The Great Smoky Mountains National Park: example of biogenic aerosols

Overview

Aerosols, also known as particulates, are tiny suspended solid or liquid particles in the atmosphere. Their sizes range from 10 nanometers (nm) to 100 microns (mm) in diameter. They are very important in atmospheric sciences because of their effects on health, visibility and climate. In general, aerosols tend to cool the earth by directly reflecting sunlight and by providing seed particles for formation of cloud droplets.

There are large uncertainties in predicting mass of aerosols produced from anthropogenic (human) and biogenic (non-human) sources. In particular, secondary organic aerosol (SOA), which is not directly emitted, but instead formed from oxidation of precursor volatile organic compounds (VOCs) in the atmosphere, are significantly underestimated by current atmospheric models.

Postdoctoral Research: Chemical Composition of Ambient Organic Aerosol

• Utilize thermal desorption aerosol gas-chromatograph mass spectrometry to carry out both in-situ and offline measurements of aerosol composition from urban areas, remote forests and biomass burning sources

• Technique described previously by other members of our group:
  • Thermal desorption aerosol gas-chromatograph (TAG)
  • Comprehensive 2D gas chromatography

Graduate Research: Mechanisms of Secondary Organic Aerosol Formation

• Effect of nitrogen oxides (NOx) and particle acidity on the mechanism of SOA formation:

  • Chan, A. W. H.; Chan, M. N.; Surratt, J. D.; Chhabra, P. S.; Loza, C. L.; Crounse, J. D.; Yee, L. D.; Flagan, R. C.; Wennberg, P. O.; Seinfeld, J. H. Role of aldehyde chemistry and NOx concentrations in secondary organic aerosol formation, Atmos. Chem. Phys., 10, 7169–7188, 2010 link

  • Surratt, J. D.; Chan, A. W. H.; Eddingsaas, N. C.; Chan, M. N.; Loza, C. L.; Kwan, A. J.; Hersey, S. P.; Flagan, R. C.; Wennberg, P. O.; Seinfeld, J. H. Reactive intermediates revealed in secondary organic aerosol formation from isoprene, Proc. Natl. Acad. Sci. USA, 107, 6640–6645, 2010 link

• Contribution of biogenic (2-methyl-3-buten-2-ol) and anthropogenic (naphthalene and other PAHs) hydrocarbons to SOA formation:
  • Chan, A. W. H.; Galloway, M. M.; Kwan, A. J.; Chhabra, P. S.; Keutsch, F. N.; Wennberg, P. O.; Flagan, R. C.; Seinfeld, J. H. Photooxidation of 2-methyl-3-buten-2-ol (MBO) as a potential source of secondary organic aerosol. Environ. Sci. Technol., 43, 4647-4652, 2009 link
  • Chan, A. W. H.; Kautzman, K. E.; Chhabra, P. S.; Surratt, J. D.; Chan, M. N.; Crounse, J. D.; Kuerten, A.; Wennberg, P. O.; Flagan, R. C.; Seinfeld, J. H. Secondary organic aerosol formation from photooxidation of naphthalene and alkylnaphthalenes: Implications for oxidation of intermediate volatility organic compounds (IVOCs). Atmos. Chem. Phys., 9, 3049-3060, 2009 link

• Kinetic modeling of SOA formation:

  • Kroll, J. H.; Chan, A. W. H.; Ng, N. L.; Flagan, R. C.; Seinfeld. J. H. Reactions of semivolatile organics and their effects on secondary organic aerosol formation. Environ. Sci. Technol., 41, 3545-3550, 2007 link
  • Chan, A. W. H.; Kroll, J. H.; Ng, N. L.; Seinfeld. J. H. Kinetic modeling of secondary organic aerosol formation: effects of particle- and gas-phase reactions of semivolatile products. Atmos. Chem. Phys. , 7, 4135-4147, 2007 link