Alexei Khalizov
| Title | Assistant Research Scientist |
| Research Interests | Gas-phase processes leading to the formation and growth of aerosol particles in the atmosphere. Alteration of hygroscopic and optical properties of atmospheric aerosols upon their physical and chemical processing (aging). |
| Education | Ph.D., Physical Chemistry, Ufa Research Center of the Russian Academy of Sciences, 1997 |
| Office Location | 1112A |
| Office Phone | 979-458-1822 |
| Fax | 979-862-4466 |
| khalizov@tamu.edu | |
| Mailing Address |
Department of Atmospheric Sciences Texas A&M University 3150 TAMU College Station, TX 77843-3150 |
Research Interests
(1) Changes in hygroscopic and optical properties of carbon soot aerosols upon aging. Aerosol particles affect climate by scattering and absorbing solar and thermal radiation (direct aerosol effect), and by acting as cloud condensation nuclei (CCN), (indirect aerosol effect). Once emitted or formed, aerosol particles undergo complex chemical and physical transformations, changing their optical and hygroscopic properties. In laboratory experiments (H-TDMA and DMA-APM) we discovered that initially hydrophobic carbon soot particles within a time period of a few days can acquire sufficient sulfate coating to become efficient CCN (Cloud Condensation Nuclei). The internal mixing with sulfuric acid has a profound effect on the optical properties of soot since a transparent coating increases the absorption efficiency of an insoluble core. To quantify this, we are measuring the extinction and scattering of light by fresh and aged soot particles using a Cavity Ring-Down Spectrometer (CRDS) and a Nephelometer in combination with H-TDMA.
(2) The enhancement of new particle formation upon nucleation of gaseous sulfuric acid in the presence of organic acids. Despite the intensive research over the last decade, the mechanism of new particles formation in the atmosphere is still unclear. Field measurements show atmospheric nucleation events for sulfuric acid concentration of 107 molecules cm-3. Similar nucleation rates were obtained in chamber and flow tube studies using sulfuric acid generated in situ upon dark or photochemical oxidation of sulfur dioxide. In contrast, in the experiments where sulfuric acid vapor was sampled from liquid H2SO4, much higher concentrations on the order of 1010 molecules cm-3 were necessary to produce new particles. A recent study from our laboratory has shown that minute amounts of organic acids greatly enhance the nucleation of sulfuric acid with water vapor. We are currently quantitatively mapping the nucleation rates by varying the concentrations of all three components (sulfuric acid, organic acid, and water). An ID-CIMS (ion drift-chemical ionization mass spectrometer) technique is used to measure the absolute concentrations of sulfuric and organic acids in the range of 10 ppt – 1 ppb, on-line with the nucleation experiment.
Selected Publications
A. F. Khalizov, M. E. Earle, W. J.W. Johnson, G. D. Stubley and J. J. Sloan, ‘Modeling of flow dynamics in laminar aerosol flow tubes’, (2006) Journal of Aerosol Science, in press, corrected proof, available online
A. Y. Zasetsky, A. F. Khalizov, M. E. Earle, J. J. Sloan, ‘Frequency Dependent Complex Refractive Indices of Supercooled Liquid Water and Ice Determined from Aerosol Extinction Spectra’, (2005) Journal of Physical Chemistry A, 109(14)
A. Y. Zasetsky, A. F. Khalizov, J. J. Sloan (2004). ‘Local order and dynamics in supercooled water: A study by IR spectroscopy and molecular dynamic simulations’, Journal of Chemical Physics, 121(14), 6941
A. F. Khalizov, B. Viswanathan, P. Larregaray and P. A. Ariya (2003). ‘A Theoretical Study on the Reactions of Hg with Halogens: Atmospheric Implications.’ Journal of Physical Chemistry A, 107(33), 6360
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