Examination of the modified monostandard method in neutron activation analysis

The reproducibility, the small scale as well as the large scale variability of¹³⁷Cs extracted sequentially from the soil by using a modified Tessier procedure was investigated at several grassland sites in Bavaria/Germany and in the Chemobyl area. Because undisturbed grassland soils are never homogeneous with respect to their soil properties, all sequential extractions at the German sites were carried out at each plot separately for different soil layers (e.g., 0–2, 2–5, 5–10, 10–15, 15–20 and 20–30 cm). The results show that the coefficients of variation (CV) for the reproducibility of the extraction procedure for¹³⁷Cs was (with some exceptions) around 10–20% for all fractions. For the small scale variability of¹³⁷Cs (samples within an area of 10×10m²) the values for theCV were (again with a few exceptions) in the same range. Compared to that, the large scale variability of extractable¹³⁷Cs (random soil samples within an area of 100×200 km²) was higher for all fractions, even though only moderately. The implications of these results with respect to a sampling design are discussed.     

The effect of the tropical cloud (fog) forest on the spatial distribution of cesium-137 in soils in the Henri Pittier National Park (Edo. Aragua, Venezuela)

Soils were collected at different elevations (m.a.s.l.) near the two roadways, that pass through the Henri Pittier National Park (Edo. Aragua, Venezuela) in order to determine the distribution of the concentrations of the ¹³⁷Cs fallout and its relation to the tropical cloud forest. Duplicate samples were taken at most elevations between 2–5 cm below the soil surface to confirm that the samples were representative of the area. In many cases, it was difficult or impossible to locate areas that were undisturbed by man or nature. The ¹³⁷Cs (Bq/kg) content was determined by conventional high resolution gamma ray spectroscopy employing a standard comparison method. The background of the ¹³⁷Cs fallout in soils, below the cloud (fog) baseline was calculated to be about 5 Bq/kg on both the south (land) side and north (ocean) side for both roadways. The concentrations of ¹³⁷Cs (Bq/kg) were between 2–3 times higher at the baseline of the cloud (fog) on both sides of the mountain range. The ¹³⁷Cs values at the highest elevations (1105 and 1625 m.a.s.l.) near the roadways were about 5–6 times higher than the determined background levels. Our estimates of the baseline of the cloud (fog) are in good agreement with other visual observations. Finally, we have concluded that the distribution of ¹³⁷Cs in soils in cloud forests can be employed to estimate the baseline and the concentrations of ¹³⁷Cs fallout can be related to the relative density of the cloud (fog) when it was deposited.     

Fallout from Chernobyl in Bologna and its environs: Radioactivity in airborne,rain water and soil

The Chernobyl fallout was estimated in Emilia-Romagna, a Northeastern region of Italy. Nuclide composition of airborne and the time evolution of the radioactivity were investigated. The comparison of the activity ratio of¹⁰³Ru to¹³⁷Cs allows to conclude that Italy was not influenced by the first release. The trend of the total activity and¹³⁷Cs percentage in rain water was very similar to those of air particulates. A calculation model to estimate¹³⁷Cs deposition onto the ground has been developed and validated by comparison of the calculated and experimental values for soil samples. The activity range was 2–40 kBq ·m^–2.     

A study on radionuclide association with soil components using a sequential extraction procedure

Measurements performed in 1986–1988 demonstrate that most of the radiocesium isotopes (¹³⁷Cs and¹³⁴Cs) deposited after the Chernobyl accident are still located in the upper soil layers (0–2 cm). The vertical migration appears to be slow, and only a small fraction of the radiocesium has been transferred into the biological cycle. Sequential extraction techniques have been utilized in order to investigate the degree of binding or association between deposited radionuclides (¹³⁷Cs,¹³⁴Cs and⁹⁰Sr) and components in soil. The results indicate that a major fraction of the radiocesium is associated strongly with organic and mineral materials in the litter or upper soil layers: less than 10% is easily leachable. The distribution of¹³⁷Cs throughout the fractions was similar to that determined for naturally occurring stable cesium (¹³³Cs), implying that isotopic exchange had been extensive. For⁹⁰Sr, the results show a relatively high leachable fraction. Therefore, present results indicate that radiocesium should be less mobile, and less available for root uptake, than⁹⁰Sr in soil.     

