Development and Characterization of the NanoAPA, a Portable Instrument for Real-Time Measurement of the Size and Number of Airborne Nanoparticles

TERENCE BARRETT (1), Britt Holmén (1)

(1) University of Vermont

     Abstract Number: 647
     Last modified: May 14, 2010

Abstract
Nanoparticle emissions in motor-vehicle exhaust are associated with cardiopulmonary health impacts and increased mortality. The emission, evolution, and exposure-uptake of these particles, 100 nanometers and smaller in diameter, are fundamentally quantified by the number concentration as a function of particle size. Nanoparticle number distributions are widely varying and fast changing as they are strongly influenced by local environmental conditions and variation in vehicle operation and maintenance. Research and regulation to quantify and control such emissions rely on measurement of the number distribution of nanoparticles in vehicle exhaust and by the roadside. Instruments to make such measurements are commercially available, but they are expensive, non-portable, and have slow response times. The NanoAPA was developed as an inexpensive, portable, and real-time instrument designed to meet this need. The instrument performs nanoparticle sizing and counting through electronic control of a microfabricated device that charges sampled airborne particles with a corona ionizer and then incrementally collects and counts the number of particles from 10 to 100 nanometers in a serial-condenser aspiration capacitor utilizing voltage-and-flowrate-variable electrophoresis. Performance characterization of the NanoAPA instrument will be presented: Reference aerosols comprised of 10 to 100 nanometer exhaust-analog particles of oleic acid and emery oil were used to characterize the charge distribution, charging efficiency, and size selection of the instrument’s microfabricated corona ionizer and aspiration capacitor, for the operating conditions of 0.1 to 1.5 liter per minute flow rate and 0 to 3000 volt separator voltage, with an apparatus that included a TSI Engine Exhaust Particle Sizer (EEPS) and a TSI Scanning Mobility Particle Sizer (SMPS).