A study of the NO<sub>x</sub> dependence of isoprene oxidation

Barket, Dennis J.; Grossenbacher, John W.; Hurst, Julia M.; Shepson, P. B.; Olszyna, Kenneth J.; Thornberry, T. D.; Carroll, Mary Anne; Roberts, J. M.; Stroud, Craig; Bottenheim, J. W.; Biesenthal, T.

doi:10.1029/2003jd003965

Cited by 38 publications

(51 citation statements)

References 57 publications

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“…The rate of isoprene oxidation by OH is also dependent on NO x mixing ratios in a non-linear way. Barket et al (2004) found a crossover from NO x -sensitive to VOC-sensitive conditions at ∼8 ppb of NO x comparing four North American sites. At low NO x conditions, peroxy radicals terminate via self-reaction and reaction with HO 2 .…”

Section: Isoprene Oxidation Pathways: Change Frommentioning

confidence: 99%

Impact of Manaus City on the Amazon Green Ocean atmosphere: ozone production, precursor sensitivity and aerosol load

et al. 2010

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Abstract. As a contribution to the Large-Scale BiosphereAtmosphere Experiment in Amazonia -Cooperative LBA Airborne Regional Experiment (LBA-CLAIRE-2001) field campaign in the heart of the Amazon Basin, we analyzed the temporal and spatial dynamics of the urban plume of Manaus City during the wet-to-dry season transition period in July 2001. During the flights, we performed vertical stacks of crosswind transects in the urban outflow downwind of Manaus City, measuring a comprehensive set of trace constituents including O 3 , NO, NO 2 , CO, VOC, CO 2 , and H 2 O. Aerosol loads were characterized by concentrations of total aerosol number (CN) and cloud condensation nuclei (CCN), and by light scattering properties. Measurements over pristine rainforest areas during the campaign showed low levCorrespondence to: U. Kuhn (uwe.kuhn@art.admin.ch) els of pollution from biomass burning or industrial emissions, representative of wet season background conditions. The urban plume of Manaus City was found to be joined by plumes from power plants south of the city, all showing evidence of very strong photochemical ozone formation. One episode is discussed in detail, where a threefold increase in ozone mixing ratios within the atmospheric boundary layer occurred within a 100 km travel distance downwind of Manaus. Observation-based estimates of the ozone production rates in the plume reached 15 ppb h −1 .Within the plume core, aerosol concentrations were strongly enhanced, with CN/ CO ratios about one order of magnitude higher than observed in Amazon biomass burning plumes. CN/ CO ratios tended to decrease with increasing transport time, indicative of a significant reduction in particle number by coagulation, and without substantial new particle nucleation occurring within the time/space observed. While in the background atmosphere a large Published by Copernicus Publications on behalf of the European Geosciences Union. 9252 U. Kuhn et al.: Impact of Manaus City on the Amazon Green Ocean atmosphere fraction of the total particle number served as CCN (about 60-80% at 0.6% supersaturation), the CCN/CN ratios within the plume indicated that only a small fraction (16 ± 12 %) of the plume particles were CCN. The fresh plume aerosols showed relatively weak light scattering efficiency. The COnormalized CCN concentrations and light scattering coefficients increased with plume age in most cases, suggesting particle growth by condensation of soluble organic or inorganic species.We used a Single Column Chemistry and Transport Model (SCM) to infer the urban pollution emission fluxes of Manaus City, implying observed mixing ratios of CO, NO x and VOC. The model can reproduce the temporal/spatial distribution of ozone enhancements in the Manaus plume, both with and without accounting for the distinct (high NO x ) contribution by the power plants; this way examining the sensitivity of ozone production to changes in the emission rates of NO x . The VOC reactivity in the Manaus region was dominated by a high burden of biogenic isoprene from the b...

