Chemistry of atmospheric aerosol particles and impact on processes such as urban smog formation, toxic pollutant chemistry and transport, acid rain, and global climate change. We have recently developed a thermal desorption particle beam mass spectrometer for real-time characterization of particle chemical composition. This instrument is now being used in laboratory experiments along with other aerosol and gas measurement techniques to investigate fundamental processes responsible for gas-to-particle conversion in the atmosphere. The research is aimed at elucidating mechanisms by which gas-phase molecules (e.g. anthropogenic and biogenic organics, sulfur and nitrogen oxides) become incorporated into particulate material through photochemical reactions, homogeneous nucleation, and heterogeneous surface chemistry.
Tobias, H. J., and P. J. Ziemann. Compound identification in organic aerosols using temperature-programmed thermal desorption particle beam mass spectrometry. Anal. Chem. 71, 3428-3435 (1999).
Tobias, H. J., P. M. Kooiman, K. S. Docherty, and P. J. Ziemann. Real-time chemical analysis of organic aerosols using a thermal desorption particle beam mass spectrometer. Aerosol Sci. Technol. 33, 170-190 (2000).
Tobias, H. J., and P. J. Ziemann. Thermal desorption mass spectrometric analysis of organic aerosol formed from reactions of 1-tetradecene and O3 in the presence of alcohols and carboxylic acids. Env. Sci. Technol. 34, 2105-2115 (2000).
Tobias, H. J., K. S. Docherty, D. E. Beving, and P. J. Ziemann. Effect of relative humidity on the chemical composition of secondary organic aerosol formed from reactions of 1-tetradecene and O3. Env. Sci. Technol. 34, 2116-2125 (2000).
Tobias, H. J., D. E. Beving, P. J. Ziemann, H. Sakurai, M. Zuk, P. H. McMurry, D. Zarling, R. Waytulonis, and D. B. Kittelson. Chemical analysis of diesel engine nanoparticles using a nano-DMA/thermal desorption particle beam mass spectrometer. Env. Sci. Technol. 35, 2233-2243 (2001).
Docherty, K. S. and P. J. Ziemann. On-line, inlet-based trimethylsilane derivatization for gas chromatography of mono- and dicarboxylic acids. J. Chromatog. A 921, 265-275 (2001).
Tobias, H. J. and P. J. Ziemann. Kinetics of the gas-phase reactions of alcohols, aldehydes, carboxylic acids, and water with the C13 Criegee intermediates formed from ozonolysis of 1-tetradecene. J. Phys. Chem. A 105, 6129-6135 (2001).
Chattopadhyay, S., H. J. Tobias, and P. J. Ziemann. A method for measuring vapor pressures of low-volatility organic aerosol compounds using a thermal desorption particle beam mass spectrometer. Anal. Chem. 73, 3797-3803 (2001).
I teach an undergraduate course in aquatic chemistry and a graduate course in aerosol science that are offered through the Department of Environmental Sciences and the Department of Chemistry.