Migration of iodine-129 and iodine-127 in soils

To draw the balance of anthropogenic 129I input into European soils, the concentrations of 129I and 127I in seven soils from Lower Saxony were analyzed down to a depth of 250 cm. In comparison with pre-nuclear soils and Ukrainian soils, we detected a significant anthropogenic input of 129I. Considering the different time periods for the input of 129I and 127I it was possible to assess the dynamics of sorption processes which dominate migration and accumulation. Anthropogenic 129I was successfully used as a tracer for a clarification of the migration processes of trace elements in soils.

The effect of repeated passaging on the susceptibility of human proximal tubular HK-2 cells to toxic compounds

The human proximal tubular HK-2 cell line is an immortalized cell line commonly used for studying proximal tubular toxicity. Even as their use is presently increasing, there unfortunately are no studies focused on functional changes in HK-2 cells associated with passaging. The aim of the present study, therefore, was to evaluate the functional stability of HK-2 cells during 13 weeks of continuous passaging after 6 and 24 h of treatment with model nephrotoxic compounds (i.e., acetaminophen, cisplatin, CdCl(2)). Short tandem repeat profile, the doubling time, cell diameter, glutathione concentration, and intracellular dehydrogenase activity were measured in HK-2 cells at each tested passage. The results showed that HK-2 cells exhibit stable morphology, cell size, and cell renewal during passaging. Mean doubling time was determined to be 54 h. On the other hand, we observed a significant effect of passaging on the susceptibility of HK-2 cells to toxic compounds. The largest difference in results was found in both cadmium and cisplatin treated cells across passages. We conclude that the outcomes of scientific studies on HK-2 cells can be affected by the number of passages even after medium-term cultivation and passaging for 13 weeks.

Transient increase in cellular dehydrogenase activity after cadmium treatment precedes enhanced production of reactive oxygen species in human proximal tubular kidney cells

Cadmium is a heavy metal causing toxicity especially in kidney cells. The toxicity is linked also with enhanced oxidative stress leading to cell death. On the other hand, our recent experiments have shown that an increase of total intracellular dehydrogenases activity can also occur in kidney cells before declining until cell death. The aim of the present study, therefore, was to evaluate this transient enhancement in cell viability after cadmium treatment. The human kidney HK-2 cell line was treated with CdCl(2) at concentrations 0-200 microM for 2-24 h and intracellular dehydrogenase activity was tested. In addition, we measured reactive oxygen species (ROS) production, glutathione levels, mitochondrial membrane potential, and C-Jun-N-terminal kinase (JNK) activation. We found that significantly increased dehydrogenase activity could occur in cells treated with 25, 100, and 200 microM CdCl(2). Moreover, the results showed an increase in ROS production linked with JNK activation following the enhancement of dehydrogenase activity. Other tests detected no relationship with the increased in intracellular dehydrogenase activity. Hence, the transient increase in dehydrogenase activity in HK-2 cells preceded the enhancement of ROS production and our finding provides new evidence in cadmium kidney toxicity.

Mycotoxin occurrence in commodities, feeds and feed ingredients sourced in the Middle East and Africa

Between February and October 2009, 324 grain, feed and feed commodity samples were sourced directly at animal farms or feed production sites in Middle East and Africa and tested for the presence of A- and B-trichothecenes, zearalenone, fumonisins, aflatoxins and ochratoxin A, or for selected groups of mycotoxins only. Samples were analyzed after clean-up by immunoaffinity or solid-phase extraction followed by HPLC with derivatization where appropriate and fluorescence, UV or mass spectrometric detection. The percentage of positive samples of B-trichothecenes ranged from 0 to 87% of tested samples. The prevalence of fumonisins in the different countries was >50% in most cases. Zearalenone was present in tested commodities from all countries except three. The presence of aflatoxin in analyzed samples varied from 0 to 94%. Ochratoxin A was present in 67% of samples in Sudan and in 100% of Nigerian samples. No A-trichothecenes were found in this survey.

