Forest-atmosphere exchange of ozone: sensitivity to very reactive biogenic VOC emissions and implications for in-canopy photochemistry

Wolfe, G. M.; Thornton, Joel A.; McKay, M.; Goldstein, Allen H.

doi:10.5194/acp-11-7875-2011

Cited by 85 publications

(87 citation statements)

References 75 publications

(91 reference statements)

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“…Since the OH reactivity is highly underestimated due to missing sinks, it is also possible that our modelled O 3 and NO 3 reactivities are underestimated due to potentially missing sinks (Wolfe et al, 2011, and references therein).…”

Section: O 3 Reactivitymentioning

confidence: 99%

Simulations of atmospheric OH, O3 and NO3 reactivities within and above the boreal forest

et al. 2015

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Abstract. Using the 1-D atmospheric chemistry transport model SOSAA, we have investigated the atmospheric reactivity of a boreal forest ecosystem during the HUMPPA-COPEC-10 campaign (summer 2010, at SMEAR II in southern Finland). For the very first time, we present vertically resolved model simulations of the NO 3 and O 3 reactivity (R) together with the modelled and measured reactivity of OH. We find that OH is the most reactive oxidant (R ∼ 3 s −1 ) followed by NO 3 (R ∼ 0.07 s −1 ) and O 3 (R ∼ 2 × 10 −5 s −1 ). The missing OH reactivity was found to be large in accordance with measurements (∼ 65 %) as would be expected from the chemical subset described in the model. The accounted OH radical sinks were inorganic compounds (∼ 41 %, mainly due to reaction with CO), emitted monoterpenes (∼ 14 %) and oxidised biogenic volatile organic compounds (∼ 44 %). The missing reactivity is expected to be due to unknown biogenic volatile organic compounds and their photoproducts, indicating that the true main sink of OH is not expected to be inorganic compounds. The NO 3 radical was found to react mainly with primary emitted monoterpenes (∼ 60 %) and inorganic compounds (∼ 37 %, including NO 2 ). NO 2 is, however, only a temporary sink of NO 3 under the conditions of the campaign (with typical temperatures of 20-25 • C) and does not affect the NO 3 concentration. We discuss the difference between instantaneous and steadystate reactivity and present the first boreal forest steady-state lifetime of NO 3 (113 s). O 3 almost exclusively reacts with inorganic compounds (∼ 91 %, mainly NO, but also NO 2 during night) and less with primary emitted sesquiterpenes (∼ 6 %) and monoterpenes (∼ 3 %). When considering the concentration of the oxidants investigated, we find that OH is the oxidant that is capable of removing organic compounds at a faster rate during daytime, whereas NO 3 can remove organic molecules at a faster rate during night-time. O 3 competes with OH and NO 3 during a short period of time in the early morning (around 5 a.m. local time) and in the evening (around 7-8 p.m.). As part of this study, we developed a simple empirical parameterisation for conversion of measured spectral irradiance into actinic flux. Further, the meteorological conditions were evaluated using radiosonde observations and ground-based measurements. The overall vertical structure of the boundary layer is discussed, together with validation of the surface energy balance and turbulent fluxes. The sensible heat and momentum fluxes above the canopy were on average overestimated, while the latent heat flux was underestimated.

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Section: O 3 Reactivitymentioning

confidence: 99%

Simulations of atmospheric OH, O3 and NO3 reactivities within and above the boreal forest

et al. 2015

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“…Improvements can be expected by more accurate representations of land cover (and subsequent changes) (Hardacre et al, 2015), or by including a more process-based model of deposition that depends on soil moisture and vapor deficit (Büker et al, 2012;Pleim et al, 2001). There is also evidence that a significant fraction of the O 3 uptake observed over forest canopies is actually an unaccounted for chemical sink (Kurpius and Goldstein, 2003;Rannik et al, 2012;Schade and Goldstein, 2003;Wolfe et al, 2011), but changes in this above-canopy chemistry are not captured in our current set of simulations.…”

Section: J a Geddes Et Al: Land Cover Change Impacts On Atmospherimentioning

confidence: 81%

“…The impacts of canopy uptake and canopy chemistry resulting from changes in vegetation density and composition could be explored in more detail with future work using a 1-D forest canopy-chemistry model (e.g., Wolfe, 2011;Ashworth et al, 2015) for the regions where we project large impacts. We have assumed that the basal emissions from the soil after the disturbance will be the same as those prior to the disturbance, but large-scale tree mortality and forest succession have the potential to alter soil biogeochemistry (Gao et al, 2015;Norton et al, 2015;Trahan et al, 2015).…”

Section: J a Geddes Et Al: Land Cover Change Impacts On Atmospherimentioning

confidence: 99%

Land cover change impacts on atmospheric chemistry: simulating projected large-scale tree mortality in the United States

