Effects of FeSO4 Seeds on Secondary Organic Aerosol Formation from Photooxidation of α-pinene/NOx and Toluene/NOx

摘要

A series of photooxidation experiments with α-pinene and toluene in the presence of nitric oxides (NOx) were conducted using a Tsinghua-Toyato smog chamber. Both gas phase compounds and secondary organic aerosol (SOA) concentrations were measured in each experiment. Iron(II) sulfate (FeSO4) or iron(III) sulfate (Fe2(SO4)3) seeds were introduced to observe their effect on photochemical reactions. FeSO4 seeds indicate negative effects on SOA formation. However, the effects of FeSO4 seeds on gas phase compounds, including ozone (O3), nitrogen oxides (NOx) and hydrocarbons (HC), are not obvious. Nor are effects of Fe2(SO4)3 seeds on SOA formation observed. Based on the experiment results, a preliminary mechanism for FeSO4 seeds’ effects during the photooxidation process is proposed. The reduction of oxidized products of hydrocarbons is not sufficient for explaining the suppression effects of FeSO4 seeds on SOA formation and some catalytic action of ferrous iron during SOA formation may be existed.