Year Established: 2011 Start Date: 2011-03-01 End Date: 2012-08-31
Total Federal Funds: $6,508 Total Non-Federal Funds: $13,017
Principal Investigators: James Cizdziel
Abstract: Sediments are complex deposits of inorganic and organic matter that can serve as a natural storage system for metals and anthropogenic contaminants. Sediment cores can provide a window on the past because they can go back years, decades, even centuries and serve as environmental proxies. Dating of recent (<100 years) sediments is important in many studies and applications, including determining the source and timing of pollution events, establishing sedimentation patterns, and in reservoir management. Linking sediment "dates" (typically in years) with sediment characteristics or specific chemical constituents is also crucial for examining the effectiveness of both pollution and erosion control measures. Conventional dating techniques which use 210Pb and 137Cs are slow and costly, in part because extended times are needed to measure the radioactive decay emissions from low-activity samples. In this study, I propose to use two newly acquired state-of-the-art inductively coupled plasma mass spectrometers (ICP-MS) to: 1) develop a rapid method to measure global fallout plutonium (Pu) in sediment core samples for dating purposes, and 2) examine the feasibility of using modern ICP-MS for determining 210Pb in sediments. Recent advances in mass spectrometry have made it an alternative to radioactive decay spectrometry for determining Pu, and possibly 210Pb, in environmental samples. This study will take advantage of well-characterized core samples previously collected from strategic locations within the Mississippi Delta region. Select samples will be digested with mineral acids and the Pu and Pb isotopes will be selectively removed from the matrix using chromatographic extraction resins, effectively pre-concentrating the elements prior to analysis. Isotopes will be determined using isotope dilution mass spectrometry and 210Pb activity calculated using its specific activity. The most important benefit obtained from this study will be a rapid and more cost-effective technique for the determination of the chronology of sediments layers obtained from sediment coring devices. Specific objectives of the study are to: 1) validate the methodology using isotope dilution techniques and standard reference materials, 2) test the methodology on well-characterized sediment cores obtained from Beasley Lake, and possibly others, from Mississippi Delta Region, and 3) present the results to the USDA’s National Sedimentation Laboratory, located near the University of Mississippi (UM) campus, and others in the state, to promote collaboration. Moreover, the newly developed approaches will allow confirmation of 210Pb geochronology (using the Pu-based method), more detailed and refined examination of sediment chronology and/or greater spatial data coverage (i.e., more data for the same cost), and finally more confidence in study results.