村松 康行

Nuclear weapons tests conducted by the United States in the Marshall Islands produced significant quantities of regional or tropospheric fallout contamination. Here we report on some preliminary inductively coupled plasma-mass spectrometry (ICP-MS) measurements of plutonium isolated from seven composite soil samples collected from Bikini, Enewetak and Rongelap Atolls in the northern Marshall Islands. These data show that 240Pu/239Pu isotopic signatures in surface soils from the Marshall Island vary significantly and could potentially be used to help quantify the range and extent of fallout deposition (and associated impacts) from specific weapons tests. 137Cs and 60Co were also determined on the same set of soil samples for comparative purposes. © 2001 Elsevier Science B.V. All rights reserved.

Nuclear weapons tests conducted by the United States in the Marshall Islands produced significant quantities of regional or tropospheric fallout contamination. Here we report on some preliminary inductively coupled plasma-mass spectrometry (ICP-MS) measurements of plutonium isolated from seven composite soil samples collected from Bikini, Enewetak and Rongelap Atolls in the northern Marshall Islands. These data show that 240Pu/239Pu isotopic signatures in surface soils from the Marshall Island vary significantly and could potentially be used to help quantify the range and extent of fallout deposition (and associated impacts) from specific weapons tests. 137Cs and 60Co were also determined on the same set of soil samples for comparative purposes. © 2001 Elsevier Science B.V. All rights reserved.

Methyl iodide (CH3I) plays an important role in the natural iodine cycle and participates in atmospheric ozone destruction. However, the main source of this compound in nature is still unclear. Here we report that a wide variety of bacteria including terrestrial and marine bacteria are capable of methylating the environmental level of iodide (0.1 μM). Of the strains tested, Rhizobium sp. strain MRCD 19 was chosen for further analysis, and it was found that the cell extract catalyzed the methylation of iodide with S-adenosyl-L-methionine as the methyl donor. These results strongly indicate that bacteria contribute to iodine transfer from the terrestrial and marine ecosystems into the atmosphere.

Methyl iodide (CH3I) plays an important role in the natural iodine cycle and participates in atmospheric ozone destruction. However, the main source of this compound in nature is still unclear. Here we report that a wide variety of bacteria including terrestrial and marine bacteria are capable of methylating the environmental level of iodide (0.1 μM). Of the strains tested, Rhizobium sp. strain MRCD 19 was chosen for further analysis, and it was found that the cell extract catalyzed the methylation of iodide with S-adenosyl-L-methionine as the methyl donor. These results strongly indicate that bacteria contribute to iodine transfer from the terrestrial and marine ecosystems into the atmosphere.

The concentrations of iodine in cereal grains cultivated at 38 locations in Austria from cereal-producing sites in agricultural areas and soil-to-grain transfer factors (TF) were determined. The concentrations of iodine in cereal grains, which were analyzed by radiochemical neutron activation analysis ranged from 0.002 to 0.03 μg g-1, the arithmetic mean and the median were 0.0061 μg g-1 and 0.0046 μg g-1, respectively. The TF values for cereal grains were calculated to be 0.0005-0.02 and the median was 0.0016. The TF values correlated positively with the iodine concentrations in cereal grains. However, the TF values correlated negatively with the iodine concentrations in soils as well as with the amount of clay contents of soils. The TF values were almost independent on pH values (5.4-7.6) of soils. Copyright © 2001 Elsevier Science B.V.

The concentrations of iodine in cereal grains cultivated at 38 locations in Austria from cereal-producing sites in agricultural areas and soil-to-grain transfer factors (TF) were determined. The concentrations of iodine in cereal grains, which were analyzed by radiochemical neutron activation analysis ranged from 0.002 to 0.03 μg g-1, the arithmetic mean and the median were 0.0061 μg g-1 and 0.0046 μg g-1, respectively. The TF values for cereal grains were calculated to be 0.0005-0.02 and the median was 0.0016. The TF values correlated positively with the iodine concentrations in cereal grains. However, the TF values correlated negatively with the iodine concentrations in soils as well as with the amount of clay contents of soils. The TF values were almost independent on pH values (5.4-7.6) of soils. Copyright © 2001 Elsevier Science B.V.

