The Dependence of Hydrocarbon Concentrations on Sampling Protocol

Participants: Chris Bigley (Biology, 2009), Gabriele Canzi (Chemistry, 2008), Kevin Entzminger (Biochemistry, 2009), Joyce Lee (Chemistry, 2008), Nick Von der Ahe (Chemistry, 2010)

Faculty: Lambert A. Doezema, Department of Chemistry and Biochemistry

Sampling protocol was found to have a significant influence on hydrocarbon concentrations in ambient air samples. Samples were collected in Los Angeles on eight different sampling days throughout 2007-2008 following the varying protocols of four different, well-cited, U.S. urban hydrocarbon studies. Samples were collected in 2-liter stainless steel canisters and analyzed using GC-FID (gas chromatography with flame ionization detectors). It was found that the four different sampling procedures resulted in hydrocarbon concentrations that varied from between two and eight times of each other on the same sampling day. Time of day was found to have the largest influence on hydrocarbon concentrations, with peak concentrations occurring in the early morning hours. Location had a smaller effect on hydrocarbon concentrations, with higher levels found in industrial and downtown sampling locations. In addition to absolute concentrations, certain hydrocarbon ratios varied significantly depending on the sampling protocol. These results suggest that researchers need to take note of differences in sampling strategy when comparing hydrocarbon concentrations from different field studies.

Presentations: J. Lee, N. Von der Ahe, L.A. Doezema. The Dependence of Hydrocarbon Concentrations on Sampling Protocol. Poster at Southern California Conference of Undergraduate Research, Cal State University, Los Angeles, November 17, 2007.

Funding: Rains Research

Image caption (above): Nick Von der Ahe collects a sample of Los Angeles air.