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Using mobile measurements to update on-road transportation emission inventory
Citation:
Zhang, S., K. Zhang, P. Deshmukh, Y. Wu, R. Baldauf, R. Snow, AND J. Faircloth. Using mobile measurements to update on-road transportation emission inventory. EPA National Emissions Inventory Conference, TX, Dallas, July 28 - August 02, 2019.
Impact/Purpose:
Motor vehicles are a significant contributor to air pollution and adverse health effects throughout the world. Understanding the amount of emissions is critical in designing effective air pollution control strategies. This presentation describes the use of chase mbile monitoring to identify motor vehicle emissions during on-road operations, which enhances the accuracy of air ollution emission inventories and the accuracy of air quality models. The results of this work can be used by environmental agencies as a tool for determining real-world emissions and improving national emission inventories.
Description:
Portable emission measurement systems (PEMS) have effectively characterize potentially high real-world emissions as highlighted by the Volkswagen diesel emissions scandal. PEMS testing has been adopted by emissions regulations in the US, Europe and China. However, the expensive instrument costs and long times needed to set up and operate the equipment can be major limitations of implementing PEMS, which has led to the development of more cost-effective, efficient methods, such as mobile chasing measurements 1, 2, to improve current emission inventories for on-road motor vehicles. In this study, a mobile platform was developed by equipping one Minivan with a series of fast-response pollutant analyzers for measuring CO2, CO, NO/NOX, particle number, and black carbon (BC) to identify real-world vehicle emission rates. To evaluate the accuracy of mobile measurement results, we compared on-road measurements of NOX emissions between mobile chasing and PEMS for 12 heavy-duty diesel trucks in China. For each vehicle, multiple chasing tests were conducted on both freeways and local roads. Various data processing methods and key parameters were used to optimize an algorithm to calculate fuel consumption-based emission factors. The results show that, with multiple chasing results averaged, the relative errors of vehicle-specific emission factors for NOx ranged within ± 20% for all tested vehicles. Since 2017, We have dispatched the mobile platform to have measured thousands of vehicles across nearly ten provincial regions in China. The emissin factors identified from these chasing measurement studies are being applied to improve key components of China’s on-road transportation emission inventory (called the EMBEV model) 3-5. Key components of the EMBEV model being updated include after-treatment efficiency, characteristics of high emitting vehicles, and emissions from natural gas vehicles. A significant contribution from chasing data has been the identification of higher NOX emission factors than expected for SCR-equipped trucks. These improved NOX emission factors are also important for near future (2020) air quality and health impac assessments being conducted using the EPA WRF/CMAQ modeling system.