Interception of caesium-contaminated rain by vegetation

Abstract A series of experiments were carried out to quantify the interception of rain-borne caesium by crops of grass ( Lolium perenne ), broad beans ( Vicia faba ) and wheat ( Triticum aestivum ) under rainfall intensities typical of those encountered in the U.K. (1–18 mm h −1 ). The fraction of contamination deposited on the vegetation decreased with time, as the plant surface approached a saturation level of contamination. Surface contamination was dependent upon the total amount of rainfall rather than the rainfall intensity. The total surface water storage capacity of wheat and beans was determined, and found to approach a saturation level as total rainfall increased in a manner similar to the measured contamination levels. Total accumulation of caesium from aqueous solution onto bean leaves was found to increase linearly with time over the range of concentrations tested (0.0001–10 mM), the rate of accumulation increasing with concentration according to a power law. The combination of results obtained suggests that deposition of rain-borne contaminants could be modelled appropriately by a water storage capacity term and a “chemical term” derived from the contaminant concentration and its affinity for a particular plant surface.