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For many years, the IAEA has published materials aimed at supporting the assessment of radiation impacts on human beings and the environment. Two major publications, Sediment Kd s and Concentration Factors for Radionuclides in the Marine Environment (Technical Reports Series No. 247), published in 1985, and the Handbook of Parameter Values for the Prediction of Radionuclide Transfer in Temperate Environments (Technical Reports Series No. 364), published in 1994, together provided a full set of available transfer parameter values for the marine, freshwater and terrestrial environments. For many years, these two publications have served as key references for radioecologists, modellers and authorities, providing data for use in environmental impact assessments. Since the publication of these two collections of data, a number of publications on transfer parameter values have been produced and merit consideration. Therefore, in 2000 the IAEA initiated a revision of Technical Reports Series No. 247 which resulted in the publication, in 2004, of Sediment Distribution Coefficients and Concentration Factors for Biota in the Marine Environment (Technical Reports Series No. 422), covering newly obtained data as well as changes in the regulatory framework. In 2003, within the framework of the Environmental Modelling for Radiation Safety (EMRAS) programme, the IAEA undertook a revision of Technical Reports Series No. 364. The current publication was prepared by the members of Working Group 1 of the EMRAS programme, chaired by P. Calmon (IRSN, France). This publication focuses on transfer parameter values; the models in which they are used generally are not described here. It is therefore supported by IAEA-TECDOC-1616, which accompanies this report and contains the full collection of the reviewed data and provides radioecological concepts and models facilitating the use of these values in specific situations. This publication is intended to supplement existing IAEA reports on env

For more than thirty years, the IAEA has published a set of documents aimed at the limitation of the radiation exposure of the population from various nuclear activities. In particular, in 1994 the IAEA published Technical Reports Series No. 364, Handbook of Parameter Values for the Prediction of Radionuclide Transfer in Temperate Environments. Over the years, it has proved to be a valuable reference for radioecologists, modellers and authorities in Member States, and has been quoted in numerous impact assessments. Technical Reports Series No. 364 was based on a review of available data up to the end of 1992. However, a number of high quality critical reviews have been produced in recent years for some of the transfer parameter values which merit consideration. Thus, it was assumed that there is sufficient new information available to warrant reconsideration of a significant proportion of the values given in Technical Reports Series No. 364 and to initiate an updating of Technical Reports Series No. 364 in the framework of the IAEA EMRAS (Environmental Modelling for RAdiation Safety) project. It is expected that the revision of Technical Reports Series No. 364 will initiate further updating of related IAEA publications, and international and national radiological models. The present IAEA-TECDOC is intended to be a support to the update of Technical Reports Series No. 364, overcoming the limitations of the former, and comprises both revised transfer parameter values, as well as missing data, key transfer processes, concepts and models that were found to be important for radiation safety. The publication was prepared by members of the EMRAS project Working Group 1, Theme 1 Revision of IAEA Technical Reports Series No. 364. The group was chaired initially by P. Santucci, followed by P. Calmon. The IAEA wishes to express its gratitude to M. Thorne, A. Gondin da Fonseca and B.Varga for their kind assistance in editing and preparation of the document for publishing, and.t

This review summarizes current knowledge on the contribution of mycorrhizal fungi to radiocesium immobilization and plant accumulation. These root symbionts develop extended hyphae in soils and readily contribute to the soil-to-plant transfer of some nutrients. Available data show that ecto-mycorrhizal (ECM) fungi can accumulate high concentration of radiocesium in their extraradical phase while radiocesium uptake and accumulation by arbuscular mycorrhizal (AM) fungi is limited. Yet, both ECM and AM fungi can transport radiocesium to their host plants, but this transport is low. In addition, mycorrhizal fungi could thus either store radiocesium in their intraradical phase or limit its root-to-shoot translocation. The review discusses the impact of soil characteristics, and fungal and plant transporters on radiocesium uptake and accumulation in plants, as well as the potential role of mycorrhizal fungi in phytoremediation strategies.

Contamination by uranium (U) occurs principally at U mining and processing sites. Uranium can have tremendous environmental consequences, as it is highly toxic to a broad range of organisms and can be dispersed in both terrestrial and aquatic environments. Remediation strategies of U-contaminated soils have included physical and chemical procedures, which may be beneficial, but are costly and can lead to further environmental damage. Phytoremediation has been proposed as a promising alternative, which relies on the capacity of plants and their associated microorganisms to stabilize or extract contaminants from soils. In this paper, we review the role of a group of plant symbiotic fungi, i.e. arbuscular mycorrhizal fungi, which constitute an essential link between the soil and the roots. These fungi participate in U immobilization in soils and within plant roots and they can reduce root-to-shoot translocation of U. However, there is a need to evaluate these observations in terms of their importance for phytostabilization strategies.

