Missing peroxy radical sources within a summertime ponderosa pine forest

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dc.contributor.authorWolfe, G. M.
dc.contributor.authorCantrell, C.
dc.contributor.authorKim, S.
dc.contributor.authorMaudlin III, R. L.
dc.contributor.authorKarl, T.
dc.contributor.authorHarley, P.
dc.contributor.authorTurnipseed, A.
dc.contributor.authorZheng, W.
dc.contributor.authorFlocke, F.
dc.contributor.authorApel, E. C.
dc.contributor.authorHornbrook, R. S.
dc.contributor.authorHall, S. R.
dc.contributor.authorUllmann, K.
dc.contributor.authorHenry, S. B.
dc.contributor.authorDiGangi, J. P.
dc.contributor.authorBoyle, E. S.
dc.contributor.authorKaser, L.
dc.contributor.authorSchnitzhofer, R.
dc.contributor.authorHansel, A.
dc.contributor.authorGraus, M.
dc.contributor.authorNakashima, Y.
dc.contributor.authorKajii, Y.
dc.contributor.authorGuenther, A.
dc.contributor.authorKeutsch, F. N.
dc.date.accessioned2020-09-17T18:19:35Z
dc.date.available2020-09-17T18:19:35Z
dc.date.issued2014-05-13
dc.description.abstractOrganic peroxy (RO₂) and hydroperoxy (HO₂) radicals are key intermediates in the photochemical processes that generate ozone, secondary organic aerosol and reactive nitrogen reservoirs throughout the troposphere. In regions with ample biogenic hydrocarbons, the richness and complexity of peroxy radical chemistry presents a significant challenge to current-generation models, especially given the scarcity of measurements in such environments. We present peroxy radical observations acquired within a ponderosa pine forest during the summer 2010 Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H₂O, Organics and Nitrogen – Rocky Mountain Organic Carbon Study (BEACHON-ROCS). Total peroxy radical mixing ratios reach as high as 180 pptv (parts per trillion by volume) and are among the highest yet recorded. Using the comprehensive measurement suite to constrain a near-explicit 0-D box model, we investigate the sources, sinks and distribution of peroxy radicals below the forest canopy. The base chemical mechanism underestimates total peroxy radicals by as much as a factor of 3. Since primary reaction partners for peroxy radicals are either measured (NO) or underpredicted (HO₂ and RO₂, i.e., self-reaction), missing sources are the most likely explanation for this result. A close comparison of model output with observations reveals at least two distinct source signatures. The first missing source, characterized by a sharp midday maximum and a strong dependence on solar radiation, is consistent with photolytic production of HO₂. The diel profile of the second missing source peaks in the afternoon and suggests a process that generates RO₂ independently of sun-driven photochemistry, such as ozonolysis of reactive hydrocarbons. The maximum magnitudes of these missing sources (~120 and 50 pptv min⁻¹, respectively) are consistent with previous observations alluding to unexpectedly intense oxidation within forests. We conclude that a similar mechanism may underlie many such observations.en_US
dc.description.sponsorshipThe National Center for Atmospheric Research is operated by the University Corporation for Atmospheric Research under sponsorship from the US National Science Foundation. Any opinions, findings and conclusions or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of the National Science Foundation. The authors also thank the National Science Foundation (ATM 0852406) and the Austrian Science Fund (FWF) under the project number L518-N20. Lisa Kaser is a recipient of a DOC-fFORTE fellowship of the Austrian Academy of Sciences at the Institute of Ion Physics and Applied Physics. This work was also supported by the EC Seventh Framework Programme (Marie Curie Reintegration Program, “ALP-AIR”, grant no. 334084) to T. Karl. G. M. Wolfe acknowledges support from the NOAA Climate and Global Change Postdoctoral Fellowship Program. We thank the US Forest Service, specifically Richard Oakes, for logistical support during BEACHON. Finally, we a grateful for the insightful comments of three anonymous referees.en_US
dc.description.urihttps://acp.copernicus.org/articles/14/4715/2014/en_US
dc.format.extent18 pagesen_US
dc.genrejournal articlesen_US
dc.identifierdoi:10.13016/m2t6k2-19s8
dc.identifier.citationWolfe, G. M., Cantrell, C., Kim, S., Mauldin III, R. L., Karl, T., Harley, P., Turnipseed, A., Zheng, W., Flocke, F., Apel, E. C., Hornbrook, R. S., Hall, S. R., Ullmann, K., Henry, S. B., DiGangi, J. P., Boyle, E. S., Kaser, L., Schnitzhofer, R., Hansel, A., Graus, M., Nakashima, Y., Kajii, Y., Guenther, A., and Keutsch, F. N.: Missing peroxy radical sources within a summertime ponderosa pine forest, Atmos. Chem. Phys., 14, 4715–4732, https://doi.org/10.5194/acp-14-4715-2014, 2014.en_US
dc.identifier.urihttps://doi.org/10.5194/acp-14-4715-2014
dc.identifier.urihttp://hdl.handle.net/11603/19679
dc.language.isoen_USen_US
dc.publisherCopernicus Publicationsen_US
dc.relation.isAvailableAtThe University of Maryland, Baltimore County (UMBC)
dc.relation.ispartofUMBC Joint Center for Earth Systems Technology
dc.relation.ispartofUMBC Physics Department
dc.rightsThis item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.*
dc.rightsPublic Domain Mark 1.0*
dc.rightsThis work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
dc.rights.urihttp://creativecommons.org/publicdomain/mark/1.0/*
dc.titleMissing peroxy radical sources within a summertime ponderosa pine foresten_US
dc.typeTexten_US

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