Soil samples collected from three forest sites within the 30-km zone around the Chernobyl reactor were analyzed for 239Pu and 240Pu by ICP-MS. The average 240Pu/239Pu atom ratio in contaminated surface soil samples, values of which are scarce in the literature, was 0.408. There were almost no differences in the 240Pu/239Pu ratios between the individual samples analyzed, although the 239+240Pu levels varied very widely (i.e. from 6.3 to 1430 Bq kg-1 dry weight) depending on the distance from the reactor and on the soil layers investigated. This result corresponded to area-related activities for 239+240Pu between 1.1 kBq m-2 and 13.3 kBq m-2. It was estimated that about half of the Pu migrated from the organic layers to the underlying mineral layers. The 240Pu/239Pu ratio observed in the Chernobyl area was much higher than that attributed to weapons fallout (ca. 0.18). The high ratio was related to the high burn-up grade of the reactor fuel. The 240Pu/239Pu ratio observed might be used as a 'fingerprint' in identifying the distribution of Chernobyl-derived Pu in the environment and in distinguishing it from other sources, e.g. global fallout. Relationships between the concentrations of Pu and those of 137Cs, 60Co, and 125Sb were also discussed.

Soil samples collected from three forest sites within the 30-km zone around the Chernobyl reactor were analyzed for 239Pu and 240Pu by ICP-MS. The average 240Pu/239Pu atom ratio in contaminated surface soil samples, values of which are scarce in the literature, was 0.408. There were almost no differences in the 240Pu/239Pu ratios between the individual samples analyzed, although the 239+240Pu levels varied very widely (i.e. from 6.3 to 1430 Bq kg-1 dry weight) depending on the distance from the reactor and on the soil layers investigated. This result corresponded to area-related activities for 239+240Pu between 1.1 kBq m-2 and 13.3 kBq m-2. It was estimated that about half of the Pu migrated from the organic layers to the underlying mineral layers. The 240Pu/239Pu ratio observed in the Chernobyl area was much higher than that attributed to weapons fallout (ca. 0.18). The high ratio was related to the high burn-up grade of the reactor fuel. The 240Pu/239Pu ratio observed might be used as a 'fingerprint' in identifying the distribution of Chernobyl-derived Pu in the environment and in distinguishing it from other sources, e.g. global fallout. Relationships between the concentrations of Pu and those of 137Cs, 60Co, and 125Sb were also discussed.

A reliable method using 125I tracer for direct determination of volatile iodine formed in aqueous environmental samples was established. Soil solution, seawater and bacterial cell suspension were selected as model samples, and incubated with 125I-. Volatile inorganic and organic iodine species produced during incubation were collected in silver wool and activated charcoal traps, separately the efficiency of the traps, the storage conditions of 125I- stock solution and the procedures to expel the dissolved volatile iodine from the sample solutions were examined. Formation of biological volatile iodine was observed in all samples, and the dominant iodine species was found to be organic iodine. The advantages of this method are its simplicity, low cost and low detection limit.

An analysis method for 239Pu and 240Pu in environmental samples (including four certified reference materials) by ICP-MS was studied. Two types of chromatographic resin, Dowex 1X8 and TEVA, were examined for their applicability to the separation of Pu from the matrix elements. Sufficient decontamination factors (104-105) for many matrix elements including U, which interferes with the detection of mass 239, were obtained with both resins. The detection limit of Pu by ICP-MS was about 0.02 pg ml-1 (0.05 mBq ml-1 for 239Pu 0.17 mBq ml-1 for 240Pu) in the sample solution or 0.1 pg in the sample. Analytical results of 239+240Pu in certified reference materials (IAEA-135, -SOIL-6, -368 and -134) indicated that the accuracy of the method was satisfactory. Data on the 240Pu/239Pu atom ratios in these reference materials, which are scarce in the literature, were also obtained, i.e., 0.211 for IAEA-135, 0.191 for IAEA-SOIL-6, 0.043 for IAEA-368 and 0.200 for IAEA-134. Compared with alpha-spectrometry, the ICP-MS method has significant advantages in terms of its simple analytical procedures, prompt measurement time and capability of determining the 240Pu/239Pu ratio.

