Final Post: Summary for summer research experience

This summer, my research focused on two major parts: 1) chemical characterization of urban organic aerosols; 2) chemical analysis on composition of biomass burning aerosols.

For the first part, during this summer, we received aerosol samples collected in Downsview, Lethbridge, Halifax, and Sherbrooke, Canada. These samples are examined using a Aerosol Mass Spectrometer (AMS), and the mass spectrometric data was analyzed by the Igor program. Both qualitative and quantitative information can be obtained through the data processing. Qualitative information can be acquired by studying the mass spectra. Noticeable ion species in a mass spectrum include: CO2+ as trace ion for acids, CHO+ for alcohols, CH3SO2+ for marine aerosols, and C2H4O2+ for saccharides. From a mass spectrum, we are able to learn: 1) the carbon oxidation state for this sample, 2) the kinds of chemical functional groups in the aerosol sample, and 3) probable sources of the aerosol sample. Quantitative information can tell us exactly how much organics exists in an aerosol sample. Combined with field data on air flow in the sampling area, we may able to tell the concentration of atmospheric organics in each urban site.

For the second part, we examined filter-collected aerosols from emissions of controlled burnings of various biomass fuels. Fuel types include: douglas fir, loblolly pine, englemann spruce, etc. We cut each filter into pieces, and irradiated the pieces with Xenon lamp for different amount of time in order to simulate the kind of aging processes aerosol experienced in atmosphere. We used both Infrared Spectroscopy (IR) and AMS techniques to analyze the photolyzed filter pieces in order to track the chemical changes happened to the aerosols during the photolysis processes. By using IR, we are able to have an accurate account of the kinds of functional groups in the filter samples. Similar to a mass spectrum, in an IR spectrum, we can see the changes in chemical compositions of the samples by tracking the grows and decays of peaks.

In order to interpret the chemical changes happened to the examined aerosol samples, I also did literature research on recent aerosol studies. Through literature reading, I acquired more understanding and knowledge on the aerosol chemistry. My advisor, Prof. Rachel O’Brien also helped me gain more insight on atmospheric sciences, and the field of environmental chemistry in general. My research on organic aerosols will continue in fall semester, and my research experience this summer will serve as a valuable resource.