Estimation of global vehicular methyl bromide emissions: Extrapolation from a case study in Santiago, Chile

Between June 1 and June 8, 1996, 144 whole air samples were collected in Sa ntiago, Chile. The temporal and geographical enhancement of CH3Br correlate d with incomplete combustion tracers emitted from vehicles during the morni ng commute. From these, a city-wide CH3Br/CO volume emission ratio of 2.2 x 10(-6) was measured in ambient air. Without using the CO measurements, we estimate an annual release of 8.9 tons of CH3Br in Santiago based solely up on enhanced concentrations observed throughout the study area during the mo rning traffic period. This enhancement corresponds to 8.0 x 10(-6) kg CH3Br emitted for each liter of gasoline used (leaded and unleaded). By scaling the annual gasoline usage in Santiago to countries still using leaded gasol ine, and assuming the above 8.0 x 10(-6) kg/L value holds true, a global ve hicular CH3Br emission of 4 +/- 3 Gg/year is calculated. This small vehicul ar CH3Br emission source strength will not improve the current CH3Br budget imbalance.