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Section: Isoprene Oxidation Pathways: Change Frommentioning

confidence: 99%

Impact of Manaus City on the Amazon Green Ocean atmosphere: ozone production, precursor sensitivity and aerosol load

et al. 2010

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“…Too high isoprene and MVK would fit to the overestimation of HCHO in the Lagrange as well as the steady state model over land, while a higher dry deposition alone cannot alleviate the discrepancy over the sea. Regarding the representation of isoprene chemistry in the used chemical mechanism some authors have reported that there can be a strong dependency of the product yields of isoprene oxidation on the complexity of the applied condensed mechanism (Paulson and Seinfeld, 1992;Barket et al, 2004;Fan and Zhang, 2004). Pöschl et al (2000) conclude that a box model with the condensed Mainz Isoprene Mechanism (MIM) included also in MECCA v0.1p produces rather lower organic peroxide mixing ratios under tropical low NO x conditions compared to the extended Master Chemical Mechanism (MCM).…”

Section: Errant Sources or Sinks Of Organic Peroxidesmentioning

confidence: 99%

Chemistry, transport and dry deposition of trace gases in the boundary layer over the tropical Atlantic Ocean and the Guyanas during the GABRIEL field campaign

et al. 2007

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Abstract. We present a comparison of different Lagrangian and chemical box model calculations with measurement data obtained during the GABRIEL campaign over the tropical Atlantic Ocean and the Amazon rainforest in the Guyanas, October 2005. Lagrangian modelling of boundary layer (BL) air constrained by measurements is used to derive a horizontal gradient (≈5.6 pmol/mol km −1 ) of CO from the ocean to the rainforest (east to west). This is significantly smaller than that derived from the measurements (16-48 pmol/mol km −1 ), indicating that photochemical production from organic precursors alone cannot explain the observed strong gradient. It appears that HCHO is overestimated by the Lagrangian and chemical box models, which include dry deposition but not exchange with the free troposphere (FT). The relatively short lifetime of HCHO implies substantial BL-FT exchange. The mixing-in of FT air affected by African and South American biomass burning at an estimated rate of 0.12 h −1 increases the CO and decreases the HCHO mixing ratios, improving agreement with measurements. A mean deposition velocity of 1.35 cm/s for H 2 O 2 over the ocean as well as over the rainforest is deduced assuming BL-FT exchange adequate to the results for CO. The measured increase of the organic peroxides from the ocean to the rainforest (≈0.66 nmol/mol d −1 ) is significantly overestimated by the Lagrangian model, even when using high values for the deposition velocity and the entrainment rate. Our results point at either heterogeneous loss of organic peroxides and/or their radical precursors, underestimated photodissociation or missing reaction paths of peroxy radicals not forming peroxides in isoprene chemistry. We calculate a mean integrated daytime net ozone production (NOP) in the Correspondence to: A. Stickler (alexander.stickler@env.ethz.ch) BL of (0.2±5.9) nmol/mol (ocean) and (2.4±2.1) nmol/mol (rainforest). The NOP strongly correlates with NO and has a positive tendency in the boundary layer over the rainforest.

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“…During the day, (MVK+MACR)/ISO is mainly driven by the OH chemistry, which destroys isoprene while producing (and concurrently destroying) MVK and MACR. As for every reactive scalar, the vertical profile of (MVK+MACR)/ISO is a function of turbulent mixing, surface deposition, distance from the emission source (transport time), and photochemical degradation (Montzka et al, 1995;Biesenthal et al, 1998;Barket et al, 2004).…”

Section: (Mvk+macr)/iso Ratios and Implications For Chemistry And Tramentioning

confidence: 99%

Isoprene and monoterpene fluxes from Central Amazonian rainforest inferred from tower-based and airborne measurements, and implications on the atmospheric chemistry and the local carbon budget

Kühn

Andreae²,

Ammann³

et al. 2007

Atmos. Chem. Phys.

