Rapid formation of isoprene photo-oxidation products observed in Amazonia

Karl, SC

doi:10.5194/acpd-9-13629-2009

Cited by 31 publications

(42 citation statements)

References 52 publications

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“…Other studies have shown also minor (Fares et al, 2015) or negligible (Karl et al, 2009 emission of MVK/MACR; however, in these studies there was a net uptake to the leaf. Part of the MVK/MACR concentration and fluxes may also be misattributed fragments from higher oxygenated hydrocarbons (Liu et al, 2013;Rivera-Rios et al, 2014).…”

Section: Mvk/macr and Their Sourcescontrasting

confidence: 60%

Characterization of total ecosystem-scale biogenic VOC exchange at a Mediterranean oak–hornbeam forest

et al. 2016

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Abstract. Recently, the number and amount of biogenically emitted volatile organic compounds (VOCs) has been discussed in great detail. Depending on the ecosystem, the published number varies between a dozen and several hundred compounds. We present ecosystem exchange fluxes from a mixed oak-hornbeam forest in the Po Valley, Italy. The fluxes were measured by a proton transfer reaction-timeof-flight (PTR-ToF) mass spectrometer and calculated using the eddy covariance (EC) method. Detectable fluxes were observed for up to 29 compounds, dominated by isoprene, which comprised over 60 % of the total upward flux (on a molar basis). The daily average of the total VOC upward flux was 10.4 nmol m −2 s −1 . Methanol had the highest concentration and accounted for the largest downward flux. Methanol seemed to be deposited to dew, as the downward flux happened in the early morning, right after the calculated surface temperature came closest to the calculated dew point temperature.We estimated that up to 30 % of the upward flux of methyl vinyl ketone (MVK) and methacrolein (MACR) originated from atmospheric oxidation of isoprene. A comparison between two methods for the flux detection (manual and automated) was made. Their respective advantages and disadvantages were discussed and the differences in their results shown. Both provide comparable results.

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Section: Mvk/macr and Their Sourcescontrasting

confidence: 60%

Characterization of total ecosystem-scale biogenic VOC exchange at a Mediterranean oak–hornbeam forest

et al. 2016

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“…The products MVK and MACR have been studied in many atmospheric environments both by proton transfer reaction mass spectrometry (PTR-MS) and gas chromatography (GC) (21). Large data sets are available (7,8,21,22). By comparison, ambient measurements of ISOPOOH isomers are sparse, and available data sets are limited to temperate regions (23,24).…”

Section: Significancementioning

confidence: 99%

Isoprene photochemistry over the Amazon rainforest

Liu

Brito

Dorris

et al. 2016

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

103

165

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Isoprene photooxidation is a major driver of atmospheric chemistry over forested regions. Isoprene reacts with hydroxyl radicals (OH) and molecular oxygen to produce isoprene peroxy radicals (ISOPOO). These radicals can react with hydroperoxyl radicals (HO 2 ) to dominantly produce hydroxyhydroperoxides (ISOPOOH). They can also react with nitric oxide (NO) to largely produce methyl vinyl ketone (MVK) and methacrolein (MACR). Unimolecular isomerization and bimolecular reactions with organic peroxy radicals are also possible. There is uncertainty about the relative importance of each of these pathways in the atmosphere and possible changes because of anthropogenic pollution. Herein, measurements of ISOPOOH and MVK + MACR concentrations are reported over the central region of the Amazon basin during the wet season. The research site, downwind of an urban region, intercepted both background and polluted air masses during the GoAmazon2014/5 Experiment. Under background conditions, the confidence interval for the ratio of the ISOPOOH concentration to that of MVK + MACR spanned 0.4-0.6. This result implies a ratio of the reaction rate of ISOPOO with HO 2 to that with NO of approximately unity. A value of unity is significantly smaller than simulated at present by global chemical transport models for this important, nominally low-NO, forested region of Earth. Under polluted conditions, when the concentrations of reactive nitrogen compounds were high (>1 ppb), ISOPOOH concentrations dropped below the instrumental detection limit (<60 ppt). This abrupt shift in isoprene photooxidation, sparked by human activities, speaks to ongoing and possible future changes in the photochemistry active over the Amazon rainforest.isoprene photochemistry | Amazon | organic hydroperoxides

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“…These HPALDs can easily undergo photolysis and lead to additional production of OH and also HCHO. Despite some minor refinement to the scheme [ Peeters and Müller , 2010], owing to issues raised by the studies of Karl et al [2009], Paulot et al [2009a], and Archibald et al [2010b], the LIM0 mechanisms potentially represents the best option for realistic simulation of the Amazonian atmosphere, though it sill needs extensive evaluation. For example, the low‐NO x HCHO yields are largely unknown owing to uncertainties in the isomerization reaction rates and HPALD photolysis products; the formation of HPALDs also partially suppress MVK and MACR production.…”

Section: Discussionmentioning

confidence: 99%

Can a “state of the art” chemistry transport model simulate Amazonian tropospheric chemistry?

et al. 2011

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We present an evaluation of a nested high‐resolution Goddard Earth Observing System (GEOS)‐Chem chemistry transport model simulation of tropospheric chemistry over tropical South America. The model has been constrained with two isoprene emission inventories: (1) the canopy‐scale Model of Emissions of Gases and Aerosols from Nature (MEGAN) and (2) a leaf‐scale algorithm coupled to the Lund‐Potsdam‐Jena General Ecosystem Simulator (LPJ‐GUESS) dynamic vegetation model, and the model has been run using two different chemical mechanisms that contain alternative treatments of isoprene photo‐oxidation. Large differences of up to 100 Tg C yr−1 exist between the isoprene emissions predicted by each inventory, with MEGAN emissions generally higher. Based on our simulations we estimate that tropical South America (30–85°W, 14°N–25°S) contributes about 15–35% of total global isoprene emissions. We have quantified the model sensitivity to changes in isoprene emissions, chemistry, boundary layer mixing, and soil NOx emissions using ground‐based and airborne observations. We find GEOS‐Chem has difficulty reproducing several observed chemical species; typically hydroxyl concentrations are underestimated, whilst mixing ratios of isoprene and its oxidation products are overestimated. The magnitude of model formaldehyde (HCHO) columns are most sensitive to the choice of chemical mechanism and isoprene emission inventory. We find GEOS‐Chem exhibits a significant positive bias (10–100%) when compared with HCHO columns from the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) and Ozone Monitoring Instrument (OMI) for the study year 2006. Simulations that use the more detailed chemical mechanism and/or lowest isoprene emissions provide the best agreement to the satellite data, since they result in lower‐HCHO columns.

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Rapid formation of isoprene photo-oxidation products observed in Amazonia

Cited by 31 publications

References 52 publications

Characterization of total ecosystem-scale biogenic VOC exchange at a Mediterranean oak–hornbeam forest

Characterization of total ecosystem-scale biogenic VOC exchange at a Mediterranean oak–hornbeam forest

Isoprene photochemistry over the Amazon rainforest

Can a “state of the art” chemistry transport model simulate Amazonian tropospheric chemistry?

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