Single particle analysis of smoke aerosols during the Summer 2002 Yosemite Aerosol Characterization Study
EMSL Project ID
4997
Abstract
The role of smoke aerosols from biomass burning in visibility degradation is poorly understood because few studies exist that have fully characterized their physical, optical, chemical and hygroscopic properties. The Yosemite Aerosol Characterization Study of 2002 occurred during an active fire season in the western U.S., and provides an opportunity to investigate many unresolved issues related to carbonaceous aerosols in the atmosphere. Measurements during the study included high time resolution aerosol chemical composition, size distributions, hygroscopicity, optical properties, tracers for wood smoke impacts, and aerosol samples on grid-supported thin films. Estimating the radiative effects of aerosols requires information about particle size, chemical composition, and shape. Assumptions about these properties are often made because these details are not always known. These assumptions include the hygroscopic properties of aerosols, degree of mixing (internal versus external mixtures), and particle shape. These issues are often treated individually, however, in reality they would be inter-related. For example, the degree of mixing can affect hygroscopic properties, and particle shape may be dependent on whether aerosols have deliquesced. This proposal is designed to investigate these issues on a single particle basis, and will serve to provide information related to the radiative effects of smoke aerosols and their contribution to visibility degradation.
The hygroscopic properties of aerosols measured during the Yosemite study suggest limited water uptake during smoke episodes. SEM-EDX analysis as a function of time and relative humidity will be used to investigate the hygroscopic nature of single particles during these time periods. We will investigate whether the relative humidity of deliquescence varies depending on the aerosol size, composition, degree of mixing, or amount of organics (or inorganics) present in the aerosol.
The degree of internal versus external mixing will be explored to understand how organic and inorganic aerosols exist together. An inorganic core may be coated with an organic shell (or vice-versa) or two separate pieces connected together, or particles may exist as ?pure? inorganic or organic compounds. The degree of mixing of these particles will affect their hygroscopic and radiative properties. The shape of the individual particles will also be investigated because visibility estimates are computed assuming spherical particles.
The aerosol samples will be analyzed for composition with CCSEM/EDX methods to understand changes in individual aerosol composition and possible relations between aerosol species during smoke episodes. For example, soluble potassium was correlated with organic carbon during the Yosemite study, and is a possible biomass smoke indicator.
Project Details
Project type
Exploratory Research
Start Date
2003-10-01
End Date
2006-10-08
Status
Closed
Released Data Link
Team
Principal Investigator
Related Publications
Hand, J. L. et al. (2005), Optical, physical, and chemical properties of tar balls observed during the Yosemite Aerosol Characterization Study, Journal of Geophysical Research (Atmospheres), 110, D21210, doi:10.1029/2004JD005728
Smercina D.N., A. Bowsher, S. Evans, M.L. Friesen, E. Eder, D.W. Hoyt, and L.K. Tiemann. 2021. "Switchgrass Rhizosphere Metabolite Chemistry Driven by Nitrogen Availability." Phytobiomes Journal 5, no. 1:88-96. PNNL-SA-152631. doi:10.1094/PBIOMES-09-19-0055-FI