Depth distribution of239,240Pu and137Cs in soils of South Korea

Depth distribution of^239,240Pu and¹³⁷Cs in the soils of South Korea have been studied. The average accumulated depositions were estimated roughly to be 54.8±32.1 Bq·m^–2 for^239,240Pu, 1.6±1.0 Bq· ·m^–2 for²³⁸Pu and 1982.8±929.1 Bq·m^–2 for¹³⁷Cs. The activity ratios of^239,240Pu/¹³⁷Cs in soils were found to be in the narrow range of 0.0153 to 0.0364 with a mean value of 0.0230±0.006. The concentrations of^239,240Pu and¹³⁷Cs in soils decrease exponentially with increasing the soil depth. A significant correlation was found between the concentration of^239,240Pu and that of¹³⁷Cs. The activity ratios of^239,240Pu/¹³⁷Cs tend to increase slightly with increasing soil depth.     

Radionuclide concentration in sewage sludge at several location in Austria after the Chernobyl accident

The concentration of the radionuclides¹⁰³Ru,¹³⁴Cs and¹³⁷Cs in sewage sludge samples which were collected between July and September 1986, were measured by -ray spectrometry. High concentration of¹⁰³Ru,¹³⁴Cs and¹³⁷Cs were found in sewage sludge samples from Lower-Austria /Scheibbs, Zwettl/ and Styria /Eisenerz, Leoben/. the radioactivity concentration of¹³⁷Cs was two times higher than that of¹³⁴Cs. Following concentration values were found:¹⁰³Ru 0.1–63.0 nCi kg^–1,¹³⁴Cs 0.3–41.6 nCi kg^–1, and¹³⁷Cs 0.3–83.3 nCi kg^–1. The activity of these nuclides decreased from July 1986 to September 1986.     

137Cs in Biota and Sediment Samples from Turkish Coast of the Black Sea, 1997–1998

During the periods of 1997–1998, macroalgae, sea snail, mussel, fish and sediment samples were collected from different stations at Turkish Black Sea coast in order to determine activity levels of ¹³⁷Cs radionuclide. ¹³⁷Cs activity in the tested algae species and in soft parts of mussel and sea snail, were found to be below the lower limit of detection. On the other hand, the ¹³⁷Cs concentration in muscle tissue of the sea snail samples were found from 6±2 to 19±7 Bq·kg^–1 dry weight. The range of the ¹³⁷Cs concentration in anchovy fish muscles were found between 4±2 – 10±5 Bq·kg^–1 dry weight. The ¹³⁷Cs concentration in the whiting fish muscle was found below the lower limit of detection. However, this activity found in shad fish muscle to be 25±10 Bq·kg^–1 dry weight. The concentrationsof the ¹³⁷Cs activity in the sediment samples proved that the eastern region of the Black Sea was affected by Chernobyl at a very high degree compared with the western part. The measured ²³⁸U, ²³²Th and ⁴⁰K concentrations in sediment samples are within the range of the cited values in the previous works at the Turkish Black Sea coast.     

Determination of131I,134Cs,137Cs in grass and cheese after Chernobyl accident in Austria

Various samples from Styria /grass/ and Salzburg /cheese/ were analyzed for¹³¹I,¹³⁴Cs and¹³⁷Cs concentration during April–July 1986 by -ray spectrometry. The concentrations are reported in nCi kg^–1 wet weight. The concentration values found for¹³¹I 0.2–17.2 nCi kg^–1 /grass/, 0.1–0.5 nCi kg^–1 /cheese/, for¹³⁴Cs 1.1–6.2 nCi kg^–1 /grass/, 0.2–1.3 nCi kg^–1 /cheese/, for¹³⁷Cs 1.6–15.7 nCi kg^–1 /grass/, 0.3–2.2 nCi kg^–1 /cheese/. While radioactivity of¹³¹I,¹³⁴Cs and¹³⁷Cs in cheese samples increases from May to June, it decreases in grass samples from May to July 1986.     

