A new aerosol collector for quasi on-line analysis of particulate organic matter: the Aerosol Collection Module (ACM) and first applications with a GC/MS-FID

摘要

In many environments organic matter significantly contributes to thecomposition of atmospheric aerosol particles influencing its properties.Detailed chemical characterization of ambient aerosols is critical in orderto understand the formation process, composition, and properties of aerosolsand facilitates source identification and relative contributions from different types of sources to ambient aerosols in the atmosphere. However, current analytical methods are far from full speciation of organic aerosols and often require sampling times of up to one week. Offlinemethods are also subjected to artifacts during aerosol collection andstorage.In the present work a new technique for quasi on-line compound specificmeasurements of organic aerosol particles was developed. The AerosolCollection Module (ACM) focuses particles into a beam whichis directed to a cooled sampling surface. The sampling takes place in a highvacuum environment where the gas phase from the sample volume is removed.After collection is completed volatile and semi-volatile compounds are evaporated from the collectionsurface through heating and transferred to a detector.For laboratory characterization the ACM was interfaced with a GasChromatograph Mass Spectrometer, Flame Ionization Detector system (GC/MS-FID), abbreviated as ACM GC-MS. The particle collectionefficiency, gas phase transfer efficiency, and linearity of the ACM GC-MSwere determined using laboratory generated octadecane aerosols. The ACM GC-MSis linear over the investigated mass range of 10 to 100 ng and a recoveryrate of 100% was found for octadecane particles.The ACM GC-MS was applied to investigate secondary organic aerosol (SOA)formed from β-pinene oxidation. Nopinone, myrtanal, myrtenol,1-hydroxynopinone, 3-oxonopinone, 3,7-dihydroxynopinone, andbicyclo[3,1,1]hept-3-ene-2-one were found as products in the SOA. The ACM GC-MSresults are compared to quartz filter samples taken in parallel to the ACM GC-MSmeasurements. First measurements of ambient atmospheric aerosols arepresented.