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1.
In Japan, about 70% of land area is covered by forest. Therefore, forest ecosystem plays a vital role in ultimate fate of radionuclides and carbon cycle in terrestrial environment. In this study, three undisturbed forest soil profiles were collected from Ibaraki Prefecture, Japan. The 137Cs data illustrate that maximum fallout deposition of 137Cs took place around 1964. 14C determination shows that 14C also has peak values in the top 10 cm of the soil profiles ascribed to the highest bomb 14C level in 1960's. The 13C data show that the turnover dynamics of soil organic carbon could be described very well by progressive enrichment values of d 13C. 相似文献
2.
Water, plant and soil samples from forested area were analyzed in order to study the behavior of radionuclides in the forest ecosystem. The concentration of 137Cs in the soil decreased with depth, while stable Cs and 40K were almost constant. It is suggested that most of the 137Cs once entered in the forest ecosystem is trapped in the upper part of the soil. 相似文献
3.
Preliminary picture of 137Cs radioactivity levels in forested areas in and around Izmir is illustrated. Both activity concentrations and activity depositions
of 137Cs in soil samples were determined. Their values varied from 8.29±0.27 to 445±3.16 Bq.kg −1 (d.w.) and 0.63±0.01 to 11.6±0.08 kBq.m –2 (d.w.), respectively. It was found that while activity deposition of 137Cs is normally distributed, activity concentration of 137Cs is log-normally distributed in forest soils and the activity deposition is less variable than the activity concentration.
Cesium-137 activities in soils increase with increasing elevation, annual average rainfall and soil organic matter. 相似文献
4.
The activity of 137Cs was determined in mosses and their surrounding soils in three Venezuelan cloud forests. The concentration of 137Cs in both the mosses and their respective soils were correlated with elevation (m.a.s.l.). This relationship was the result
of the cloud forest effect, no direct deposition by condensation below the base of the clouds and increasing deposition of 137Cs with the density of the clouds. The ratio of the activity of 137Cs in the mosses to their surrounding soils was in general the same for sites near the top of the mountains, but the ratio
at the Altos de pipe location was 3.5 times higher than that of the La Sierra mountain. This was explained by the difference
in the water content of the surface and the top soil layer. It was concluded that the 137Cs measured in the mosses was from the soil effect rather than new deposition of 137Cs in the last three years. 相似文献
5.
The cumulative depositions of 137Cs, 90Sr and fallout Pu in the volcanic ash soil of Korea were determined. The average accumulated depositions of 137Cs, 90Sr and fallout Pu in the volcanic soil were much higher than those in other forest sites of Korea. From depth profiles, it
was found that 137Cs, 90Sr and 239,240Pu in the volcanic soil are more mobile than those in other forest sites of Korea, and that the downward movement of 90Sr is faster than 137Cs and 239,240Pu. A significant correlation was found between the concentration of 137Cs and those of 90Sr and 239,240Pu. The activity ratios of 238Pu/ 239,240Pu and 241Pu/ 239,240Pu in soils are close to those observed in the cumulative deposit from the global fallout of nuclear weapon testings. 相似文献
6.
The distribution of 137Cs through soil layers has been investigated by field sampling. The investigation deals with 137Cs 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 total 137Cs is located in the upper soil layer. 相似文献
7.
The aim of the study is to present the results of determination of radioactivity of artificial 137Cs and natural 40K and certain heavy metals in soil samples collected from the eastern part of the Main Ridge of Carpathians, including the Beskid Niski Mts and the Bieszczady Mts. The evaluation of level of radionuclides was based on the bulk density analysis of the soil. A valuable finding of the study was a good linear correlation between the level of 137Cs concentration and bulk density of the soil as well as an inverse correlation between radioactivity of natural 40K and tested soil density. This might indicate though a high competitiveness of these elements between each other. Moreover, a good correlation between the concentrations of artificial element 137Cs and Pb has been also observed in soil samples collected from the Beskid Niski Mts. In most cases, the level of artificial 137Cs was lower comparing to an average 137Cs concentration established for soils in Poland. 相似文献
8.
