Iodine-129 in the environment of a nuclear fuel reprocessing plant: V. The transfer of 129I and 127I in the soil-pasture-cow-milk/meat pathway, as obtained by field measurements

Abstract

A field investigation of the transfer of 129I and of natural 127I in the soil-pasture-cow-milk/meat pathway has been carried out at a dairy farm situated 5400 m to the north of the small Karlsruhe nuclear fuel reprocessing plant. Soil and herbage samples were collected during the period between April 1986 and April 1987. Milk samples were collected during the 1986 grazing season (28 April to 30 December) and again at the beginning of the 1987 grazing season. The concentrations of 129I and 127I were determined in all soil, herbage and milk samples. The concentrations of 129I and 127I in the soil samples (dry weight) were found to be: for 129I, between 1·4 × 10 −13 and 7·1 × 10 −13 g/g (geometric mean 3·5 × 10 −13 g/g and for 127I, between 2·2 × 10 −6 and 1·8 × 10 −5 g/g (geometric mean 6·3 × 10 −6 g/g). The concentrations of 129I and 127I in the samples of pasture vegetation (wet weight) were: for 129I, between 8·2 × 10 −15 and 2·4 × 10 −13 g/g (geometric mean 4·1 × 10 −14 g/g) and for 127I, between 1·2 × 10 −8 and 4·1 × 10 −7 g/g (geometric mean 5·0 × 10 −8 g/g). Those in the milk samples (wet weight) were: for 129I, between 1·1 × 10 −12 and 1·1 × 10 −11 g/litre (geometric mean 3·4 × 10 −12 g/litre) and for 127I, between 4·8 × 10 −6 and 3·1 × 10 −5 g/litre (geometric mean 1·4 × 10 −5 g/litre). From the concentrations of 129I and 127I in soil and pasture vegetation, soil-to-plant concentration factors for 129I and 127I in pasture vegetation could be calculated. Geometric means for the concentration factors for 129I and 127I for pasture vegetation of B v = 9·9 × 10 −2 and 7·9 × 10 −3, respectively, were obtained. For the grazing season, the transfer coefficients for 129I and 127I from feed to milk could be determined. The F M values found were: for 129I, between 2·6 × 10 −4 and 1·1 × 10 −2 d/litre (geometric mean 1·1 × 10 −3 d/litre) and for 127I, between 3·5 × 10 −4 and 9·3 × 10 −3 d/litre (geometric mean 2·6 × 10 −3 d/litre). Since one cow and one calf were slaughtered during this field investigation, the transfer coefficients F f for 129I and 127I from feed to beef and veal could be determined. These were F f = (11±6) × 10 −3 d kg −1 and F f = (3·9±2) × 10 −3 d kg −1 for 129I and 127I, respectively, in beef, and F f = (3±1) × 10 −3 d kg −1 and F f = (0·2±0·06) × 10 −3 for 129I and 127I, respectively, in veal.