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Secondary Organic Aerosol Formation from the Reaction of Decamethylcyclopentasiloxane (D5) with Chlorine Atoms
ANITA AVERY, Francesca Majluf, Jordan Krechmer, Harald Stark, Lea Hildebrandt Ruiz, William Brune, Manjula Canagaratna, Andrew Lambe, Aerodyne Research, Inc.
Abstract Number: 457
Working Group: Indoor Aerosols
Abstract
Indoor emissions of siloxanes from personal care products have been studied extensively, as they often dominate total VOCs in occupied spaces. The oxidative aging of the siloxane decamethylcyclopentasiloxane (D5) by hydroxyl radicals (OH) and corresponding secondary organic aerosol (SOA) formation have recently been characterized. Chlorine atoms (Cl) may compete with OH for the oxidative loss of D5 under certain conditions, particularly following bleach cleaning activities that emit Cl precursors such as molecular chlorine and hypochlorous acid. However, the SOA formation potential of D5 + Cl reactions has not been studied. Here, we characterized the chemical composition and yield of SOA generated from the Cl oxidation of D5 in an oxidation flow reactor at Cl concentrations ranging from approximately 5*107 to 2*109 cm-3 in several minutes’ exposure time. D5 + Cl SOA was characterized with several state-of-the-art mass spectrometry techniques, including aerosol mass spectrometry, and a Vocus proton-transfer-reaction mass spectrometer (PTR-MS) with a heated aerosol inlet. Results are compared to SOA generated from D5 + OH using OH concentrations ranging from approximately 5*109 to 5*1010 cm-3 to identify molecular tracers for Cl- versus OH-initiated oxidative aging of D5. These results emphasize the importance of secondary chemistry during and after bleach cleaning activity.