The concentration of the radionuclides 103Ru, 134Cs and 137Cs in sewage sludge samples which were collected between July and September 1986, were measured by -ray spectrometry. High concentration of 103Ru, 134Cs and 137Cs were found in sewage sludge samples from Lower-Austria /Scheibbs, Zwettl/ and Styria /Eisenerz, Leoben/. the radioactivity concentration of 137Cs was two times higher than that of 134Cs. Following concentration values were found: 103Ru 0.1–63.0 nCi kg –1, 134Cs 0.3–41.6 nCi kg –1, and 137Cs 0.3–83.3 nCi kg –1. The activity of these nuclides decreased from July 1986 to September 1986. 相似文献
9.
The radioactive contamination following the Chernobyl accident resulted in high concentrations of 137Cs in several mushrooms species. Mushroom samples were collected in a forest environment between 1986 and 2007 and the transfer
of 137Cs to two edible species, Suillus variegatus and Cantharellus spp., was investigated. The 137Cs uptake by the collected samples did not decrease over time and in Cantharellus spp. a significant increase was observed. Most of the 137Cs in soil still appears to be available for uptake and radioactive decay of the radionuclide is likely the main factor for
the reduction of 137Cs in a forest ecosystem. 相似文献
10.
Vertical distributions of global fallout 137Cs and 14C were investigated in a Japanese forest soil in 2001. Even 38 years after the fallout, 137Cs was still observed mostly in the uppermost 5 cm. A preferential accumulation of 137Cs was found in a 1-cm-thick transition layer between organic-rich A and underlying B horizons. This unique observation indicated that 137Cs migrated through the A horizon at a rate of 0.20 % year−1 and the transition layer acted as a barrier for 137Cs migration to deeper layers. The vertical distributions of 137Cs and 14C were significantly correlated, suggesting a coupled downward migration of 137Cs and organic matter on a time scale of decades, along the same physical pathways. 相似文献
11.
Depth distribution of 239,240Pu and 137Cs 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 for 238Pu and 1982.8±929.1 Bq·m –2 for 137Cs. 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 and 137Cs in soils decrease exponentially with increasing the soil depth. A significant correlation was found between the concentration of 239,240Pu and that of 137Cs. The activity ratios of 239,240Pu/ 137Cs tend to increase slightly with increasing soil depth. 相似文献
12.
A variety of wild mushrooms were collected in a forest on the Noto Peninsula, Japan, to determine the concentration of 137Cs and 40K. The wild mushroom species belong to the orders Agaricales and Aphyllophorales. The concentration of 137Cs varied widely (1.4–4,100 Bq/kg dry weight) in mushrooms growing in soil. On the contrary, 137Cs concentration levels were relatively low (1.9–20 Bq/kg-dry weight) in mushrooms growing on wood. The concentration of 40K varied widely (12–2,400 Bq/kg-dry weight) in contrast with several previous reports that suggest relatively constant 40K levels in mushrooms. Unusually low concentrations of 40K were observed in a few mushroom species that had very hard fruiting bodies with peculiar shapes. The mean and median of 137Cs concentration in the present study were similar to those previously reported for Japanese mushrooms. Among the Agaricales mushrooms, Entolomataceae and Tricholomataceae families growing in soil had the highest concentration of 137Cs. Among the Aphyllophorales mushrooms, Gomphaceae and Ramariaceae families growing in soil also had the highest 137Cs concentrations. The concentrations of 137Cs and stable Cs in mushroom samples were positively correlated. The concentration ratio of 137Cs/Cs differed between Agaricales and Aphyllophorales mushrooms. The average 137Cs/Cs ratio in mushrooms growing in soil was similar to that calculated for the top soil (<5 cm deep) alone because the mycelia of the mushrooms were mainly distributed near the surface of the soil. 相似文献
13.
