Hydroxyl radical buffered by isoprene oxidation over tropical forests

Taraborrelli, Domenico; Lawrence, M. G.; Crowley, John N.; Dillon, Terry J.; Gromov, Sergey; Groß, C. B. M.; Vereecken, Luc; Lelieveld, Jos

doi:10.1038/ngeo1405

Cited by 197 publications

(254 citation statements)

References 29 publications

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“…The full theoretical mechanism has been shown to dramatically reduce model-measurement discrepancies in OH concentrations for at least one case. 21 On the other hand, recent work has also called into question the accuracy of OH concentrations observed via laser-induced fluorescence in biogenic-dominated regions. 48 As noted and accounted for in earlier theoretical work 16,20 and recently highlighted, 21 the influence of C 5 -HPALD chemistry on the radical budget depends on the relative rates of C 5 -HPALD photolysis (which generates OH) and OH reaction (which removes C 5 -HPALDs and, possibly, also OH).…”

Section: Atmospheric Implicationsmentioning

confidence: 99%

“…Global models 20,22 have demonstrated dramatic increases in OH-by factors of 3 or more in some regions-upon incorporating the ISO 2 isomerization and C 5 -HPALD chemistry as originally proposed. 21,22 This mechanism also affects the distribution of oxidized VOC, leading Archibald et al 22 to suggest that calculated isomerization rates should be reduced by an order of magnitude. In a recent experimental study, Crounse et al 18 observed a C 5 -HPALD production rate that is 25 to 75 times slower than the original quantum mechanical prediction.…”

Section: Atmospheric Implicationsmentioning

confidence: 99%

“…Photolysis of the PACALD is assumed to be even more efficient, leading to further production of OH and HO 2 . Incorporation of this chemistry into numerical simulations improves model-measurement agreement for OH in some cases 20,21 but can create additional problems, such as misrepresentation of other oxidized VOC 22 and over-prediction of HO 2 . 11 Ultimately, the impact of this mechanism on HO x abundance depends on both the rate of C 5 -HPALD production from ISO 2 isomerization and the photolysis and OH reaction rates of the C 5 -HPALD products.…”

Section: Introductionmentioning

confidence: 99%

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

Wolfe

Crounse

Parrish

et al. 2012

Phys. Chem. Chem. Phys.

103

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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.

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Section: Atmospheric Implicationsmentioning

confidence: 99%

Section: Atmospheric Implicationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Wolfe

Crounse

Parrish

et al. 2012

Phys. Chem. Chem. Phys.

103

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“…MVK, methacrolein (MACR), hydroxyacetone and methyl glyoxal (Taraborrelli et al, 2009 (Taraborrelli et al, 2012). In MIM3, the extended chemistry following the OH and O3 pathways has been thoroughly revised, tested in a box model, and shown to reproduce HOx measurements, even for challenging conditions with high isoprene mixing ratios (>1 nmol mol -1 ) and low NO (< 40 pmol mol -1 ) (Taraborrelli et al, 2012). For the numerical integration, MECCA uses the KPP software (Sandu and Sander, 2006).…”

Section: The Caaba/mecca Modelmentioning

confidence: 99%

“…MIM2 was further developed to improve the tropospheric chemistry under a 35 wide range of NOx regimes, and provided a better evaluation of NOx and organic nitrogen-containing species due to a detailed representation of the alkyl and peroxy acyl nitrates as well as isoprene oxidation products, some of which can be measured by modern instrumentation e.g. MVK, methacrolein (MACR), hydroxyacetone and methyl glyoxal (Taraborrelli et al, 2009 (Taraborrelli et al, 2012). In MIM3, the extended chemistry following the OH and O3 pathways has been thoroughly revised, tested in a box model, and shown to reproduce HOx measurements, even for challenging conditions with high isoprene mixing ratios (>1 nmol mol -1 ) and low NO (< 40 pmol mol -1 ) (Taraborrelli et al, 2012).…”

mentioning

confidence: 99%

Oxidation processes in the Eastern Mediterranean atmosphere: Evidence from the Modelling of HO<sub>x</sub> Measurements over Cyprus

