RESEARCH

Atmospheric Chemistry (Aerosol) and Analytical Chemistry (Mass Spectrometry) Understanding atmospheric aerosols is important to understanding the effects of aerosol on climate, atmospheric composition, air quality, and human health. There are high uncertainties in the current global climate predictions largely because of our limited understanding of aerosols and clouds. Nucleation is a gas to particle conversion process in which solid or liquid aerosol particles form directly from gas phase species and thus is an important step in the chain reactions that lead to cloud formation, but the mechanisms are poorly understood. The current nucleation theories are also hampered by high uncertainties because of the lack of laboratory and atmospheric measurements. Our research is designed to overcome some of these shortcomings in the field to yield a better understanding of aerosol formation processes in the atmosphere. The current research projects include: (1) aerosol nucleation kinetics studies, (2) atmospheric observations of new particle formation at the ground level, (3) high altitude new particle formation studies in the upper troposphere and lower stratosphere, and (4) development of mass spectrometry for ammonia and organic compounds.   1. Kinetics Studies of Particle Formation with a Chemical Ionization Mass Spectrometer We study chemical processes of nucleation under the atmospheric conditions. In this experiment, we use a high-sensitivity Chemical Ionization Mass Spectrometer (CIMS) to measure low concentrations of aerosol precursors. We want to explore thermodynamic characteristics of nucleation. These results will provide information of immediate use to modelers who are trying to predict aerosol and cloud condensation nuclei concentrations. 2. Atmospheric Observations of New Particle Formation at the Ground Level From long-term, simultaneous measurements of aerosol particle sizes and aerosol precursors, we want to understand how gas phase precursors affect aerosol nucleation. We also want to see the effects of photochemistry, surface area and relative humidity on aerosol formation. We will compare our Kent data with nearby EPA SuperSites data. 3. High Altitude New Particle Formation Studies in the Upper Troposphere and Lower Stratosphere This is a currently ongoing field project supported by NSF. In the collaboration with the University of Denver and the National Center for Atmospheric Research (NCAR), we perform aerosol size measurements on a new NSF / NCAR GV High-Performance Instrumented Airborne Platform for Environmental Research (HIAPER) using DU aerosol instruments in NCAR. We also plan to employ our CIMS instrument to measure atmospheric sulfuric acids in the future. 4. Development of Mass Spectrometry for Ammonia and Organic Compounds There are hundreds of organic compounds in the atmosphere. These organic species, together with ammonia, can contribute to aerosol nucleation and growth. However, it is difficult to detect these compounds at atmospheric concentrations with currently available methods. We want to develop a CIMS technique to detect low concentrations of these compounds.

For further information on our research activities, please visit our group homepage.

Selected Publications:

1. L.-H. Young, D. R. Benson, F. R. Kamee, J. R. Pierce, H. Juninnen, M. Kulmala, S.-H. Lee, Laboratory studies of sulfric acid and water binary homogeneous nucleation: Evaluation of laboratory setup and preliminary results, Atmos. Chem. Phys. 8, 1-20, 2008.

2. David R. Benson, Li-Hao Young, F. Rifkha Kameel, Shan-Hu Lee, Laboratory-Measured Sulfuric Acid and Water Homogeneous Nucleation Rates from the SO2 + OH Reaction, Geophys. Res. Lett., 35, L11801, Doi:2008GL033387, 2008.

3. Lee, S.-H., L.-H. Young, D. R. Benson, M. Kulmala, H. Junninen, T. Suni, T. L. Campos, D. C. Rogers, J. Jensen, Observations of Nighttime New Particle Formation in the Troposphere, J. Geophys. Res., 113, D10210, Doi:2007jd009351, 2008.

4. David R. Benson, Li-Hao Young, Shan-Hu Lee, Teresa Campos, and Jorgen Jenson, The effects of air mass history on new particle formation in the free troposphere, Atmos. Chem. Phys. , 8, 3015-3024, 2008.

5. Heikki Junninen, Mira Hulkkonen, Ilona Riipinen, Tuomo Nieminen, Anne Hirsikko, Tanja Suni, Michael Boy, Shan-Hu Lee, Marko Vana, Hannes Tammet, Markku Kulmala, Observations on night time growth of atmospheric clusters, Tellus B, 60B, 365-371, 2008.

