Using Isotopes to Track the Passage of a Spring 2002 Dust Storm Over Hefei, China

Research over the past decade has highlighted the importance of intercontinental transport and exchange of atmospheric aerosols, including soil-derived dust and industrial pollutants. These far-traveled aerosols can affect air quality, atmospheric radiative forcing and cloud formation and can be an important component in soils. Principal component analysis of elemental data for aerosols collected over California has identified a persistent Asian soil dust component that peaks with Asian dust storm events [1]. Isotopic fingerprinting can provide an additional and potentially more discriminating tool for tracing the sources of dust. A time series of aerosol samples was collected on Teflon filters (PM2.5) near Hefei, China, during a dust storm in Spring 2002. We analyzed these samples for isotopic composition, including 87Sr/86Sr and 143Nd/144Nd, and also measured the amounts of K, Rb, Sr, Sm, and Nd by isotope dilution. Samples were collected on a daily basis between April 6 and May 4, 2002, a period that included the passage of a dust storm and coincided with the ITCT-2K2. Samples were dissolved off the filters using HF-HNO3-HCl, chemically separated, and analyzed for Sr and Nd isotopes using thermal ionization mass spectrometry. Total amounts of Sr and Nd were small (5-10 ng Sr in typical samples) but high-quality isotopic analyses were obtained. A sharp rise in Sr loading and 87Sr/86Sr is observed to coincide with the dust storm arrival. After the storm's passage, Sr loads fall relatively quickly while 87Sr/86Sr falls more gradually back to background levels over nearly a week. These results provide a basis for our isotopic study of California mineral aerosols, including the identification and apportionment of local and far-traveled Asian dust and their variation in time. [1] VanCuren et al. (2005) J. Geophys. Res., 110, D09S90, doi: 10.1029/2004JD004973