Potassium depletion in the soil solution around plant roots promotes the root uptake of radiocesium. However, it can also induce the transformation of mica through the release of interlayer K. In bulk soil, the formation of frayed edge sites (FES) with a high selectivity for Cs adsorption is usually related with mica weathering. We studied the effect of K level in the nutrient solution on the root-induced weathering of phlogopite as well as on the root uptake of radiocesium by willow (Salix viminalis L. var. Orm). The willows were grown for 7 wk in column lysimeters filled with a quartz-phlogopite mixed substrate continuously irrigated with nutrient solutions differing in K concentration (0-2 mM). From a potassium supply of 0.4 mM downward, we observed a decrease in root uptake of potassium as well as an increase in (i) potassium release from pblogopite, (ii) degree of transformation of phlogopite into vermiculite, and (iii) root uptake of radiocesium. Increasing K depletion had thus two effects: a decrease of the root uptake of potassium and an increase of phlogopite weathering in the rhizosphere, both of which promoted the root uptake of radiocesium.

Acute K depletion in the rhizosphere can lead to increased root uptake of radiocesium. Two processes can govern this increase: the very low uptake of potassium and the weathering of Cs-fixing clay minerals. Their respective importance is, however, unknown. We investigated the effects of these processes on radiocesium mobilization by roots of willow (Salix viminalis L.) from three micas: muscovite, biotite, and phlogopite. Willows were grown in a mixed quartz-mica substrate with the three respective Cs-134-contaminated micas as sole sources of potassium and radiocesium. After 7 wk of plant growth, the micas were partially weathered. The degree of mica weathering and the prevalent potassium concentration in the solution increased in the order muscovite (5-11 mu M K) < biotite (25-32 mu M K) < phlogopite (25-35 mu M K). The mobilization and root uptake of radiocesium were negligible with muscovite but increased in the same order. These results show that mica weathering directly and chiefly governs the mobility of radiocesium in K-depleted rhizosphere soil. The low mobility of trace Cs in the muscovite rhizosphere is linked with the dioctahedral character of this mica, and hence to its very low alterability.

Because plants significantly affect radionuclides (RN) cycling and further dispersion into the biosphere, it is important to understand the biological factors influencing RN plant uptake, accumulation and redistribution. In this respect, mycorrhizal fungi are of particular interest. The effects of ecto-mycorrhizal (ECM) and arbuscular mycorrhizal (AM) fungi on the transport of uranium (U) or radiocaesium (Cs) were investigated both under pot and in vitro culture conditions. Results obtained in vitro demonstrated that AM hyphae can take up and translocate U and Cs towards roots, while this uptake and translocation were not perceptible using pot culture systems with soil. These contrasting results could be due to different experimental conditions, including the K level in the external solution and the bio-availability of Cs. The in vitro studies also indicated that root colonisation by AM fungi might limit U and Cs root transport. Under pot culture conditions, they appeared to significantly reduce root to shoot translocation of U. Under the same conditions, ECM transport of Cs was demonstrated, and appeared to be dependent on fungal species. A better estimation of the potential use of mycorrhizal fungi for the phytoremediation of RN-contaminated areas is now available and will be further discussed.

The OAh horizons in forest acid soils are reported to fix more radiocesium than the mineral horizons beneath and organic horizons above them. We determined the respective contributions of the Of, OAh, Ah, and Bw horizons in an acid brown soil to the total Cs-137 soil-to-plant transfer by using young spruce plants [Picea abies (L.) H. Karst.] grown on reconstituted micro-pedons in which these respective horizons were contaminated by carrier-free Cs-137. The plants were grown in a greenhouse at 20 degrees C during a period of 5 mo. The respective contributions to the Cs-137 soil-to-plant transfer were 92.71% in Of, 0.18% in OAh, 3.28% in Ah, and 3.83% in Bw, The very high contribution of Of was due to its high organic matter (OM) content, while the very low contribution of OAh was related to Cs+ fixation by vermiculitic clay minerals. The higher Cs-137 transfer from Ah and Bw vs, OAh was probably associated with Al interlayering of vermiculite, Our data suggest that plant roots and soil vermiculite acted as competitive sinks for Cs-137 in the acid brown soil.

In forest soils polluted by radiocesium, the surface horizons are known to contribute differently to Cs plant contamination. A precise quantification of the horizon contributions is, however, seldom realized. We quantified the respective contributions of the Of, OAh, Ah, and Bw horizons in an acid brown soil to the total Cs-137 soil-to-plant transfer through a rhizospheric approach. The macroscopic rhizosphere was realized by creating a close contact between Cs-137-contaminated soil horizons earlier mixed with agar and a dense root mat previously developed by young, K-stressed ryegrass seedlings (Lolium multiflorum Lam., rv Lemtal) during a period of 7 d. The intimate mot-soil contact was maintained for 4 d. The uptake of radiocesium by plant roots was readily effective as the Cs-137 rhizospheric mobilization (RM) amounted to 0.07 to 23.42% of the initial Cs-137 soil contamination, Assuming negligible horizon to horizon transfer and equivalent root exploration in each horizon, the respective contributions of the horizons to the Cs-137 soil-to-plant transfer were 96.7% in Of, 0.13% in OAh, 1.34% in Ah, and 1.84% in Bw. Our data confirm the very high contribution of the organic horizon in the Cs-137 soil-to-plant transfer. They further suggest that the rhizospheric approach could be well suited to classify soils for their potential effect on Cs-137 plant contamination.

