Development of a Novel Condensation Nuclei Counter and Application to Ultrafine Particle FormationEPA Grant Number: R826654
Title: Development of a Novel Condensation Nuclei Counter and Application to Ultrafine Particle Formation
Investigators: Hopke, Philip K. , Wang, Hwa-Chi
Current Investigators: Hopke, Philip K. , Lee, Doh-Won , Wang, Hwa-Chi , Mavliev, Rashid , Smoridin, Vladimir
Institution: Clarkson College , Illinois Institute of Technology
EPA Project Officer: Hahn, Intaek
Project Period: October 1, 1998 through September 30, 2001
Project Amount: $393,657
RFA: Exploratory Research - Environmental Chemistry (1998) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Sustainability , Land and Waste Management , Air , Engineering and Environmental Chemistry
Ultrafine particles play an important role in atmospheric processes such as cloud formation, and thus in indirect effects on the albedo and the radiation balance, and ozone depletion. The health effect of small particles also became a concern in recent years. Although several formation mechanisms for small particles are discussed in the literature, complete theoretical models are not available. One reason is that the atmosphere is a very complicated multi-phase and multi-component system with strong cross-influences and a complete, detailed description of this system is practically impossible. Any simplified description can only be proposed based on solid experimental data. Thus, it is important to examine experimentally the formation of ultrafine particles in the atmosphere. Limited experimental techniques are available to investigate particle formation process. Ideal experiments would include the measurements of all relevant gas phase (trace gases, precursors, and reactive gases), aerosol phase (the number concentration, size distribution, chemical composition) parameters as well as the rate of gas-to- particle conversion, and temperature, pressure, radiation fields, etc. In order to move toward more ideal experiments, an improved condensation nuclei counter will be developed to measure nucleation of model compounds onto ions and charged particles of various kinds to examine the relationship between molecular properties of the working fluid and the particles.
Condensation nuclei counter (CNCs) detection efficiency is sensitive to particle size near the detection limit. This principle will be used in this project. We will develop a novel CNC which scans a range of supersaturations via turbulent mixing and uses different working fluids to investigate vapor-to-particle conversion. Factors affecting ion-induced and heterogeneous nucleation for different type of nuclei and working fluids will be examined by turbulent and laminar flow systems. From these experimental results, we will develop models correlating the chemical properties of the fluid, particles, and ions with their nucleation activities.
The results will include: development of a scanning CNC which measures the onset of heterogeneous nucleation in the presence of nuclei or ions using different working fluids and comparisons with a flow diffusion cloud chamber; correlation of the nucleation rates for particles or ions with the physical chemical nature of commonly found nuclei; a self-calibrating CNC using homogeneous nucleation as a reference for unattended monitoring of particulate matter; effects of composition on the detection efficiency for different fluids; improvement of heterogeneous nucleation theory; and optimization of CNCs with respect to the particle composition.