Dynamic Modeling of the Cesium, Strontium and Ruthenium Transfer to Grass and Vegetables

Abstract

From 1988 to 1993, the Nuclear Safety and Protection Institute (Institut de Protection et de Sûreté Nucléaire--IPSN) conducted experimental programs focused on transfers to vegetation following accidental localized deposits of radioactive aerosols. In relation to vegetable crops (fruit, leaves, and root vegetables) and meadow grass these experiments have enabled a determination of the factors involved in the transfer of cesium, strontium, and ruthenium at successive harvests, or cuttings, in respect of various time lags after contamination. The dynamic modeling given by these results allows an evaluation of changes in the mass activity of vegetables and grass during the months following deposit. It constitutes part of the ASTRAL post-accident radioecology model.

Transfer of 131I from Fukushima to the Vegetation and Milk in France

“…The root transfer is insignificant here; therefore, we only take into account the foliar transfer. From the comparison of air and vegetation data (see previous section), it appears that dry deposition was significant for iodine, and thus the contamination of grass and leaves of vegetables was computed as dry deposition of iodine, following eqs and respectively, derived from ASTRAL model , C g r a s s ( d ) = R c Y × ∑ 0 d D false( d false) × exp nobreak.25em − [ false( normalλ w b + normalλ r false) × Δ t ] C v e g ( d ) = ∑ 0 d D false( d false) × F t × exp nobreak.25em − [ false( normalλ w b + normalλ r false) × Δ t ] where C grass ( d ) or C veg ( d ) is the grass or vegetable measured concentration due to the deposit of the considered day d (Bq kg –1 fresh weight); D ( d ) is the deposited iodine on day d (Bq m –2 ); Y and R c are the yield (kg fresh weight m –2 ) of grass and the retention ratio for deposit on grass, respectively. R c / Y ratio varies linearly between 1.4 (March) to 0.56 m 2 kg –1 fresh weight (May); the value Y used in ASTRAL (0.7 kg fresh weight m –2 ) is quite close to the yield given by field: 1.65, 0.48, and 1.18 kg fresh weight m –2 in Cadarache, Tricastin, and Agen, respectively; Ft is the dry foliar transfer factor of iodine for ...…”

“…The root transfer is insignificant here; therefore, we only take into account the foliar transfer. From the comparison of air and vegetation data (see previous section), it appears that dry deposition was significant for iodine, and thus the contamination of grass and leaves of vegetables was computed as dry deposition of iodine, following eqs 2 and 3 respectively, derived from ASTRAL model 12,13 C grass ðdÞ ¼ Rc Y Other parameters apart from deposition velocity were considered as default values in the equations. Indeed default parameters of ASTRAL fit well with values given by the IAEA EMRAS working group which aim to validate the 131 I ecological transfer models: the yield of grass ranging between 0.1 and 0.6 (kg fresh weight m À2 ) and the R c /Y ratio ranging between 0.5 to 1.65.…”

Inter-taxa differences in root uptake of 103/106Ru by plants

“…Despite being deposited primarily in fuel particles which settled close to the Chernobyl reactor (Krouglov et al, 1998), 106 Ru was detected in significant quantities in Chernobyl fall-out in, for example, Sweden (Kresten and Chyssler, 1989), Italy (Adamo et al, 2004) and Turkey (Polar and Bayülgen, 1991). 106 Ru is also a contributor to effluents from Cap de la Hague (Salbu et al, 2003) and has been a focus of attention in modelling potential accidents with Pressurised Water Reactors (Renaud et al, 1999). Given the potential radioecological importance of 106 Ru it is important to understand its ecosystem transfer processes, such as that from soil-to-plant.…”