Nitrous acid (HONO) emission factors for diesel vehicles determined using a chassis dynamometer

Abstract

Vehicle exhaust gases are important sources of nitrous acid (HONO). In this study, HONO in diesel vehicle exhaust was measured by incoherent broadband cavity-enhanced absorption spectroscopy using a chassis dynamometer system. The mean HONO concentrations in exhaust gases emitted by passenger cars and light-duty trucks were high when the after treatment devices were not fully working during the warming up period. The HONO/NOx ratio is a good index of HONO formation. The HONO/NOx ratios were 9.7 × 10−3–18.1 × 10−3, and were higher than what we found in a previous study. The estimated HONO emission factors were 7.71–64.70 mg (kg fuel)−1, and were lower than were found in previous studies. The results indicated that the frequency particulate matter is removed from a diesel particle filter affects the HONO concentration in the emitted gases and the HONO emission factor.