Fibre crops as alternative land use for radioactively contaminated arable land

The transfer of radiocaesium, one of the most important and widespread contaminants following a nuclear accident, to the fibre crops hemp (Cannabis sativa L.) and flax (Linum usitatissimum L.) as well as the distribution of radiocaesium during crop conversion were studied for sandy soil under greenhouse and lysimeters conditions. Soil parameters did not unequivoqually explain the transfer factors (TF) observed. TFs to flax stems ranged from 1.34 to 2.80x10(-3) m2 kg(-1). TFs to seeds are about a factor of 4 lower. During the retting process for separating the fibres from the straw, more than 95% of the activity was removed with the retting water. For hemp, the TF to the stem was about 0.6x10(-3) m2 kg(-1). For hemp, straw and fibres were mechanically separated and TF to straw was about 0.5x10(-3) m2 kg(-1) and to fibres 1.0x10(-3) m2 kg(-1). Generally, the TFs to the useable plant parts both for hemp and flax, are low enough to allow for the production of clean end-products (fibre, seed oil, biofuel) even on heavily contaminated land. Given the considerable decontamination during retting, contamination levels in flax fibres would only exceed the exemption limits for fibre use after production in extreme contamination scenarios (>12,300kBq m(-2)). Since hemp fibres are mechanically separated, use of hemp fibres is more restricted (contamination <740kBq m(-2)). Use of stems as biofuel is restricted to areas with contamination levels of <250 and 1050kBq m(-2) for flax and hemp, respectively. Use of seeds for edible oil production and flour is possible almost without restriction for flax but due to the high TFs to seed observed for hemp (up to 3x10(-3) m2 kg(-1)) consumption of hemp seed products should be considered with care.     

Will the application of Ammonium-Ferric-Hexacyano-Ferrate enhance the vertical migration of radiocaesium?

The consideration of a possible enhanced vertical migration of radiocaesium with the application of ammonium-ferric-hexacyano-ferrate (AFCF) as countermeasure, due to the colloidal nature of AFCF, made us set up a series of migration experiments. For the study two soil types were considered, which were either left unplanted or cultivated with ryegrass. Two AFCF concentrations, 1 and 10 g m^-2, and an untreated control were applied. A simple diffusion–convection model was fitted to the data.The application of AFCF did not enhance the downward migration of radiocaesium in the profile. Moreover, for an unplanted sandy soil the application of AFCF significantly retarded the migration: 10 g AFCF m^-2 decreased the convection term, V, from 0·78 to 0·42 cm a^-1 and the diffusion component, D, from 0·21 to 0·09 cm² a^-1. For all other experimental conditions (unplanted loamy soil, ryegrass cultivated sandy and loamy soil), the application of AFCF did not have any effect on radiocaesium migration. Since AFCF does not promote the vertical migration of radiocaesium, enhanced groundwater contamination is improbable.     

Short rotation coppice for revaluation of contaminated land.

When dealing with large-scale environmental contamination, as following the Chernobyl accident, changed land use such that the products of the land are radiologically acceptable and sustain an economic return from the land is a potentially sustainable remediation option. In this paper, willow short rotation coppice (SRC) is evaluated on radiological, technical and economic grounds for W. European and Belarus site conditions. Radiocaesium uptake was studied in a newly established and existing SRC. Only for light-texture soils with low soil potassium should cultivation be restricted to soils with contamination levels below 100-370 kBq m-2 given the TFs on these soils (5 x 10(-4) and 2 x 10(-3) m2 kg-1) and considering the Belarus exemption limit for firewood (740 Bq kg-1). In the case of high wood contamination levels (> 1000 Bq kg-1), power plant personnel working in the vicinity of ash conveyers should be subjected to radiation protection measures. For appropriate soil conditions, potential SRC yields are high. In Belarus, most soils are sandy with a low water retention, for which yield estimates are too low to make production profitable without irrigation. The economic viability should be thoroughly calculated for the prevailing conditions. In W. Europe, SRC production or conversion is not profitable without price incentives. For Belarus, the profitability of SRC on the production side largely depends on crop yield and price of the delivered bio-fuel. Large-scale heat conversion systems seem the most profitable and revenue may be considerable. Electricity routes are usually unprofitable. It could be concluded that energy production from SRC is potentially a radiologically and economically sustainable land use option for contaminated agricultural land.     

The combined effect of uranium and gamma radiation on biological responses and oxidative stress induced in Arabidopsis thaliana

Uranium never occurs as a single pollutant in the environment, but always in combination with other stressors such as ionizing radiation. As effects induced by multiple contaminants can differ markedly from the effects induced by the individual stressors, this multiple pollution context should not be neglected. In this study, effects on growth, nutrient uptake and oxidative stress induced by the single stressors uranium and gamma radiation are compared with the effects induced by the combination of both stressors. By doing this, we aim to better understand the effects induced by the combined stressors but also to get more insight in stressor-specific response mechanisms. Eighteen-day-old Arabidopsis thaliana seedlings were exposed for 3 days to 10 μM uranium and 3.5 Gy gamma radiation. Gamma radiation interfered with uranium uptake, resulting in decreased uranium concentrations in the roots, but with higher transport to the leaves. This resulted in a better root growth but increased leaf lipid peroxidation. For the other endpoints studied, effects under combined exposure were mostly determined by uranium presence and only limited influenced by gamma presence. Furthermore, an important role is suggested for CAT1/2/3 gene expression under uranium and mixed stressor conditions in the leaves.     

