Plant transfer factors of naturally occurring radioactive decay series radionuclides, 7Be, and 137Cs in a semi-arid climate

Arid and semi-arid climates give rise to drought stress in plants, implying an increased uptake of radionuclides through both leaves and roots. This study was carried out in the Tabernas Desert (Almer & iacute;a, Spain), classified as an arid climate. Seventeen plants were analyzed, collected from four areas of the study site. The soils in the four areas were statistically comparable and showed a chemical composition and activity concentrations characteristic of uncontaminated soils, with activity concentrations corresponding to world averages, i.e., 31 +/- 4 Bq<middle dot>kg(-1) for the uranium series, 37 +/- 4 Bq<middle dot>kg(-1) for thorium one, and 344 +/- 17 Bq<middle dot>kg(-1) for K-40. Conversely, the soils showed that Be-7 was below the limit of detection, levels of Cs-137 equivalent to fallout, but an average Pb-210(ex) of 19 +/- 9 Bq<middle dot>kg(-1). The radionuclides of the three naturally occurring radioactive decay series are mainly present in the insoluble fraction, with Ra-226 being the most abundant. The transfer factors showed the usual behaviour of Cs > Ra > U > Th. The activity concentrations of Be-7 and Pb-210 showed a statistically significant linear relationship, indicating greater incorporation through the plant leaves.