Heterogeneous uptake of octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5) onto mineral dust aerosol under variable RH conditions |
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| Authors: | Juan G Navea Shihe Xu Charles O Stanier Mark A Young Vicki H Grassian |
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| Institution: | 1. Wadsworth Center, New York State Department of Health, and Department of Environmental Health Sciences, School of Public Health, State University of New York at Albany, Empire State Plaza, P.O. Box 509, Albany, NY 12201-0509, United States;2. Faculty of Chemistry, Hanoi University of Science, Vietnam National University, Hanoi, 19 Le Thanh Tong, Hoan Kiem, Hanoi, Viet Nam;3. Biochemistry Department, Faculty of Science, Experimental Biochemistry Unit, King Fahd Medical Research Center and Bioactive Natural Products Research Group, King Abdulaziz University, Jeddah, Saudi Arabia;4. Toxicological Center, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk-Antwerp, Belgium;5. Environmental Management Program, Environment and Life Sciences Center, Kuwait Institute for Scientific Research, P.O. Box 24885, Safat 13109, Kuwait;6. Environmental and Chemistry Group, Sede San Pablo, University of Cartagena, Cartagena, Bolívar 130015, Colombia;7. Biochemistry Department, Faculty of Science, Experimental Biochemistry Unit, King Fahd Medical Research Center and Production of Bioproducts for Industrial Applications Research Group, King Abdulaziz University, Jeddah, Saudi Arabia;8. Department of Marine Sciences and Convergent Technology, College of Science and Technology, Hanyang University, Ansan, South Korea;9. Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan;10. Department of Zoology, Patna University, Patna, 800 005, India;1. Institute for Chemical and Bioengineering, ETH Zurich, 10 Wolfgang Pauli Strasse, 8093 Zurich, Switzerland;2. Radboud University Medical Centre, Department for Health Evidence (133), P.O. Box 9101, 6500 HB Nijmegen, The Netherlands |
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| Abstract: | We have carried out kinetic studies to characterize the heterogeneous decay of octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5) in the presence of representative mineral dust aerosol in order to obtain a better understanding of the atmospheric fate of these siloxanes. The heterogeneous chemistry of D4 and D5 with various mineral dusts was studied in an environmental aerosol reaction chamber using FTIR absorption spectroscopy to monitor the reaction. The apparent heterogeneous uptake coefficient, γapp, for D4 and D5 with various mineral dusts was measured under dry conditions and as a function of relative humidity (RH). In addition, the effect of initial D4 and D5 concentration on the rate and yield of the reaction was examined. The uptake coefficient, γapp, for D4 and D5 was similar for the most reactive aerosols tested, with kaolinite ≈hematite > silica. Limited uptake onto carbon black and calcite surfaces was observed for either siloxane. Reaction with hematite and kaolinite resulted in multilayer coverages, suggesting extensive polymerization of D4 and D5 on the aerosol surface. |
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