Effect of K and bentonite additions on Cs-transfer to ryegrass

Bentonite amendments are generally ineffective in reducing the soil-to-plant radiocaesium transfer but have previously been shown that bentonites in the K-form having been subjected to wetting-drying cycles had pronounced radiocaesium binding capacities. We have investigated the effect of wetting-drying (WD) on Radiocaesium Interception Potential (RIP) development in three K-bentonites and K-bentonite soil mixtures, using a variety of procedures: homogenisation of the bentonites with K through dialysis (K(B)), or partial transformation of the bentonite to the K-form in the presence of a solution of K2CO3 (K(L)) or in presence of solid K2CO3 (K(S)). Of the three strategies tested, addition of K2CO3 (solid) at a dose of 2 meq g(-1) clay and adding the K-bentonite mixtures to the soil resulted in the highest RIP increase after 20 WD cycles. The procedure giving the highest RIP yield is the most practical for further applications and was used in a pot experiment under greenhouse condition. When expressing the RIP increase of the soil-bentonite mixtures per unit bentonite added (RIP yield), 28- to 110-fold RIP increases were observed up to a value of approximately 60,000 meq kg(-1) (6 times higher than the RIP for illite). The beneficial effect following K-bentonite application was shown to be dependent both on a sorption enhancement effect (direct RIP effect) and fixation effects (indirect RIP effect). Greenhouse testing proved that the RIP effects observed in greenhouse could be predicted by making use of the sorption data from the laboratory tests. Optimum soil-amendment would be obtained with bentonites with high initial sorption RIP and a high sorption RIP increase when subjected to WD in the presence of potassium. Hypothised Transfer Factor (TF)-reductions of at least 10-fold could result when mixing approximately 1% bentonite, like Otay bentonite (RIP yield 99,000 meq kg(-1) after WD in presence of K if only fine particle size of <1mm considered) with the contaminated ploughing layer.     

Proposal for new best estimates for the soil solid–liquid distribution coefficient and soil-to-plant transfer of nickel

The objective of this study was to compile data, based on an extensive literature survey, for the soil solid–liquid distribution coefficient (K_d) and soil-to-plant transfer factor (TF) for nickel. The K_d best estimates were calculated for soils grouped according to texture and organic matter content (sand, loam, clay and organic) and soil cofactors affecting soil–nickel interaction, such as pH, organic matter, and clay content. Variability in K_d was better explained by pH than by soil texture.     

Uranium distribution and cycling in Scots pine (Pinus sylvestris L.) growing on a revegetated U-mining heap

We determined the uranium distribution in soil and its allocation in compartments of 35-year-old Scots pine developed on a revegetated U-mining heap. The processes controlling the dynamics of U recycling were identified and further quantified in terms of annual fluxes. As pine developed, an acid humus layer emerged leading to weathering of the alkaline mining debris but this had little effect on U mobility in the soil profile. Increased U mobility mainly involved a translocation of U to metal-humus chelates in surface layers. The root compartment accounted for 99.3% of the U budget in tree, thus serving as an effective barrier which restricts U uptake. The current root uptake and transfer of U to upper parts of the tree amounted to about 3g ha(-1) y(-1), i.e. less than 0.03% of the current NH4-exchangeable U pool in the soil (0-30 cm). Allocation and translocation pattern made it clear that a dominant fraction of the translocated U moves passively with the ascent xylem sap, most likely as a soluble complex, and steadily accumulates in the needles. Consequently, 97% of the U annual uptake is returned to the soil through litterfall. At the studied site, the risk of U dissemination due to biomass turnover or trunk harvest was low when considered in relation to the current "exemption level" for U.     

Can barium and strontium be used as tracers for radium in soil-plant transfer studies?

Radium is one of the prominent potential contaminants linked with industries extracting or processing material containing naturally occurring radionuclides. In this study we investigate if 133Ba and 85Sr can be used as tracers for predicting 226Ra soil-to-plant transfer. Three soil types were artificially contaminated with these radionuclides and transfer to ryegrass and clover was studied. Barium is considered a better tracer for radium than strontium, given the significant linear correlation found between the Ra and Ba-TF. For strontium, no such correlation was found. The relationship between soil characteristics and transfer factors was investigated. Cation exchange capacity, exchangeable Ca+Mg content and soil pH did not seem to influence Ra, Ba or Sr uptake in any clear way. A significant relation (negative power function) was found between the bivalent (Ca+Mg) concentration in the soil solution and the Ra-TF. A similar dependency was found for the Sr and Ba-TF, although less significant.     

Pre- and perinatal findings in partial trisomy 7q resulting from balanced parental translocations t(7;21) and t(4;7)

We report on a fetus and a newborn, both with partial trisomy 7q21→qter due to different familial translocations, t(7;21)(q21.2;p12) and t(4;7)(q35;q21.2). Postmortem examination of the 19-week-old female fetus disclosed dysmorphic features, cleft palate, anomalies of the great vessels, intestinal malrotation and uterus bicornis. The newborn girl revealed a pattern of minor anomalies, cleft palate, cerebellar hypoplasia, and anomalies of pancreas, gall bladder and appendix. The clinical findings in three other reported fetuses with partial trisomy 7q described so far are reviewed. A duplication 7q21→qter, as found in the propositi, has only been described in 11 patients who all had a concurrent partial monosomy. Patient 1 is particularly interesting since she is, to our knowledge, the first reported case with pure trisomy 7q21/22→qter. We reviewed the phenotype of the previously described patients, compared it with the propositae, and summarized the clinical features of pure trisomy 7q21/22→qter. Copyright © 2001 John Wiley & Sons, Ltd.