An analysis method for 239Pu and 240Pu in environmental samples (including four certified reference materials) by ICP-MS was studied. Two types of chromatographic resin, Dowex 1X8 and TEVA, were examined for their applicability to the separation of Pu from the matrix elements. Sufficient decontamination factors (104-105) for many matrix elements including U, which interferes with the detection of mass 239, were obtained with both resins. The detection limit of Pu by ICP-MS was about 0.02 pg ml-1 (0.05 mBq ml-1 for 239Pu 0.17 mBq ml-1 for 240Pu) in the sample solution or 0.1 pg in the sample. Analytical results of 239+240Pu in certified reference materials (IAEA-135, -SOIL-6, -368 and -134) indicated that the accuracy of the method was satisfactory. Data on the 240Pu/239Pu atom ratios in these reference materials, which are scarce in the literature, were also obtained, i.e., 0.211 for IAEA-135, 0.191 for IAEA-SOIL-6, 0.043 for IAEA-368 and 0.200 for IAEA-134. Compared with alpha-spectrometry, the ICP-MS method has significant advantages in terms of its simple analytical procedures, prompt measurement time and capability of determining the 240Pu/239Pu ratio.

Analytical data by ICP-MS measurements after pyrohydrolysis on a reasonably large series of samples representing about 300 rocks of major units and subunits of the earth's crust, and a few organic materials, are provided for a genetic discussion. Biogenic accumulation and volatilization of iodine from metamoprhosed sediments and magmatic rocks has caused extreme gradients of concentrations towards the top of the oceanic and continental crust. Transporting agents for recycling into surface water were hydrothermal fluids and partial volatilization from surface waters which occurred as methyl iodide. Because of the low iodine concentrations in magmatic and metamorphic rocks such samples exposed at the earth's surface not far from the seashore could have undergone contamination by iodine which escaped from the oceans. The high average concentrations of 30 ppm I in deep-sea carbonates and of 2.5 ppm I in continental limestones were accumulated by planktonic and shallow sea organisms, respectively. Deep-sea clays (3.9 ppm I) and continental shales (1.8 ppm I) contain the residual iodine after dissolution and oxidation of a major fraction of carbonates and organic carbon, respectively. Shales vary more in iodine than deep-sea clays because of greater variations in the environments of deposition and diagenesis. The I/C weight ratio increases from 10-3 to 2 × 10-1 from reduced to oxygenated recent nearshore sediments. Iodine is more stable than carbon during diagenesis of biogenic sediments. Greywackes and sandstones contain on average 150 and 120 ppb I, respectively. Metasedimentary gneisses, mica schists and granulites have as little as 12 to 25 ppb I and have lost from 75 to &gt 95% of their iodine at metamorphic temperatures. Granites, granodiorites, tonalites and basalts are even lower in iodine and contain 4 to 9 ppb I almost independent of the species of magmatic rock. The continental crust, the oceanic crust (including seawater) and bulk Earth's crust contain 119 ppb, 777 ppb and ~ ppb I, respectively. Nearly 70% of I is calculated to exist in ocean sediments. The Cl/I weight ratios of the continental, oceanic and bulk Earth's crust are 3800, 4500 and 4300, respectively, to be compared with 1210 and 403 in the Orgueil and Ivuna Cl chondrites.

