On-board Measurements of Ammonia in Automobile Exhaust Using Laser Absorption Spectroscopy

Abstract

As ammonia (NH₃) contributes to the formation of secondary particulate matter, the real-world levels of NH₃ emitted from automobiles need to be examined. However, only a few studies have reported real-world measurements of NH₃ in automobile exhaust. In this study, we developed an on-board system to measure NH₃ emissions using near-IR laser absorption spectroscopy. This system was used to measure the real-world emission level of NH₃ from both gasoline and diesel vehicles. In the case of gasoline vehicles, NH₃ was found to be emitted mainly under high-load driving conditions such as running on a highway. In the case of diesel vehicles, NH₃ was emitted just after the engine was started; after which, only low levels of NH₃ were emitted when the vehicles were running. The amount of NH₃ emitted from gasoline vehicles was found to be larger than that from diesel vehicles.