Remote sensing of NO and NO2 emissions from heavy-duty diesel trucks using tunable diode lasers

摘要

On-road remote sensors can measure the emissions of motor vehicles under real-world conditions. The most sensitive and versatile remote sensor reported to date is based on Tunable Infrared Laser Differential Absorption Spectroscopy (TILDAS). This study applied this TILDAS remote sensor to the measurement of the emissions from heavy-duty diesel trucks (HDDTs). The remote sensor could operate with an optical pathlength of 88 m, or more than 5 times that of competing instruments. Remote sensing of NO$-2$/ emissions was demonstrated for the first time. Good agreement was obtained when comparing the TILDAS measurements with the on- board measurements of an instrumented HDDT. The distribution of NO emissions from HDDT was found not to be skewed. HDDTs are estimated to contribute about 3/5 of the on-road NO$-x$/ emission inventory. These emissions are underestimated by a factor of 2.2 in the latest EPA inventory.