Analytical data by ICP-MS measurements after pyrohydrolysis on a reasonably large series of samples representing about 300 rocks of major units and subunits of the earth's crust, and a few organic materials, are provided for a genetic discussion. Biogenic accumulation and volatilization of iodine from metamoprhosed sediments and magmatic rocks has caused extreme gradients of concentrations towards the top of the oceanic and continental crust. Transporting agents for recycling into surface water were hydrothermal fluids and partial volatilization from surface waters which occurred as methyl iodide. Because of the low iodine concentrations in magmatic and metamorphic rocks such samples exposed at the earth's surface not far from the seashore could have undergone contamination by iodine which escaped from the oceans. The high average concentrations of 30 ppm I in deep-sea carbonates and of 2.5 ppm I in continental limestones were accumulated by planktonic and shallow sea organisms, respectively. Deep-sea clays (3.9 ppm I) and continental shales (1.8 ppm I) contain the residual iodine after dissolution and oxidation of a major fraction of carbonates and organic carbon, respectively. Shales vary more in iodine than deep-sea clays because of greater variations in the environments of deposition and diagenesis. The I/C weight ratio increases from 10-3 to 2 × 10-1 from reduced to oxygenated recent nearshore sediments. Iodine is more stable than carbon during diagenesis of biogenic sediments. Greywackes and sandstones contain on average 150 and 120 ppb I, respectively. Metasedimentary gneisses, mica schists and granulites have as little as 12 to 25 ppb I and have lost from 75 to &gt 95% of their iodine at metamorphic temperatures. Granites, granodiorites, tonalites and basalts are even lower in iodine and contain 4 to 9 ppb I almost independent of the species of magmatic rock. The continental crust, the oceanic crust (including seawater) and bulk Earth's crust contain 119 ppb, 777 ppb and ~ ppb I, respectively. Nearly 70% of I is calculated to exist in ocean sediments. The Cl/I weight ratios of the continental, oceanic and bulk Earth's crust are 3800, 4500 and 4300, respectively, to be compared with 1210 and 403 in the Orgueil and Ivuna Cl chondrites.

Laboratory experiments on the desorption phenomena of iodine from rice paddy soil under waterlogged conditions, with a special reference to soil redox potential (Eh) and pH, have been conducted. Radioiodine tracer (125I), added to the soil, was readily sorbed on it. At the beginning of the waterlogging, the iodine desorption was low. However, iodine was desorbed into soil solution with time. The iodine desorption was enhanced markedly by the addition of organic substances such as straw pieces and glucose to the soil. Cultivation of rice plants in soil also affected the iodine desorption, suggesting root exudates and/or root autolysis might be participating in the desorption process. Eh dropped considerably after soil was waterlogged due to microbial metabolisms. Particularly low Eh values were observed in soils with plants and also with added organic substances. A negative correlation was seen between the desorption and soil Eh. High desorption was frequently observed when the Eh dropped to about -100 mV or below. Due to the reducing conditions (low Eh) by waterlogging, iodine in soil was leached into the soil solution consequently total iodine concentration in paddy soil was considerably lower than forest and upland field soils. These iodine desorption phenomena under anaerobic conditions should be considered in assessing transfer of the long-lived radioiodine (129I) in the environment, especially in rice fields and marshland.

Laboratory experiments on the desorption phenomena of iodine from rice paddy soil under waterlogged conditions, with a special reference to soil redox potential (Eh) and pH, have been conducted. Radioiodine tracer (125I), added to the soil, was readily sorbed on it. At the beginning of the waterlogging, the iodine desorption was low. However, iodine was desorbed into soil solution with time. The iodine desorption was enhanced markedly by the addition of organic substances such as straw pieces and glucose to the soil. Cultivation of rice plants in soil also affected the iodine desorption, suggesting root exudates and/or root autolysis might be participating in the desorption process. Eh dropped considerably after soil was waterlogged due to microbial metabolisms. Particularly low Eh values were observed in soils with plants and also with added organic substances. A negative correlation was seen between the desorption and soil Eh. High desorption was frequently observed when the Eh dropped to about -100 mV or below. Due to the reducing conditions (low Eh) by waterlogging, iodine in soil was leached into the soil solution consequently total iodine concentration in paddy soil was considerably lower than forest and upland field soils. These iodine desorption phenomena under anaerobic conditions should be considered in assessing transfer of the long-lived radioiodine (129I) in the environment, especially in rice fields and marshland.