Distribution of fallout radionuclides through soil surface layer

The distribution of¹³⁷Cs through soil layers has been investigated by field sampling. The investigation deals with¹³⁷Cs concentration found after the Chernobyl accident. The relationship between important soil characteristics, total precipitation and cesium distribution are analyzed. Cesium is strongly sorbed in the top soil layer and its migration downward is limited. Measurements performed over a 3-year period revealed that approximately 20–38 per cent of total¹³⁷Cs is located in the upper soil layer.     

Correlation of natural and artificial radionuclides in soils with pedological,climatological and geographic parameters

Various types of soil samples were collected in the southern part of Brazil, with depth intervals of 5 cm, down to 50 cm, using a specially designed sampler. Pedological analysis of these soils were performed. Nuclear activities of¹³⁷Cs (expressed in Bq m^–2) and radioactive natural element (²²⁶Ra,²²⁸Ra and⁴⁰K) concentrations were determined by low background gamma-ray spectrometry.¹³⁷Cs concentrations were correlated with radioactive natural element concentrations and pedological, climatological and geographic parameters related to the soil samples collected.     

Determination of131I,134Cs,137Cs in plants and cheese after Chernobyl accident in Roumania

Various samples from the south-east region of Roumania/greens, fodder, cheese/were analyzed for¹³¹I,¹³⁴Cs and¹³⁷Cs concentrations in May and July 1986 by -ray spectrometry. The concentrations are reported in nCi. kg^–1 wet weight. For greens, a considerable decrease was observed for¹³¹I/to 3.0–7.0 nCi. kg^–1/,¹³⁴Cs/to 0.5–2.0 nCi.kg^–1/ and¹³⁷Cs /to 1.0–4.0 nCi. kg^–1/ from the first half /5–15 May/ till the end of May 1986. For cheese, maximum values were measured between 5 and 15 May /sheep cottage cheese: 500–800 nCi.kg^–1 for¹³¹I, 25–50 nCi. kg^–1 for¹³⁴Cs, 40–80 nCi. kg^–1 for¹³⁷Cs/; at the beginning of July a considerable decrease /to 5–10 nCi. kg^–1 for¹³¹I, 1.2–2.0 nCi.kg^–1 for¹³⁴Cs, 2.2–3.0 nCi. kg^–1 for¹³⁷Cs/ was observed. In autumn 1986 a small increase up to 2.0–3.0 nCi. kg^–1 for¹³⁴Cs and 3.4–5.0 nCi. kg^–1 for¹³⁷Cs /in November/ was reported. The population's internal possible contamination was strongly limited by the authorities' severe control of the food-stuff.     

Determination and correlation of 137Cs and unsupported 210Pb activities in soil

To ascertain the feasibility of using ¹³⁷Cs and ²¹⁰Pb in soil erosion models a Compton suppression system with a Be window was used to simultaneous detect both of the naturally occurring isotopes. In particular, the system allowed the use of only 20 g of soil material instead of the usual needed 0.5-1.0 kg in similar soil studies.     

Inventories of 239+240Pu, 137Cs, and excess 210Pb in sediment cores from brackish Lake Obuchi, Rokkasho Village, Japan

The aim of this study was to measure the distribution and inventories of ^239+240Pu, ¹³⁷Cs, and excess ²¹⁰Pb (²¹⁰Pb_excess) in sediment core samples from brackish Lake Obuchi, which is in the vicinity of nuclear fuel facilities in Rokkasho Village, Japan. The inventory of the ^239+240Pu activity in the sediment samples from the estuary of a freshwater river, the central point of the lake, and the deepest point in the lake were 0.18, 0.29, and 0.24 kBq·m^–2, respectively. The inventories of ¹³⁷Cs and ²¹⁰Pb_excess in sediments were 0.83–1.2 kBq·m^–2 and 25–30 kBq·m^–2, respectively. The mean ^239+240Pu/¹³⁷Cs and ²¹⁰Pb_excess/¹³⁷Cs activity ratios were 0.23 and 28, respectively. The^239+240Pu/¹³⁷Cs activity ratios were approximately 13–24 times the ratio expected from global fallout. The inventories of ^239+240Pu and ²¹⁰Pb in sediments were higher than the inventory expected from atmospheric fallout, but the ¹³⁷Cs inventory was significantly lower than expected.This revised version was published online in November 2005 with corrections to the Cover Date.     

