Novel method of generation of Ca(HCO3)2 and CaCO3 aerosols and first determination of hygroscopic and cloud condensation nuclei activation properties

D. F. Zhao, A. Buchholz, Th. F. Mentel, K.-P. Müller, J. Borchardt, A. Kiendler-Scharr, C. Spindler, R. Tillmann, A. Trimborn, T. Zhu, A. Wahner
2010 Atmospheric Chemistry and Physics Discussions  
Atmospheric mineral aerosols contain CaCO 3 as a reactive component. A novel method to produce CaCO 3 aerosol was developed by spraying Ca(HCO 3 ) 2 solutions, which were generated from CaCO 3 suspensions and CO 2 . By aerosol mass spectrometry the freshly sprayed aerosol was characterized to be Ca(HCO 3 ) 2 which under an-5 nealing in a tube furnace transformed into CaCO 3 . Transmission Electron Microscopy demonstrated that the particles produced were spherical. The method is easy to operate
more » ... is easy to operate and was able to generate aerosol of sufficient concentration and proper size for the study of physiochemical properties as was demonstrated for hygroscopicity and CCN activity measurements, and investigations of heterogeneous reactions of min-10 eral aerosol. Fresh Ca(HCO 3 ) 2 particles are somewhat more hygroscopic than CaCO 3 particles although both have small growth factors of 1.03 and 1.01, respectively, at 95% relative humidity. The CCN activity of Ca(HCO 3 ) 2 aerosol is remarkably higher than that of CaCO 3 aerosol and only slightly less than that of Ca(NO 3 ) 2 . Experiments in the Large Jülich Aerosol Chamber showed that Ca(HCO 3 ) 2 can exist for several 15 hours under dry atmospheric conditions which is in contrast to the current believe that Ca(HCO 3 ) 2 is unstable in the atmosphere. We conclude that Ca(HCO 3 ) 2 maybe be formed in the atmosphere in cloud droplets of activated mineral dust by reaction of CaCO 3 with CO 2 and H 2 O. The presence of Ca(HCO 3 ) 2 and as a consequence an enhanced CCN activity may alter the influence of mineral aerosol on global climate. 20 25 into the atmosphere (Jonas et al., 1995). While mineral aerosol is typically considered 8010
doi:10.5194/acpd-10-8009-2010 fatcat:pryxntjabnegxcv62bixje54vm