Postdoc Research of Juliane L. Fry
2006 - 2008 University of California, Berkeley

Investigating air quality – climate interactions in the laboratory:
Does NOx pollution influence atmospheric aerosol production?

Photo of UC Berkeley campanile courtesy Charles C. Benton, Kite Aerial Photography

From July 2006-July 2008, I worked as a postdoctoral research scientist in the group of Prof. Ron Cohen in the UC Berkeley Chemistry Department. Using laboratory kinetics flow tube and spectroscopy techniques, I plan to investigate the role of NOx pollution in atmospheric aerosol production.

Climate is strongly influenced by the presence of aerosol particles through scattering and absorption of radiation. However, aerosol formation is ill understood. My research addresses one major gap in understanding: the chemistry of formation of secondary organic aerosol (SOA), i.e., aerosol formed by gas-to-particle conversion in the atmosphere.

One potential source of SOA is the low-volatility oxidation products of naturally emitted organic compounds. These biogenic compounds are emitted to the atmosphere in large quantities, providing a significant source of organic carbon. Nitrate radical (NO3), a night-time reservoir for NOx molecules present in polluted air, may react with biogenic compounds to form SOA. Field measurements are inconclusive on the nitrate content of SOA, and the chemical mechanisms for the formation of condensable product are not understood.

I hope to quantify the contribution of NO3 oxidation of biogenic carbon compounds to SOA formation by laboratory kinetics experiments with direct detection of product organic nitrates in the gaseous and aerosol phase, and subsequently to determine the optical properties of resultant organic nitrate-containing aerosols. These laboratory studies will allow evaluation of the potential climate impact of the nitrate SOA source.

As a complement to the laboratory measurements described above, we recently participated in a collaborative experiment at the SAPHIR (Simulation Atmosphärischer PHotochemie In einer großen Reaktionskammer) chamber facitiliy at Forschungszentrum Juelich in Germany. The campaign was focused on simulations of atmospheric NO3 radical. After comparing 13 research groups' instruments for measuring NO3 radical, we had time to do several experiments on aerosol formation from NO3-initiated chemistry, taking advantage of the excellent aerosol measurement capabilities available at the SAPHIR chamber. The insight we gain from this campaign will help direct our laboratory research.

SAPHIR chamber, Juelich, Germany

NO3 intercomparison campaign group, June 2007