Towards a generalized model for the primary and secondary contamination of lakes by Chernobyl-derived radiocesium.
As part of the UK Ministry of Agriculture Fisheries and Food Directorate of Fisheries Research (MAFF/DFR) post-Chernobyl monitoring program, a detailed study was carried out of the change over time in dissolved-phase 137Cs concentrations in a number of lakes in Cumbria, UK. These measurements have been combined with published data on 137Cs in Cumbrian and other European lakes in order to develop and test a "double exponential" model for changes in lakewater concentrations: A exp(-k1t) + B exp(-k2t) where the exponential terms correspond, respectively, to the initial fast flush of activity through the system followed by longer-term transfers (timescale, years) from the catchment. Parameter values have been determined for this model by curve-fitting to the set of measurements of post-Chernobyl 137Cs activities in lakes. Values of fitted parameters are shown to be related, in a simple manner, to the physical characteristics of the system, in particular water residence time and mean lake depth. These parameters are generalized to give a simple empirical model for the full set of study lakes. The model is shown to give estimates of 137Cs activity to within a factor of 5 of field data for a period of several years after the fallout. Initial fractional losses of activity from catchment to lake were determined to be within the range 0.44-8.7% per year, declining exponentially with a mean rate constant 0.98 x 10(-3) d(-1).
Smith
J T
JT
Institute of Freshwater Ecology, East Stoke, Wareham, Dorset, United Kingdom.
Leonard
D R
DR
Hilton
J
J
Appleby
P G
PG
D055592:Biophysical Phenomena; D001703:Biophysics; D002588:Cesium Radioisotopes / Q000032:analysis; D005618:Fresh Water / Q000032:analysis; D008433:Mathematics; D008962:Models, Theoretical; D011210:Power Plants; D018788:Radioactive Hazard Release; D012680:Sensitivity and Specificity; D013997:Time Factors; D014455:Ukraine; D006113:United Kingdom; D014878:Water Pollution, Radioactive / Q000032:analysis
D002588:Cesium Radioisotopes