Daniel A. Knopf Assistant Professor Ph.D., 2003, Swiss Federal Institute of Technology, Switzerland E-mail: Daniel.Knopf@stonybrook.edu Atmospheric Chemistry, Microphysics and Chemistry of Atmospheric Aerosols, Heterogeneous Atmospheric Chemistry and Kinetics, Instrument Development Knopf Laboratory Page

Research Interests

My research focuses on the physical and chemical properties of aerosol particles and their interaction with the atmosphere. Aerosol particles play a key role in air pollution, cloud formation, and global warming. Phase transitions of aerosol particles e.g. the formation of ice and its corresponding impact on the global radiation budget is one of the least understood processes in the atmosphere. Aerosol particles also provide a medium for gas-to-particle reactions, so-called heterogeneous reactions, which can significantly alter atmospheric chemistry. The Antarctic ozone hole is the most prominent example for efficient heterogeneous chemistry. Heterogeneous reactions can in turn change the physical and chemical properties of the particles, thus influencing air quality, cloud formation, and climate. In addition, these reactions can also contribute to new particle formation.

The growth, crystallization, nucleation, and freezing of aerosol particles are studied in the laboratory under atmospherically relevant conditions. The understanding of these particle phase transitions is crucial to accurately predict the effects of aerosol particles in the atmosphere. The aerosols studied here range from aqueous inorganic solution droplets to bio-aerosols. In the laboratory phase transitions of aerosol particles are investigated using a novel aerosol nucleation cell coupled to an optical microscope. Continuous development of these experimental techniques is performed to improve our understanding of the microphysical and chemical processes that govern atmospheric aerosol particles.

Heterogeneous reactions, e. g. oxidation mechanisms, also termed aging processes, of particles by atmospheric trace gases such as O₃, NO₃, and OH are investigated in the laboratory. These reactions can lead not only to changes in the physical and chemical properties of the particles but also to oxygenated volatile organic compounds which both affect atmospheric chemistry, air quality, particle formation, and health related issues. The impact of these heterogeneous reactions on the growth and freezing of the particles is studied. Heterogeneous reactions are investigated using a home made chemical ionization mass spectrometer coupled to aerosol flow reactors and coated wall flow reactors.

Selected Publications

Cosman, L. M., Knopf, D. A., Bertram, A. K., N2O5 reactive uptake on aqueous sulfuric acid solutions coated with branched and straight-chain insoluble organic surfactants, , J. Phys. Chem. A, 112, 2386-2396, 2008.

Knopf, D. A., Cosman, L. M., Mousavi, P., Mokamati, S., Bertram A. K., A rectangular channel flow reactor for studying reactions on liquid surfaces coated by an organic monolayer: methods and initial results, J. Phys. Chem. A, 111, 11021-11032, 2007.

Knopf, D. A., Reply to “Comment “Do NAD and NAT form in liquid stratospheric aerosols by pseudo-heterogeneous nucleation?"", J. Phys. Chem. A, 111, 1376-1377, 2007.

Knopf, D. A., Mak, J., Gross, S., Bertram, A. K., Does Atmospheric Processing of Saturated Hydrocarbon Surfaces by NO3 Lead to Volatilization?, Geophys. Res. Lett., 33, L17816, 2006.

Knopf, D. A., Koop, T., Heterogeneous Nucleation of Ice on Surrogates of Mineral Dust, J. Geophys. Res., 111 (D12), D12201, 2006.

Knopf, D. A., Do NAD and NAT form in liquid stratospheric aerosols by pseudo-heterogeneous nucleation?, J. Phys. Chem. A, 110, 5745-5750, 2006.

Dymarska, M., Murray, B. J., Sun, L., Eastwood, M., Knopf, D. A., Bertram, A. K., Ice nucleation on soot at temperatures relevant for the lower troposphere, J. Geophys. Res., 111 (D4), D04204, 2006.

Knopf, D. A., Anthony, L. M., Bertram A. K., Reactive Uptake of O3 by Multicomponent and Multiphase Mixtures Containing Oleic Acid, J. Phys. Chem. A, 109, 5579-5589, 2005.

Murray, B. J., Knopf, D. A., Bertram A. K., The formation of cubic ice under conditions relevant to Earth's atmosphere, Nature, 434, 202-205, 2005.

Knopf, D. A., Luo B. P., Krieger, U. K., Koop, T., Reply to “Comment on ‘Thermodynamic Dissociation Constant of the Bisulfate Ion from Raman and Ion Interaction Modeling Studies of Aqueous Sulfuric Acid at Low Temperature”’, J. Phys. Chem. A, 109, 2707-2709, 2005.

Parsons, M. T., Knopf, D. A., Bertram, A. K., Deliquescence and Crystallization of Ammonium Sulfate Particles Internally Mixed with Water-Soluble Organic Compounds, J. Phys. Chem. A, 108, 11600-11608, 2004.

Knopf, D. A., Luo B. P., Krieger, U. K., Koop, T., Thermodynamic Dissociation Constant of the Bisulfate Ion from Raman and Ion Interaction Modeling Studies of Aqueous Sulfuric Acid at Low Temperatures, J. Phys. Chem. A, 107, 4322-4332, 2003.

Knopf, D. A., Koop, T., Luo B. P., Weers, U. G., Peter, T., Homogeneous nucleation of NAD and NAT in liquid stratospheric aerosols: insufficient to explain denitrification, Atmos. Chem. Phys., 2, 207-214, 2002.

Zink P., Knopf, D. A., Schreiner, J., Mauersberger, K., Möhler, O., Saathof, H., Seifert, M., Tiede, R., Schurath, U., Cryo-chamber simulation of stratospheric H2SO4/H2O  particles: Composition analysis and model comparison, Geophys. Res. Lett., 11, Vol. 29, 46-1-46-4, 2002.

Schreiner J., Voigt, C., Zink, P., Kohlmann, A., Knopf, D., Weisser, C., Budz, P., Mauersberger, K., A Mass Spectrometer System for Analysis of Polar Stratospheric Aerosols, Rev. Sci. Inst., 73, 446-452, 2002.

Knopf, D. A., Zink, P., Schreiner J., Mauersberger, K., Calibration of an Aerosol Composition Mass Spectrometer with Sulfuric Acid Water Aerosol, Aerosol Sci. Technol., 35, 924-928, 2001.