Effects of seed aerosols on the growth of secondary organic aerosols from the photooxidation of toluene

Hydroxyl radical(.OH)-initiated photooxidation reaction of toluene was carried out in a self-made smog chamber.Four individualseed aerosols such as ammonium sulfate,ammonium nitrate,sodium silicate and calcium chloride,were introduced into the chamberto assess their influence on the growth of secondary organic aerosols(SOA).It was found that the low concentration of seed aerosolsmight lead to high concentration of SOA particles.Seed aerosols would promote rates of SOA formation at the start of the reaction andinhibit its formation rate with prolonging the reaction time.In the case of ca.9000 pt/cm3 seed aerosol load,the addition of sodiumsilicate induced a same effect on the SOA formation as ammonium nitrate.The influence of the four individual seed aerosols on thegeneration of SOA decreased in the order of calcium chloride>sodium silicate and ammonium nitrate>ammonium sulfate.