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Organic material in tropospheric aerosols: incorporation and impact on hygroscopic growth
The Intergovernmental Panel of Climate Change (IPCC) reported that aerosols might counteract the global warming of greenhouse gases. However, the specific chemical composition of aerosols as well as the impact this varying composition has on aerosol properties is not well characterized, and thus the impact of aerosols on climate change is not clear. Tropospheric aerosols can be up to 80% by mass organic material (Saxena and Hildemann 1996; Middlebrook et al. 1998; Molnar et al. 1999; Turpin et al. 2000), with the remaining mass consisting of inorganic compounds such as ammonium sulfate. The composition of atmospheric aerosols can impact their optical and hygroscopic properties, cloud condensation abilities and chemical reactivity in heterogeneous reactions. Many of these properties, such as hygroscopic growth, are well characterized for pure inorganic compounds, though the impact that the addition of organics will have is not well understood. Our research focuses on the water uptake by mixed ammonium sulfate and organic (both water-soluble and water insoluble) aerosols as well as the incorporation of organic vapors into sulfuric acid aerosols. We use a variety of techniques (i.e. mass spectrometry, cavity ring-down spectroscopy, FTIR spectroscopy, transmission electron microscopy, 1H-NMR) to characterize the aerosols and their growth when exposed to water vapor. By understanding both the incorporation of organics into aerosols, through which we can better understand speciation, as well as the impact these different species of organics have on water uptake we hope to constrain the impact of aerosols on climate change.
Middlebrook, A. M., D. M. Murphy and D. S. Thomson. "Observations of organic material in individual marine particles at Cape Grim during the First Aerosol Characterization Experiment (ACE 1)." J. Geophys. Res., 103, D13: 16475-16483, 1998.
Molnar, A., E. Meszaros, H. C. Hansson, H. Karlsson, A. Gelencser, G. Y. Kiss and Z. Krivacsy. "The importance of organic and elemental carbon in the fine atmospheric aerosol particles." Atmospheric Environment, 33, 17: 2745-2750, 1999.
Saxena, P. and L. M. Hildemann. "Water-soluble organics in atmospheric particles: A critical review of the literature and application of thermodynamics to identify candidate compounds." Journal of Atmos. Chem., 24: 57-109, 1996.
Turpin, B. J., P. Saxena and E. Andrews. "Measuring and simulating particulate organics in the atmosphere: problems and prospects." Atmospheric Environment, 34, 18: 2983-3013, 2000.