HR: 1340h
AN: A33B-0887    [Abstracts]
TI: Two New Water-Based Condensation Particle Counters
AU: * Hering, S V
EM: susanne@aerosol.us
AF: Aerosol Dynamics Inc., 935 Grayson St, Berkeley, CA 94710 United States
AU: Quant, F R
EM: fred@quanttechnologies.com
AF: Quant Technologies, LLC, 1463 94th Lane NE, Blaine, MN 55449 United States
AB: Described here are two new, thermally-diffusive, water-based condensation particle counters (WCPC) for determination of aerosol number concentrations. One of these, the TSI Model 3786 ultrafine WCPC, detects particles as small as 2.5 nm at an aerosol flow rate of 300 cm3/min. The second is a not-yet-commercialized, compact, 12-volt instrument (ME-WCPC) weighing 2.5 kg with a lower size limit of 5 nm, and an upper concentration limit in single-count mode of ~10E7cm-3. In contrast to the cold-walled condensers of the older butanol-based particle counters, these WCPCs use a warm, wet-walled "growth tube" that explicitly takes into account the high diffusivity of water vapor. Because the mass diffusivity of water vapor exceeds the thermal diffusivity of air, the flux of water vapor to the centerline is faster than the heat flux from the walls, thereby producing the supersaturation necessary for particle activation and growth (1). An obvious advantage of the WCPCs over the butanol-based particle counters is the elimination of odor, toxicity and waste disposal issues with the use of butanol. Reported is the field evaluation of the ultrafine- and ME-WCPCs, with comparison to the more well-established butanol-based TSI Model 3010 and 3025 counters. A passive flow system provided a 9:1 dilution of ambient air for the TSI 3010 in order to stay within an acceptable concentration range for that instrument. Equivalency of aerosol sampling rates for all instruments was evaluated through comparison of counting efficiency for near-monodisperse aerosols at with diameters ranging from 50 to 200 nm. Over four weeks of measurements the ultrafine WCPC reported 6% higher concentrations than the ultrafine butanol Model 3025 counter, consistent with the slightly lower size cutoff of the ultrafine WCPC. Concentrations from the ME-WCPC units were higher than for the 10nm cutpoint TSI 3010, but lower than for the 3 nm cutpoint TSI 3025 ultrafine. For all comparisons, the correlation coefficient R>0.97. (1) S V Hering, M R Stolzenburg, F R Quant, D R Oberriet, P B Keady, Aerosol Science and Technology, 39: 659-672, 2005.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 4801 Aerosols (0305, 4906)
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005