Occurrence of mycotoxins in Southern Europe

Contamination of feed materials with mycotoxins is an important issue for farmers, as dietary exposure to these toxins may cause acute or chronic intoxication in animals, resulting in major economic losses. Although prevention methods to avoid mycotoxin contamination on the field prior to harvest, during harvesting or storage have been developed, it is currently not possible to eliminate the risk of a mycotoxin contamination entirely. Here we present a survey over a 4.5 year period that was performed to evaluate the incidence of mycotoxins in feed materials and compounded feed samples originating from Southern European countries, including Portugal, Spain, Italy, Greece and Cyprus. The 416 samples received were tested for the most relevant mycotoxins that are found in feed materials, such as aflatoxins, zearalenone (ZEA), type B trichothecenes (deoxynivalenol and acetyldeoxynivalenol), type A trichothecenes (T-2 toxin and HT-2 toxin), fumonisins and ochratoxin A (OTA), by two different methods, a commercial ELISA and by validated HPLC methods. The Fusarium mycotoxins (type B trichothecenes, ZEA and fumonisins) were the major contaminants. Average concentrations of type B trichothecenes were 365 µg/kg or 445 µg/kg analysed by HPLC or ELISA, respectively. In the case of zearalenone the average concentration was 27 µg/kg by ELISA or 32.5 µg/kg by HPLC. Fumonisin contamination was found with an average of 1,411 µg/kg by HPLC or 6,260 µg/kg by ELISA. Aflatoxins and OTA as well as the type A trichothecenes were detected less frequently and the average concentration was lower in comparison to the other mycotoxins tested. The average concentration of aflatoxins, OTA and the type A trichothecenes was 1 µg/kg or 3 µg/kg, 4 µg/kg or 2 µg/kg, 2 µg/kg or 18 µg/kg, respectively, by HPLC or ELISA analysis.

Accumulation of (137)Cs in Brazilian soils and its transfer to plants under different climatic conditions

The spatial distribution and behaviour of the global fallout (137)Cs in the tropical, subtropical and equatorial soil-plant systems were investigated at several upland sites in Brazil selected according to their climate characteristics, and to the agricultural importance. To determine the (137)Cs deposition density, undisturbed soil profiles were taken from 23 environments situated between the latitudes of 02 degrees N and 30 degrees S. Sampling sites located along to the equator exhibited (137)Cs deposition densities with an average value of 219Bqm(-2). Extremely low deposition densities of 1.3Bqm(-2) were found in the Amazon region. In contrast, the southern part of Brazil, located between latitudes of 20 degrees S and 34 degrees S, exhibited considerably higher deposition densities ranging from 140Bqm(-2) to 1620Bqm(-2). To examine the (137)Cs soil-to-plant transfer in the Brazilian agricultural products, 29 mainly tropical plant species, and corresponding soil samples were collected at 43 sampling locations in nine federal states of Brazil. Values of the (137)Cs concentration factor plant/soil exhibited a large range from 0.020 (beans) to 6.2 (cassava). Samples of some plant species originated from different collecting areas showed different concentration factors. The (137)Cs content of some plants collected was not measurable due to a very low (137)Cs concentration level found in the upper layers of the incremental soils. Globally, the soil-to-plant transfer of (137)Cs can be described by a logarithmic normal distribution with a geometric mean of 0.3 and a geometric standard deviation of 3.9.

