Bomb-fallout Cs-137 as a marker of geomorphic stability in dune sands and soils, Pinery Provincial Park, Ontario, Canada

The anthropogenic radionuclide Cs-137 has been extensively utilized as a tr acer of geomorphic processes in the northern hemisphere since its depositio n during atmospheric testing of nuclear devices in the 1950s and 1960s. The distribution of bomb-fallout Cs-137 was measured on a sequence of coastal dune sands and soils at Finery Provincial Park, on the coast of Lake Huron in southern Ontario, Canada. The depth distribution within the stabilized, developed soils inland reflected the relationship between clay content and the adsorption and immobilization of the radionuclide. However, the influen ce of soil organic matter, silt-sized particles and vegetation cycling on t he profile distribution could not be discounted. Within the geomorphically dynamic dune sands near the coast, there was a significant activity of Cs-1 37 even though the sands were lacking in clay-sized particles. Within a bur ied soil on the inland side of a large active dune blowout, the distributio n of Cs-137 with depth was useful as a stratigraphic marker of the rates of accumulation of sands at that position. Therefore Cs-137 may be a useful a lternative to erosion pins, sequential air photos and sediment traps in the monitoring of dune destabilization in coastal environments. Copyright (C) 2001 John Wiley & Sons, Ltd.