Multi-Component Remote Sensing of Vehicle Exhaust by Dispersive Absorption Spectroscopy

Abstract

<div class="htmlview paragraph">Direct remote sensing of vehicle exhaust emissions under real-world driving conditions is desirable for a number of reasons, including: identifying high emitters, investigating the chemical composition of the exhaust, and probing fast reactions in the plume. A novel remote sensor, incorporating IR and UV dispersive spectrometers, was developed. Emissions from a fleet of vehicles powered by a range of fuels (gasoline, diesel, natural gas, and methanol) were tested. The exhaust from “hot” gasoline- and methanol-powered cars contained high levels of NH<sub>3</sub>, up to 1500 ppm. These emissions were up to 14 times higher than the corresponding NO<sub>x</sub> emissions. Subsequent on-road remote sensing measurements on over 4,500 vehicles showed that NH<sub>3</sub> emissions follow a μ-distribution, with 10 % of the fleet being responsible for 66 % of the total emissions. Mean NH<sub>3</sub> emissions for the measured fleet were 78.6 ppm, significantly higher than previously estimated.</div>