Ant-based clustering and topographic mapping

Ant-based clustering and sorting is a nature-inspired heuristic first introduced as a model for explaining two types of emergent behavior observed in real ant colonies. More recently, it has been applied in a data-mining context to perform both clustering and topographic mapping. Early work demonstrated some promising characteristics of the heuristic but did not extend to a rigorous investigation of its capabilities. We describe an improved version, called ATTA, incorporating adaptive, heterogeneous ants, a time-dependent transporting activity, and a method (for clustering applications) that transforms the spatial embedding produced by the algorithm into an explicit partitioning. ATTA is then subjected to the most rigorous experimental evaluation of an ant-based clustering and sorting algorithm undertaken to date: we compare its performance with standard techniques for clustering and topographic mapping using a set of analytical evaluation functions and a range of synthetic and real data collections. Our results demonstrate the ability of ant-based clustering and sorting to automatically identify the number of clusters inherent in a data collection, and to produce high quality solutions; indeed, we show that it is particularly robust for clusters of differing sizes and for overlapping clusters. The results obtained for topographic mapping are, however, disappointing. We provide evidence that the solutions generated by the ant algorithm are barely topology-preserving, and we explain in detail why results have--in spite of this--been misinterpreted (much more positively) in previous research.

Iodine-129 in soils from Northern Ukraine and the retrospective dosimetry of the iodine-131 exposure after the Chernobyl accident

Forty-eight soil profiles down to a depth of 40 cm were taken in Russia and Ukraine in 1995 and 1997, respectively, in order to investigate the feasibility of retrospective dosimetry of the 131I exposure after the Chernobyl accident via the long-lived 129I. The sampling sites covered areas almost not affected by fallout from the Chernobyl accident such as Moscow/Russia and the Zhitomir district in Ukraine as well as the highly contaminated Korosten and Narodici districts in Ukraine. 129I was analyzed by radiochemical neutron activation analysis (RNAA) and accelerator mass spectrometry (AMS). 127I was measured for some profiles by RNAA or ion chromatography (IC). The results for 127I demonstrated large differences in the capabilities of the soils to store iodine over long time spans. The depth profiles of 129I and of 137Cs showed large differences in the migration behavior between the two nuclides but also for each nuclide among the different sampling sites. Though it cannot be quantified how much 129I and 137Cs was lost out of the soil columns into deeper depths, the inventories in the columns were taken as proxies for the total inventories. For 129I, these inventories were at least three orders of magnitude higher than a pre-nuclear value of 0.084+/-0.017 mBq m(-2) derived from a soil profile taken in 1939 in Lutovinovo/Russia. From the samples from Moscow and Zhitomir, a pre-Chernobyl 129I inventory of (44+/-24) mBq m(-2) was determined, limiting the feasibility of 129I retrospective dosimetry to areas where the 129I inventories exceed 100 mBq m(-2). Higher average 129I inventories in the Korosten and Narodici districts of 130 and 848 mBq m(-2), respectively, allowed determination of the 129I fallout due to the Chernobyl accident. Based on the total 129I inventories and on literature data for the atomic ratio of 129I/131I=13.6+/-2.8 for the Chernobyl emissions and on aggregated dose coefficients for 131I, the thyroid exposure due to 131I after the Chernobyl accident was estimated for the inhabitants of four villages in the Korosten and of three villages in the Narodici districts. The limitations and uncertainties of the 129I retrospective dosimetry are discussed.

Evaluation of radioactive exposure from 137Cs in contaminated areas of Northern Ukraine

The paper gives averages of 137Cs deposition densities in soils from three areas in Northern Ukraine measured 12 to 15 y following the Chernobyl accident: in an area near Narodici (75 km west of the Chernobyl nuclear power plant in the so-called zone II) heavily contaminated by the Chernobyl fall-out and in areas around Korosten and Zhitomir showing contamination levels to be much lower. The three areas exhibited very different 137Cs deposition densities of 2.2 MBq m(-2), 400 kBq m(-2), and 5 kBq m(-2), respectively. During a 1-y observation, measurements of the 137Cs transfer in the food chain to humans and 137Cs whole body contents dependent on the 137Cs daily intake were carried out under realistic conditions of the rural inhabitants who lived in settlements within zone II. Detailed investigations of components of the daily diet showed that the high 137Cs contamination levels found in soils of zone II do not affect in any way low 137Cs concentrations of all important agricultural products harvested and consumed by villagers. With regard to consumption habits of the population of zone II, mushrooms and wild berries were found to contribute more than 95% of the 137Cs daily intake to the 137Cs whole body content of about 12 kBq (with maximum values up to 760 kBq) measured in a group of inhabitants of zone II during a period from July 1998 to July 1999. The median of the annual dose of these inhabitants from external and internal exposures was 1.2 mSv y(-1) with a geometric standard deviation of 2.6. Excluding extreme habits, the geometric mean of the total exposure was 1.0 mSv y(-1) with a geometric standard deviation of 1.3.

