our experiments. In the presence of isoprene new particle formation was suppressed compared to non-isoprene containing VOC mixtures. Compared to isoprene/monoterpene systems emitted from other plants the suppression of nucleation by isoprene was less effective for the VOC mixture emitted from stressed poplar. This is explained by the observed high efficiency of new particle formation for emissions from stressed poplar. Direct measurements of OH in the reaction chamber revealed that the steady state concentration of OH is lower in the presence of isoprene than in the absence of isoprene, supporting the hypothesis that isoprenes' suppressing effect on nucleation is related to radical chemistry. In order to test whether isoprene contributes to SOA mass formation, fully deuterated isoprene (C 5 D 8 ) was added to the stress-induced emission profile of an isoprene free poplar mutant. Mass spectral analysis showed that, despite the isoprene-induced suppression of particle formation, fractions of deuterated isoprene were incorporated into the SOA. A fractional mass yield of 2.3 % of isoprene was observed. Future emission changes due to land use and climate change may therefore affect both gas phase oxidation capacity and new particle number formation.

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Section: Introductionmentioning

confidence: 96%

Isoprene in poplar emissions: effects on new particle formation and OH concentrations

Kiendler‐Scharr¹,

Andres²,

Bachner³

et al. 2012

Atmos. Chem. Phys.

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“…[12][13][14][15] Briefly, air is drawn from the experiment bag at a rate of B1. Neutral analytes react with CF 3 O À ions primarily through CF 3 O À clustering and/or fluoride transfer reactions to form product ions observed at m/z = mass neutral + 85 amu and m/z = mass neutral + 19 amu, respectively. For certain isobaric analytes, CF 3 O À tandem MS analysis provides separate quantification.…”

Section: Methodsmentioning

confidence: 99%

“…Neutral analytes react with CF 3 O À ions primarily through CF 3 O À clustering and/or fluoride transfer reactions to form product ions observed at m/z = mass neutral + 85 amu and m/z = mass neutral + 19 amu, respectively. For certain isobaric analytes, CF 3 O À tandem MS analysis provides separate quantification. 13 Several analytes which are undetectable using CF 3 O À ion chemistry were monitored using positive mode via H + Á(H 2 O) n ion chemistry.…”

Section: Methodsmentioning

confidence: 99%

“…For certain isobaric analytes, CF 3 O À tandem MS analysis provides separate quantification. 13 Several analytes which are undetectable using CF 3 O À ion chemistry were monitored using positive mode via H + Á(H 2 O) n ion chemistry. H 2 O 2 was monitored using the CF 3 O À cluster ion at m/z = 119 and quantified using calibration factors obtained from gas phase standard addition.…”

Section: Methodsmentioning

confidence: 99%

“…A number of recent analyses have cast doubt on the traditional representation of peroxy radical chemistry (R2a-R3). In particular, motivated by the inability to explain measured concentrations of OH in regions with elevated levels of biogenically-derived hydrocarbons, [2][3][4][5][6] investigators have hypothesized that the peroxy radicals of the dominant VOC, isoprene, may not follow the traditional reactive pathways. Most recently, Peeters et al 7 and da Silva et al 8 have estimated from quantum mechanical calculations that intramolecular hydrogen transfer reactions of the isoprene peroxy radicals (R4) may diminish the impact of isoprene oxidation on HO x concentrations.…”

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confidence: 99%

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Peroxy radical isomerization in the oxidation of isoprene

Crounse

Paulot

Kjaergaard

et al. 2011

Phys. Chem. Chem. Phys.