The OAh and Ah horizons of acid brown and podzolic forest soils are reported to hx more radiocaesium than the mineral B horizons beneath them. We determined the respective influence of organic matter and clay minerals on the magnitude of Cs+ retention in a strongly acid brown forest soil in Belgium. The soil contained mica throughout the profile. Vermiculite was identified in the OAh and Ah horizons, and hydroxy interlayered vermiculite (HIV) in the Bw horizon. The OAh and Ah clay fraction retained much more Cs+ than the Bw horizon. The extraction of Al interlayers by Na-citrate resulted in a marked increase in Cs+ fixation in the Bw clays as well as the collapse of the vermiculitic layers after K+ saturation. Organic matter had a strong but indirect effect on Cs+ fixation. In the Bw horizon, acid weathering of layer silicates releases free Al and produces HIV minerals in which Al polymers block the access of radiocaesium onto Cs+-specific sites. In OAh and Ah horizons, free Al is complexed by organic acids. Consequently, the interlayer specific sites remain accessible for Cs+ fixation.

The type of soil and humus has to be considered as primordial for the evaluation of the Cs availability and for its transfer dynamics. Previous studies on the radiocesium distribution through a forest soil profile indicate that the intermediate layer, OAh (organic and mineral particles intimately mixed) accumulates Cs in a more efficient way than the deeper mineral layer. Our study on the physico-chemical parameters influencing Cs retention shows however, that humic compounds do not particularly influence the Cs retention. On the contrary, the K interaction with mineral particles induces a clear increase in the Cs fixation. This observation suggests that K inducing collapse is responsible for a higher Cs retention. In the OAh layer, an original collapsed state of the mica structure would benefit the Cs fixation.

The organic and mineral horizons of a forest brown acid soil sampled in Belgium (Haute Ardenne, Vielsalm) were artificially contamined with a solution of (CsCl)-Cs-137. If the sequential extractions (CaCl2, NH4Ac, CuCl2 and HNO3, 1N) realised on a pure mineral substrate remove 40% of the total Cs-137 content, the same reagents can only remove 8% of total caesium when they react with the organic substrate (Of + OAh). Other controlled experiments with the different layers of the soil profile show, on the other hand, that if a pool of Cs-137 is available for exchange in the Of and B horizons (31 and 18%, respectively, of total caesium for NH4Ac), the quantities of exchangeable Cs-137 (CaCl2 and NH4Ac) and the present one in soil solution of the transition OAh and Ah horizons are near zero (0.1 and 2.7% of total caesium for NH4Ac, respectively). This result seems to contradict the available quantities of potassium cation. This suggests, firstly, that the organic matter, or more probably organomineral complexes, interact strongly on the behaviour of Cs-137 in the profile hemiorganic layers and, secondly, that the Cs-137 has a special behaviour of its own.

After the Chernobyl nuclear reactor accident in April 1986, Cs-137 was found to be one of the most abundant radionuclides released and the forest ecosystem was one of the most contaminated environments. Long-term management of the forests to minimize the radiation dose to man requires understanding of the cycles of the Cs-137 and the other radionuclides which were also deposited. Thus, the health physicists responsible for remediation programs in the contaminated zones must have information on the long-term behaviour of the deposited radioactivity. The similarity between the chemical properties of Cs and K and the fact that K has been studied previously as a nutrient in forest productivity may provide an analogue to evaluate the long-term mechanism of the deposited radioactivity. One of the goals of this study is to describe the global cycle of K in forests related to the Cs-137 contaminant. The first results of an experimental program to measure the deposition of Cs-137 in the several forest compartments is presented, together with the complementary K results. These data provide information which is necessary to construct a useable model describing the Cs-137-transfer after atmospheric contamination of a woodland ecosystem.

The migration potentials for Cs-134 in spruce soil columns (undisturbed profile) following a surface contamination and also the redistribution of the radionuclide through the profile have been investigated. The radiocaesium bioavailability in the different horizons was estimated by activity measurements in the soil solution and from extractions made of the solid phase. The calculation of a Kd ratio indicates that retention mechanisms increase very rapidly with depth. Cs-134 speciation reveals the high affinity of the radionuclide for specific sites on mineral components. In spite of its organic nature, the O Ah horizon has a great efficiency for Cs accumulation; the role of humic clay components and/or microflora is unforeseen.