Rapid deposition of oxidized biogenic compounds to a temperate forest
Abstract
We report fluxes and dry deposition velocities for 16 atmospheric compounds above a southeastern United States forest, including: hydrogen peroxide (H_2O_2), nitric acid (HNO_3), hydrogen cyanide (HCN), hydroxymethyl hydroperoxide, peroxyacetic acid, organic hydroxy nitrates, and other multifunctional species derived from the oxidation of isoprene and monoterpenes. The data suggest that dry deposition is the dominant daytime sink for small, saturated oxygenates. Greater than 6 wt %C emitted as isoprene by the forest was returned by dry deposition of its oxidized products. Peroxides account for a large fraction of the oxidant flux, possibly eclipsing ozone in more pristine regions. The measured organic nitrates comprise a sizable portion (15%) of the oxidized nitrogen input into the canopy, with HNO_3 making up the balance. We observe that water-soluble compounds (e.g., strong acids and hydroperoxides) deposit with low surface resistance whereas compounds with moderate solubility (e.g., organic nitrates and hydroxycarbonyls) or poor solubility (e.g., HCN) exhibited reduced uptake at the surface of plants. To first order, the relative deposition velocities of water-soluble compounds are constrained by their molecular diffusivity. From resistance modeling, we infer a substantial emission flux of formic acid at the canopy level (∼1 nmol m^(−2)⋅s^(−1)). GEOS−Chem, a widely used atmospheric chemical transport model, currently underestimates dry deposition for most molecules studied in this work. Reconciling GEOS−Chem deposition velocities with observations resulted in up to a 45% decrease in the simulated surface concentration of trace gases.
Additional Information
Copyright © 2015 National Academy of Sciences. Freely available online through the PNAS open access option. Edited by Mark H. Thiemens, University of California, San Diego, La Jolla, CA, and approved December 22, 2014 (received for review September 28, 2014) Published online before print January 20, 2015 We thank the organizers and committee members of the SOAS campaign: A. G. Carlton, A. H. Goldstein, J. L. Jimenez, R. W. Pinder, J. de Gouw, B. J. Turpin, and A. B. Guenther. We acknowledge C. J. Groff at Purdue University for his help with leaf area index measurements and tree surveys. We thank D. J. Jacob and the Atmospheric Chemistry Modeling Group at Harvard University for making GEOS−Chem available for this work. Meteorological data used in the GEOS−Chem simulations were provided by the Global Modeling and Assimilation Office at NASA Goddard Space Flight Center. We acknowledge funding from the National Science Foundation (NSF) under Grant AGS-1240604 and NSF Postdoctoral Research Fellowship program Award AGS-1331360. Financial and logistical support for SOAS was provided by the NSF, the Earth Observing Laboratory at the National Center for Atmospheric Research (operated by NSF), the personnel at Atmospheric Research and Analysis, and the Electric Power Research Institute. Author contributions: P.O.W. designed research; T.B.N., J.D.C., A.P.T., J.M.S.C., F.P., and G.M.W. performed research; J.D.C. contributed new reagents/analytic tools; T.B.N. analyzed data; and T.B.N. and P.O.W. wrote the paper. The authors declare no conflict of interest. This article is a PNAS Direct Submission. This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1418702112/-/DCSupplemental.Attached Files
Published - E392.full.pdf
Supplemental Material - pnas.1418702112.sapp.pdf
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Additional details
- PMCID
- PMC4321284
- Eprint ID
- 53113
- DOI
- 10.1073/pnas.1418702112
- Resolver ID
- CaltechAUTHORS:20141222-144149377
- NSF
- AGS-1240604
- NSF Postdoctoral Fellowship
- AGS-1331360
- National Center for Atmospheric Research (NCAR)
- Electric Power Research Institute (EPRI)
- Created
-
2015-01-20Created from EPrint's datestamp field
- Updated
-
2021-11-10Created from EPrint's last_modified field
- Caltech groups
- Division of Geological and Planetary Sciences