Superfund Research Program
Combustion Processes: Emissions, Monitoring, and Intervention
Project Leader: Catherine P. Koshland
Grant Number: P42ES004705
Funding Period: 1995 - 2006
Final Progress Reports
Small particles from combustion adversely affect human health and contribute to climate change. In addition, recent growth in the field of nanoparticle production raises questions about its potential adverse impact on human health and necessitates improved methods to measure accurately the chemical composition of particles and other physical parameters. This project has focused in part on developing real-time, in situ laser diagnostic techniques as well as other methods to detect hazardous and/or toxic species.
The fundamental mechanisms and processes involved in laser-particle interactions are not well understood, and even less is known when nano-particles are involved. Dr. Koshland and her research team are studying the formation, control, and measurement of these particles using ultraviolet laser light. They use 193 nm laser light, which fragments the particles into atoms, ions, molecules, and smaller particles, and measure light emitted by the fragments. They also observe how the size distribution of the particles changes, and found that they could synthesize nanoparticles in the 5 to 50 nm range with a controlled size and morphology. They have measured soot, sodium chloride, polystyrene, gold, and salt-coated soot particles, and determined that a similar photolytic disintegration mechanism dominates for all of these particles, even though they vary widely in physical and chemical properties. They developed a scaling parameter, called the photon-atom ratio (PAR), which can be used to analyze the interactions. Using PAR values, the researchers determined that UV photolysis is an extremely efficient method to dissociate particles, and that 193 nm laser photolysis is a promising technique for nanostructure synthesis and analysis.
The growing field of nanotechnology offers several intriguing possibilities for detecting many species of interest to Superfund sites and their associated research projects. The different and sometimes unique behavior of materials as their dimensions shrink below 100 nanometers can be exploited to produce sensors that are compact, less expensive, and use little power. Project investigators have started research using gold nanoparticles in the 6 – 20 nm diameter range to measure atomic mercury. When mercury atoms combine with the gold nanoparticles, there is a measurable change in the visible absorption spectrum – both the peak wavelength and absorption strength can be used to quantify the amount of mercury.
Project investigators also invented a downflow diffusion burner, which can be used to reproducibly produce soot and other particles with different size distributions and concentrations. The inverted flame is a consistent source of soot particles that may be used for many applications. Particle sizes and concentrations are in the range of those generated by modern engines, which makes it a good source of particles for inhalation health studies. This flame could also be used as a source of particles for developing or comparing particle sizing techniques.