Comprehensive airborne characterization of aerosol from a major bovine source A. Sorooshian1,*, S. M. Murphy1, S. Hersey1, H. Gates1, L. T. Padro2, A. Nenes2,3, F. J. Brechtel1,4, H. Jonsson5, R. C. Flagan1, and J. H. Seinfeld1 1Departments of Environmental Science and Engineering and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA 2School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, USA 3School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA 4Brechtel Manufacturing Inc., Hayward, CA, USA 5Center for Interdisciplinary Remotely-Piloted Aircraft Studies, Naval Postgraduate School, Monterey, CA, USA *now at: Cooperative Inst. for Research in the Atmosphere (CIRA), Colorado State University, Fort Collins, CO, USA
Abstract. We report an extensive airborne characterization of aerosol downwind of a massive
bovine source in the San Joaquin Valley (California) on two flights during July 2007.
The Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin
Otter probed chemical composition, particle size distribution, mixing state, sub-
and supersaturated water uptake behavior, light scattering properties, and the
interrelationship between these parameters and meteorology. Total PM1.0 levels
and concentrations of organics, nitrate, and ammonium were enhanced in the plume
from the source as compared to the background aerosol. Organics dominated the
plume aerosol mass (~56–64%), followed either by sulfate or nitrate,
and then ammonium. Particulate amines were detected in the plume aerosol by a
particle-into-liquid sampler (PILS) and via mass spectral markers in the Aerodyne
C-ToF-AMS. Amines were found to be a significant atmospheric base even in the
presence of ammonia; particulate amine concentrations are estimated as at least
14–23% of that of ammonium in the plume. Enhanced sub- and supersaturated water
uptake and reduced refractive indices were coincident with lower organic mass
fractions, higher nitrate mass fractions, and the detection of amines. The
likelihood of suppressed droplet growth owing to kinetic limitations from hydrophobic
organic material is explored. After removing effects associated with size
distribution and mixing state, the normalized activated fraction of cloud
condensation nuclei (CCN) increased as a function of the subsaturated hygroscopic
growth factor, with the highest activated fractions being consistent with
relatively lower organic mass fractions and higher nitrate mass fractions.
Subsaturated hygroscopic growth factors for the organic fraction of the aerosol
are estimated based on employing the Zdanovskii-Stokes Robinson (ZSR) mixing rule.
Representative values for a parameterization treating particle water uptake in
both the sub- and supersaturated regimes are reported for incorporation into
Citation: Sorooshian, A., Murphy, S. M., Hersey, S., Gates, H., Padro, L. T., Nenes, A., Brechtel, F. J., Jonsson, H., Flagan, R. C., and Seinfeld, J. H.: Comprehensive airborne characterization of aerosol from a major bovine source, Atmos. Chem. Phys., 8, 5489-5520, doi:10.5194/acp-8-5489-2008, 2008.