Interconnected riverine–lacustrine systems as sedimentary repositories: Case study in southeast Michigan using 210Pb and 137Cs-based sediment accumulation and mixing models
2011; Elsevier BV; Volume: 37; Issue: 3 Linguagem: Inglês
10.1016/j.jglr.2011.04.010
ISSN2773-0719
Autores Tópico(s)Groundwater and Isotope Geochemistry
ResumoParticle-reactive nuclides, such as 210Pb and 137Cs, serve as powerful chronometric tools in the investigations and reconstruction of historical contamination in coastal marine and lacustrine systems. Towards the first systematic establishment of sediment chronologies of river channel sediments, a set of seven sediment cores from Clinton River and Lake St. Clair riverine–lacustrine system were collected and analyzed for 210Pb, 226Ra, and 137Cs activities. Measured inventories of 210Pbxs and 137Cs were ~ 2 and ~ 9 times higher than that expected from atmospheric fallout. From the measured 210Pbxs/137Cs inventory ratios, erosional input of 137Cs was found to be significantly higher than that of 210Pb indicating that anthropogenic watershed disturbances have resulted in accelerated sediment erosion. Good agreement between accumulation rates using 210Pbxs and 137Cs using four different age models were obtained for four of the seven cores in the riverine–lacustrine environment. Average sediment mass accumulation rates, based on the 210Pbxs CFCS model, in the lower Clinton River (mean: 0.91 g cm−2 yr−1) were generally higher than those in Lake St. Clair (mean: 0.55 g cm−2 yr−1) due to a higher sediment flux and the unique riverine system characteristics. Sediment mixing coefficients, based on a 210Pbxs mixing model, were much higher in the river (mean: 64.9 cm2 yr−1) compared to the lake (mean: 4.7 cm2 yr−1), as was expected due to the frequency of perturbation and resuspension. Net accumulation of datable sediments in the Clinton River indicates that similar river channel deposits may act as repositories for the reconstruction of historical contamination and environmental changes.
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