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Title: Aerosol optical hygroscopicity measurements during the 2010 CARES campaign

Measurements of the effect of water uptake on particulate light extinction or scattering made at two locations during the 2010 Carbonaceous Aerosols and Radiative Effects Study (CARES) study around Sacramento, CA are reported. The observed influence of water uptake, characterized through the dimensionless optical hygroscopicity parameter γ, is compared with calculations constrained by observed particle size distributions and size-dependent particle composition. A closure assessment has been carried out that allowed for determination of the average hygroscopic growth factors (GFs) at 85% relative humidity and the dimensionless hygroscopicity parameter κ for oxygenated organic aerosol (OA) and for supermicron particles (defined here as particles with aerodynamic diameters between 1 and 2.5 microns), yielding κ = 0.1–0.15 and 0.9–1.0, respectively. The derived range of oxygenated OA κ values are in line with previous observations. The relatively large values for supermicron particles is consistent with substantial contributions of sea-salt-containing particles in this size range. Furthermore, analysis of time-dependent variations in the supermicron particle hygroscopicity suggest that atmospheric processing, specifically chloride displacement by nitrate and the accumulation of secondary organics on supermicron particles, can lead to substantial depression of the observed GF.
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  1. Portland State Univ., Portland, OR (United States)
  2. Portland State Univ., Portland, OR (United States); National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States)
  3. Univ. of California, Davis, CA (United States)
  4. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  5. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  6. Univ. of California, Davis, CA (United States); Swiss Federal Labs for Materials Science and Technology, Dubendorf (Switzerland)
Publication Date:
Report Number(s):
PNNL-SA-107647; DOE-UCD-SC0008937-1
Journal ID: ISSN 1680-7324; KP1701000
Grant/Contract Number:
SC0008937; FG02-11ER65293; AC05-76RL01830
Published Article
Journal Name:
Atmospheric Chemistry and Physics (Online)
Additional Journal Information:
Journal Name: Atmospheric Chemistry and Physics (Online); Journal Volume: 15; Journal Issue: 8; Journal ID: ISSN 1680-7324
European Geosciences Union
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Univ. of California, Davis, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1182860; OSTI ID: 1413652