Assessment of soil degradation in areas of nuclear explosions at the Semipalatinsk nuclear test site

The degree of the soil cover degradation at the Balapan and Experimental Field test sites was assessed on the basis of the Allium-test of soil toxicity and international guidelines on the radioactive restriction of solid materials (IAEA, 2004) and the environment (Smith, 2005). Large scale soil-cover degradation maps (1: 25000) were made. The main part of the mapped area contains highly contaminated toxic degraded soil. It was found that the relationship between soil toxicity and total radionuclide activity concentration is described by power functions. When the calculated value (413–415 Bq/kg of air-dried soil) increases, the soil becomes toxic to plants. This value is 7.8 times higher than the maximum value for background territories (53 Bq/kg) surrounding the SNTS. The Russian sanitary and hygienic guidelines (Radiation safety standards, 2009; Sanitary regulations of radioactive waste management, 2003) underestimate the degree of soil radioactive contamination for plants.     

Plutonium at the ecosystems of impact zone the Beloyarsk NPP

The distribution of the plutonium at the ecosystems of impact zone the Beloyarsk NPP was studied. Higher quantity of Pu (to 500 Bq/m2) was revealed in the bottom sediments of the Olkhovsk bog where low-level radioactive water of the Beloyarsk NPP have been discharged. The total amount of the radionuclide in a soil cover did not exceed 140 Bq/m2. The contribution of the Beloyarsk NPP to contamination of the investigated ecosystems was accounted with using ratio 238Pu/239.240Pu. It was 64.1-99.3% both in the bottom sediments and soils.     

Preliminary study of Lead (Pb) immobilization by meat and bone meal combustion residues (MBMCR) in soil: Assessment of Pb toxicity (phytotoxicity and genotoxicity) using the tobacco model (Nicotiana tabacum var. xanthi Dulieu)

Lead (Pb) is a major chemical pollutant in the environment. The present investigation evaluates the possible use of Meat and Bone Meal Combustion Residues (MBMCR), to sequester Pb from the soil compartment using the heterozygous tobacco model (Nicotiana tabacum var. xanthi Dulieu) characterized by the a1+ /a1 a2+ /a2 system. The toxic potential of Pb-contaminations (50, 100, 1,000, 2,000 and 10,000 mg Pb kg(-1)) as Pb(NO3) in standard soil was investigated in lab conditions according to three endpoints: (i) acute toxicity of plants (mortality, height and surface area parameters), (ii) Pb-accumulation in roots, stems and leaves, and (iii) genetic effects as the expression of reversion in the leaf of plants. Moreover, chemical investigations of Pb interactions with soil were realized to complete the toxicity evaluation. The results demonstrated that: (i) MBMCR were not acutely toxic or genotoxic to tobacco plants, (ii) Pb is acutely toxic to tobacco plants at 10,000 mg Pb kg(-1) of soil, (ii) but is not genotoxic, and (iii) Pb-bioaccumulation is significant in leaves, stems and roots (from 1,000, 2,000, and 50 mg Pb kg(-1) of soil, respectively). In contrast, in the presence of MBMCR, the toxic impacts of Pb were inhibited and Pb-accumulation in tobacco plants was reduced. In complement, chemical analyses highlighted the high capacity of the standard soil to immobilize Pb. The results suggest that even if Pb is bioavailable from soils to plants, complex mechanisms could occur in plants protecting them from the toxic impact of Pb.     

Radioecological problems in coastal landscapes of the Sea of Azov

The features of the spatial distribution, of the migration, and of the accumulation of natural (232Th) and manmade (137Cs) radioactive nuclides in the coastal landscapes of the Sea of Azov are studied. It was shown, that the specific activity of 232Th in the accumulation of the so-called "black sands" was shown as high as 6000 Bq/kg, that increases the natural geochemical background in 200 times. The impact of aerial transfer of the "black sands" on 232Th migration and accumulation in the soil-plant system was clarified. The 232Th distribution down the soil profile suggests that the "black sands" are likely the product of the erosion of the coastal parent materials enriched by natural radionuclides. In general, the specific activity of 137Cs in the beach sand is not high and it is close to the background (global fallout) value. It was determined that 137Cs content in the coastal ecosystems is connected only by aerial pathway as a part of global and Chernobyl-born fallout.     

