Kinetic Models for Representing the Uptake of Radionuclides in Plants

Abstract

Traditionally, radionuclide accumulation in plants due to uptake from soil has been estimated using empirically measured concentration ratios. However, over the last 40 years, there has been an increasing interest in representing radionuclide transport in soils and uptake by plants using a kinetic approach. Here, a brief account is given of the processes involved and of the fundamental equations used to represent the kinetics of radionuclide transport and plant uptake. In this account, the focus is on developing an appropriate representation of soil hydrology to provide water fluxes for use in the advective–dispersive transport equation. Following this account, a description is given of various models that have been used to represent radionuclide transport in soil–plant systems. These models illustrate how a wide variety of factors such as sorption, active uptake by roots, plant growth, changing hydrological conditions and volatilisation have been taken into account. In addition, a summary is given of how plant uptake of ¹⁴C can be estimated when the ¹⁴C enters the soil zone from below as either carbon dioxide or methane.