Motor vehicle fleet emissions by OP-FTIR

Using open-path Fourier transform infrared spectroscopy (OP-FTIR) we have m easured the variations in ambient concentrations of carbon monoxide (CO), c arbon dioxide (CO2), and nitrous oxide (N2O) caused by emissions from motor vehicles at a high traffic site in the Denver metropolitan area. Compariso n of the OP-FTIR data to average emissions results obtained from on-road ex haust analysis using individual Vehicle remote sensing revealed reasonable agreement, with a CO emission ratio (CO/CO2) of 0.050 +/- 0.004 (100 +/- 8 g CO/kg fuel) from OP-FTIR and 0.059 (118 g CO/kg fuel) from the on-road me asurements. We also report a N2O emission ratio of (1.87 +/- 0.13) x 10(-4) (0.59 +/- 0.04 g N2O/kg fuel) from OP-FTIR and outline the potential of OP -FTIR for on-road measurements of several important exhaust components.