Concentration of Radiocesium in the Wild Japanese Monkey (Macaca fuscata) over the First 15 Months after the Fukushima Daiichi Nuclear Disaster

Following the massive earthquake that struck eastern Japan on March 11, 2011, a nuclear reactor core meltdown occurred at the Fukushima Daiichi Nuclear Power Plant, operated by Tokyo Electric Power Company, and was followed by the release of large amounts of radioactive materials. The objective of this study was to measure the concentration of radiocesium ¹³⁴Cs and ¹³⁷Cs in the muscle of Japanese monkeys (Macaca fuscata) inhabiting the forest area of Fukushima City and to determine the change in concentration over time as well as the relationship with the level of soil contamination. Cesium concentrations in the muscle of monkeys captured at locations with 100,000–300,000 Bq/m² were 6,000–25,000 Bq/kg in April 2011 and decreased over 3 months to around 1,000 Bq/kg. However, the concentration increased again to 2,000–3,000 Bq/kg in some animals during and after December 2011 before returning to 1,000 Bq/kg in April 2012, after which it remained relatively constant. This pattern of change in muscle radiocesium concentration was similar to that of the change in radiocesium concentration in atmospheric fallout. Moreover, the monkeys feed on winter buds and the cambium layer of tree bark potentially containing higher concentrations of radiocesium than that in the diet during the rest of the year. The muscle radiocesium concentration in the monkeys related significantly with the level of soil contamination at the capture locations.     

Accumulation of 90Sr in field crops in conditions of radioactive pollution of agricultural lands

In the field experiment the influence of manure, peat, lake silt and their combinations on the uptake of 90Sr by barley, corn and potatoes was studied. Saturation of soil with organic substance, the decrease in soil acidity resulted in the lower accumulation of 90Sr by plants. In the beginning of the experiment, the specific activity of barley grain was from 75 to 132 Bq/kg. After three years of application of fertilizers the content of 90Sr in the barley grain decreased to 39 Bq/kg. There were no increase in 90Sr accumulation by the basic field crops with time.     

Study of the environmental hazard caused by the oil shale industry solid waste

The environmental hazard was studied of eight soil and solid waste samples originating from a region of Estonia heavily polluted by the oil shale industry. The samples were contaminated mainly with oil products (up to 7231mg/kg) and polycyclic aromatic hydrocarbons (PAHs; up to 434mg/kg). Concentrations of heavy metals and water-extractable phenols were low. The toxicities of the aqueous extracts of solid-phase samples were evaluated by using a battery of Toxkit tests (involving crustaceans, protozoa, rotifers and algae). Waste rock and fresh semi-coke were classified as of "high acute toxic hazard", whereas aged semi-coke and most of the polluted soils were classified as of "acute toxic hazard". Analysis of the soil slurries by using the photobacterial solid-phase flash assay showed the presence of particle-bound toxicity in most samples. In the case of four samples out of the eight, chemical and toxicological evaluations both showed that the levels of PAHs, oil products or both exceeded their respective permitted limit values for the living zone (20mg PAHs/kg and 500mg oil products/kg); the toxicity tests showed a toxic hazard. However, in the case of three samples, the chemical and toxicological hazard predictions differed markedly: polluted soil from the Erra River bank contained 2334mg oil/kg, but did not show any water-extractable toxicity. In contrast, spent rock and aged semi-coke that contained none of the pollutants in hazardous concentrations, showed adverse effects in toxicity tests. The environmental hazard of solid waste deposits from the oil shale industry needs further assessment.     

Degradation of Alyssum murale biomass in soil

The Ni-hyperaccumulating plant Alyssum murale accumulates exceptionally high concentrations of nickel in its aboveground biomass. The reasons for hyperaccumulation remain unproven; however, it has been proposed that elemental alelopathy might be important. High-Ni leaves shed by the plant may create a "toxic zone" around the plant where germination or growth of competing plants is inhibited. The efficacy of this argument will partially depend upon the rate at which leaves degrade in soil and free metals are released, and the subsequent rate at which metals are bound to soil constituents. To test the degradation of biomass of hyperaccumulators, A. murale was grown on both high- and low-Ni soils to achieve high- (12.0 g Ni/kg) and low- (0.445 g Ni/kg) Ni biomass. Shredded leaf and stem biomass were added to a serpentine soil from Oregon that was originally used to grow high-Ni biomass and a low-Ni control soil from Maryland. Biomass Ni was readily soluble and extractable, suggesting near immediate release as biomass was added to soil Extractable nickel in soil amended with biomass declined rapidly over time due to Ni binding in soil These results suggest that Ni released from biomass of Ni hyperaccumulators may significantly affect their immediate niche only for short periods of time soon after leaf fall, but repeated application may create high Ni levels under and around hyperaccumulators.     

