Interconnected riverine–lacustrine systems as sedimentary repositories: Case study in southeast Michigan using 210Pb and 137Cs-based sediment accumulation and mixing models

Problems with the dating of sediment core using excess 210Pb in a freshwater system impacted by large scale watershed changes

“…To the supernatant, 200 mg of ascorbic acid was added to reduce the oxidation state of oxidants such as Fe 3þ to Fe 2þ and the pH was adjusted to 2.0 by the addition of ammonium hydroxide. Polonium was plated by spontaneous deposition onto silver planchets (Jweda and Baskaran, 2011) and were analyzed by an alpha spectrometer with a surface barrier detector coupled to an Octete-PC (ORTEC Co.).…”

“…The gamma ray detector was calibrated with sediment standards [IAEA-300 for 137 Cs (661.6 keV) and RGU-1 for 226 Ra (via 214 Pb and 214 Bi at 352 keV and 609 keV, respectively)] obtained from the International Atomic Energy Agency (IAEA). Typical resolution (full-width at halfmaximum) was about~1.3 keV at 46 keV and~2.2 keV at 1.33 MeV (Jweda and Baskaran, 2011) .…”

“…However, the annual atmospheric depositional fluxes of 210 Pb vary considerably in a large number of places, depending on the amount of precipitation. If the sedimentation rates are variable, then ages of the sedimentary layers have been obtained using either: ii) the constant rate of supply (CRS) model or iii) the constant initial concentration (CIC) model (Robbins and Edgington, 1975;Robbins, 1978;Appleby et al, 1979;Appleby and Oldfield, 1992;Swarzenski et al, 2006;Jweda and Baskaran, 2011). The constant rate of supply model assumes constant flux and efficient transfer from the water to the surficial sediments.…”

Sedimentation rates and age modeling of Late Quaternary marine sediments with unsupported 230Th

“…Several papers focused on the development of methodologies, mathematical models [5][6][7], and application of these techniques [8][9][10]. They are widely used for assessing recent sedimentation rates [11,12] and age modeling [13,14] in lakes, estuaries, and other coastal systems.…”

Environmental Evolution of the Caravelas Estuary (Northeastern Brazilian Coast, 17° S, 39° W) Based on Multiple Proxies in a Sedimentary Record of the Last Century

“…The sedimentation and mass accumulation rates and core dating were determined with the application of four different mathematical models (constant initial concentration [CIC], constant flux, constant sedimentation [CFCS], constant rate of supply [CRS], and model of diffusion convection [MDC]) using a series of corrections to account for sediment porosity and dry density (Clifton et al, 1995;Hai, Liancheng, and Zhisheng, 2006;Jweda and Baskaran, 2011) (Table 1).…”