EFFECT OF OXYGENATED FUELS ON AMBIENT CARBON-MONOXIDE CONCENTRATIONS IN PROVO, UTAH, USA

Oxygenated gasoline is used to reduce wintertime urban ambient CO conc entrations by reducing CO emissions from spark-ignition motor vehicles . Our study was designed to measure background-corrected wintertime am bient CO and CO2 concentrations in Prove before, during, and after oxy fuel periods. Any oxyfuel effect would be manifested as a lower CO/CO2 ratio from spark-ignition vehicles during the oxyfuel period. Salt La ke City, which did not introduce oxyfuels, was used as a control for w eather, house heating, and other differences, unrelated to oxyfuel use , between oxyfuel and non-oxyfuel periods. An apparent effect on ambie nt-air CO/CO2 ratios at traffic sites was invariably observed but prov ed to be of marginal to low statistical significance; our best estimat e of the CO oxyfuels benefit at the traffic sites is 15 +/- 20%. In th e parking garages, a reduction variously estimated as 11% or 33% was o bserved, indicating significant CO benefits from oxyfuels during cold- start; however, the random uncertainty in this estimate is not known. A second objective of this study was to see whether this new method is feasible. Our conclusion is that improvements are needed but it was s uccessful enough to warrant evaluation against other methods.