Fallout radiocesium in an Antarctic region: deposition history, activity densities and vertical transport in soils

To improve the knowledge about the (137)Cs spatial distribution and vertical migration in soils of the Southern Hemisphere, the total areal activity density and the vertical transport parameters of this radionuclide were measured in an Antarctic region. For this purpose vegetation and incremental soil samples were collected at 21 representative sites located at 4 islands of the South Shetland Archipelago: King George, Robert, Greenwich and Snow (62-63 degrees S and 58-62 degrees W). The total (137)Cs activity density varied considerably from 118 to 662 Bq m(-2) (median 384 Bq m(-2), reference date 1995), with a high percentage of the total activity retained in the vegetation cover (5-98% in moss, 3-20% in lichen and 4-12% in grass). At most sites, the maximum activity density in soil was observed in the top layer from where it decreased continuously. To evaluate the transport parameters of (137)Cs from the activity-depth profiles, the classical convection-diffusion model was used based on the time-course of the annual deposition density of (137)Cs at the studied region. The values for the diffusion coefficient D(s) (median 0.043 cm(2) year(-1)) and the convection velocity v(s) (median -0.012 cm year(-1)) of radiocesium observed under a polar climate are small compared to the transport parameters determined in temperate zones. The data also indicate that at these sites the convectional transport of (137)Cs is almost negligible compared to the transport by diffusion. The high vulnerability of the Antarctic soils to (137)Cs deposition, as a consequence of its very slow transport due to the extreme climatic conditions at these latitudes, has been confirmed.

Global weapons' fallout 137Cs in soils and transfer to vegetation in south-central Chile

The contamination and depth distribution of 137Cs in soil due to the fallout from atmospheric weapons' tests were measured at 29 sites in the 9th and 10th administrative regions in Chile located in the 40 degrees latitude in the southern hemisphere. The depth distribution in most of the sites follows no systematic pattern in the upper few centimetres, but below this depth an exponential decline could be deduced. The calculated relaxation depth appears to be a good indicator for estimating the long-term 137Cs distribution in these soil profiles. It ranges from 4.4 +/- 1.9 cm in Palehumults to 8.4 +/- 4.4 and 9.7 +/- 5.1 cm in Hapludands and Psamments, respectively. For these soil types the value for the relaxation depth tends to increase with decreasing clay content and increasing volume of coarse pores. 137Cs activity densities at the selected sites ranged from 450 to 5410 Bq m(-2) and correlate significantly (r = 0.791) with the mean annual rainfall rate of the sampling sites. 137Cs concentration ratios of prairie plants/soil were found to be in the range 0.008-2.3 and could be related to relaxation depths in undisturbed soils.

On the analysis of iodine-129 and iodine-127 in environmental materials by accelerator mass spectrometry and ion chromatography

Based on a review of literature about the abundances of 129I (T1/2 = 15.7 Ma) in the environment we show that there is a severe lack of knowledge, in particular about natural, pre-nuclear levels. Among the two analytical techniques which are sensitive enough to investigate 129I in environmental materials, namely radiochemical neutron activation analysis (RNAA) and accelerator mass spectrometry (AMS), only AMS is capable of covering the natural, pre-nuclear levels. Since such AMS measurements require chemical separation of iodine from the matrix, a wide variety of separation schemes are necessary for environmental analyses. We report here on such schemes for the analysis of soils, plants and soft tissue. They are applied exemplarily to analyses of soils from the vicinity of Chernobyl. For chemical separations prior to analysis, contamination control and blank analyses are essential. Here, we discuss quality control procedures in detail, both for RNAA and AMS. In the case of AMS we use ion-chromatography (IC) for the determination of stable iodine. The IC analysis is included in the separation schemes for environmental materials. First AMS-analyses of terrestrial biospheric materials demonstrate that natural environmental levels of 129I are lower than previously deduced from investigations using RNAA, but higher than expected from model calculations. AMS is capable of providing the missing knowledge about the radioecology of 129I.