The interaction between poisonous plants and soil quality in response to grassland degradation in the alpine region of the Qinghai-Tibetan Plateau

The objective of this study was to explore the distribution of poisonous plants and soil quality in relation to grassland degradation in the Qinghai-Tibetan Plateau (QTP) by employing poisonous plants characteristics including diversity index, coverage and composition and the soil properties including soil physical, chemical, and biological indicators. The degraded grasslands (DGs) had significantly increased cover and diversity values of poisonous plants compared with the non-DGs (NDGs). Grassland use types had significant effects on the composition and characteristics of poisonous plants. The NDGs had increased levels of soil nutrients and soil enzyme activities, with decreased soil pH and bulk density (BD), indicating a higher and better soil nutrient status compared with DGs. The soil texture, soil pH, and soil BD were very important in affecting the structures of poisonous plants. We concluded that grassland degradation had significant effect on poisonous plants coverage and diversity; conversely, poisonous plants also aggregated the grassland degradation, decreasing the soil fertility in the QTP.     

The dependence of accumulation of 137Cs and 90Sr radionuclides in the forages cultivation degree of sod-podzolic soils

For prognosis of accumulation of 137Cs and 90Sr in forages harvested in radionuclide contaminated sod-podzolic soils, it is suggested to use transfer factors (TF9a) (Bq/kg)/(kBq/m2)) established not only by the content of mobile potassium (137Cs, r = -0.53) and the value of exchange acidity (90Sr, r = -0.73), but also by the index of agrochemical soil cultivation I(cd) (137Cs, r = -0.69; 90Sr, r = -0.64). The possibility of obtaining forages conforming to the state standards on the haymaking and pasture areas with high density of radioactive contamination of soils was shown by the example of "Sudkovo" collective farm. The approach is based on achievement of a high degree of cultivation (l(cd) - 0.81-1.0) due to a complex of protective measures, which resulted in a 10-fold decrease in the specific activity of 137Cs and a 4-fold decrease in the activity of 90Sr, compared to the soils with a low degree of cultivation (I(cd) - 0.41-0.60).     

Fate of radiocesium in freshwater aquatic plants and algae in the vicinity of the Fukushima Daiichi nuclear power plant

The behavior of radiocesium (¹³⁷Cs) in aquatic plants (five species) and algae (three genera) grown in either a river (one sampling point) or pond (four sampling points) in the vicinity of the Fukushima Daiichi nuclear power plant was investigated. The ¹³⁷Cs concentration of <0.45-μm fractions of water taken from the river and ponds was between 5.01 × 10^?1 and 2.98 Bq/L, while that of sediment was between 4.85 × 10³ and 5.72 × 10⁴ Bq/kg dry weight. The ratio of ¹³⁷Cs concentration of sediment/water in ponds was ~10⁴. The sediment-to-plant transfer factor (TF) [(¹³⁷Cs concentration Bq/kg dry weight_plant) × (¹³⁷Cs concentration Bq/kg dry weight_sediment)^?1] was also measured. For aquatic plants, the highest value was 5.55 for Potamogeton crispus from the river, while the lowest was 3.34 × 10^?2 for P. distinctus from a pond. There were significant differences in values between aquatic plants belonging to the same genus. The water-to-plant TF [(¹³⁷Cs concentration Bq/kg dry weight_plant) × (¹³⁷Cs concentration Bq/L_water)^?1] of filamentous algae (Spirogyra sp.) and cyanobacteria (coexisting Anabaena sp. and Microcystis sp.) were 2.39 × 10³ and 1.26 × 10³, respectively. The ¹³⁷Cs concentration of cyanobacteria in pond water was 4.87 × 10^?1 Bq/L, which was the same order of magnitude as the ¹³⁷Cs concentration of pond water. Enrichment of ¹³⁷Cs in cyanobacteria was not observed.     

