Contractor investigated the use of Pb and Sr isotopic measurements of PM2.5 to evaluate the impact of Asian (Chinese) sourced aerosols (including pollutants, and mineral dust) on air quality in California. Aerosols transported across the Pacific can raise local “background” pollutant burdens, limiting the amount of local emissions that can be permitted and still attain State and Federal Air Quality Standards. PM2.5 samples collected at Mt. Tamalpais and Chabot Space and Science Center in the Oakland Hills, archived ARB PM2.5 samples and samples from the Eastern Sierra were analyzed for Pb and Sr isotopes. The Mt. Tamalpais and Chabot samples were also analyzed for elemental composition. The Pb isotopic measurements demonstrated that the collected aerosols contain Pb that was a variable (with time and location) mixture of locally-derived and China-sourced Pb. Likewise, Sr isotopic measurements combined with elemental data show that the aerosols at Mt. Tamalpais contain a variable fraction of Chinese sourced mineral aerosol (“Loess”). These data clearly track Asian sourced transport events and demonstrate the utility of isotopic signatures for portioning the sources of PM2.5, particular elements, and perhaps ozone in California. For example, during the week of 7/21/08 about 45% of the PM2.5 mass at Chabot was sourced in Asia.
For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753
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