Long-term decrease of atmospheric test 137Cs in the soil-prairie plant-milk pathway in southern Chile

The time dependency of nuclear test 137Cs in soil, prairie plants, and milk was observed on pastures of seven dairy farms in the 10th Region, Chile, from 1982 to 1997, without any appreciable deposition of radioactive fallout after 1983. Whereas the 137Cs concentration in the soil decreased at a rate close to that of the radionuclide's physical decay during the whole observation period, the rate of decrease of the 137Cs concentration in the prairie plants and in the milk, having been very rapid between 1982-1990, became slower between 1991-1997. The effective half-lives of the concentration in plants were found to be 5.6 y and 12 y during the first and second observation periods, respectively. Similar half-lives of 5.5 y and 13 y were found for the concentration decline in milk during each period. These data clearly demonstrate a reduction in the long-term decrease of the 137Cs plant uptake, and consequently in the decrease of the 137Cs concentration in milk, resulting from a decline of 137Cs availability for prairie plants in the Hapludand soils over the whole 15-y observation period.

129I, 131I and 127I in animal thyroids after the Chernobyl nuclear accident

A small number of animal thyroids from Bad Hall, Austria; Ulm, Germany; and Steinkjer, Norway had 131I (half-life 8.06 d) measured between 21 and 72 d following the nuclear accident at Chernobyl on 26 April 1986. Nine years later 129I (half-life 1.57 x 10(7) y) fission product and natural 127I were measured in the same thyroids. The mass ratios, 129I/131I were calculated to the date of the Chernobyl accident and they ranged between 13 and 71. These ratios are compared to the expected ratios within an operating nuclear reactor during 2 y of operation, where the 129I/131I(-1) ratio never exceeded 30. The observed ratio of 129I to natural 127I in thyroids ranged from 5 to 200 times the ratio before the accident, except that the Norwegian thyroids had 129I/127I ratios which were less than the ratios of pre-Chernobyl thyroids from Ulm. These studies show the 129I and 131I from the Chernobyl accident were accumulated with natural 127I in animal thyroids but the isotope ratios, calculated to the release date, had wide ranges. The 131I radioactive exposure might be estimated from a fission product mixture by measuring 129I in thyroids long after the exposure to 131I, but the results would probably show a wide range of possibilities. The determining variables should be evaluated. We know of no previous data regarding both 131I and 129I in thyroid glands during the first 3 mo after the Chernobyl accident.

Biospheric 129I concentrations in the pre-nuclear and nuclear age

In order to detect characteristic regional differences or temporal changes of 129I concentrations in the biosphere, thyroids from humans, grazing livestock, and herbivorous wildlife species (reindeer and roedeer) were collected in various areas of the world which are not affected by reprocessing plants. For reasons of comparison, all samples were analyzed for their 129I:127I atom ratios. Human and bovine thyroids taken from the 10th region in Southern Chile (39 degrees-41 degrees South) indicated values of the 129I:127I atom ratio between 1.1 x 10(-9) and 2.0 x 10(-9) and between 1.2 x 10(-10) and 9 x 10(-9), respectively. They showed no significant increase in the concentration of biospheric 129I in comparison with that established in the pre-nuclear age. Atom ratios found in human thyroids collected in Lower Saxony (Federal Republic of Germany), which is a region not directly affected by reprocessing plants, exhibited 129I:127I values between 8 x 10(-9) and 6 x 10(-8) from February 1988 to September 1990. Thyroid glands of reindeer and roedeer as well as heather, moss, and lichen were taken from the Vilhelmina, Heby, and Gävle communes in Sweden and analyzed for 129I and 127I. All three communes were found to be seriously contaminated by fallout from the Chernobyl accident. Highest 129I:127I atom ratios between 3.5 x 10(-7) and 1 x 10(-6) were found in the Gävle commune (approximately 150 km northwest of Stockholm) where the highest 137Cs ground deposition (70-80 kBq m-2) was measured. Two soil samples taken from Krasnaya Gora and Mirny locations in Russia (approximately 200 km northeast of Chernobyl) exhibited ratios of about 1 x 10(-6). These locations showed a 137Cs ground deposition of 370 and 1,300 kBq m-2, respectively.

