Aggregated Transfer Coefficients Research Articles

Determination of Lichens’ Bioaccumulation Capacity for Radioactive Isotopes Under Laboratory Conditions as a Basis for Their Application as Biomonitors

This study investigates the bioaccumulation capacity of the lichen Cladonia uncialis for radioactive isotopes, aiming to establish its potential as a biomonitor. Conducted under controlled laboratory conditions, the experiment utilised gamma-emitting isotopes to simulate fallout. The lichens were exposed to varying concentrations of these isotopes in three aquariums. The results demonstrated that the bioaccumulation of 54Mn, 57Co, 60Co, 65Zn, 137Cs, and 241Am by C. uncialis was proportional to their initial deposition levels, and this occurred in the first days of the experiment. Analysis of isotope activity in washed and unwashed lichens showed that retention primarily occurred intracellularly, indicating effective bioaccumulation. The study derived the Aggregated Transfer Coefficient (Tag) for each isotope, which ranged from 0.34 to 0.64, and the absorption capacity of the elements increased in the following order: 54Mn < 57Co < 60Co ≤ 65Zn < 241Am < 137Cs. Absorption efficiency, amounting to approximately 50% for 137Cs and 241Am, highlights the potential for lichens to serve as reliable biomonitors for environmental monitoring and estimation of deposition when knowing only the activity of the isotopes in lichen.

Current 137Cs accumulation by mushrooms in different site types of scots pine forests of Ukrainian Polissia

The study of 137Cs radioactive contamination of fruiting bodies of mushrooms was carried out in September - October 2022 in 18 sampling sites laid out in the Korosten district of Zhytomyr region in 3 of the most widespread forest site types (FST): fresh infertile pine site type (А2), fresh fairly infertile pine site type (В2) and moist fairly infertile pine site type (В3). It was found that the highest levels of 137Cs content in investigated FST were characteristic of symbiotrophic mushroom species - Сortinarius mucosus, Сortinarius caperatus, Sarcodon imbricatus, Imleria badia, Tricholoma equestre, Paxillus involutus, Hygrophorus hypothejus, and the lowest - for xylotrophes-saprotrophes such as Armillaria mellea and Tapinella atrotomentosa. When analyzed, it was shown that interspecific differences of average values of 137Cs aggregated transfer coefficient (Tag) among mushrooms in each FST varied in a wide range: they reached 1.1⋅103 times in FST-A2 - from 435 in Cortinarius mucosus to 0.4 m2⋅kg-1⋅10-3 in Armillaria mellea; 71.4 times - in FST-B2 - from 162 in Sarcodon imbricatus to 2.3 m2⋅kg-1⋅10-3 in Armillaria mellea; and 12 times - in FST-B3 - from 111 in Imleria badia to 9.2 m2⋅kg-1⋅10-3 in Leccinum scabrum. Also, it was shown that in genus Russula even in the same FST-B2 among five studied species a 24-fold change in average values of 137Cs Tag are observed - from 67 in Russula vinosa to 2.8 m2⋅kg-1⋅10-3 in Russula aeruginea. The results of ANOVA were discussed as well as the essentiality of the difference of the average values of Tag in mushroom species in different FST.

