In situ measurements of water uptake by black carbon-containing aerosol in wildfire plumes

Anne E. Perring, Joshua P. Schwarz, Milos Z. Markovic, David W. Fahey, Jose L. Jimenez, Pedro Campuzano-Jost, Brett D. Palm, Armin Wisthaler, Tomas Mikoviny, Glenn Diskin, Glen Sachse, Luke Ziemba, Bruce Anderson, Taylor Shingler, Ewan Crosbie, Armin Sorooshian, Robert Yokelson, Ru Shan Gao

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23 Scopus citations

Abstract

Water uptake by black carbon (BC)-containing aerosol was quantified in North American wildfire plumes of varying age (1 to ~40 h old) sampled during the SEAC4RS mission (2013). A Humidified Dual SP2 (HD-SP2) is used to optically size BC-containing particles under dry and humid conditions from which we extract the hygroscopicity parameter, κ, of materials internally mixed with BC. Instrumental variability and the uncertainty of the technique are briefly discussed. An ensemble average κ of 0.04 is found for the set of plumes sampled, consistent with previous estimates of bulk aerosol hygroscopicity from biomass burning sources. The temporal evolution of κ in the Yosemite Rim Fire plume is explored to constrain the rate of conversion of BC-containing aerosol from hydrophobic to more hydrophilic modes in these emissions. A BC-specific κ increase of ~0.06 over 40 h is found, fit well with an exponential curve corresponding to a transition from a κ of 0 to a κ of ~0.09 with an e-folding time of 29 h. Although only a few percent of wildfire particles contain BC, a similar κ increase is estimated for bulk aerosol and the measured aerosol composition is used to infer that the observed κ change is driven by a combination of incorporation of ammonium sulfate and oxidation of existing organic materials. Finally, a substantial fraction of wildfire-generated BC-containing aerosol is calculated to be active as cloud condensation nuclei shortly after emission likely indicating efficient wet removal. These results can constrain model treatment of BC from wildfire sources.

Original languageEnglish
Pages (from-to)1086-1097
Number of pages12
JournalJournal of Geophysical Research
Volume122
Issue number2
DOIs
StatePublished - 2017

Funding

All data for the SEAC4RS project are publicly available at DOI 10.5067/Aircraft/SEAC4RS/Aerosol-TraceGas-Cloud. NOAA SP2 research conducted by A.P., M.M., J.S., R.S.G., and D.F. was supported by the NOAA Atmospheric Composition and Climate Program, the NASA Radiation Sciences Program, and the NASA Upper Atmosphere Research Program. A.S. and T.S. were funded by NASA grants NNX12AC10G, NNX14AP75G, and NNX14AK79H. P.C.J., B.D.P., and J.L.J. were supported by NASA grants NNX12AC03G and NNX15AT96G. R.Y. was supported by NASA Earth Science Division Awards NNX12AC20G and NNX14AP45G.

FundersFunder number
National Aeronautics and Space AdministrationNNX12AC03G, NNX14AK79H, NNX14AP45G, NNX12AC10G, NNX15AT96G, NNX12AC20G, NNX14AP75G
National Oceanic and Atmospheric Administration

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