The impact of α-pinene on urban smog formation: an outdoor smog chamber study

Abstract

The effect on ozone production of replacing or adding 20 % carbon as α-pinene to an eleven component urban-tike hydrocarbon mixture is explored in a large outdoor smog chamber. Although apinene is somewhat more reactive than the hydrocarbon mixture, direct replacement of ~ 20 % carbon results in no change in overall reactivity as indicated by NO x and O 3 behavior. The addition of 20 % extra carbon as α-pinene produces changes similar to increasing carbon concentration in the hydrocarbon mixture by 20 %. If α-pinene and ozone are first reacted, their products do not impart any unusual reactivity to a hydrocarbon-NO x smog system. In one experiment a loss of reactivity as measured by ozone production was observed. Aerosol measurements made when α-pinene and ozone reacted indicate that the majority of particles which form reside in the 0.1 μm diameter range; most of the mass, however, is in panicles ~ 0.6 μm diameter. Carbon accountability in the product condensed phase is estimated to be 25–90 %, but a very high uncertainty is associated with this estimate.