331

455

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We report experimental evidence for the formation of C 5 -hydroperoxyaldehydes (HPALDs) from 1,6-H-shift isomerizations in peroxy radicals formed from the hydroxyl radical (OH) oxidation of 2-methyl-1,3-butadiene (isoprene). At 295 K, the isomerization rate of isoprene peroxy radicals ðISO 2 Þ relative to the rate of reaction of ISO 2 þ HO 2 is k 295 isom k 295 ISO 2 þHO 2 ¼ ð1:2 AE 0:6Þ Â 10 8 mol cm À3 , or k 295 isom C 0.002 s À1 . The temperature dependence of this rate was determined through experiments conducted at 295, 310 and 318 K and is well described by k isom ðTÞ k ISO 2 þHO 2 ðTÞ ¼ 2:0 Â 10 21 expðÀ9000=TÞ mol cm À3 . The overall uncertainty in the isomerization rate (relative to k ISO 2 þHO 2 ) is estimated to be 50%. Peroxy radicals from the oxidation of the fully deuterated isoprene analog isomerize at a rate B15 times slower than non-deuterated isoprene. The fraction of isoprene peroxy radicals reacting by 1,6-H-shift isomerization is estimated to be 8-11% globally, with values up to 20% in tropical regions.Approximately 500 Tg of isoprene (C 5 H 8 ) originating primarily from plants is released to Earth's atmosphere each year. 1 The oxidation of isoprene in the atmosphere is primarily initiated by reaction with hydroxyl radicals (OH). The bulk of this reaction proceeds through addition of the OH to one of the two external olefinic carbon atoms. In the presence of oxygen, six different peroxy radicals (collectively ISO 2 ) are formed from reaction with O 2 (R1).In nearly all chemical mechanisms used to describe atmospheric photochemistry, the subsequent fate of ISO 2 is determined by reaction with either NO (R2a and R2b) or HO 2 (R3).where NY = nitrate yield.This representation is consistent with a wealth of laboratory studies of the reactivity of peroxy radicals. Such studies have typically been performed with sufficient concentrations of NO or HO 2 that the lifetimes of the peroxy radicals are very short-often less than 0.1 s. For vast regions of the atmosphere (including most of the tropics), however, the peroxy radicals are estimated to live for 10's of seconds before finding a reactive partner in either NO or HO 2 (e.g., for observed NO and HO 2 levels over Amazonia, 2 ISO 2 lifetime with respect to R2a-R3 is calculated to be 30-60 s). A number of recent analyses have cast doubt on the traditional representation of peroxy radical chemistry (R2a-R3). In particular, motivated by the inability to explain measured concentrations of OH in regions with elevated levels of biogenically-derived hydrocarbons, 2-6 investigators have hypothesized that the peroxy radicals of the dominant VOC, isoprene, may not follow the traditional reactive pathways. Most recently, Peeters et al. 7 and da Silva et al. 8 have estimated from quantum mechanical calculations that intramolecular hydrogen transfer reactions of the isoprene peroxy radicals (R4) may diminish the impact of isoprene oxidation on HO x concentrations.Here, we report product yields in the oxidation of isoprene and its fully deuterated analog by OH ...

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Chemistry‐turbulence interactions and mesoscale variability influence the cleansing efficiency of the atmosphere

Kaser

Karl

Yuan

et al. 2015

Geophysical Research Letters

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The hydroxyl radical (OH) is the most important oxidant in the atmosphere and the primary sink for isoprene, the dominant volatile organic compound emitted by vegetation. Recent research on the atmospheric oxidation capacity in isoprene‐dominated environments has suggested missing radical sources leading to significant overestimation of the lifetime of isoprene. Here we report, for the first time, a comprehensive experimental budget of isoprene in the planetary boundary layer based on airborne flux measurements along with in situ OH observations in the Southeast and Central U.S. Our findings show that surface heterogeneity of isoprene emissions lead to a physical separation of isoprene and OH resulting in an effective slowdown in the chemistry. Depending on surface heterogeneity, the intensity of segregation (Is) could locally slow down isoprene chemistry up to 30%. The effect of segregated reactants in the planetary boundary layer on average has an influence on modeled OH radicals that is comparable to that of recently proposed radical recycling mechanisms.

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HO_x budgets in a deciduous forest: Results from the PROPHET summer 1998 campaign

Cited by 224 publications

References 37 publications

Isoprene in poplar emissions: effects on new particle formation and OH concentrations

Isoprene in poplar emissions: effects on new particle formation and OH concentrations

Peroxy radical isomerization in the oxidation of isoprene

Chemistry‐turbulence interactions and mesoscale variability influence the cleansing efficiency of the atmosphere

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HOx budgets in a deciduous forest: Results from the PROPHET summer 1998 campaign

Cited by 224 publications

References 37 publications

Isoprene in poplar emissions: effects on new particle formation and OH concentrations

Isoprene in poplar emissions: effects on new particle formation and OH concentrations

Peroxy radical isomerization in the oxidation of isoprene

Chemistry‐turbulence interactions and mesoscale variability influence the cleansing efficiency of the atmosphere

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HO_x budgets in a deciduous forest: Results from the PROPHET summer 1998 campaign