In order to assess the levels and behavior of129I (half-life: 1.6×107 y) and127I (stable) in the environment, we have developed analytical procedures involving neutron activation analysis (NAA). Environmental samples collected around Tokaimura, Ibaraki Prefecture, Japan, have been analyzed using this method. Ranges of129I and127I concentrations in surface soil were 0.9-180 mBq kg-1 and 1-60 mg kg-1, respectively. Higher129I concentrations were found in soil samples collected from coniferous forests, suggesting a contribution from tree canopies in the deposition of this nuclide. Most of the129I in soil, was found to be retained in the first 10 cm. The129I/127I ratios in wheat fields were lower than those in rice paddy fields. A soil sample collected by IAEA from an area contaminated by the Chemobyl accident was also determined. The129I concentration and the129I/127I ratio were 1.6 mBq kg-1 and 1.7×10-7, respectively. The129I level in this sample was higher than the values obtained in areas far from nuclear facilities in Japan. It was suggested that the analysis of129I in soils in the Chernobyl area may be useful in evaluating the131I levels at the time of the accident. Analyses of129I and127I by ICP-MS in water samples were also made. The analytical speed of this method was very high, i.e., 3 minutes for a sample. However, there is a sensitivity limitation for129I detection due to interference from129Xe with the129I peak. The detection limits for129I and127I in water samples were about 0.5 mBq ml-1 and 0.1 ng ml-1, respectively. © 1995 Akadémiai Kiadó.

In order to assess the levels and behavior of129I (half-life: 1.6×107 y) and127I (stable) in the environment, we have developed analytical procedures involving neutron activation analysis (NAA). Environmental samples collected around Tokaimura, Ibaraki Prefecture, Japan, have been analyzed using this method. Ranges of129I and127I concentrations in surface soil were 0.9-180 mBq kg-1 and 1-60 mg kg-1, respectively. Higher129I concentrations were found in soil samples collected from coniferous forests, suggesting a contribution from tree canopies in the deposition of this nuclide. Most of the129I in soil, was found to be retained in the first 10 cm. The129I/127I ratios in wheat fields were lower than those in rice paddy fields. A soil sample collected by IAEA from an area contaminated by the Chemobyl accident was also determined. The129I concentration and the129I/127I ratio were 1.6 mBq kg-1 and 1.7×10-7, respectively. The129I level in this sample was higher than the values obtained in areas far from nuclear facilities in Japan. It was suggested that the analysis of129I in soils in the Chernobyl area may be useful in evaluating the131I levels at the time of the accident. Analyses of129I and127I by ICP-MS in water samples were also made. The analytical speed of this method was very high, i.e., 3 minutes for a sample. However, there is a sensitivity limitation for129I detection due to interference from129Xe with the129I peak. The detection limits for129I and127I in water samples were about 0.5 mBq ml-1 and 0.1 ng ml-1, respectively. © 1995 Akadémiai Kiadó.

In order to obtain information on the behavior of long-lived129I in the soil-plant-atmosphere system, two different experiments, transfer factors and volatilization of iodine, have been conducted by radiotracer techniques using125I. Soil-to-plant transfer factors varied very widely. Low values were found in tomato (0.0003) and rice (0.0019). The highest value for an edible part was seen in komatsuna, Brassica rapa L. (0.016), which is comparable to the IAEA recommended value of iodine for common crops (0.02). There was a tendency for older leaves to show higher concentrations than younger ones. The values for fruit, grain and beans were significantly lower than those for their leaves. Thus translocation of iodine with photosynthate from leaves into these plant organs was very small. Iodine in soil was found to be volatilized from the soil-rice plant system into the atmosphere as an organic iodine. Volatilization markedly decreased in the late cultivation period of rice plants. © 1995 Akadémiai Kiadó.

Iodine volatilization from the soil-plant system has been studied by radiotracer experiments and gas chromatography. Iodine emission was highly stimulated by the presence of plants. A marked emission of gaseous iodine from rice plants grown on flooded soil was observed, whereas oat plants showed considerably lower emission. Seasonal patterns in the iodine emission were observed for both plants. The emission rate increased with time from planting and the maximum value was observed in the late tillering stages (shortly before heading) of the plants. The chemical species of volatilized iodine was identified as methyl iodide (CH3I) from gas chromatography. It was presumed that iodine in the flooded soil was methylated by the action of roots or microorganisms. The methyl iodide produced was mainly emitted, not from the soil surface, but from the plant shoot into the atmosphere. © 1994.