FUKUSHIMA FALLOUT IN SAKHALIN REGION, RUSSIA, PART 3: 137CS AND 134CS IN COW’S MILK

The study was conducted on Kunashir, Shikotan and Iturup Islands (Sakhalin Region of Russia) in order to evaluate the impact of the Fukushima accident on the “soil–grass–cow’s milk” exposure pathway. A total of 22 samples of cow’s milk were collected in the May 2011 – September 2012 period. Radiocaesium was isolated from thermally treated specimens using the antimony–iodide radiochemical method. The activity concentrations of 134Cs and 137Cs were measured by γ-ray spectrometry using high purity germanium detectors. Caesium-134 was detected in 18 of the total 22 samples of milk. The activity concentration of 134Cs in the samples varied from 0.08 Bq kg–1 to 2.00 Bq kg–1. Caesium-137 was quantified in all 22 samples: range = 0.088–2.43 Bq kg–1. On average, more than a half of the total 137Cs in the milk samples from Sakhalin Region was of Fukushima origin (mean = 60%, median = 57%, range = 13–95%). The highest activity concentrations and values of the soil–to–milk aggregated transfer coefficient, Tag, for 134Cs (and Fukushimaderived 137Cs) were observed in milk samples collected in mid-May 2011. The mean Tag values decreased in the May–October period of 2011 from 12 × 10−3 m2 kg–1 to 2.3 × 10−3 m2 kg–1. In September 2012, the Tag values remained unchanged (mean = 2.8 × 10−3 m2 kg–1) compared to those in September–October 2011. In the autumns of 2011 and 2012, the calculated values of Tag for Fukushima-derived radiocaesium were on average 17 times larger than the ones for pre-Fukushima 137Cs. The higher transfer of Fukushima-derived 137Cs (compared to pre-Fukushima 137Cs) for milk reflected the difference between the “new” and “aged” radiocaesium in the intensity of the radionuclide transfer from soil to grassland plants which were the major component of the cow’s diet in the area of our study. The ratio between the 137Cs activity concentration in the milk (fresh weight) and that in the grassland plants (dry weight) ranged from 0.028 to 0.11. The effective dose from ingestion of Fukushima-derived radiocaesium in locally produced cow’s milk for critical group of adult residents of the southern Kuril in the first year after the accident is conservatively estimated as 0.0027 mSv. The Fukushima accident has had a negligible impact on radiocaesium contamination of cow’s milk and the corresponding human exposure on the southern Kuril Islands: Shikotan, Kunashir and Iturup .

FUKUSHIMA FALLOUT IN SAKHALIN REGION, RUSSIA, PART 2: 137Cs AND 134Cs IN GRASSLAND VEGETATION

Samples of vegetation (vascular plants) were collected at 14 grasslands on Kunashir, Iturup, Urup and Paramushir Islands in August–September 2012. All surveyed grasslands were virgin lands with respect to Fukushima fallout. Four plots were used as pastures for cattle in 2012. About 1 kg of green vegetation (mixed grass-forb crop) was taken from each of 13 plots. Seven samples of wormwood (Artemisia sp.) and three samples of Kuril dwarf bamboo (Sasa sp.) of the same mass were collected for comparison. A density of the above ground biomass was estimated at one of the plots. Activities of134Cs and137Cs radionuclides were determined by direct γ-ray spectrometry method using HP-germanium detectors. Inventories of134Cs and137Cs in the top 20 cm layer of soil were estimated by the authors earlier for each of these 14 plots based of the soil samples analysis. Caesium-134, a marker of Fukushima fallout, was determined in 18 of 24 vegetation samples. Caesium-137 activity was quantified in all of 24 samples. The activity concentration of the radionuclides in plants (wet weight) ranged from <0.05 Bq kg−1to 1.6 Bq kg-1for134Cs and from 0.06 Bq kg−1to 5.8 Bq kg-1for137Cs. About 2/5 (median = 41%, n = 18) of the total activity of137Cs in plants was associated with the Fukushima accident. The soil-to-plant aggregated transfer coefficient (Tag) values in mixed grass-forb crop ranged from <0.2 × 10–3m2kg-1to 11 × 10–3m2kg-1for134Cs and from 0.08 × 10–3m2kg-1to 3.3 × 10–3m2kg-1for137Cs. The Tagvalues for134Cs were statistically significantly higher compared to the Tag values for 137Cs. The median Tagfor134Cs in mixed grass-forb crop decreased in the 2011–2012 period by a factor of about two: from 12 × 10–3m2kg-1to 6.6 × 10–3m2kg-1. The ecological half-time, Teco, of134Cs in the plants was approximately one year. In 2011–2012, the median Tagfor pre-Fukushima137Cs in mixed grass-forb crop was estimated as 0.12 × 10–3m2kg-1. This value is lower by a factor of 100 and 50 compared to the median values of Tagthat were deduced for Fukushima-derived radiocaesium in 2011 and 2012, respectively. The radiocaesium Tagvalues for Sasa sp. and Artemisia sp. agreed with those for mixed grass-forb crop. At grasslands with the aboveground biomass density of 1 kg m–2and the Tagof 6 × 10–3m2kg-1 for134Cs, the contribution of the vegetation contamination to total inventory of the radionuclide did not exceed 1%. For137Cs, this contribution was less than 0.1%.

