Radical Formation by Fine Particulate Matter Associated with Highly Oxygenated Molecules

Highly oxygenated molecules (HOMs) play an important role in the formation and evolution of secondary organic aerosols(SOA). However, the abundance of HOMs in different environments and their relation to the oxidative potential of fineparticulate matter (PM) are largely unknown. Here, we investigated the relative HOM abundance and radical yield of laboratory-generated SOA and finePM in ambient air ranging from remote forest areas to highly polluted megacities. By electron paramagnetic resonance and mass spectrometric investigations, we found that the relative abundance of HOMs, especially the dimeric and low-volatility types, in ambient finePM was positively correlated with the formation of radicals in aqueous PM extracts. SOA from photooxidation of isoprene, ozonolysisof α- and β- pinene, and finePM from tropical (central Amazon) and boreal (Hyytiala, Finland) forests exhibited a higher HOM abundance and radical yield than SOA from photooxidation of naphthalene and finePM from urban sites (Beijing,...