To date, the use of 137Cs in soil erosion and sediment delivery
investigations has focussed primarily on providing estimates of
average (mean annual) rates of soil and sediment redistribution for
the period extending from the onset of bomb fallout to the time of
sampling. As generally applied, the approach does not permit
subdivision of this period. Where Chernobyl fallout inputs have
occurred, the dual input introduces problems in using measurements
of present 137Cs inventories to estimate average erosion and
soil redistribution rates for the entire period since the onset of
bomb fallout. However, in some areas affected by Chernobyl fallout
it is possible to assume that the present inventories are dominated
by Chernobyl fallout and thus provide information on soil and
sediment redistribution for the period 1986 to the time of sampling.
Alternatively, in other areas it is possible to assume that the Chernobyl
fallout made only a minor contribution to the present inventory
and thus that the present inventories reflect soil and
sediment redistribution during the entire period since bomb
fallout. Where both bomb and Chernobyl fallout inputs represent
significant contributions to the total 137Cs inventory, procedures
also exist to incorporate information on the Chernobyl fallout input
into the conversion model used to estimate soil redistribution rates
(e.g. Walling et al., 2006)