Evaluation of pollutant emissions related to the use of MMT in gasoline

Since 1976, methylcyclopentadienyl manganese tricarbonyl (MMT), an organic derivative of Mn, has been used in Canada as an anti-knock agent in unleade d gasoline. In a preliminary evaluation of the contribution of MMT to urban air pollution, the CO and NOX emissions of 10 vehicles each having travele d less than 17 000 miles were sampled. Five of these vehicles were filled w ith MMT-free gasoline and the remaining five with MMT-added gasoline. The e missions were evaluated according to the Federal Test Procedure which simul ates urban and highway driving cycles. As for the NOX and CO analysis, it w as carried out by means of infrared spectrometry, while the concentration o f Mn in the gasoline was determined through neutron activation. Overall, th e amount of CO emitted by the vehicles using MMT-added gasoline was 1.48 g mile(-1) +/- 1.77. The amount emitted by the vehicles using clear (MMT-free ) gasoline was 0.74 g mile(-1) +/- 0.58. As for the NOX emission level, it was 0.20 g mile(-1) +/- 0.15 for the vehicles using MMT-added gasoline vs 0 .17 g mile(-1) +/- 0.18 for the vehicles using clear gasoline. However, pro bably due to the small sample size and the very high level of emission of o ne of the vehicles using MMT-added gasoline, these differences are not stat istically significant. Further studies should take into account variables s uch as the driving history and the representativity of the fleet of vehicle s tested.