A. Garciaolivares et A. Aguero, A MODEL FOR THE BEHAVIOR OF CS-137 IN WATERSHED SCENARIOS, Journal of contaminant hydrology, 13(1-4), 1993, pp. 183-211
Citations number
13
Categorie Soggetti
Water Resources","Environmental Sciences","Geosciences, Interdisciplinary
A mathematical model of radiocesium transfer in a lake and its catchme
nt is presented in an attempt to improve previous approaches. The expe
rimental data base of the Esthwaite Water location, U.K., prepared in
the international program on Validation of Model Predictions (VAMP) of
IAEA/CEC, was used as a test scenario. Radiocesium enters the lake vi
a: (1) a quick pulse of atmospheric deposition for 1-2 days; and (2) a
lasting but smaller contribution from the catchment carried by the wa
ter runoff and the dragged sediments. An auxiliary model of the catchm
ent was used to quantify these two source terms. The temporal evolutio
n of the Cs-137 concentration in this lake after the contamination by
the Chernobyl accident is modelled using a compartmental approach foll
owing the Codell model. The desorption/adsorption dynamics between wat
er and sediments are considered both in the drainage water and in the
lake boundary layer. The most important processes transferring contami
nation out of the lake water are adsorption of radioactivity by suspen
ded sediments and their sedimentation; these processes are modelled th
rough a distribution coefficient and through an aerial removal rate. S
ummer stratification is modelled introducing some auxiliary hypotheses
. When using a priori probability distributions for the parameters bas
ed both on experimental evidence and on information from the literatur
e the model simulates the observed radiocesium concentrations with an
expected underprediction bias of 30% in the integrated concentrations
in water. The concentration in sediments is inside the observed range
in most of the runs. After the calibration of the model to the best fi
ts observed with parameters inside their expected ranges, the bias dec
reases to -6% in the epilimnion, 8% in the hypolimnion and -4.4% in se
diments, with an unexplained variance of +3.2%, +3% and +1%, respectiv
ely.