6. Young, L.-H., D. R. Benson, W. M. Montanaro, S.-H. Lee, L. L. Pan, D. C. Rogers, J. Jensen, J. L. Stith, C. A. Davis, T. L. Campos, K. P. Bowman, W. A. Cooper, L. R. Lait, Enhanced new particle formation observed in the northern midlatitude tropopause region, J. Geophys. Res. - Atmos, 112, Doi:10.1029/2006JD008109, 2007.

7. J. C. Wilson, S.-H. Lee, J. M. Reeves, C. A. Brock, H. H. Jonsson, B. G. Lafleur, M. Loewenstein, J. Podolske, E. Atlas, S. Wofsy, K. Boering, G. Toon, D. Fahey, K.K. Kelly, P. Bui, G. Diskin, G. Sachse, The establishment of steady-state aerosol distributions in the extra-tropical, lower stratosphere and the processes that maintain them, Atmos. Chem. Phys. Discuss., 8, 3665-3692, 2008. (in press for Atmos. Chem. Phys.)

8. Hamill, P., C. Brogniex, L. Thomason, T. Deshler, L. C. Antuna, D. Baumgardner, R. Bevilacqua, C. A. Brock, C. David, M. Fromm, D. Fussen, M. Hervig, C. A. Hostettler, S.-H. Lee, J. Mrenethaler, M. T. Osborn, G. B. Roga, J. M. Reeves, J. Rosen, J. C. Wilson, Chapter 3: Instrument Description, in Stratospheric Processes and Their Role in Global Climate (SPARC), A Project of WMO/ICSU/IOC World Climate Research Program: Assessment of Stratospheric Aerosol Properties (ASAP), Eds. L. Thomason, Th. Peter, SPARC Scientific Steering Group, February 2006, (available at http://www.atmosp.physics.utoronto.ca/SPARC/ASAP%20V3c1.pdf).

9. Lee, S.-H., J. C. Wilson, D. Baumgardner, R. L. Herman, E. M. Weinstock, B. G. LaFleur, G. Kok, B. Anderson, P. Lawson, B. Baker, A. Strawa, J. V. Pittman, J. M. Reeves1, T. Bui, New particle formation observed in the tropical/subtropical cirrus clouds, J. Geophys. Res., 109, Doi:10.1029/2004JD005033, 2004.

10. Lee, S.-H., J. M. Reeves, J. C. Wilson, D. E. Hunton, A. A. Viggiano, T. M. Miller, J. O. Ballenthin, L. R. Lait, Particle formation by ion nuclation in the upper troposphere and lower stratosphere, Science, 301, 1886-1889, 2003.

11. Lee, S.-H., D. M. Murphy, D. S. Thomson, and A. M. Middlebrook, Nitrate and oxidized organics in single particle mass spectra during the 1999 Atlanta Supersites project, J. Geophys. Res., 108, doi:10.1029/2001JD001455, 2003.

12. Middlebrook, A. M., D. M. Murphy, S-H. Lee, D. S. Thomson, , K. A. Prather, R. J. Wenzel, D.-Y. Liu, D. J. Phares, K. Rhoads, A. S. Wexler, M. V. Jonston, J. L. Jimenez, J. T. Jayne, D. R. Worsnop, I. Yourshaw, J. H. Seinfeld, and R. C. Flagan, , A comparison of particle mass spectrometers during the 1999 Atlanta SuperSite Experiments, J. Geophys. Res., 108, doi:10.1029/JD2001000660, 2003.

13. Lee, S.-H., D. C. Leard, R. Zhang, L. T. Molina, and M. J. Molina, The HCl + ClONO2 reaction rate on various water ice surfaces, Chem. Phys. Lett., 315, 7-11. 1999.

14. Lee, S.-H., H. Akimoto, H. Nakane, S. Kurnosenko, and Y. Kinjo, Lower Tropospheric ozone trend observed in 1989-1997 at Okinawa, Japan, Geophys. Res. Lett., 25, 1637-1640, 1998.

Last Updated: 20 November 2008