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Atmos. Chem. Phys. Discuss., 8, 6903-6947, 2008
www.atmos-chem-phys-discuss.net/8/6903/2008/ doi:10.5194/acpd-8-6903-2008 © Author(s) 2008. This work is distributed under the Creative Commons Attribution 3.0 License. |
Laboratory studies of H2SO4/H2O binary homogeneous nucleation from the SO2+OH reaction: evaluation of the experimental setup and preliminary results
1Kent State University, Chemistry Department, Kent, OH 44240, USA
2China Medical University, Department of Occupational Safety and Health, Taichung, Taiwan
Abstract. We have developed a new laboratory nucleation setup to study binary homogeneous nucleation (BHN) of sulphuric acid and water (H2SO4/H2O). Here we provide a detailed evaluation of this new experimental setup and also discuss our preliminary results by comparing with other laboratory studies. H2SO4 is produced from the SO2+OH →HSO3 reaction and OH radicals are produced from water vapor UV absorption. The residual H2SO4 concentrations ([H2SO4]) are measured at the end of the fast flow nucleation reactor with a chemical ionization mass spectrometer. The measured BHN rates (J) ranged from 0.02 and 550 cm−3 s−1 at the residual [H2SO4] from 108 to 1010 cm−3, a temperature of 288 K and relative humidity (RH) from 6 to 23%; J increased with increasing [H2SO4] and RH. J also showed a power dependence on [H2SO4] with the exponential power of 3 to 8. These results are consistent with other laboratory studies under similar [H2SO4] and RH, but different from atmospheric field observations which showed that particle number concentrations are often linearly dependent on [H2SO4]. Both particle sizes and number concentrations increased with increasing [H2SO4], RH, and nucleation time, consistent with the predictions from nucleation theories. Particle growth rates were estimated between 28 to 127 nm h−1, much higher than those seen from atmospheric field observations, because of the higher [H2SO4] used in our study. While these experimental results demonstrate a validation of our laboratory setup, there are also technical difficulties associated with nucleation studies, including wall loss and H2SO4 measurements.
Citation: Young, L.-H., Benson, D. R., Kameel, F. R., and Lee, S.-H.: Laboratory studies of H2SO4/H2O binary homogeneous nucleation from the SO2+OH reaction: evaluation of the experimental setup and preliminary results, Atmos. Chem. Phys. Discuss., 8, 6903-6947, doi:10.5194/acpd-8-6903-2008, 2008.