American Association for Aerosol Research - Abstract Submission

AAAR 36th Annual Conference
October 16 - October 20, 2017
Raleigh Convention Center
Raleigh, North Carolina, USA

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Development and Field Test of a Compact Diluter and Optical Particle Counter for Emissions Measurements

AMARA HOLDER, Brannon Seay, William Mitchell, Johanna Aurell, Brian Gullett, U.S. EPA

     Abstract Number: 442
     Working Group: Instrumentation and Methods

Abstract
EPA has developed a lightweight, portable emissions measurement platform that can be lofted into plumes to sample for an array of pollutants from open area sources such as prescribed forest burns. However, the measurement of particle size distribution, a key characteristic of particle emissions that determine their lifetime in the atmosphere and potential for impacts on human health, has been unavailable until recently due to the large size, weight, and limited dynamic range of available particle sizing instruments. With the advent of lightweight, low-profile optical particle counters, a portable size distribution measurement is now possible at low particle concentrations. However, these devices quickly become saturated in typical smoke plumes.

We have developed a compact aerosol diluter to work in conjunction with an optical particle counter (OPC-N2, αlphasense) to measure aerosol size distribution in the concentrated plumes often observed from open burning. The diluter uses a bifurcated flow design with a capillary tube and miniature particle filter to achieve dilution ratios in the range of 1:10 to 1:80. The dilution ratio is continuously monitored with a pressure sensor to account for the impact of filter loading. The diluter and optical particle counter were deployed on an instrumented, helium-filled aerostat to sample emissions from grassland burns in the Konza prairie. PM1 concentrations from the particle counter were highly correlated (r2 = 0.80) with PM1 measured by a DustTrak (DRX, TSI), demonstrating the potential of the diluter and particle counter for in-plume size distribution measurements