Radiocaesium transfer from forest soils to wild edible fruits and radiation dose assessment through their ingestions in Czech Republic

ABSTRACTDue to the Chernobyl nuclear power plant accident in 1986, the environment of forest ecosystems is still contaminated by radiocaesium (137Cs). Currently the average surface soil activity of 137Cs is 3.87 kBq m−2 in the Czech Republic. Depending on the soil properties of the sample locality, the 137Cs content in selected edible forest fruits and related radiocaesium soil-to-fruit transfer was analysed. In addition, radiation doses through ingestion were estimated with regards to the potential health risk caused by consumption of the fruits. Fruits (blueberry, rowanberry, blackberry and raspberry) and soil samples were collected in some locations of the Jeseníky Protected Landscape Area (PLA), the north-eastern mountains of the Czech Republic most severely contaminated with radiocaesium (137Cs). The average aggregated transfer coefficient (TFag) for radiocaesium (137Cs) reached values ranging from 2.73 × 10−5 to 2.20 × 10−2 m2 kg−1. The values of TFag correlated with the soil reaction, with the content of humus and with the content of clay particles in the soil of the sample areas, that is, r = –0.90 (p < 0.001), r = 0.81 (p < 0.001) and r = –0.68 (p < 0.01), respectively. Only the soil reaction pH (KCl) had an effect on TFag (p < 0.01). The highest radiation dose which the average Czech consumer would receive after consumption of the fruits was calculated as 1.78 × 10−2 mSv year−1, and such a dose of radiocaesium should not present a serious health problem.

Long-term transfer of global fallout 137Cs to cow’s milk in Iceland

The aim of this study was to provide improved information on the long-term transfer of global nuclear weapons (137)Cs fallout to cow's milk in Iceland many years after deposition. The spatial variation in deposition was confirmed to be explained by precipitation. Soil samples showed a significant difference in (137)Cs deposition density between the main agricultural areas, with the South having the highest values, then the West and North and the lowest in the Northeast. There was no significant difference between the effective half-lives in (137)Cs activity concentrations in milk and milk powder from the main dairies in Iceland based on data for milk from 1990 to 2007 and for milk powder from 1986 to 2007. There was, however, a significant difference between the effective half-lives obtained for these two regions, 13.5 years for the Northern and 10.5 years for the Southern regions. These half-lives for global fallout are longer than those previously reported for similar time periods in other Arctic areas. The transfer of (137)Cs to cow's milk was quantified for different agricultural regions using aggregated transfer coefficients (T (ag)) for the period of peak global fallout soil inventory in 1965-1967. The values ranged from 2.8 × 10(-3) to 10.6 × 10(-3) m(2) kg(-1). By 2001-2004, the T (ag) values had only declined, in the main agricultural areas, to 0.6 × 10(-3)-1.0 × 10(-3) m(2) kg(-1). Long-term transfer rates to milk many years after deposition were high in Iceland compared with most other reported data. The transfer is potentially relevant for some of the contaminated areas around the Fukushima Nuclear Power Plant after the accident in March 2011 since limited information is available on uptake from Andosols and associated effective half-lives.

Radiostrontium uptake by plants from different soil types in Kazakhstan

The transfer of 90Sr to a range of different plant species grown on a range of different soil types in Kazakhstan, including three from the Semipalatinsk Test Site (STS), has been measured in a lysimeter experiment. 90Sr uptake by Stipa spp was significantly higher than for other vegetation species. The uptake of 90Sr from chernozem was significantly lower than that from the other soil types which is consistent with other literature. There was a significant negative relationship between 90Sr uptake and calcium, humus and CEC concentration in the soil for Agropyrum spp, Artemisia spp but not for Stipa spp or Bromus spp. The transfer to vegetation from soil has been quantified using the aggregated transfer coefficients for each species. Tag values range from 0.6 to 11.9 m2 kg-1x10(-3) over all measurements. The transfer of 90Sr to plants from the Kazakh soils was low compared to previously reported data and to that given from literature reviews.

Concentrations of 137Cs in lynx ( Lynx lynx) in relation to prey choice

Concentrations of 137Cs were determined in 747 lynxes killed in Norway during the period 1986–2001. Highly variable 137Cs concentrations and aggregated transfer coefficient values were observed, probably caused by variable 137Cs concentrations in prey and the lynx's extensive home ranges and roaming distances. Adult lynxes had higher 137Cs concentrations than sub-adults, and lynxes killed in regions with extensive reindeer grazing areas were more contaminated than others. A model with 137Cs deposition density, the year lynxes were killed, age, and extent of reindeer grazing area accounted for 50% of the variability in observed 137Cs concentrations. The analyses were equivocal regarding the influence of stomach content on 137Cs concentrations in lynx muscle, i.e., on the lynx's specialization in prey species. Gender was not significant. Information on caesium retention in lynx and better estimates of deposition densities in lynxes' home ranges are important for further elucidation of factors influencing 137Cs contamination in lynxes.

