Objective
The objectives of the research project are focused on the physico-chemical and biological processes at the soil-root interface which govern fluxes of Cs and Sr and, their root-uptake and subsequent transfer to important food crops. Identification and quantification of key parameters in the dynamic interactions of radionuclides between soil, soil solution and plant roots are important prerequisites to predict their biogeochemical cycling and transfers to plants based on the development of mechanistic models.
The work content of the proposal is articulated in three complementary research lines which comprise laboratory experiments, Iysimeter studies and the development and improvement of mechanistic models.
In laboratory experiments, soil-radionuclide interactions will be studied according to soil moisture, ageing and competitive effects of chemical analogues of Cs and Sr. For the various soils, specific relationships between soil water potential and water content will be determined and related to the concentration of radionuclides in the soil solution. The results will then be compared with realistic measurements of the water potential and soil solution composition in the Iysimeters in order to interpret the observed variability of transfer factors for Cs and Sr. The effect of the soil moisture content on transfer factors will be investigated by manipulating the water potential in the Iysimeters.
Soil-radionuclide interactions are also closely related to chemical availability, spatial distribution and migration of Cs and Sr in the different soils. Kinetics of migration and vertical distribution of radionuclides in the Iysimeters will be studied according to soil type, climate and ageing, while the chemical availability (extractability) of Cs and Sr in the different soils will be determined with respect to depth, water content and ageing (adsorption/desorption).
Over two growing seasons repeated twice (shallow and deep rooting plants) the variability of Cs and Sr transfer factors will be determined from Iysimeter cultures considering soil types, crop species, agricultural practises, climate/water regimes and ageing. Interpretation of the transfer factors variability will be supported both by laboratory and Iysimeter measurement results.
The modelling effort will be devoted to vertical migration and root-uptake of Cs and Sr. For vertical migration, two complementary modelling approaches will be considered which both reflect that migration of radionuclides is mainly controlled by water fluxes. The prediction of water fluxes is achieved by an advection dispersion calculation which computes solute transport driven by water flow in the vertical direction. Parameterisation and verification of the models will be carried out based on small scale column experiments and Iysimeter studies investigating the behaviour of Cs and Sr in the different soils.
Modelling radionuclides root-uptake will adapt mechanistic models of nutrients plant uptake which have been developed for macro-concentrations. This type of models integrates processes of soil nutrient supply with nutrient absorption kinetics at the root surface. The root uptake model will first be adapted to micro-concentrations typical for radionuclides in the natural environment, considering also the strong competitive effects of analogous ions. This model will then be improved with experimental data from laboratory, Iysimeter and field experiments.
Validation and refinement of the overall model, integrating vertical migration and root-uptake, will be attempted in an iterative way by exploiting an elaborated data base of Cs and Sr soil-to-plant transfers originating from field investigations around Chernobyl.
Programme(s)
Topic(s)
Call for proposal
Data not availableFunding Scheme
CSC - Cost-sharing contractsCoordinator
92265 Fontenay-aux-Roses
France