181

157

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Abstract. We estimated the isoprene and monoterpene source strengths of a pristine tropical forest north of Manaus in the central Amazon Basin using three different micrometeorological flux measurement approaches. During the early dry season campaign of the Cooperative LBA Airborne Regional Experiment (LBA-CLAIRE-2001), a towerbased surface layer gradient (SLG) technique was applied simultaneously with a relaxed eddy accumulation (REA) system. Airborne measurements of vertical profiles within and above the convective boundary layer (CBL) were used to estimate fluxes on a landscape scale by application of the mixed layer gradient (MLG) technique. The mean daytime fluxes of organic carbon measured by REA were 2.1 mg C m −2 h −1 for isoprene, 0.20 mg C m −2 h −1 for α-pinene, and 0.39 mg C m −2 h −1 for the sum of monoterpenes. These values are in reasonable agreement with fluxes determined with the SLG approach, which exhibited a higher scatter, as expected for the complex terrain investigated. The observed VOC fluxes are in good agreement with simulations using a single-column chemistry and climate model (SCM).In contrast, the model-derived mixing ratios of VOCsCorrespondence to: U. Kuhn (kuhn@mpch-mainz.mpg.de)were by far higher than observed, indicating that chemical processes may not be adequately represented in the model. The observed vertical gradients of isoprene and its primary degradation products methyl vinyl ketone (MVK) and methacrolein (MACR) suggest that the oxidation capacity in the tropical CBL is much higher than previously assumed. A simple chemical kinetics model was used to infer OH radical concentrations from the vertical gradients of (MVK+MACR)/isoprene. The estimated range of OH concentrations during the daytime was 3-8×10 6 molecules cm −3 , i.e., an order of magnitude higher than is estimated for the tropical CBL by current state-of-theart atmospheric chemistry and transport models. The remarkably high OH concentrations were also supported by results of a simple budget analysis, based on the flux-to-lifetime relationship of isoprene within the CBL. Furthermore, VOC fluxes determined with the airborne MLG approach were only in reasonable agreement with those of the tower-based REA and SLG approaches after correction for chemical decay by OH radicals, applying a best estimate OH concentration of 5.5×10 6 molecules cm −3 . The SCM model calculations support relatively high OH concentration estimates after specifically being constrained by the mixing ratios of chemical constituents observed during the campaign.Published by Copernicus Publications on behalf of the European Geosciences Union. The relevance of the VOC fluxes for the local carbon budget of the tropical rainforest site during the measurements campaign was assessed by comparison with the concurrent CO 2 fluxes, estimated by three different methods (eddy correlation, Lagrangian dispersion, and mass budget approach). Depending on the CO 2 flux estimate, 1-6% or more of the carbon gained by net ecosystem productivity appeared to be re-...

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A study of the NO_x dependence of isoprene oxidation

Cited by 38 publications

References 57 publications

Impact of Manaus City on the Amazon Green Ocean atmosphere: ozone production, precursor sensitivity and aerosol load

Impact of Manaus City on the Amazon Green Ocean atmosphere: ozone production, precursor sensitivity and aerosol load

Chemistry, transport and dry deposition of trace gases in the boundary layer over the tropical Atlantic Ocean and the Guyanas during the GABRIEL field campaign

Isoprene and monoterpene fluxes from Central Amazonian rainforest inferred from tower-based and airborne measurements, and implications on the atmospheric chemistry and the local carbon budget

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A study of the NOx dependence of isoprene oxidation

Cited by 38 publications

References 57 publications

Impact of Manaus City on the Amazon Green Ocean atmosphere: ozone production, precursor sensitivity and aerosol load

Impact of Manaus City on the Amazon Green Ocean atmosphere: ozone production, precursor sensitivity and aerosol load

Chemistry, transport and dry deposition of trace gases in the boundary layer over the tropical Atlantic Ocean and the Guyanas during the GABRIEL field campaign

Isoprene and monoterpene fluxes from Central Amazonian rainforest inferred from tower-based and airborne measurements, and implications on the atmospheric chemistry and the local carbon budget

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A study of the NO_x dependence of isoprene oxidation