Radiocaesium in lynx in relation to ground deposition and diet.

The European lynx (Lynx lynx) might be expected to have a high intake of radiocaesium in the parts of Sweden where the main prey of the lynx, namely reindeer and roe deer, have high activity concentrations of radiocaesium because of high ground deposition. We have measured (137)Cs in muscle samples from 733 lynx during 1996-2003. The aim was to quantify the extent to which radiocaesium is transferred from fallout deposition to lynx, to test whether the transfer was higher in areas where there are reindeer present, to see if there was any decline in radiocaesium over time, and to calculate the radiation dose to lynx. Most samples were collected in central and northern Sweden during January-April. Activity concentrations in lynx varied from 13 Bq kg(-1) to about 15 kBq kg(-1) fresh weight, with the highest value corresponding to a radiation dose at 18 mGy/year. Aggregated transfer coefficients (Tag), calculated by dividing the (137)Cs activity concentration in lynx muscle by the average ground deposition (total from Chernobyl and nuclear weapon tests) within a 50 km radius around the location of the lynx, varied from 0.004 to 1.3 m(2) kg(-1) and were significantly higher within the reindeer herding area than outside. The concentration ratio (CR) for lynx/reindeer was 2.6 on average, whilst the average for lynx/roe deer outside the reindeer herding area was lower at 1.3. Based on these results, a CR of around 2 could be considered representative for the general ratio between predator and prey. A long-term decline of radiocaesium in prey species was reflected in lynx, with an effective half-life of 7 years from 1996 to 2003. The study shows that the accumulation of radiocaesium in predators, especially predators of reindeer, makes them more vulnerable to high radiocaesium deposition than most other wild species.

Estimation of radioecological sensitivity

After the release of radionuclides into the environment it is important to be able to readily identify major routes of radiation exposure, the most highly exposed individuals or populations and the geographical areas of most concern. There have been significant recent improvements in our capability to estimate spatial variation in the environmental behaviour of radionuclides through better understanding of the underlying processes and an ability to spatially apply this knowledge by integrating relevant spatial information in the form of digital data sets using geographical information systems. Thus, it is now possible to refine the estimation of spatial variation in radiation exposure, both for routine releases and in accident situations. Within a recent EC-funded concerted action (the Radioecological Sensitivity Forum), there has been a renewed consideration of the concept of radioecological sensitivity with a particular focus on identifying sensitive areas as well as processes and communities. The concept should be relevant for both terrestrial and aquatic ecosystems, and might even be applied for consideration of doses to biota, although the current focus has been restricted to a consideration of human exposure. The conclusions of the action are outlined, considering the potential usefulness of the concept, and methods by which it can be applied. A framework for the estimation of radioecological sensitivity is proposed and the various measures by which it can be considered, including (i) aggregated transfer coefficients, (ii) action loads, (iii) fluxes and (iv) individual exposure of humans are discussed. The importance of spatial and temporal consideration of each of these outputs is emphasized.

Quantifying 137Cs aggregated transfer coefficients in a semi-natural woodland ecosystem adjacent to a nuclear reprocessing facility

Radiocaesium ( 137Cs) activity concentrations and aggregated transfer factors ( T ag values) were calculated for vascular plants, fungal fruiting bodies and invertebrates in a semi-natural Picea sitchensis woodland (Lady Wood) adjacent to the British Nuclear Fuels plc. reprocessing facility at Sellafield, Cumbria, UK. The T ag values for vascular plants ranged from 7.1×10 −4–1.9×10 −2 m 2 kg −1, the maximum value being for Pteridium aquilinum. Fungal fruiting bodies had higher T ag values (1.9×10 −3–1.8×10 −1 m 2 kg −1) than vascular plants, with a maximum value for Mycena galericulata. None of the activity concentrations for edible foodstuffs collected within this study (fungi and berries) exceeded the EC recommended limits of 137Cs in foodstuffs grown within the UK. The invertebrate community sampled during the study had T ag values ranging from 3.4×10 −4 to 1.3×10 −2 m 2 kg −1. There were no systematic differences in 137Cs activity concentration between invertebrate guilds, or between seasonal cohorts within guilds. The invertebrates in Lady Wood were exposed to a dose from 137Cs (internal gamma + beta and external gamma) ranging between 4.37×10 −4 and 6.40×10 −4 mGy day −1. Including dose from radionuclides other than 137Cs and accounting for uncertainties due to the relative biological effectiveness of differing radionuclides could increase total dose by approximately an order of magnitude. These dose rates are at least three orders of magnitude lower than the 1 mGy d −1 level at which harm may be caused to terrestrial biota, hence the risk to the invertebrate community from the effects of ionising radiation in Lady Wood is low.

