AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
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Evaluating Performance of High-, Mid-, and Low-cost Analyzers for Capturing Heavy-duty Diesel Truck Exhaust Plumes
REBECCA SUGRUE, Chelsea V. Preble, Thomas W. Kirchstetter, University of California, Berkeley
Abstract Number: 780 Working Group: Air Quality Sensors: Low-cost != Low Complexity
Abstract Studies of in-use truck emissions typically employ expensive, regulatory-grade analyzers. However, there is a growing interest in using low-cost sensors in this field—for example, as a widely deployed surveillance tool that could efficiently identify high-emitting trucks that may need maintenance. To date, there has been little to no evaluation of low-cost sensor performance for truck exhaust plume capture, which requires fast and accurate analyzer response of rapidly changing pollutant concentrations when trucks pass by.
This study evaluates the performance of high-, mid-, and low-cost analyzers for measurement of exhaust plumes from trucks that pass by a fixed sampling location. This performance is based on resulting fuel-based black carbon (BC) emission factors determined with a carbon balance method. At a terminal entrance at the Port of Oakland, we measured BC emission rates from 888 in-use drayage trucks using a suite of four different BC and four different carbon dioxide (CO2) analyzers. This suite of analyzers generated 16 BC emission factors for each truck that was sampled. We considered the precision of the analyzers and the resulting limit of detection for near-zero emission factors. These data also provided a basis for evaluating the ability of each analyzer pairing to identify the highest emitting trucks that account for most of the fleet’s pollution. There was a strong correlation in emission rates calculated with the highest and lowest cost CO2 analyzers. This agreement indicates that the low-cost option is a reliable alternative. The distributions of BC emission factors computed with various pairs of high- and low-cost BC and CO2 analyzers are very similar. However, we found that many of the trucks identified as higher emitters with a pair of high-cost BC and CO2 analyzers were not identified as higher emitters with other analyzers.