Eddy covariance fluxes of acyl peroxy nitrates (PAN, PPN and MPAN) above a Ponderosa pine forest
During the Biosphere Effects on AeRosols and Photochemistry EXperiment 2007 (BEARPEX-2007), we observed eddy covariance (EC) fluxes of speciated acyl peroxy nitrates (APNs), including peroxyacetyl nitrate (PAN), peroxypropionyl nitrate (PPN) and peroxymethacryloyl nitrate (MPAN), above a Ponderosa p...
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| Format: | Article |
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Copernicus Publications
2009-01-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/9/615/2009/acp-9-615-2009.pdf |
| _version_ | 1811311047310573568 |
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| author | G. M. Wolfe J. A. Thornton R. L. N. Yatavelli M. McKay A. H. Goldstein B. LaFranchi K.-E. Min R. C. Cohen |
| author_facet | G. M. Wolfe J. A. Thornton R. L. N. Yatavelli M. McKay A. H. Goldstein B. LaFranchi K.-E. Min R. C. Cohen |
| author_sort | G. M. Wolfe |
| collection | DOAJ |
| description | During the Biosphere Effects on AeRosols and Photochemistry EXperiment 2007 (BEARPEX-2007), we observed eddy covariance (EC) fluxes of speciated acyl peroxy nitrates (APNs), including peroxyacetyl nitrate (PAN), peroxypropionyl nitrate (PPN) and peroxymethacryloyl nitrate (MPAN), above a Ponderosa pine forest in the western Sierra Nevada. All APN fluxes are net downward during the day, with a median midday PAN exchange velocity of &minus;0.3 cm s<sup>&minus;1</sup>; nighttime storage-corrected APN EC fluxes are smaller than daytime fluxes but still downward. Analysis with a standard resistance model shows that loss of PAN to the canopy is not controlled by turbulent or molecular diffusion. Stomatal uptake can account for 25 to 50% of the observed downward PAN flux. Vertical gradients in the PAN thermal decomposition (TD) rate explain a similar fraction of the flux, suggesting that a significant portion of the PAN flux into the forest results from chemical processes in the canopy. The remaining "unidentified" portion of the net PAN flux (~15%) is ascribed to deposition or reactive uptake on non-stomatal surfaces (e.g. leaf cuticles or soil). Shifts in temperature, moisture and ecosystem activity during the summer – fall transition alter the relative contribution of stomatal uptake, non-stomatal uptake and thermochemical gradients to the net PAN flux. Daytime PAN and MPAN exchange velocities are a factor of 3 smaller than those of PPN during the first two weeks of the measurement period, consistent with strong intra-canopy chemical production of PAN and MPAN during this period. Depositional loss of APNs can be 3–21% of the gross gas-phase TD loss depending on temperature. As a source of nitrogen to the biosphere, PAN deposition represents approximately 4–19% of that due to dry deposition of nitric acid at this site. |
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| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-04-13T10:10:50Z |
| publishDate | 2009-01-01 |
| publisher | Copernicus Publications |
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| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-8bff156181f4474590b87f55fb8e75222022-12-22T02:50:56ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242009-01-0192615634Eddy covariance fluxes of acyl peroxy nitrates (PAN, PPN and MPAN) above a Ponderosa pine forestG. M. WolfeJ. A. ThorntonR. L. N. YatavelliM. McKayA. H. GoldsteinB. LaFranchiK.-E. MinR. C. CohenDuring the Biosphere Effects on AeRosols and Photochemistry EXperiment 2007 (BEARPEX-2007), we observed eddy covariance (EC) fluxes of speciated acyl peroxy nitrates (APNs), including peroxyacetyl nitrate (PAN), peroxypropionyl nitrate (PPN) and peroxymethacryloyl nitrate (MPAN), above a Ponderosa pine forest in the western Sierra Nevada. All APN fluxes are net downward during the day, with a median midday PAN exchange velocity of &minus;0.3 cm s<sup>&minus;1</sup>; nighttime storage-corrected APN EC fluxes are smaller than daytime fluxes but still downward. Analysis with a standard resistance model shows that loss of PAN to the canopy is not controlled by turbulent or molecular diffusion. Stomatal uptake can account for 25 to 50% of the observed downward PAN flux. Vertical gradients in the PAN thermal decomposition (TD) rate explain a similar fraction of the flux, suggesting that a significant portion of the PAN flux into the forest results from chemical processes in the canopy. The remaining "unidentified" portion of the net PAN flux (~15%) is ascribed to deposition or reactive uptake on non-stomatal surfaces (e.g. leaf cuticles or soil). Shifts in temperature, moisture and ecosystem activity during the summer – fall transition alter the relative contribution of stomatal uptake, non-stomatal uptake and thermochemical gradients to the net PAN flux. Daytime PAN and MPAN exchange velocities are a factor of 3 smaller than those of PPN during the first two weeks of the measurement period, consistent with strong intra-canopy chemical production of PAN and MPAN during this period. Depositional loss of APNs can be 3–21% of the gross gas-phase TD loss depending on temperature. As a source of nitrogen to the biosphere, PAN deposition represents approximately 4–19% of that due to dry deposition of nitric acid at this site.http://www.atmos-chem-phys.net/9/615/2009/acp-9-615-2009.pdf |
| spellingShingle | G. M. Wolfe J. A. Thornton R. L. N. Yatavelli M. McKay A. H. Goldstein B. LaFranchi K.-E. Min R. C. Cohen Eddy covariance fluxes of acyl peroxy nitrates (PAN, PPN and MPAN) above a Ponderosa pine forest Atmospheric Chemistry and Physics |
| title | Eddy covariance fluxes of acyl peroxy nitrates (PAN, PPN and MPAN) above a Ponderosa pine forest |
| title_full | Eddy covariance fluxes of acyl peroxy nitrates (PAN, PPN and MPAN) above a Ponderosa pine forest |
| title_fullStr | Eddy covariance fluxes of acyl peroxy nitrates (PAN, PPN and MPAN) above a Ponderosa pine forest |
| title_full_unstemmed | Eddy covariance fluxes of acyl peroxy nitrates (PAN, PPN and MPAN) above a Ponderosa pine forest |
| title_short | Eddy covariance fluxes of acyl peroxy nitrates (PAN, PPN and MPAN) above a Ponderosa pine forest |
| title_sort | eddy covariance fluxes of acyl peroxy nitrates pan ppn and mpan above a ponderosa pine forest |
| url | http://www.atmos-chem-phys.net/9/615/2009/acp-9-615-2009.pdf |
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