Mallik¹,

Tomsche²,

Bourtsoukidis³

et al. 2018

Preprint

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Abstract. The Mediterranean is a climatically sensitive region located at the crossroads of air masses from three continents: 15Europe, Africa and Asia. The chemical processing of air masses over this region has implications not only for the air quality, but also for the long-range transport of air pollution. To obtain a comprehensive understanding of oxidation processes over the Mediterranean, atmospheric concentrations of the hydroxyl radical (OH) and the hydroperoxyl radical (HO2) were measured during an intensive field campaign (CYprus PHotochemistry EXperiment, CYPHEX-2014) in the north-west of Cyprus in the summer of 2014. Very low local anthropogenic and biogenic emissions around the measurement location 20 provided a vantage point to study the contrasts in atmospheric oxidation pathways under highly processed marine air masses and those influenced by relatively fresh emissions from mainland Europe.The CYPHEX measurements were used to evaluate OH and HO2 simulations using a photochemical box model (CAABA/MECCA) constrained with CYPHEX observations of O3, CO, NOx, hydrocarbons, peroxides and other major HOx (OH + HO2) sources and sinks in a low NOx environment (<100 pptv NO). The model simulations for OH showed very good 25 agreement with in-situ OH observations. Model simulations for HO2 also agreed fairly well with in-situ observations except when pinene levels exceeded 80 pptv. Different schemes to improve the agreement between observed and modelled HO2, including changing the rate coefficients for the reactions of terpene generated peroxy radicals (RO2) with NO and HO2 as well as the autoxidation of terpene generated RO2 species, are explored in this work. The main source of OH in Cyprus was its primary production from O3 photolysis during the day and HONO photolysis during early morning. Recycling contributed 30 about one-third of the total OH production, and the maximum recycling efficiency was about 70 %. CO, which was the largest OH sink was also the largest HO2 source. Lowest HOx production and losses occurred when the air masses had higher residence time over the oceans.Atmos. Chem. Phys. Discuss., https://doi.org/10. 5194/acp-2018-25 Manuscript under review for journal Atmos. Chem. Phys. Air pollution and HOx chemistryThe chemical and photochemical processing of air pollutants, in conjunction with local emissions, meteorology and atmospheric transport, strongly influences the air quality over a region. The regional air quality impacts human health, agriculture, the overall condition of the biosphere and subsequently the climate. Studies attribute 2-4 million premature 5 deaths globally to outdoor air pollution (Silva et al., 2013;Lelieveld et al., 2015). Oxidants in the Earth's atmosphere prevent the pollutants released into it from building up to toxic levels. These oxidants not only convert many toxic pollutants into less toxic forms (e.g. CO to CO2) but also help in their removal (e.g. NOx and SO2 are converted into soluble HNO3 and H2SO4 respectively), although some toxic chemicals may s...

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Wavelength-dependent isotope fractionation in visible light O₃ photolysis and atmospheric implications

Früchtl

Janssen

Taraborrelli

et al. 2015

Geophys. Res. Lett.

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The 17O and 18O isotope fractionation associated with photolysis of O3 in the Chappuis band was determined using a broadband light source with cutoff filters at 455, 550, and 620 nm and narrowband light sources at 530, 617, and 660 nm. The isotope effects follow a mass‐dependent fractionation pattern (δ17O/δ18O = 0.53). Contrary to theoretical predictions, fractionations are negative for all wavelength ranges investigated and do not change signs at the absorption cross‐section maximum. Our measurements differ from theoretical calculations by as much as 34‰ in εO3+hν18 = (18J/16J − 1). The wavelength dependence is also weaker than predicted. Photo‐induced fractionation is strongest when using a low‐wavelength cutoff at 620 nm with εO3+hν18 = −26.9(±1.4)‰. With decreasing wavelength, fractionation values diminish to εO3+hν18 = −12.9(±1.3)‰ at 530 nm. Results from an atmospheric model demonstrate that visible light photolysis is the most important tropospheric sink of O3, which thus contributes about one sixth to the ozone enrichment.

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Hydroxyl radical buffered by isoprene oxidation over tropical forests

Cited by 197 publications

References 29 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)

Oxidation processes in the Eastern Mediterranean atmosphere: Evidence from the Modelling of HO<sub>x</sub> Measurements over Cyprus

Wavelength-dependent isotope fractionation in visible light O₃ photolysis and atmospheric implications

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Hydroxyl radical buffered by isoprene oxidation over tropical forests

Cited by 197 publications

References 29 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)

Oxidation processes in the Eastern Mediterranean atmosphere: Evidence from the Modelling of HO&lt;sub&gt;x&lt;/sub&gt; Measurements over Cyprus

Wavelength-dependent isotope fractionation in visible light O3 photolysis and atmospheric implications

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Product

Resources

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Oxidation processes in the Eastern Mediterranean atmosphere: Evidence from the Modelling of HO<sub>x</sub> Measurements over Cyprus

Wavelength-dependent isotope fractionation in visible light O₃ photolysis and atmospheric implications