Aerosol Size Distributions for UAV Platforms

Statement of the Problem: The size-dependent concentration of airborne particles plays a critical role in the direct scattering and absorption of light, and in the physical characteristics, lifetime and spatial extent of clouds. These factors affect the earths radiation balance, and hence climate. Yet these effects are not adequately quantified, in part because of insufficient data on the size and concentration of atmospheric aerosols. Assessment of the global extent, size and concentration of airborne particles requires more portable instruments than currently available. How the Problem is Being Addressed: Proposed is a miniature sensor, suitable for UAV and tethered balloon deployments, for the real-time measurement of the size distribution and concentration of airborne particles in the critical size range from 10nm and 1000 nm in diameter. Our sensor will combine two novel technologies: (1) the opposed migration aerosol classifier developed at the California Institute of Technology; and (2) the self-sustaining laminar-flow water condensation particle counter and collector developed by our firm. The opposed migration aerosol classifier provides particle size-selection based on electrical mobility in an inherently compact form. The self-sustaining water condensation counter provides single particle detection, does not require liquid fill reservoirs, and can be operated in any orientation. Both technologies are compatible with devices small enough for UAV or balloon deployment. Reported parameters are particle number distribution, total number concentration, geometric mean diameter. Because our system uses electrical mobility sizing, it provides a measure of particle physical size, and is independent of particle refractive index or density. What is to be done in Phase I: Preliminary work presented in the proposal shows successful application of this approach to measurements in the size range from 10nm to 200nm at urban concentration levels. In Phase I we will (1) extend this size range to span from 10nm to 1000nm, (2) increase the sample rate to provide fast time response for remote, background level particle concentrations and (3) demonstrate the precision and accuracy through comparison with bench-top instruments. In Phase II we will design, construct and test an integrated system that we will be suitable for UAV monitoring. Commercial Applications and Other Benefits: The fields of use for the proposed instrument range from atmospheric aerosol research, climate research, epidemiology studies, air quality monitoring, industrial process control, and industrial hygiene. Currently there are no tools for measuring particle size and concentration from UAV or tethered balloon platforms, or in micro-environmental and industrial spaces where ultrafine particle exposure is of concern. As an unobtrusive long-term monitor our device will provide a tool for community monitoring in schools, offices, and homes, or serve as a more compact instrument for ground-based particulate monitoring. Keywords: ultrafine particles, particle size distribution, particle number concentration, mobility analyzer, condensation particle counter. Summary for members of Congress Submicrometer and ultrafine particles affect our climate, our visual air quality and our health. This research will provide a portable tool for the accurate measurement of the size and concentration of these particles, thereby enabling these measurements in locations where such measurements are not currently feasible.