Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published October 12, 2011 | Published + Supplemental Material
Journal Article Open

Origins and composition of fine atmospheric carbonaceous aerosol in the Sierra Nevada Mountains, California


In this paper we report chemically resolved measurements of organic aerosol (OA) and related tracers during the Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX) at the Blodgett Forest Research Station, California from 15 August–10 October 2007. OA contributed the majority of the mass to the fine atmospheric particles and was predominately oxygenated (OOA). The highest concentrations of OA were during sporadic wildfire influence when aged plumes were impacting the site. In situ measurements of particle phase molecular markers were dominated by secondary compounds and along with gas phase compounds could be categorized into six factors or sources: (1) aged biomass burning emissions and oxidized urban emissions, (2) oxidized urban emissions (3) oxidation products of monoterpene emissions, (4) monoterpene emissions, (5) anthropogenic emissions and (6) local methyl chavicol emissions and oxidation products. There were multiple biogenic components that contributed to OA at this site whose contributions varied diurnally, seasonally and in response to changing meteorological conditions, e.g. temperature and precipitation events. Concentrations of isoprene oxidation products were larger when temperatures were higher during the first half of the campaign (15 August–12 September) due to more substantial emissions of isoprene and enhanced photochemistry. The oxidation of methyl chavicol, an oxygenated terpene emitted by ponderosa pine trees, contributed similarly to OA throughout the campaign. In contrast, the abundances of monoterpene oxidation products in the particle phase were greater during the cooler conditions in the latter half of the campaign (13 September–10 October), even though emissions of the precursors were lower, although the mechanism is not known. OA was correlated with the anthropogenic tracers 2-propyl nitrate and carbon monoxide (CO), consistent with previous observations, while being comprised of mostly non-fossil carbon (>75%). The correlation between OA and an anthropogenic tracer does not necessarily identify the source of the carbon as being anthropogenic but instead suggests a coupling between the anthropogenic and biogenic components in the air mass that might be related to the source of the oxidant and/or the aerosol sulfate. Observations of organosulfates of isoprene and α-pinene provided evidence for the likely importance of aerosol sulfate in spite of neutralized aerosol although acidic plumes might have played a role upwind of the site. This is in contrast to laboratory studies where strongly acidic seed aerosols were needed in order to form these compounds. These compounds together represented only a minor fraction (<1%) of the total OA mass, which may be the result of the neutralized aerosol at the site or because only a small number of organosulfates were quantified. The low contribution of organosulfates to total OA suggests that other mechanisms, e.g. NO_x enhancement of oxidant levels, are likely responsible for the majority of the anthropogenic enhancement of biogenic secondary organic aerosol observed at this site.

Additional Information

© 2011 the Author(s). This work is distributed under the Creative Commons Attribution 3.0 License. Published by Copernicus Publications on behalf of the European Geosciences Union. Received: 1 June 2011; Published in Atmos. Chem. Phys. Discuss.: 20 June 2011; Revised: 23 September 2011; Accepted: 26 September 2011; Published: 12 October 2011. Funding for UCB was provided by the National Science Foundation (NSF, Grant #0922562) and a University of California Agriculture and Natural Resources (ANR) core issue grant. AHG was partially supported by the Miller Institute in Basic Research in Science at the University of California Berkeley. DKF, KSD and JLJ were supported by NSF ATM-0919189. JBG and JDG were partially supported by the National Science Foundation under grant ATM-0516610. This work was partially performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Analyses at the University of Aarhus were partially funded by the NSF US-NORDIC biogenic secondary organic aerosol workshop program. The authors acknowledge Sierra Pacific Industries for the use of their land and the University of California, Berkeley, Center for Forestry, Blodgett Forest Research Station for cooperation in facilitating this research. The authors thank S. S. Cliff (University of California, Davis) for the loan of the high volume filter sampler. N. C. Bouvier-Brown (Loyola Marymount University, Los Angeles), Y. Zhao and E. C. Browne (University of California, Berkeley) for their help with filter collection. N. C. Bouvier-Brown is also thanked for providing the gas phase methyl chavicol data used in the factor analysis and D. M. Matross (University of California, Berkeley) for making the PTR-MS gradient measurements used to normalize the gas phase methyl chavicol data used in the factor analysis. A. Frossard (University of California, San Diego) for assistance with TAG and Brian LaFranchi (Lawrence Livermore National Laboratory) for writing the data merging code. We are grateful to Nathan Eddingsaas (Caltech) for providing the BEPOX-derived organosulfate standard and Yoshiteru Iinuma (Leibniz-Institut fuer Troposphaerenforschung) for providing the -pinene oxide derived organosulfate standard used for quantification of IEPOX- and -pinene-derived organosulfates, respectively, by LC/ESI-MS techniques. Additionally, we would also like to thank Man Nin Chan and Katherine Schilling (Caltech) for their assistance with filter extractions and UPLC/ESI-HR-TOFMS analyses. Edited by: N. M. Donahue.

Attached Files

Published - Worton2011p16298Atmos_Chem_Phys.pdf

Supplemental Material - acp-11-10219-2011-supplement.pdf


Files (10.9 MB)
Name Size Download all
2.7 MB Preview Download
8.2 MB Preview Download

Additional details

August 19, 2023
October 24, 2023