Oxidation of Volatile Organic Compounds as the Major Source of Formic Acid in a Mixed Forest Canopy

Alwe, H. D.; Millet, Dylan B.; Chen, Xin; Raff, Jonathan D.; Payne, Zachary; Fledderman, Kathryn

doi:10.1029/2018gl081526

Cited by 39 publications

(58 citation statements)

References 66 publications

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“…In‐canopy ambient chemistry impacts not only ozone but also other molecules. Reactions between ozone and highly reactive BVOCs may account for observed emission of oxidized organic species from the canopy (Alwe et al, ; Choi et al, ; Holzinger et al, ; Schobesberger et al, ) and subsequent secondary organic aerosol formation (Bouvier‐Brown et al, ; Buzorius et al, ; Farmer et al, ; Goldstein et al, ; Wolfe et al, ), production of the hydroxyl radical (Faloona et al, ; Kurpius & Goldstein, ), and emission of reactive nitrogen oxides (Farmer & Cohen, ; Wolfe et al, ). Fluxes of oxidized organic and inorganic compounds may provide observational constraints on the location and mechanism of chemical influences on observed ozone fluxes.…”

Section: Theory Models and Observations Of Terrestrial Ozone Deposimentioning

confidence: 99%

Dry Deposition of Ozone Over Land: Processes, Measurement, and Modeling

Clifton

Fiore

Massman

et al. 2020

Reviews of Geophysics

107

133

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Dry deposition of ozone is an important sink of ozone in near‐surface air. When dry deposition occurs through plant stomata, ozone can injure the plant, altering water and carbon cycling and reducing crop yields. Quantifying both stomatal and nonstomatal uptake accurately is relevant for understanding ozone's impact on human health as an air pollutant and on climate as a potent short‐lived greenhouse gas and primary control on the removal of several reactive greenhouse gases and air pollutants. Robust ozone dry deposition estimates require knowledge of the relative importance of individual deposition pathways, but spatiotemporal variability in nonstomatal deposition is poorly understood. Here we integrate understanding of ozone deposition processes by synthesizing research from fields such as atmospheric chemistry, ecology, and meteorology. We critically review methods for measurements and modeling, highlighting the empiricism that underpins modeling and thus the interpretation of observations. Our unprecedented synthesis of knowledge on deposition pathways, particularly soil and leaf cuticles, reveals process understanding not yet included in widely used models. If coordinated with short‐term field intensives, laboratory studies, and mechanistic modeling, measurements from a few long‐term sites would bridge the molecular to ecosystem scales necessary to establish the relative importance of individual deposition pathways and the extent to which they vary in space and time. Our recommended approaches seek to close knowledge gaps that currently limit quantifying the impact of ozone dry deposition on air quality, ecosystems, and climate.

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Section: Theory Models and Observations Of Terrestrial Ozone Deposimentioning

confidence: 99%

Dry Deposition of Ozone Over Land: Processes, Measurement, and Modeling

Clifton

Fiore

Massman

et al. 2020

Reviews of Geophysics

107

133

View full text Add to dashboard Cite

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“…Physical VOC sinks in GEOS-Chem include dry deposition following the Wesely (1989) scheme as implemented by Wang et al (1998), and wet deposition as described by Amos et al (2012). Wet deposition assumes liquid-phaseonly uptake of VOCs (except formic acid and acetic acid) with a retention efficiency of 1 in warm clouds and 0.02 in mixed clouds (Mari et al, 2000).…”

Section: Depositionmentioning

confidence: 99%

On the sources and sinks of atmospheric VOCs: an integrated analysis of recent aircraft campaigns over North America

et al. 2019

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Abstract. We apply a high-resolution chemical transport model (GEOS-Chem CTM) with updated treatment of volatile organic compounds (VOCs) and a comprehensive suite of airborne datasets over North America to (i) characterize the VOC budget and (ii) test the ability of current models to capture the distribution and reactivity of atmospheric VOCs over this region. Biogenic emissions dominate the North American VOC budget in the model, accounting for 70 % and 95 % of annually emitted VOC carbon and reactivity, respectively. Based on current inventories anthropogenic emissions have declined to the point where biogenic emissions are the dominant summertime source of VOC reactivity even in most major North American cities. Methane oxidation is a 2× larger source of nonmethane VOCs (via production of formaldehyde and methyl hydroperoxide) over North America in the model than are anthropogenic emissions. However, anthropogenic VOCs account for over half of the ambient VOC loading over the majority of the region owing to their longer aggregate lifetime. Fires can be a significant VOC source episodically but are small on average. In the planetary boundary layer (PBL), the model exhibits skill in capturing observed variability in total VOC abundance (R2=0.36) and reactivity (R2=0.54). The same is not true in the free troposphere (FT), where skill is low and there is a persistent low model bias (∼ 60 %), with most (27 of 34) model VOCs underestimated by more than a factor of 2. A comparison of PBL : FT concentration ratios over the southeastern US points to a misrepresentation of PBL ventilation as a contributor to these model FT biases. We also find that a relatively small number of VOCs (acetone, methanol, ethane, acetaldehyde, formaldehyde, isoprene + oxidation products, methyl hydroperoxide) drive a large fraction of total ambient VOC reactivity and associated model biases; research to improve understanding of their budgets is thus warranted. A source tracer analysis suggests a current overestimate of biogenic sources for hydroxyacetone, methyl ethyl ketone and glyoxal, an underestimate of biogenic formic acid sources, and an underestimate of peroxyacetic acid production across biogenic and anthropogenic precursors. Future work to improve model representations of vertical transport and to address the VOC biases discussed are needed to advance predictions of ozone and SOA formation.

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“…To investigate the ubiquity of this surface phenomenon, we compare volatile organic acid fluxes from the dry pine forest of MEFO to a humid continental, mixed canopy forest in Michigan (UMBS) (Alwe et al, 2019) and a Mediterranean‐to‐semiarid California orange orchard (Fares et al, 2012; Park et al, 2013). The same linear relationship between exchange velocity and dew point depression for volatile organic acids occurs at the MEFO pine forest and the UMBS mixed forest, but not the California orange orchard (Figures S2–S4).…”

Section: Evidence For Partitioning To Surface Wetnessmentioning

confidence: 99%

Surface Wetness as an Unexpected Control on Forest Exchange of Volatile Organic Acids

Fulgham

Millet

Alwe

et al. 2020

Geophysical Research Letters

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We report bidirectional exchange of volatile acids, including isocyanic and alkanoic acids, over a pine forest across multiple seasons. The exchange velocity of these acids is well correlated with dew point depression, suggesting an equilibrium‐driven continuum of flux. Wetness on forest surfaces impacts the vertical exchange of gases, and we suggest that water films and droplets drive equilibrium partitioning, with acids being solvated in surface wetness and released through evaporation. Despite their volatility, these acids partition into neutral‐to‐alkaline aqueous films, consistent with reported dew pH. This relationship between exchange velocity and dew point depression holds for a wetter mixed forest, but not a very dry orchard. Dew point depression is an excellent indicator of acid fluxes so long as the canopy is occasionally wetted.

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Oxidation of Volatile Organic Compounds as the Major Source of Formic Acid in a Mixed Forest Canopy

Cited by 39 publications

References 66 publications

Dry Deposition of Ozone Over Land: Processes, Measurement, and Modeling

Dry Deposition of Ozone Over Land: Processes, Measurement, and Modeling

On the sources and sinks of atmospheric VOCs: an integrated analysis of recent aircraft campaigns over North America

Surface Wetness as an Unexpected Control on Forest Exchange of Volatile Organic Acids

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