et al. 2016

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Abstract. Land use and land cover changes impact climate and air quality by altering the exchange of trace gases between the Earth's surface and atmosphere. Large-scale tree mortality that is projected to occur across the United States as a result of insect and disease may therefore have unexplored consequences for tropospheric chemistry. We develop a land use module for the GEOS-Chem global chemical transport model to facilitate simulations involving changes to the land surface, and to improve consistency across land-atmosphere exchange processes. The model is used to test the impact of projected national-scale tree mortality risk through 2027 estimated by the 2012 USDA Forest Service National Insect and Disease Risk Assessment. Changes in biogenic emissions alone decrease monthly mean O 3 by up to 0.4 ppb, but reductions in deposition velocity compensate or exceed the effects of emissions yielding a net increase in O 3 of more than 1 ppb in some areas. The O 3 response to the projected change in emissions is affected by the ratio of baseline NO x : VOC concentrations, suggesting that in addition to the degree of land cover change, tree mortality impacts depend on whether a region is NO x -limited or NO x -saturated. Consequently, air quality (as diagnosed by the number of days that 8 h average O 3 exceeds 70 ppb) improves in polluted environments where changes in emissions are more important than changes to dry deposition, but worsens in clean environments where changes to dry deposition are the more important term. The influence of changes in dry deposition demonstrated here underscores the need to evaluate treatments of this physical process in models. Biogenic secondary organic aerosol loadings are significantly affected across the US, decreasing by 5-10 % across many regions, and by more than 25 % locally. Tree mortality could therefore impact background aerosol loadings by between 0.5 and 2 µg m −3 . Changes to reactive nitrogen oxide abundance and partitioning are also locally important. The regional effects simulated here are similar in magnitude to other scenarios that consider future biofuel cropping or natural succession, further demonstrating that biosphere-atmosphere exchange should be considered when predicting future air quality and climate. We point to important uncertainties and further development that should be addressed for a more robust understanding of land cover change feedbacks.

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“…This indicates that SQTs and escpecially β-caryophyllene ( Figure S8d) have much higher effect for example on local ozone deposition than MTs. Several studies have shown that measured ozone deposition fluxes cannot be 25 explained by modelled stomatal and known non-stomatal sinks, such as reactions with measured VOCs in the gas phase (Clifton et al 2017;Wolfe et al 2011;Rannik et al 2012). Higher than expected impact of the SQTs could explain at least part of the discrepancy.…”

Section: Reactivity Of Measured Bvocsmentioning

confidence: 99%

Sesquiterpenes identified as key species for atmospheric chemistry in boreal forest by terpenoid and OVOC measurements

Hellén

Praplan

Tykkä

et al. 2018

Preprint

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Abstract. Concentrations of terpenoids (isoprene, monoterpenes, sesquiterpenes) and oxygenated volatile organic compounds (OVOCs, i.e. aldehydes, alcohols, acetates and volatile organic acids) were investigated during two years at a boreal forest site in Hyytiälä, Finland, using in situ gas chromatograph-mass spectrometers (GC-MS). Seasonal and diurnal variations of terpenoid and OVOC concentrations as well as their relationship with meteorological factors were studied.Of the studied VOCs, C2-C7 unbranched volatile organic acids (VOAs) were found to have the highest concentrations mainly 20 due to their low reactivity. Of the terpenoids, monoterpenes (MTs) had highest concentrations at the site, but also 7 different highly reactive sesquiterpenes (SQTs) were detected. Monthly and daily mean concentrations of most terpenoids, aldehydes and VOAs were found to be highly dependent on the temperature. Highest exponential correlation with temperature was found for a SQT (β-caryophyllene) in summer. The diurnal variations of the concentrations could be explained by sources, sinks and vertical mixing. Especially the diurnal variations of MT concentrations were strongly affected by vertical mixing. Based on 25 the temperature correlations and mixing layer height simple proxies were developed for estimating MT and SQT concentrations.To estimate the importance of different compound groups and compounds for the local atmospheric chemistry, reactivity with main oxidants (OH, NO3 and O3) and production rates of oxidation products (OxPR) were calculated. MTs dominated OH and NO3 radical chemistry, but SQTs had a major impact on ozone chemistry, even though concentrations of SQT were 30 times 30 lower than MT concentrations. SQTs were the most important also for the production of oxidation products. Since SQTs have high secondary organic aerosol (SOA) yields, results clearly indicate the importance of SQTs for local SOA production.Atmos. Chem. Phys. Discuss., https://doi

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Forest-atmosphere exchange of ozone: sensitivity to very reactive biogenic VOC emissions and implications for in-canopy photochemistry

Cited by 85 publications

References 75 publications

Simulations of atmospheric OH, O<sub>3</sub> and NO<sub>3</sub> reactivities within and above the boreal forest

Simulations of atmospheric OH, O<sub>3</sub> and NO<sub>3</sub> reactivities within and above the boreal forest

Land cover change impacts on atmospheric chemistry: simulating projected large-scale tree mortality in the United States

Sesquiterpenes identified as key species for atmospheric chemistry in boreal forest by terpenoid and OVOC measurements

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Forest-atmosphere exchange of ozone: sensitivity to very reactive biogenic VOC emissions and implications for in-canopy photochemistry

Cited by 85 publications

References 75 publications

Simulations of atmospheric OH, O&lt;sub&gt;3&lt;/sub&gt; and NO&lt;sub&gt;3&lt;/sub&gt; reactivities within and above the boreal forest

Simulations of atmospheric OH, O&lt;sub&gt;3&lt;/sub&gt; and NO&lt;sub&gt;3&lt;/sub&gt; reactivities within and above the boreal forest

Land cover change impacts on atmospheric chemistry: simulating projected large-scale tree mortality in the United States

Sesquiterpenes identified as key species for atmospheric chemistry in boreal forest by terpenoid and OVOC measurements

Contact Info

Product

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Simulations of atmospheric OH, O<sub>3</sub> and NO<sub>3</sub> reactivities within and above the boreal forest

Simulations of atmospheric OH, O<sub>3</sub> and NO<sub>3</sub> reactivities within and above the boreal forest