Fate of long-lived radioactive halogens, (³⁶Cl, ¹²⁹I), in agricultural ecosystems: Field investigations

¹ Laboratory of Radioecology and Ecotoxicology, Institute for Radioprotection and Nuclear Safety, DEI/SECRE/LRE, Cadarache, Bd. 186, BP. 3, 13115 St. Paul-lez-Durance Cedex, France
² Ukrainian Institute of Agricultural Radiology (UIAR), Mashinostroiteley Str.7, Chabany,Kiev Region 08162, Ukraine

Abstract

Field experiments in the Chernobyl exclusion zone have been carried out to determine the behaviour of the radioactive halogens ³⁶Cl and ¹²⁵I (as a surrogate for ¹²⁹I) in the soil-plant system and along human food chains. The investigations on the migration in four types of soil of the two radionuclides showed that the vertical transport of chlorine was the most rapid: 9 months after the contamination the residual fractions of ³⁶Cl in the 20 cm arable layer varied from 1% to 3% according to soil type. For iodine this percentage was less than 3% in any case. The soil to plant transfers were quantified for various agricultural crops (cereals, grass, root vegetables, leaves vegetables and fruit vegetables) and for several kinds of soils. The root uptake of ³⁶Cl by plants was particularly important. As a result of this very high biological assimilation about 60% of the contamination was extracted from the soils by the plants after one vegetation period. For iodine the concentration ratios values are 2 or 3 order of magnitude lower than for chlorine.