Iodine volatilization from the soil-plant system has been studied by radiotracer experiments and gas chromatography. Iodine emission was highly stimulated by the presence of plants. A marked emission of gaseous iodine from rice plants grown on flooded soil was observed, whereas oat plants showed considerably lower emission. Seasonal patterns in the iodine emission were observed for both plants. The emission rate increased with time from planting and the maximum value was observed in the late tillering stages (shortly before heading) of the plants. The chemical species of volatilized iodine was identified as methyl iodide (CH3I) from gas chromatography. It was presumed that iodine in the flooded soil was methylated by the action of roots or microorganisms. The methyl iodide produced was mainly emitted, not from the soil surface, but from the plant shoot into the atmosphere. © 1994.

Measurements of some selected radionuclides were carried out in rain waters collected from Ibaraki Prefecture, Japan, following the nuclear accident at Tomsk-7, Russian Federation, in April 1993. The concentrations obtained for artificial radionuclides were90Sr≦1.8 mBq l-1,137Cs≦0.1 Bq l-1,131I≦0.1 Bq l-1 and129I≦4 μBq l-1. Uranium (238U) concentrations in rainfalls in April 1993 were 6.3-39 ng l-1. These data were compared to control values obtained previously and there was no appreciable influence on the radioactivity levels in Japan after the Tomsk-7 accident. Since only limited data on the concentrations of129I and uranium in rain water are available, these new analytical results contribute to understanding the background levels for these nuclides. © 1994 Akadémiai Kiadó.

A simple pre-irradiation procedure for the separation of iodine from soil has been developed. A soil sample was heated in a quartz tube for 15 min at about 900 °C. The evaporated iodine was collected in activated charcoal, which was produced from phenol resin with low impurities. The charcoal, with sorbed iodine, was irradiated by neutrons and the128I produced was measured. A successful elimination of the background radioactivity due to the matrix elements was possible with this separation procedure. The detection limit by this method for soil samples was about 0.1 mg/kg (dry). The method has been applied to analyze selected soil samples. © 1993 Akadémiai Kiadó.

A simple pre-irradiation procedure for the separation of iodine from soil has been developed. A soil sample was heated in a quartz tube for 15 min at about 900 °C. The evaporated iodine was collected in activated charcoal, which was produced from phenol resin with low impurities. The charcoal, with sorbed iodine, was irradiated by neutrons and the128I produced was measured. A successful elimination of the background radioactivity due to the matrix elements was possible with this separation procedure. The detection limit by this method for soil samples was about 0.1 mg/kg (dry). The method has been applied to analyze selected soil samples. © 1993 Akadémiai Kiadó.

radioiodine/rice plants /root-uptake /desorption of iodine Root-uptake of iodine by rice plants from two different soil types was studied using an 125I tracer. At harvest, the 125I concentration was lowest in brown rice (hulled rice) followed by the rachis, stem and leaves. The transfer factors of iodine for brown rice grown on Andosol and Gray lowland soil (fine texture) respectively were 0.007 and 0.002. The ratio of the radioiodine concentrations between flag leaf (first leaf blade) and brown rice was about 400. Transfer factors in plants grown on Andosol were higher than those grown on Gray lowland soil. This may be related to the high 125I concentration in the Andosol soil solutions, particularly after the flowering period. The adsorption and desorption of iodine in the soil was effected by flooding with water and also by the cultivation of rice plants. The radioiodine concentration in the soil solutions first increased in the upper soil layer then in the lower layer. The desorption pattern of iodine was influenced by the soil types. © 1993, Journal of Radiation Research Editorial Committee. All rights reserved.

radioiodine/rice plants /root-uptake /desorption of iodine Root-uptake of iodine by rice plants from two different soil types was studied using an 125I tracer. At harvest, the 125I concentration was lowest in brown rice (hulled rice) followed by the rachis, stem and leaves. The transfer factors of iodine for brown rice grown on Andosol and Gray lowland soil (fine texture) respectively were 0.007 and 0.002. The ratio of the radioiodine concentrations between flag leaf (first leaf blade) and brown rice was about 400. Transfer factors in plants grown on Andosol were higher than those grown on Gray lowland soil. This may be related to the high 125I concentration in the Andosol soil solutions, particularly after the flowering period. The adsorption and desorption of iodine in the soil was effected by flooding with water and also by the cultivation of rice plants. The radioiodine concentration in the soil solutions first increased in the upper soil layer then in the lower layer. The desorption pattern of iodine was influenced by the soil types. © 1993, Journal of Radiation Research Editorial Committee. All rights reserved.

