Articles | Volume 14, issue 12
Atmos. Chem. Phys., 14, 5959–5967, 2014
Atmos. Chem. Phys., 14, 5959–5967, 2014

Research article 17 Jun 2014

Research article | 17 Jun 2014

Cloud condensation nuclei (CCN) activity of aliphatic amine secondary aerosol

X. Tang1,2,*, D. Price1,2, E. Praske3,**, D. N. Vu1,2, K. Purvis-Roberts3, P. J. Silva4,5, D. R. Cocker III1,2, and A. Asa-Awuku1,2 X. Tang et al.
  • 1Department of Chemical and Environmental Engineering, Bourns College of Engineering, University of California, Riverside, CA 92521, USA
  • 2Bourns College of Engineering, Center for Environmental Research and Technology (CE-CERT), Riverside, CA 92507, USA
  • 3W.M. Keck Science Department of Claremont McKenna, Pitzer, and Scripps Colleges, 925 N. Mills Ave., Claremont, CA 91711, USA
  • 4USDA-ARS, 230 Bennett Lane, Bowling Green, KY 42104, USA
  • 5Department of Chemistry and Biochemistry, 0300 Old Main Hill, Utah State University, Logan, UT 84322-0300, USA
  • *now at: Department of Civil and Environmental Engineering, University of California, Berkeley, USA
  • **now at: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA

Abstract. Aliphatic amines can form secondary aerosol via oxidation with atmospheric radicals (e.g., hydroxyl radical and nitrate radical). The particle can contain both secondary organic aerosol (SOA) and inorganic salts. The ratio of organic to inorganic materials in the particulate phase influences aerosol hygroscopicity and cloud condensation nuclei (CCN) activity. SOA formed from trimethylamine (TMA) and butylamine (BA) reactions with hydroxyl radical (OH) is composed of organic material of low hygroscopicity (single hygroscopicity parameter, κ, ≤ 0.25). Secondary aerosol formed from the tertiary aliphatic amine (TMA) with N2O5 (source of nitrate radical, NO3) contains less volatile compounds than the primary aliphatic amine (BA) aerosol. As relative humidity (RH) increases, inorganic amine salts are formed as a result of acid–base reactions. The CCN activity of the humid TMA–N2O5 aerosol obeys Zdanovskii, Stokes, and Robinson (ZSR) ideal mixing rules. The humid BA + N2O5 aerosol products were found to be very sensitive to the temperature at which the measurements were made within the streamwise continuous-flow thermal gradient CCN counter; κ ranges from 0.4 to 0.7 dependent on the instrument supersaturation (ss) settings. The variance of the measured aerosol κ values indicates that simple ZSR rules cannot be applied to the CCN results from the primary aliphatic amine system. Overall, aliphatic amine aerosol systems' κ ranges within 0.2 < κ < 0.7. This work indicates that aerosols formed via nighttime reactions with amines are likely to produce hygroscopic and volatile aerosol, whereas photochemical reactions with OH produce secondary organic aerosol of lower CCN activity. The contributions of semivolatile secondary organic and inorganic material from aliphatic amines must be considered for accurate hygroscopicity and CCN predictions from aliphatic amine systems.

Final-revised paper