A reconsideration of the safety of fenoxycarb (IGR) in soil environment: The toxicity of fenoxycarb to Yuukianura szeptyckii (Collembola)

Fenoxycarb, a juvenile hormone agonist has been widely used to control various insect pests in agriculture. Fenoxycarb has been considered environmentally safe because it degrades quickly and has lower mammalian toxicity compared with many conventional pesticides. To date, fenoxycarb is reported safe for soil organisms, but this conclusion is based solely on toxicity studies with Folsomia candida (Collembola) and Eisenia fetida (earthworm). The aim of this study was to investigate the toxic effect of fenoxycarb on Yuukianura szeptyckii (Collembola) to assess further whether this chemical is environmentally safe or not. After 28 d of exposure of fenoxycarb in the soil, adult survival and juvenile production were assessed. The median lethal concentration (LC₅₀) value for adult was 955.2 mg/kg and the median effective concentration (EC₅₀) and no observed effect concentration (NOEC) value for juvenile production was 0.2 mg/kg and <0.15 mg/kg, respectively. The effect of fenoxycarb on egg production and hatching rate was evaluated using a compressed soil substrate. A significant reduction in egg production was observed at 300 mg/kg or more, and the hatching rate was significantly reduced at 0.15 mg/kg or more. These results indicated that the adverse effects of fenoxycarb on juvenile production at concentrations of 0.15, 9.4, and 75 mg/kg were mainly due to a reduced hatching rate. The toxicity/exposure ratio (TER) for fenoxycarb in Y. szeptyckii was <5, indicating risk to Y. szeptyckii from fenoxycarb residues in soil. This study suggests that fenoxycarb poses high potential risk to Y. szeptyckii at environmentally relevant concentrations. Thus, further research, such as higher tier study is needed to clarify fenoxycarb risk in soil ecosystems.     

Plant critical levels for the evaluation of boron toxicity in spring barley (Hordeum vulgare L.)

Summary Pot experiments on B toxicity in spring barley (Hordeum vulgare L., cv. Trumpf) using sandy soils indicated that there are significant relationships between B content of the leaves and of the shoots respectively in the toxic range and degree of damage of the leaves at stage 7–8 of the Feekes scale, which may be used to derive plant critical levels of B toxicity. Symptoms due to B excess begin to develop on the leaves (leaf tip necroses) relatively independently of the ontogenetical stage of development as soon as the B content of the leaf tissue reaches 60–80 mg/kg DM.The corresponding symptom-related toxic plant critical level of shoots (i.e. the B content of the whole shoot at which the first damage in leaves begins to occur) ranges from 30 mg/kg shoot DM (related to older leaves) to 80 mg/kg shoot DM (related to younger leaves). Grain yield is significantly reduced only when the B content of shoots at Feekes stages 7–8 exceeds the yield-related toxic plant critical level (yield reduction to 90% of the optimum yield) of 120–130 mg/kg shoot DM.B contents of the shoots at Feekes stages 7–8 from 80–120 mg/kg shoot DM define the range at which plants have marked toxicity symptoms, but at which there are no yield reductions.     

Recovery of bean plants from boron-induced oxidative damage by zinc supply

The effects of zinc on growth, boron uptake, lipid peroxidation, membrane permeability (MP), lypoxygenase (LOX) activity, proline and H₂O₂ accumulation, and the activities of major antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX)) in bean plants were investigated under greenhouse conditions. Treatments consisted of control, 20 mg/kg B, and 20 mg/kg B plus 20 mg/kg Zn. When the plants were grown with 20 mg/kg Zn, B toxicity was less severe. Zinc supplied to soil counteracted the deleterious effects of B on root and shoot growth. Excess B significantly increased and Zn treatment reduced B concentrations in shoot and root tissues. Applied Zn increased the Zn concentration in the roots and shoots. While the concentrations of H₂O₂ and proline were increased by B toxicity, their concentrations were decreased by Zn supply. Boron toxicity increased the MP, malondialdehyde content, and LOX activity in excised bean leaves. Applied Zn significantly ameliorated the membrane deterioration. Compared with control plants, the activity of SOD was increased while that of CAT was decreased and APX remained unchanged in B-stressed plants. However, application of Zn decreased the SOD and increased the CAT and APX activities under toxic B conditions. It is concluded that Zn supply alleviates B toxicity by preventing oxidative membrane damage. Published in Russian in Fiziologiya Rastenii, 2009, Vol. 56, No. 4, pp. 555–562. This text was submitted by the authors in English.     

