Photochemical aerosol formation from pinene and pinene

Aerosol formation from ot-pinene and •-pinene was studied in a series of outdoor smog chamber experiments. Since a previous tudy focused on •-pinene (Pandis et al., 1991), more attention was given here to ot-pinene. The initial hydrocarbon and NO x concentrations ranged from 37 to 582 ppb and 31 to 380 ppb, respectively. The aerosol carbon yield, the fraction of the carbon initially present that is converted to aerosol, varied from 0 to 5.3% for ot-pinene, depending on the initial hydrocarbon-to-NO x ratio. Dual-bag experiments demonstrate that ot-pinene is more rapidly photooxidized, and produces higher yields of both aerosol and ozone in a given period of time than •-pinene, although given sufficient ime •pinene can produce equivalent aerosol yields. Although aerosol formation solely from isoprene photooxidation was found in a previous study to be negligible under ambient conditions, the addition of isoprene to the ot-pinene/NO x system leads to an increased aerosol yield through the enhanced photochemical activity generated.