137Cs concentration in soil, prairie plants, and milk from sites in southern Chile

Soil, prairie plants, and milk samples were collected at 39 dairy farms in the 9th and 10th Region in Southern Chile (38 degrees 44'-41 degrees 08' S) between 1982 and 1990. 137Cs concentrations found in soil, plant, and milk samples ranged from 3.8-17.1 Bq kg-1 for soil, from < 0.3-20 Bq kg-1 dry mass for plants, and from 0.10-0.71 Bq kg-1 for milk. Cesium concentration levels resulting from soil sample measurements exhibit a close similarity with corresponding values found in soils from Central Europe before 1986. The concentration ratio prairie plants:soil ranged from 0.05-0.62, 0.52-5.0, and < 0.02-0.40 corresponding to Dystrandepts, Placandepts, and Palehumults soil groups, respectively. At seven selected dairy farms in the vicinity of Valdivia city (10th Region), soil, prairie plant, and milk samples were taken yearly during the grazing period between 1982 and 1990. Results obtained from soil samples taken after April 1986 show no significant increase of the 137Cs concentration. Concentrations in plants and milk for 137Cs decreased during the observation time. 134Cs (as an indicator of Chernobyl fallout) was not found in soil, plant, or milk samples during 1986-1990.

The influence of soil parameters on 137Cs+-uptake by plants from long-term fallout on forest clearings and grassland

An attempt was made to show if and to what extent the 137Cs transfer from soil to plants (grass) in forest clearings and grassland is related closely enough to different soil parameters to make it worthwhile to develop mathematical models for the prediction of transfer coefficients for certain plants and sites based solely on soil parameters. For this reason 62 soil samples from 0- to 5-cm in depth as well as from 5- to 10-cm in depth were measured for worldwide 137Cs fallout and analyzed for exchangeable potassium content, total potassium content, clay fraction, potential exchange capacity, pH value and carbon content. For both ecosystems, large variations of the transfer coefficients were observed: between 0.01 and 0.1 for grassland and 0.05 and 6 for forest clearings . Correlations, such as has been found between soil parameters, specific activities of the plants and transfer coefficients can in principle be integrated into different calculations for the estimation of radiation burden.

Content and heterogeneity of distribution of iodine in human and bovine thyroid glands determined by neutron activation analyses

While performing activation analytical investigations on the actual concentration of the long-lived radioactive 129iodine in human and bovine thyroid glands the absolute natural nonradioactive 127 iodine content was determined. In all thyroid glands an uneven distribution of 127I was found (in human thyroids from 0 to 0.75 micrograms 127I /mg, in bovine thyroids from 0 to 3.5 micrograms 127I /mg). The mean value of iodine concentration in human thyroid glands ranged from 230 micrograms/g to 490 micrograms/g. This is important because TSH independent autonomy is found at a cellular and follicular level during the development from diffuse to nodular goiter. Both processes may, however, not be related to each other. The resolution of the method used in our study is between the microscopic and the scintigraphic level with an accuracy of +/- 1%, and it shows an intermediate heterogeneity of iodine in thyroid glands.