Effect of origin of radiocaesium on the transfer from fallout to reindeer meat

Data on radiocaesium contamination of reindeer from five regions in Sweden have been used, together with interpolated radiocaesium deposition data, to quantify spatial variation in transfer to reindeer meat and to consider how it changes with time in different areas. Since the regions were contaminated to different extents by global and Chernobyl fallout, it was also possible to determine the influence of the origin or age of radiocaesium fallout on the transfer to reindeer meat. The regions differed significantly with regard to transfer of radiocaesium to reindeer meat. In two regions in the North of Sweden, where there was less Chernobyl 137Cs, aggregated transfer coefficients (Tag), estimated for the main slaughter period in the first year after the Chernobyl fallout, were low (0.15 and 0.36 m 2 kg −1 in January–April). Average Tag values calculated for the winter period (January–April) in two regions in the middle of Sweden, where deposition from Chernobyl dominated (83 and 94%, respectively, of the total deposition), were 0.78 and 0.84 m 2 kg −1, respectively with a maximum Tag for an individual reindeer of 1.87 m 2 kg −1. There was a threefold increase in Tag values from early autumn to late winter reflecting the change in the reindeer diet from less contaminated vascular plants to more contaminated lichens. The decline of 137Cs in reindeer meat from 1986 to 2000 differed between regions with longer effective half-lives ( T ef) in the northerly regions (11.0 and 7.1 years, respectively) with less Chernobyl fallout, and shorter half-lives in the other three regions (3.5–3.8 years). This observation, together with a lack of a decline in early autumn in the region with least Chernobyl fallout, supports the theory of a gradual, but reversible, fixation of radiocaesium in the soil over the mid-long term. The results suggest that both the extent of transfer of 137Cs to reindeer meat, and its subsequent decline with time, are affected by the differing origins of radiocaesium and that previous contamination may substantially influence radiocaesium transfer in the event of a further accident.

Seasonal variation in radiocaesium concentration in willow ptarmigan and rock ptarmigan in central Norway after the chernobyl fallout

Radioactive caesium (20–60 kBq m -2) was deposited after the Chernobyl accident in the mountains of central Norway. Two sympatric ptarmigan species, willow ptarmigan Lagopus lagopus and rock ptarmigan L. mutus, inhabit this alpine ecosystem and are important game species. In 1987 and 1988, a study was carried out to try to identify factors affecting radioactive caesium concentration in these birds. Juvenile willow ptarmigan contained more radiocaesium than adults, but the two sexes did not differ in radiocaesium concentration. The radiocaesium concentration of food plants correlated with radiocaesium concentration of rock ptarmigan, and a seasonal variation in radiocaesium concentration of both ptarmigan species was seen. Rock ptarmigan contained more radiocaesium than willow ptarmigan during winter, but not in summer. This difference was related to differences in diet. The bioconcentration factor was 0·4–0·6. The aggregated transfer coefficient was 0·003–0·009 m 2 kg -1 for both species. In spite of the high deposition, the radiocaesium concentration in muscle rarely exceeded the limit recommended for human food consumption (600 Bq kg -1).

Factors affecting the transfer of radiocaesium from soil to roe deer in forest ecosystems of southern Germany

