Although foliar deposition is an important route by which plants become contaminated, the data base for modelling foliar uptake is poor. As a result, large uncertainties are associated with the contamination of food crops via the foliar pathway yet simple approaches are used to estimate the contamination of plants via foliar uptake.
It is well known that four main processes relate to the contamination of vegetation by foliar uptake. These processes are the interception by the plant surface, the retention after weathering processes have occurred, the absorption into the plant and the translocation or movement within the plant to other plant parts such as roots, fruit, etc. To overcome the large uncertainties associated with the foliar pathway, more experiments are needed to investigate these four processes as function of the element, the plant species, the stage of plant development at which the deposition occurs and the time after the contamination. Humidity and temperature can also be important as shown by the research done on foliar fertilisation by mineral nutrients.
The aim of this PhD proposal is to provide data on the interception, retention and translocation of radionuclides at different stages of plant development for wet deposition simulating sprinkling irrigation and as such contribute to a better quantification of the foliar uptake. The main research question is: Is the internal contamination of the plant ruled mainly by the leaf surface area and the amount intercepted on the leaves? Other research questions are: Is it possible to make a distinction between the amount retained on the plant surface and the amount absorbed internally and available for translocation? Is the chemical form of the radionuclide more or less important than the differences between the plants? The effect of temperature may also be investigated at a later phase of the research.