Feasibility of Phytoextraction to Clean Up Low-Level Uranium-Contaminated Soil

The potential to phytoextract uranium (U) from a sandy soil contaminated at low levels was tested in the greenhouse. Two soils were tested: a control soil (317 Bq ²³⁸U kg^-1) and the same soil washed with bicarbonate (69 Bq ²³⁸U kg^-1). Ryegrass (Lolium perenne cv. Melvina), Indian mustard (Brassica juncea cv. Vitasso), and Redroot Pigweed (Amarathus retroflexus) were used as test plants.

The annual removal of the soil activity with the biomass was less than 0.1%. The addition of citric acid (25 mmol kg^-1) 1 week before the harvest increased U uptake up to 500-fold. With a ryegrass and mustard yield of 15000 kg ha^-1 and 10000 kg ha^-1, respectively, up to 3.5% and 4.6% of the soil activity could annually be removed with the biomass.

With a desired activity reduction level of 1.5 and 5 for the bicarbonate washed and control soil, respectively, it would take 10 to 50 years to attain the release limit.

A linear relationship between the plant ²³⁸U concentration and the ²³⁸U concentration in the soil solution of the control, bicarbonate-washed, or citric acid-treated soil points to the importance of the soil solution activity concentration in determining U uptake and hence to the importance of solubilising agents to increase plant uptake.

However, citric acid addition resulted in a decreased dry weight production (all plants tested) and crop regrowth (in case of ryegrass).     

Effects of nano-sized zero-valent iron on DDT degradation and residual toxicity in soil: a column experiment

Background and aims

Nanoscale zero-valent iron (nZVI) application is a promising technology for degradation of chlorinated contaminants in soil. Plants also play an important role in soil remediation and nZVI should not adversely affect plants growing on treated soils. Large amounts of DDT are still found in certain soils and means to remediate these soils are limited. Our aims were to investigate the effect of nZVI on DDT degradation and evaluate possible negative effects of nZVI on plants.

Methods

Columns with spiked (20 mg DDT kg^?1) soil were percolated with nZVI (1 g nZVI L^?1) and leached with five pore volumes of water to assess leaching of nZVI and residual toxicity of leachates and soil to plants using seed germination and plant growth tests (barley, flax).

Results

Addition of nZVI led to degradation of 45 % of the added DDT. Percolation with water significantly oxidized and transported iron through the columns. The first leachates had negative effects on plant development, but after leaching with 4 pore volumes, neither soil nor leachates affected plant negatively.

Conclusions

nZVI is efficient for degradation of DDT and adverse effects of nZVI on plants seem ephemeral and are alleviated after oxidation mediated by percolating water.     

纳米氧化锌和接种丛枝菌根真菌对大豆生长及营养吸收的影响

纳米氧化锌是应用最广的人工纳米颗粒(nanoparticles,NPs)之一,具有一定生物毒性。丛枝菌根(arbuscular mycorrhizal,AM)真菌能与陆地上80%以上的高等植物形成丛枝菌根共生体,并能改善宿主植物矿质营养,提高其抗逆性。然而纳米ZnO与丛枝菌根的关系尚不清楚。通过温室沙培盆栽试验,研究了施加不同水平纳米ZnO(0、500、1000、2000、3000 mg/kg)和接种AM真菌Acaulospora mellea对大豆生长及营养状况的影响。结果表明,3000 mg/kg的纳米ZnO显著抑制大豆植株生长,表现出植物毒性,在其他水平时没有显著影响。纳米ZnO在施加水平500、1000 mg/kg时没有抑制AM真菌对大豆根系的侵染,但是高施加水平(2000 mg/kg)时对AM真菌产生毒害,几乎完全抑制大豆根系菌根侵染。接种AM真菌仅在500 mg/kg纳米ZnO时显著促进大豆生长,增加大豆植株对P、K、N的吸收,降低根系Zn含量。纳米ZnO可能会持续释放锌离子,并抑制大豆根系对矿质营养元素的吸收,从而产生生物毒性,而AM真菌与大豆根系的共生可起到有益作用。     

A split-root experiment shows that translocated phosphorus does not alleviate aluminium toxicity within plant tissue

Background and aims

My previous experimental findings suggested that phosphorus (P) enhances aluminium (Al) tolerance in both Al-tolerant and Al-sensitive wheat seedlings. However, the role of P in the amelioration of Al toxicity within plant tissue is still unclear. Therefore, a soil culture horizontal split-root system was used to quantify whether or not translocated P alleviates Al toxicity within the plant tissue.

