Radiocaesium in upland herbage in Cumbria, UK: A three year field study

Abstract

Between April 1987 and November 1989, the uptake of radiocaesium by herbaceous vegetation growing on a variety of upland soils contaminated in May 1986 by Chernobyl fallout was measured and found to be related to soil type. The uptake on peat was found to be an order of magnitude greater than on acid brown earth. The levels of radiocaesium in all the soils reflected both pre-Chernobyl and Chernobyl deposition, but levels in vegetation arose almost entirely from the Chernobyl fallout. Soil profiles showed all the radiocaesium to be within the rooting zone of the vegetation but uptake of Chernobyl radiocaesium was up to an order of magnitude greater than that of radiocaesium deposited 20–30 years earlier. The rate of uptake of the Chernobyl radiocaesium is therefore also expected to decrease markedly over a period of decades. On a shorter timescale, from the measurements reported here, soil-to-plant transfer on brown earth fell by about 77% in three years but on soils with an organic matter content of 88% the decrease was only about 17%. The levels of radiocaesium in the vegetation showed a seasonal pattern.