Estimation of annual Mn emissions from MMT source in the Canadian environment and the Mn pollution index in each province

Abstract

Methylcyclopentadienyl manganese tricarbonyl (MMT), is an organic derivative of Mn used as an anti-knock agent in Canadian unleaded gasoline since 1976. This study aims to estimate Mn emissions from MMT source in the Canadian environment as well as the Mn pollution index per capita in each of the Canadian provinces. In concomitance, lead emissions will also be addressed. The quantities of Mn and Pb used in gasoline were calculated from data on annual gasoline sales in Canada supplied by Statistics Canada. Obviously, the Pb emission profile shows a substantial decrease with an annual average of −28% until 1991, when MMT totally replaced Pb in Canadian gasoline. The case of Mn is quite different. Since emission rates of Mn at the tailpipe vary between 6 and 45%, the quantities released into the atmosphere were calculated for each of these rates, as well as for 100 and 25% emission rate scenarios. For 1981 and 1999, the quantities of Mn used in gasoline were estimated at 101 122 and 344 880 kg, respectively. Based on the realistic 25% emission rate scenario and a concentration of 0.009 g/l of Mn in gasoline, Mn emissions from car exhausts were estimated to 25 280 and 86 220 kg, respectively. The mean annual increase in emission rate between 1981 and 1999 is 7.34%. The atmospheric Mn pollution index seems to be stable over time, and it varies from 0.0024 kg/capita to 0.0041 kg/capita in 1999. In the context of a notable decrease in Mn emissions from industrial sources, these results suggest that the combustion of MMT used in gasoline may be an important factor contributing to maintaining stable atmospheric Mn concentrations instead of a significant decrease due to reduced industrial emissions.