Characterization of ammonia emissions from light-duty gasoline vehicles based on real-world driving and dynamometer...

Ammonia (NH₃) contributes significantly to the formation of particulate matter, and vehicles represent a major source of NH₃ in urban areas. However, there remains a lack of comprehensive understanding regarding the emission characteristics of NH₃ from vehicles. This study conducted real-world driving emission (RDE) measurements and dynamometer measurements on 33 light-duty gasoline vehicles (LDGVs) to investigate their emission characteristics and impact factors. The tested vehicles include China 3 to China 6 emission standards. The results show that the average NH₃ emission factors of LDGVs decreased by >80 % from China 3 to China 6 emission standards. The results obtained from dynamometer measurements reveal that independent from other conventional pollutants (such as HCHO and NOx), NH₃ emissions do not exhibit significant emission peaks during the hot- or cold-start phase. The RDE measurement covers a more comprehensive range of the vehicle's real-world driving conditions, resulting in higher NH₃ emission factors compared with dynamometer measurements. The analysis of RDE measurements revealed that NH₃ emissions are influenced by vehicle speeds and accelerations. Acceleration processes contribute approximately 50 % of total NH₃ emissions over a driving period. Finally, using real driving speed, acceleration, and road gradient as input parameters, an NH₃ emission rate model based on vehicle specific power was developed. This emission rate model enables a more precise reflection of LDGVs' NH₃ emissions of LDGVs across diverse driving conditions and provides valuable data support for high-resolution inventories of vehicle NH₃ emissions.