Interception, retention and translocation of radionuclides in agricultural crops under greenhouse conditions, following sprinkling irrigation

Cristina Antonella

Promoter

Samson Roeland, (UA), roeland.samson@uantwerpen.be

SCK•CEN Mentor

Sweeck Lieve
lieve.sweeck@sckcen.be
+32 14 33 28 52

Expert group

Biosphere Impact Studies

PhD started

2016-11-01

Short project description

The production and application of nuclear energy has led to enhanced radioactivity in the environment, resulting in an increased exposure of humans to ionising radiation. Among the various pathways by which humans can get exposed to ionising radiation, the uptake of radionuclides by agricultural plants is one of the most important routes. Agricultural plants can get contaminated by direct contamination of the surfaces of aerial parts of plants or by indirect contamination when radionuclides deposited on the soil are taken up by the root systems together with water and nutrients. Past experiences have shown that for most radionuclides, the contamination of the crops by interception is much higher than the indirect contamination via root uptake during the first year of a nuclear accident or if contamination occurs via yearly irrigation with contaminated water. A good estimate of the foliar uptake by plants is therefore necessary to reliably assess the exposure dose from the consumption of contaminated agricultural foodstuffs.

This research can also be seen a broader perspective. Foliar fertilsation is a technique that is commonly applied to increase the plant yield. The plant yield responses to foliar applications are however inconsistent and seem to depend on plant type and time of application. A better understanding of the mechanisms underlying the absorption and movement of elements may lead to an optimisation of the fertilisation treatments.

Objective

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.