Concentrations of 137Cs, 134Cs and 40K in about 60 mushroom samples (fruit bodies of basidiomycetes) belonging to 25 species collected in Japan have been studied. The levels of 137Cs varied very widely, ranging from &lt 3 to 1520 Bq kg-1 (dry wt), while those of 40K were relatively constant. Concentrations of 137Cs in common edible mushrooms of Japan such as Lentinus edodes, Flammulina velutipes, Pleurotus ostreatus and Pholiota nameko were low (normally &lt 50 Bq kg-1, dry wt). Concentrations of 134Cs in many samples were below the limit of detection (usually &lt 5 Bq kg-1, dry wt). The median concentrations of 137Cs and 40K were 41 (dry wt) and 1150 Bq kg-1 (dry wt), respectively. From the 137Cs/40K ratios it was found that cesium rather than potassium was selectively taken up from the soils fungi such as Suillus granulatus and Lactarius hatsudake. The 134Cs/137Cs ratios in mushrooms are related to the depth of the mycelium in the soil. The effective dose equivalent due to the dietary intake of radiocesium through mushrooms was estimated to be only 1.6 × 10-7 Sv. © 1991.

Concentrations of 137Cs, 134Cs and 40K in about 60 mushroom samples (fruit bodies of basidiomycetes) belonging to 25 species collected in Japan have been studied. The levels of 137Cs varied very widely, ranging from &lt 3 to 1520 Bq kg-1 (dry wt), while those of 40K were relatively constant. Concentrations of 137Cs in common edible mushrooms of Japan such as Lentinus edodes, Flammulina velutipes, Pleurotus ostreatus and Pholiota nameko were low (normally &lt 50 Bq kg-1, dry wt). Concentrations of 134Cs in many samples were below the limit of detection (usually &lt 5 Bq kg-1, dry wt). The median concentrations of 137Cs and 40K were 41 (dry wt) and 1150 Bq kg-1 (dry wt), respectively. From the 137Cs/40K ratios it was found that cesium rather than potassium was selectively taken up from the soils fungi such as Suillus granulatus and Lactarius hatsudake. The 134Cs/137Cs ratios in mushrooms are related to the depth of the mycelium in the soil. The effective dose equivalent due to the dietary intake of radiocesium through mushrooms was estimated to be only 1.6 × 10-7 Sv. © 1991.

Neutron activation analysis of129I and127I in soil has been studied. The limit of detection for129I in soil was about 0.05 mBq/kg or 1×10-9 as129I/127I atom ratio. The range of129I concentration in surface soils collected around Tokaimura (Ibaraki Prefecture) was 0.9-41 mBq/kg. Tracer experiments on the adsorption of iodine were also carried out, in order to obtain information on the behaviour of iodine in soil-water systems. Different adsorption patterns of iodide and iodate on soil were found. It was supposed that iodide was adsorbed by the soil fraction which became unstable at about 200° C and iodate by the fraction which was relatively stable to heating. © 1990 Akadémiai Kiadó.

Neutron activation analysis of129I and127I in soil has been studied. The limit of detection for129I in soil was about 0.05 mBq/kg or 1×10-9 as129I/127I atom ratio. The range of129I concentration in surface soils collected around Tokaimura (Ibaraki Prefecture) was 0.9-41 mBq/kg. Tracer experiments on the adsorption of iodine were also carried out, in order to obtain information on the behaviour of iodine in soil-water systems. Different adsorption patterns of iodide and iodate on soil were found. It was supposed that iodide was adsorbed by the soil fraction which became unstable at about 200° C and iodate by the fraction which was relatively stable to heating. © 1990 Akadémiai Kiadó.