Translocation and depuration of137Cs in tea plants

Translocation and percent distribution of¹³⁷Cs in different parts of the tea plant have been investigated from the foliar aborption and root uptake in Chemobyl contaiminated soil during 1987–1994. The results showed that the transfer of the radionuclide from soil to the plant occurred only in the roots during this long period. On the other hand, the present data confirmed that the new leaves of the plant directly accumulated¹³⁷Cs from the stem in growing seasons after translocation into the stem from leaves during the Chemobyl accident. The natural depuration rate of¹³⁷Cs in the stem part of tea plant is estimated as on effective half-life 1750 days.     

Plutonium and cesium isotopes in river waters in Japan

Concentrations of cesium isotopes and plutonium in river water samples in Japan, collected during the period from June 1985 to February 1987, have been measured. The total¹³⁷Cs concentrations in the Japanese river waters ranged from 0.063 to 1.89 mBq·l^–1. The portion of particulate¹³⁷Cs to total was observed to be less than 10 to 35%. The total^239,240Pu concentrations ranged from 0.56 to 1.93 Bq·l^–1. Particulate^239,240Pu occupied 13 to 95% of the total. After the Chernobyl fallout, elevated¹³⁷Cs concentrations were observed in the Japanese river waters as well as the detection of¹³⁴Cs, whereas there was no effect on the river plutonium from the Chernobyl fallout. The partition coefficients of¹³⁷Cs and plutonium between suspended particulate and dissolved phases in the Japanese rivers were determined: from 1.0·10⁴ to 3.2·10⁵ and from 4.1·10⁴ to 2.3·10⁶ for¹³⁷Cs and plutonium, respectively. The result suggests that these radionuclides, especially plutonium, are tightly associated with soil particles and/or suspended matter.     

Some aspects of environmental radioactivity around the former Soviet Union"""s Semipalatinsk nuclear test site: Local fallout Pu in Ust"""-Kamenogorsk district

The ¹³⁷Cs, ²³⁸Pu and ^239,240Pu activity concentrations were determined together with the atomic ratios of ²⁴⁰Pu/²³⁹Pu for the soil samples at 19 sites from the Ust"-Kamenogorsk district, located more than 300 km east of the Semipalatinsk nuclear test site (SNTS). The mean areal deposition of ¹³⁷Cs ranged from 1,500 to 4,100 Bq/m². However, some hot spot-like areas showing high concentrations of 5,500–7,700 Bq/m² were foundat some sites within the city. The ^239,240Pu levels ranged from <50 to 510 Bq/m², however most of them ranged between 120–200 Bq/m². These levels are nearly the same as those around the Semipalatinsk City. At most of the sites within the city and its adjacent areas, both nuclides were found in the soil layers up to a depth of 30 cm. A fraction of 20–50% of ^239,240Pu was not leached by hot digestion with concentrated HNO₃ containing a small amount of H₂O₂. Generally, such tightly bound fraction showed a trend to decrease with increasing distance from the SNTS. The fraction of these radionuclides that were deposited in Ust"-Kamenogorsk district from global and from SNTS fallouts have been determined using the ²⁴⁰Pu/²³⁹Pu atomic ratios in both Pu fractions: one which can be leached with hot HNO₃ + H₂O₂ and another that is a non-leacheable for each soil layer of core samples. As a result a fraction of 21–80% (mostly 30–60%) of total ^239,240Pu were found to be due to the local fallout of Pu from the SNTS debris. For ¹³⁷Cs, the contribution (mostly 10–20%) of local fallout from the SNTS were estimated to be far lower as compared to ^239,240Pu.     

Activities evolution of Chernobyl103Ru,134Cs and137Cs in Cluj fallout

The evolution of Chernobyl¹⁰³Ru,¹³⁴Cs and¹³⁷Cs in accumulated fallout is rigorously followed. The¹⁰³Ru activity of about 12 kBq.m^–2 in the middle of May 1986 became insignificant at the end of 1986, while the levels of¹³⁴Cs and¹³⁷Cs have changed during 3 years from 2.5 kBq.m^–2, respectively, 5 kBq.m^–2 to about 0.9 kBq.m^–2, respectively 4.7 kBq.m^–2 according to their proper half-lives.     

