Abstract
The stratigraphy of the upper clay sediments in the northern basin of Lake Tyrrell, a saline playa in northwestern Victoria, is described. The 137Cs activity in sediment profiles was measured at two sites and shows redistribution of the radioisotope to depths well below post-bomb sediments, as indicated by 14C dates and surface pollen spectra. The distribution coefficient ( K D) of 137Cs on Lake Tyrrell sediments was measured and found to range from ∼3600 at 0% NaCl to ∼600 at 26% NaCl. This low K D for halite-saturated sediments suggests that adsorption sites in the clay lattice are saturated by Na +. An advection-diffusion model with constant input indicates an effective diffusion coefficient of ∼1.7 × 10 −8 cm 2 s −1 and a K D of 280, in good agreement with laboratory measurements. More realistic input functions indicate that this is a lower limit on K D. It is concluded that 137Cs is redistributed in the upper sediments by diffusion due to the low K D resulting from the high salinity. This radioisotope is not useful in locating post-bomb sediments in this and probably other highly saline environments.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call