Dating Sediments from Oxbow Lakes in the Mississippi Delta using 239Pu, 240Pu and 210Pb determined by ICPMS: a feasibility study

Author(s): Cizdziel, J.; Chakravarty, P.

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, we examined the feasibility of using inductively coupled plasma mass spectrometry (ICP-MS) to: measure global fallout plutonium (Pu) and 210Pb in sediment core samples from Mississippi for dating purposes. 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 utilized core samples previously collected from strategic locations within the Mississippi Delta region. Select samples were be digested with mineral acids and the Pu and Pb isotopes were selectively removed from the matrix using chromatographic extraction resins, effectively pre-concentrating the elements prior to analysis. Plutonium was determined using isotope dilution mass spectrometry and 210Pb using external standardization. In this talk and associated poster we will discuss the methodology and present our findings.

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Technical Sessions

1 Best Management Practices #1
2 Delta Water Assessment
3 Flood Assessment & Mgmt.
4 Wetlands
5 Watershed Mgmt. #1
6 Non-Point Source Assessment
7 Modeling
8 Water Quality
9 Best Mgt. Practices #2
10 Delta Water Conservation
11 Sedimentation
12 Storm Water
13 Watershed Mgt. #2
14 Public Water Systems
15 Surface Water Assessment & Evaluation

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