Tailpipe pollutants from motor vehicles are linked to environmental concerns and human health issues. Initial ignition of a gasoline engine requires fuel-enriched conditions that produce a significant portion of trip emissions. Few studies to date have quantified the exhaust air toxics emissions for light-duty vehicles during cold start, the focus of this study. Real-world tailpipe emissions were measured from a 1999 Toyota Sienna minivan with an innovative on-board measurement system. A Fourier Transform Infrared (FTIR) Spectrometer was used to measure 27 gas-phase and mobile source air toxic (MSAT) emissions for cold start, extended idle, and warm-up driving at one-second temporal resolution. Analysis demonstrated that (a) time to optimal function of emissions control devices could not be indicated by one species, as it varied for different pollutants; (b) extended idle conditions following cold start produced elevated emissions for MSAT species as compared to warm-up driving; (c) peak concentrations for species from each emission category were affected by ambient temperature, ranging from 9.5 to 38.4 °C, with the exception of carbon dioxide. Carbon monoxideproduced peak emissions three orders of magnitude higher than hot-stabilized conditions for an average of 90 seconds, regardless of operation conditions, while nitric oxide peak emissions were over an order of magnitude higher during warm-up driving than extended idle. Peak MSAT emissions, up to two orders of magnitude higher than hot-stabilized idle, were maintained or increased during extended idle and decreased to baseline within 100 to 200 seconds of warm-up driving.
Abstract