Introducing the concept of Potential Aerosol Mass (PAM)

[摘要] Potential Aerosol Mass (PAM) can be defined as themaximum aerosol mass that the oxidation of precursor gases produces. In themeasurement, all precursor gases are rapidly oxidized with extreme amountsof oxidants to low volatility compounds, resulting in the aerosol formation.Oxidation occurs in a small, simple, flow-through chamber that has a shortresidence time and is irradiated with ultraviolet light. The amount of theoxidants ozone (O₃), hydroxyl (OH), and hydroperoxyl (HO₂) weremeasured directly and can be controlled by varying the UV light and therelative humidity. Maximum values were 40 ppmv for O₃ 500 pptv for OH,and 4 ppbv for HO₂. The oxidant amounts are 100 to 1000 timestroposphere values, but the ratios OH/O₃ and HO₂/OH are similar totroposphere values. The aerosol production mechanism and the aerosol massyield were studied for several controlling variables, such as temperature,relative humidity, oxidant concentration, presence of nitrogen oxides(NO_x), precursor gas composition and amount, and the presence of acidicseed aerosol. The measured secondary organic aerosol (SOA) yield of severalnatural and anthropogenic volatile organic compounds and a mixture ofhydrocarbons in the PAM chamber were similar to those obtained in large,batch-style environmental chambers. This PAM method is being developed formeasuring potential aerosol mass in the atmosphere, but is also useful forexamining SOA processes in the laboratory and in environmental chambers.

[学科分类] 大气科学