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Title:
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Modelling fluxes and bioavailability of radiocaesium and radiostrontium in freshwaters: final report ECOPRAQ project
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Author(s):
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Published by:
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Publication date:
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ECN
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1-12-1999
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ECN report number:
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Document type:
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ECN-C--99-104
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ECN publication
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Number of pages:
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Full text:
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110
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Download PDF
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Abstract:
ECOPRAQ (ECOlogical PROcesses in AQuatic systems) refers, together withthe full title of the project, to the process- or mechanistically-based
approach to modelling the fluxes and the availability of radionuclides to the
biosphere in the aquatic environment. The global objectives of the project
are the development of mechanistic and general applicable whole-ecosystem
models. Because of their mechanistic basis, these models enable the
advancement of a sound theoretical basis for chemical and hydrological
countermeasures. The models can also be applied to test the effectiveness of
existing countermeasures. The project focuses on radiocaesium and
radiostrontium, with emphasis on the former radionuclide, and is subdivided
into the following six 'work packages': (1) Development of mechanistic
submodels for the solid/liquid partitioning and (bio)availability of
particle-bound radiocaesium and radiostrontium (WP2); (2) Development of
mechanistic submodels for the accumulation and elimination of radiocaesium
and radiostrontium by aquatic biota (WP3); (3) Development and assessment of
chemical and/or hydrological countermeasures (WP4); (4) Development of
mechanistically-based whole-ecosystem models (WP5); (5) Model validation of
sediment-water exchange and bioavailability of radionuclides in a large-scale
controlled laboratory setup and in situ (WP6); and (6) Model validation of
radionuclide scavenging by suspended particles and uptake by aquatic plants
(WP7) The development of mechanistic submodels for the basic aquatic
processes such as partitioning of the radionuclides with inorganic (suspended
and sediment) particles, accumulation and elimination by biota, transport
processes in lakes/rivers and their catchments, and the incorporation of
these basic processes/models in whole-ecosystem models, is organised in the
first 4 work packages. Useable versions of these (sub)models are available
and presented and discussed in Chapter 3 of this report. lt is clearly shown
that these models can predict transport, solid/liquid partitioning, and
biological uptake and biological elimination of radiocaesium much more
accurately and over a range of very different aquatic environments, compared
to the (more empirical) models that were available at the start of the
project. This is the case both at the submodel ecosystem level and at the
whole-ecosystem level. The key parameters that affect these basic transport
and availability processes have been identified and the (sub)models are
tested for systems that span the range over which these parameters may be
encountered in different aquatic environments. Contrary to many earlier
projects/studies, all laboratory experiments, large-scale tests, and field
measurements have been designed to identify the role of the major
environmental variables on basic model-parameters such as the solid/liquid
distribution coefficient (KD), the Concentration Factor (CF), and the rates
of radionuclide 'fixation'/ remobilization by sediments and
uptake/elimination by aquatic plants and fauna. All experimental and field
data have been collected and interpreted in the framework of the above
(sub)models. lt is shown that these monitoring data have been used for a
successful model validation and parametrisation. 13 refs.
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