Methods

Different level of Al and P were added in two compartments in various combinations for separate root halves. Constrasting Al-tolerant (ET8) and Al-sensitive (ES8) wheat genotypes were used as a testing plant.

Results

The limitation of root growth was independent to Al-toxicity in one root half. However, root proliferation occurred as a compensatory growth on the other root half that has no Al-toxicity. Where half of the roots were given 60 mg P/kg, plant did not translocated P in the other part of the root system that grown in Al toxic soil. When 40 mg P/kg were mixed with 60 mg AlCl₃/kg within one root half combinations, root dry weight of both ET8 and ES8 increased markedly in that root half. In contrast, root dry weight of both ET8 and ES8 decreased noticeably only 60 mg AlCl₃/kg treated root half. The shoot P and Al uptake in both ET8 and ES8 was lower in combined 40 mg P/kg and 60 mg AlCl₃/kg addition as compared to other combination with same P and Al level.

Conclusions

Result from this study confirm that addition of P to Al toxic acid soil played dual role like amelioration of Al-toxicity in soil and utilize P as nutrition for plant growth and development. Findings also attributed that added P was reduced by precipitation with added Al. However, evidence found that translocated P was not able to alleviate Al toxicity within plant tissue of both ES8 and ET8.     

The biodegradation of surfactants in the environment

The possible contamination of the environment by surfactants arising from the widespread use of detergent formulations has been reviewed. Two of the major surfactants in current use are the linear alkylbenzene sulphonates (LAS) and the alkyl phenol ethoxylates (APE). These pass into the sewage treatment plants where they are partially aerobically degraded and partially adsorbed to sewage sludge that is applied to land. The biodegradation of these and a range of other surfactants both in wastewater treatment plants and after discharge into natural waters and application to land resulting in sewage sludge amended soils has been considered. Although the application of sewage sludge to soil can result in surfactant levels generally in a range 0 to 3 mg kg(-1), in the aerobic soil environment a surfactant can undergo further degradation so that the risk to the biota in soil is very small, with margins of safety that are often at least 100. In the case of APE, while the surfactants themselves show little toxicity their breakdown products, principally nonyl and octyl phenols adsorb readily to suspended solids and are known to exhibit oestrogen-like properties, possibly linked to a decreasing male sperm count and carcinogenic effects. While there is little serious risk to the environment from commonly used anionic surfactants, cationic surfactants are known to be much more toxic and at present there is a lack of data on the degradation of cationics and their fate in the environment.     

Cesium and cobalt transfer from soil to vegetation on permanent pastures

Summary The Cs transfer from soil into pasture vegetation was investigated by using a variation of experimental conditions: (I) 67 pots with 7 kg soil from 3 marshy and 1 sandy site in the lower Weser region in Northwest Germany are used in a greenhouse with¹³⁴CS under 8 different experimental procedures for 2 harvests; (II) 3 undisturbed 50 kg lysimeters were observed for¹³⁷Cs and⁶⁰Co transfer under outdoor conditions for 4 harvests, depth profiles of the activity were determined afterwards; (III) the transfer of the atmospheric fallout¹³⁷Cs directly to the vegetation and from soil to vegetation after preventing its direct uptake by plastic covers was determined at 4 locations in the open pasture.The experiments resulted in higher Cs transfer in the case of podzolic soil and/or direct injection of Cs solution into the rooting zone of old permanent pasture vegetation while the Cs transfer was about 2–4 fold lower when the radioactive solution was applied to newly sown grass. Transfer often decreases with increasing age of Cs in the soil. In addition, statistical analysis of the widely scattered data did not show significant results for the influence of type of marsh, experimental procedure, soil factors with pH of (4.5–6.1), organic carbon, amount of added Cs (microquantity), exchangeable, K, and total Ca.Some figures are given for⁶⁰Co. The observed transfer factors, combined from all experiments appear lognormally distributed with median values 0.22 on podzolic and 0.09 on marshy soils (Bq/kg fresh plant per Bq/kg air dried soil).Research performed under contract with the Bundesminister des Innern (Federal Minister of Interior), Bonn, Federal Republic of Germany