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Identification of High-emitting Heavy-duty Diesel Trucks with Low-cost Sensors and the Plume Capture Method
REBECCA SUGRUE, Chelsea V. Preble, Thomas W. Kirchstetter, University of California, Berkeley
Abstract Number: 589
Working Group: Instrumentation and Methods
Abstract
The exhaust plume capture method used to characterize pollutant emissions from in-use heavy-duty diesel trucks can serve as a surveillance tool to remotely identify high emitting trucks that may warrant inspection and maintenance. Lower cost sensors offer an opportunity for wider deployment of this approach, but have not been well evaluated in this application. This study compares black carbon (BC) emission factors measured with multiple BC and carbon dioxide (CO2) analyzers for thousands of trucks at the Port of Oakland. Though the distributions of emission factors were similar across different pairs of BC/CO2 analyzers, the identification of high-emitting trucks varied and depended more on the BC than CO2 analyzer performance. For example, 90% of the high emitters classified by the Magee Scientific AE33 and LI-COR LI-7000 were also identified by the AE33 and the lower cost PP Systems SBA-5. In contrast, the lower cost BC analyzers misclassified more than half of their high emitters compared to the AE33.
The plume capture method measures only a snapshot of a passing truck’s emissions, which are transient in nature and depend on the prevailing driving conditions. An analysis of emission rates from trucks that were sampled more than once shows that a single low-emission instance does not guarantee that a truck is not occasionally high-emitting; conversely, a high-emitting truck may not always be highly polluting. Consequently, this method is unlikely to identify all high-emitting trucks with a single measurement, yet is unlikely to falsely identify a clean truck as a high emitter.