Atmos. Chem. Phys. Discuss., 11, 17759-17788, 2011
www.atmos-chem-phys-discuss.net/11/17759/2011/
doi:10.5194/acpd-11-17759-2011
© Author(s) 2011. This work is distributed
under the Creative Commons Attribution 3.0 License.
Review Status
This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Predicting the relative humidities of liquid-liquid phase separation, efflorescence, and deliquescence of mixed particles of ammonium sulfate, organic material, and water using the organic-to-sulfate mass ratio of the particle and the oxygen-to-carbon elemental ratio of the organic component
A. K. Bertram1, S. T. Martin2, S. J. Hanna1, M. L. Smith2, A. Bodsworth1, Q. Chen2, M. Kuwata2, A. Liu1, Y. You1, and S. R. Zorn2
1Department of Chemistry, University of British Columbia, Vancouver, BC CAN V6T 1Z1, Canada
2School of Engineering and Applied Sciences & Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts, USA

Abstract. Individual particles that on a mass basis consist dominantly of the components ammonium sulfate, organic material, and water are a common class of submicron particles found in today's atmosphere. Here we use (1) the organic-to-sulfate (org:sulf) mass ratio of the overall particle and (2) the oxygen-to-carbon (O:C) elemental ratio of the organic component as input variables in parameterisations that predict the critical relative humidity of several different types of particle phase transitions. These transitions include liquid-liquid phase separation (SRH), efflorescence (ERH), and deliquescence (DRH). Experiments were conducted by optical microscopy for 11 different oxygenated organic-ammonium sulfate systems covering the range 0.1 < org:sulf <12.8 and 0.29 < O:C < 1.33. These new data, in conjunction with other data already available in the literature, were used to develop the parameterisations SRH(org:sulf, O:C), ERH(org:sulf, O:C), and DRH(org:sulf, O:C). The parameterisations correctly predicted SRH within 15 % RH for 86 % of the measurements, ERH within 5 % for 86 % of the measurements, and DRH within 5 % for 95 % of the measurements. The applicability of the derived parameterisations beyond the training data set was tested against observations for organic-sulfate particles produced in an environmental chamber. The organic component consisted of secondary organic material produced by the oxidation of isoprene, α-pinene, and β-caryophyllene. The predictions of the parameterisations were also tested against data from the Southern Great Plains, Oklahoma, USA. The observed ERH and DRH values for both the chamber and field data agreed within 5 % RH with the value predicted by the parameterisations using the measured org:sulf and O:C ratios as the input variables.

Citation: Bertram, A. K., Martin, S. T., Hanna, S. J., Smith, M. L., Bodsworth, A., Chen, Q., Kuwata, M., Liu, A., You, Y., and Zorn, S. R.: Predicting the relative humidities of liquid-liquid phase separation, efflorescence, and deliquescence of mixed particles of ammonium sulfate, organic material, and water using the organic-to-sulfate mass ratio of the particle and the oxygen-to-carbon elemental ratio of the organic component, Atmos. Chem. Phys. Discuss., 11, 17759-17788, doi:10.5194/acpd-11-17759-2011, 2011.
 
Search ACPD
Discussion Paper
XML
Citation
Final Revised Paper
Share