Two simple methods, (1) isotope exchange method and (2) anion exchanger column method, are developed for the determination of chemical forms of radioiodine (iodide and iodate) in water samples. Using these methods, transformations of chemical forms of iodine in various water samples were studied. It was observed that iodate in rain water (unfiltered) and milk tended to change iodide form, whereas iodide was converted to iodate form in seawater and tap water. After the Chernobyl accident both chemical forms of131I (iodide and iodate) were found in rain water samples collected in Japan. © 1988 Akadémiai Kiadó.

Two simple methods, (1) isotope exchange method and (2) anion exchanger column method, are developed for the determination of chemical forms of radioiodine (iodide and iodate) in water samples. Using these methods, transformations of chemical forms of iodine in various water samples were studied. It was observed that iodate in rain water (unfiltered) and milk tended to change iodide form, whereas iodide was converted to iodate form in seawater and tap water. After the Chernobyl accident both chemical forms of131I (iodide and iodate) were found in rain water samples collected in Japan. © 1988 Akadémiai Kiadó.

Analytical method for the determination of129I and127I in environmental samples has been developed by using radiochemical neutron activation analysis. The129I levels in the samples such as soil (0.9-41 mBq/kg), precipitation (0.002-0.11 mBq/kg), pine needles (1.2-32 mBq/kg) and seaweed (&lt 0.1-17 mBq/kg) collected near the nuclear facilities in Tokaimura were higher than those from the other areas in Japan. The highest129I concentration was found in surface soil (0-5 cm), and the highest129I/127I ratios were found in pine needles and precipitation. The129I/127I ratio was higher in rice paddy soil than those in wheat field soil collected around Tokaimura, while the concentration of129I somewhat higher in wheat field soil. © 1988 Akadémiai Kiadó.

Analytical method for the determination of129I and127I in environmental samples has been developed by using radiochemical neutron activation analysis. The129I levels in the samples such as soil (0.9-41 mBq/kg), precipitation (0.002-0.11 mBq/kg), pine needles (1.2-32 mBq/kg) and seaweed (&lt 0.1-17 mBq/kg) collected near the nuclear facilities in Tokaimura were higher than those from the other areas in Japan. The highest129I concentration was found in surface soil (0-5 cm), and the highest129I/127I ratios were found in pine needles and precipitation. The129I/127I ratio was higher in rice paddy soil than those in wheat field soil collected around Tokaimura, while the concentration of129I somewhat higher in wheat field soil. © 1988 Akadémiai Kiadó.

Measurements were made of 131I, 137Cs, 134Cs and 103Ru in environmental samples collected from Ibaraki-Prefecture, Japan, after the Chernobyl accident. The highest values of 131I obtained in May 1986 were 98 Bq 1-1 (2.7 nCi l-1) for rain water (collected at the beginning of the rainfall), 400 Bq kg-1 (11 nCi kg-1) for pine needles (wet), 160 Bq kg-1 (4.3 nCi kg-1) for vegetables (wet) and 52 Bq kg-1 (1.4 nCi kg-1) for seaweed (wet). Most of the radioiodine in rain water was present as IO3- and I-. The proportion of IO3- in fresh rain water was higher than that of I-, but the IO3- was converted to I- during storage. About 10% of 131I was removed from leaf vegetables by washing, and about 70% by boiling. © 1987.

Measurements were made of 131I, 137Cs, 134Cs and 103Ru in environmental samples collected from Ibaraki-Prefecture, Japan, after the Chernobyl accident. The highest values of 131I obtained in May 1986 were 98 Bq 1-1 (2.7 nCi l-1) for rain water (collected at the beginning of the rainfall), 400 Bq kg-1 (11 nCi kg-1) for pine needles (wet), 160 Bq kg-1 (4.3 nCi kg-1) for vegetables (wet) and 52 Bq kg-1 (1.4 nCi kg-1) for seaweed (wet). Most of the radioiodine in rain water was present as IO3- and I-. The proportion of IO3- in fresh rain water was higher than that of I-, but the IO3- was converted to I- during storage. About 10% of 131I was removed from leaf vegetables by washing, and about 70% by boiling. © 1987.