MOTOR-VEHICLE CONTRIBUTIONS TO FINE CARBONACEOUS AEROSOL IN LOS-ANGELES

The contributions to the fine (d(p) < 3.5 mu m) carbonaceous aerosol a t Duarte, CA (a suburban site near Los Angeles) and in Lennox, CA (a s ite next to a Los Angeles freeway) by motor vehicles were estimated in 1983 and 1987-88 using Pb and CO as tracers. In 1983 motor vehicle em issions contributed about 50% of the ambient black carbon (BC) in Duar te and 80% in Lennox. In 1987-88 this contribution was increased to ab out 75% in Duarte though the ambient BC concentration was decreased. I n contrast, the contribution of primary motor vehicle emissions to org anic carbon (OC) remained virtually unchanged at about 20% in Duarte f rom 1983 to 1987-88 and 45% in Lennox for 1983.