Since 1987, in Southern Germany, as a consequence of the Chernobyl accident, the 137Cs activity concentration in roe deer (Capreolus capreolus) has been intensively monitored. A large data set is now available with approximately 5000 samples, with information about the location of the animal, the time of slaughtering, soil characteristics and distance to intensively managed agricultural land. Both the roe deer 137Cs activity concentrations and aggregated transfer coefficients soil-roe deer (Tag.r) show a considerable variability with geometric mean and geometric standard deviation in meat of 270·3.5±1 Bq·kg−1 and 0.01·3.5±1 m2·kg−1, respectively. From 1987 to 1991, Tag,r values exhibited a decline with an ecological half-life of about 3 years. Since 1991, no further decrease of the roe deer contamination level was observed. This general trend is superimposed by an increase in Tag,r in autumn that has occurred in almost every year, which is probably due to consumption of mushrooms. This hypothesis is supported by a significant positive correlation between the precipitation during July and August, stimulating the fungi's growth and the height of the maximum in Tag,r in autumn.Animals are less contaminated when living in parts of the forest from where they have access to intensively managed agricultural land. A small, but significant correlation is observed between the Tag,r and soil parameters; the total potassium content of the soil and the pH of the organic soil layer. The highest transfer coefficients soil-roe deer were found on a peat bog, where most values ranged from 0.01–0.1 m2·kg−1, and neither a pronounced seasonal variation, nor a long-term decrease was observed. On sites with coniferous forests, most Tag,r values range from 0.005 to 0.05 m2·kg−1, on sites with a mixture of coniferous and deciduous trees, the transfer coefficients range mostly from 0.002 to 0.02 m2·kg−1. This is a further indication of the importance of the uppermost soil layers and the biological processes therein with respect to the bioavailability of caesium. On the two sites, the values at the lower boundary are more typical for animals that have access to agricultural areas, whereas the higher values were observed in autumn and for animals grazing distant from agricultural areas.

Soil-fungi radiocesium transfer in forest ecosystems in Mexico

Eight different species of fungi were collected at the Nuclear Center of Mexico (NCM) together with soil samples from mushroom growing spots, during 1993. The samples were analysed for 137Cs and 40K using gamma spectrometry. To quantify the transport of 137Cs from the soil into the mushrooms, the Aggregated Transfer Coefficient (ATC) was determined. The results indicate that radiocesium absorption varies over a wide range among several fungi species as a function of factors such as mycelium deepness, and fungi symbiotic or saprophytic features. Two local species were found to have the highest ATC for 137Cs. The 40K content was found to be lower for mycorrhyzal species.

Relative importance of ewe milk and pasture in transferring radiocaesium to lambs during the summer grazing period

The relative importance of milk and pasture in transferring radiocaesium (134Cs and 137Cs) to lamb's meat was studied in 13 ewes with twin lambs grazing on pastures contaminated by deposition from the Chernobyl accident. Six of the ewes were fed a caesium binder to obtain low milk radiocaesium levels and seven were used as control. Radiocaesium activity concentration was measured in meat, blood and milk every 14 d. Milk was the major source of radiocaesium for lambs younger than 6–7 wk, but from 11 wk onwards milk had only a slight and non-significant effect on radiocaesium concentration in lamb's meat. Thus, radiocaesium intake from pasture was the major factor determining radiocaesium concentration in lambs at time of slaughter. Mean aggregated transfer coefficients to meat were 23 × 10−3 m2 kg−1 and 31 × 10−3 m2 kg−1 for ewes and lambs, respectively, and mean aggregated transfer coefficient to ewes milk was 11 × 10−3 m2 l−1.

Transfer of Radiocesium to Ruminants in Natural and Semi-natural Ecosystems and Appropriate Countermeasures

A review of studies conducted before and after the Chernobyl accident is presented, showing that both the duration and the extent of radiocesium contamination of ruminants will be more severe in unimproved ecosystems compared with agricultural areas. Although such unimproved ecosystems provide comparatively small quantities of food for human consumption, the integrated dose from these areas to the human population can be large. Ecological characteristics that make unimproved ecosystems particularly vulnerable to this form of pollution include the presence of (1) soils that do not immobilize radiocesium and therefore allow its uptake into vegetation; (2) vegetation species with high uptake rates of radiocesium; (3) the predominant utilization by small ruminants which attain higher muscle radiocesium levels than cattle. Unimproved ecosystems, which often are located at high altitudes, are predisposed to receiving higher fallout because of high precipitation rates which enhance the likelihood of deposition. Countermeasures have been developed and used successfully to reduce radiocesium levels in ruminants grazing in unimproved ecosystems. Apart from decontamination by altering farming practices and providing uncontaminated feeds, sustained reductions of 50% to 80% in the radiocesium concentrations of both milk and meat have been achieved in many ruminant species when AFCF is given via a sodium chloride lick or as a sustained-release bolus. Food production in unimproved ecosystems must be evaluated separately from that of ordinary agricultural systems. In addition to detailed studies on the behavior of radiocesium, consideration should be given to the collection of aggregated transfer coefficients from various ecosystems which were affected by Chernobyl fallout. By combining bioavailability estimates and aggregated transfer coefficients, based on Chernobyl and nuclear weapons test fallout data, it may in the future be possible to make a rapid assessment of both the immediate and the long-term impact of a future nuclear accident on food production in unimproved ecosystems.