Ozone(O3) and secondary organic aerosol (SOA) are considered to be the most serious secondary air pollutants of concern in most metropolitan areas, as well as for Beijing. In this study, O3 and SOA formation potential of α-pinene, the most abundant biogenic VOCs, is investigated at Tsinghua Indoor Chamber Facility. The experiments were conducted under atmospheric relevant HCs/NOx ratios in both presence and absence of ammonia sulfate seed aerosol. A Scanning Mobility Particle Sizer system (3936, TSI) and a Condensation Particle Counter (3010, TSI) were used to study the SOA formation and a gas chromatograph (GC) equipped with a DB-5 column and a flame ionization detector (FID) was used to measure α-pinene simultaneously. The results show that the presence of ammonia sulfate seed aerosol did not change the formation trend of O3, but significantly contribute to SOA formation. A strong linear relationship (r 2 = 0.90) between SOA yield enhancement (ΔY*) and surface concentration of seed aerosol (PM i,s )has been found, denoting that the PM i,s is the control factor for SOA yield enhancement. And the possible reason for the enhancement is acid-catalyzed heterogeneous reactions.
Supported by Toyota Central R&D Labs., Inc. (as part of “Study of Photochemical Reaction under High PM Contaminated Condition to Improve Air Quality of Beijing”), and the National Natural Science Foundation of China (Grant No. 20637001)