Anomalously high activities of <Superscript>137</Superscript>Cs in soils and vegetation on and near a diabase outcrop in La Sierra de Lema,Venezuela

As a result of routine soil sampling to determine the ¹³⁷Cs background activities country-wide in Venezuela, it was decided to further investigate El Mirador (Lookout) area at the base of the Sierra de Lema mountain range. In April 2003 (A), soil samples were collected at eight sites on and around the edge of the diabase outcrop to confirm that this area had anomalously high ¹³⁷Cs activities. In July 2003 (B), not only soil samples were collected again, but also black mat, palm tree leaves and trunks, fruit bushes leaves and its fruit and fern leaves. The ¹³⁷Cs content was measured by high resolution gamma-ray spectroscopy by a comparative method with reference materials. The ¹³⁷Cs activity values range from 16.3 to 30.8 Bq·kg-1 in the soil samples collected in July 2003, 20.7–32.1 Bq·kg⁻¹ for the black mat, 26.3–38.4 Bq·kg⁻¹ for the palm leaves, 16.8–31.2 Bq·kg⁻¹ for the palm trunks and 17.6–27.3 Bq·kg⁻¹ for the fruit bush leaves, while, the ¹³⁷Cs activity values for the whole fruit were between 23.4 and 30.7 Bq·kg⁻¹; but, the value of the ¹³⁷Cs activity in the center of the fruit (the edible part) was 51.6 Bq·kg⁻¹, and the value of the ¹³⁷Cs activity for the fern leaves was 51.8 Bq·kg⁻¹. Thus, most of the ¹³⁷Cs activity values determined in the soil, black mat and vegetation samples from El Mirador (Lookout) were considered anomalously high with respect to those found near the equator and in other areas of Venezuela. Only the center of the fruit from the Clusia grandiflora bushes and the fern leaves had high activity ratios, about a factor of three and could be considered as biomonitors that concentrate and retain the ¹³⁷Cs. Finally, these anomalously high ¹³⁷Cs activities have been attributed not only to the rich organic soils, as sinks, but also due to the affect of the cloud forests.     

Accumulation of103Ru,137Cs and134Cs in fruitbodies of various mushrooms from Austria after the Chernobyl incident

Various mushrooms from Austria were analyzed for¹⁰³Ru,¹³⁷Cs and¹³⁴Cs after the reactor accident at Chernobyl /19.6.–26.10. 1986/ by -spectroscopy. The following concentration (nCi/kg wet weight) values were found:¹⁰³Ru 0.1–4 nCi/kg,¹³⁷Cs 0.5–104 nCi/kg,¹³⁴Cs 0.3–42 nCi/kg. The concentration of cesium isotopes in Cantharellus cibarius /lower Austria/, Leccinum scabrum /lower Austria/ and Xevocomus badius /lower Austria/ was considerably higher than in other mushroom samples.     

137Cs activity in surface water in the western North Pacific

Temporal and spatial variations of ¹³⁷Cs activity in surface waters in the western North Pacific are examined along the 165°E transect. ¹³⁷Cs in seawater of the western North Pacific has been introduced by global fallout originating from atmospheric nuclear weapons tests, which caused major fallout in the early 1960's. At this time ¹³⁷Cs activities in the surface waters in mid latitudes of the North Pacific were 10–20 Bq·m^-3. South of 30°N, ¹³⁷Cs activity decreased gradually towards the south. The surface ¹³⁷Cs activity was about 5 Bq·m^-3 in the Equatorial region. In the 1970's, the difference in ¹³⁷Cs activities in surface water between mid latitudes and the Equatorial region became smaller. The ¹³⁷Cs activity in surface water at 40°N – Equatorial region was almost constant at the level of 1.7–3.7 Bq·m^-3 in the late 1990's. In the Equatorial region, the ¹³⁷Cs activity in surface water showed no temporal change except for radioactive decay over these four decades. The surface ¹³⁷Cs level was 1.4–1.8 Bq·m^-3 in the north subarctic region around 50°N in the late 1990's. The lower ¹³⁷Cs activity may have been caused by deeper convection in this sea area and dilution by fresh water flux.