New Electrical Mobility Techniques for Nano-aerosol Measurements

New Electrical Mobility Techniques for Nano-aerosol Measurements

Abstract

Airborne nanoparticles, produced as a result of natural and anthropogenic activities, are critically important from an environmental and human health perspective. The interaction of these particles with their immediate environment is strongly dependent on their size. Size distributions of these particles are best made using electrical mobility techniques. A classical instrument for electrical mobility measurements is the differential mobility analyzer (DMA). In the DMA, particles are classified based on their response to applied electrical and flow fields, and a narrow range of particle sizes (mobilities) are output. The size of the output particles is varied by changing the operating conditions and the output monodisperse particles are counted by a condensation particle counter (CPC) to obtain the size distribution of particles smaller than ~ 500 nm over a measurement time of ~ 2-5 minutes. While the DMA-based instruments provide high-resolution measurements, the high cost and large weight of these instruments makes it inconvenient for their use in large-scale ambient monitoring or personal measurements. In our lab, we have recently developed a instrument, called the Miniature Electrical Aerosol Spectrometer (MEAS), that enables real-time size distribution measurements with a compact, low-cost design. I will present background information on electrical mobility measurements, details of the theoretical and experimental development of the MEAS instrument. I will also present the possibilities of extending this measurement technique for size-integrated concentration measurements and its application for air quality studies.