Environmental samples of beach sand taken at northern Taiwan have been monitored using a coincident gamma-ray spectrometer. The concentration of 134Cs, under intense interference from natural and other artificial radioactivity, is determined as low as 0.2 Bq/kg dry. The accumulation of trace levels of 134Cs originates from the discharge of nuclear power plants nearby. 相似文献
14.
The concentration of 137Cs, potassium, thorium and uranium for 6 monitoring sites and 32 other sites at the Venezuelan Institute for Scientific Research (IVIC) were presented, as well as, the estimated air dose and exposure rates for each site. The concentration of 137Cs was found to be much higher at many sites at IVIC in respect to the average estimated value of 137Cs in Venezuela. But, this was determined to be due to a natural cause, the cloud forest which surrounds the higher elevations. The values of potassium, thorium and uranium were compared to values from other parts of northern Venezuela and were found to agree for sites at similar elevations. They were also shown to be about two to three times higher than global estimates. Thus, the air dose and exposure rates were correspondingly two to three times higher too, but the annual dose from the primordial radionuclides in the soil was estimated to be less than 0.1 mSv, which is considered negligible for health risks. 相似文献
15.
This paper presents the results of radioactivity studies of environmental factors such as surface water, sediment, aquatic vegetation and soil. The concentrations of 137Cs, 90Sr, 3H, U, Ca, and Mg in water samples were determined by radiochemical and chemical methods. Gamma-spectrometric analyses were performed for all the samples. The analysis showed a decrease in concentrations of 137Cs in water, aquatic vegetation and sediment, but a constant level of 137Cs activity in soil (0–5 cm depth). The average concentrations of 90Sr, 3H, U, Ca and Mg were about 7 mBq/l, 11 Bq/l, 0.6 g/l 60 mg/l and 11 mg/l, respectively. 相似文献
16.
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 of 103Ru to 137Cs allows to conclude that Italy was not influenced by the first release. The trend of the total activity and 137Cs percentage in rain water was very similar to those of air particulates. A calculation model to estimate 137Cs 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. 相似文献
17.
Radiocesium in ground layer atmospheric aerosol and fallout in Prague has been examined. After a decline in 1986–1988, controlled by a sum of two negative exponentials, 137Cs aerosol concentration reached a constant level based on an equilibrium between its deposition and resuspension. Deposition velocity was compared to that of 7Be and 226Ra. It confirmed the supposed source of 137Cs as resuspension from the ground. Resuspension factor of the order of magnitude of 10 –9 was determined, reminding similar values found earlier in Prague as well as those found in Munich. It also agrees well with the USAEC resuspension model. Solubility of 137Cs was measured in combined wet and dry fallout. The average undissolved fraction of 137Cs was found to be about 70% which can be explained by the conditions of the 137Cs aerosol formation in Chernobyl. 相似文献
18.
The reproducibility, the small scale as well as the large scale variability of 137Cs 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 for 137Cs was (with some exceptions) around 10–20% for all fractions. For the small scale variability of 137Cs (samples within an area of 10×10m 2) the values for the CV were (again with a few exceptions) in the same range. Compared to that, the large scale variability of extractable 137Cs (random soil samples within an area of 100×200 km 2) was higher for all fractions, even though only moderately. The implications of these results with respect to a sampling design are discussed. 相似文献
19.
The vertical distribution of 137Cs is shown for two types of soil: silly loamy “supposed” soil and silly lessive one, slightly eroded, occuring in the vicinity
of Lublin (Eastern Poland). Based on the distribution data the vertical migration rates of 137Cs are calculated for both soils. These rates are found to be 0.045 and 0.3 cm/year respectively. The percent contribution
of 137Cs originating from the damaged reactor in Chernobyl is also calculated. The kinetics of cesium adsorption and its adsorption
isotherms on minerals separated from the tested soils are also studied. The sorption of Cs on soil minerals markedly affects
the migration rate of 137Cs in soil. The experimental results indicate that, among the extracted mineral fractions, the largest adsorption takes place
on marls from the silly loamy soil. This work is supplemented by results of a physicochemical analysis of the studied soils. 相似文献
20.
An intercomparison of sampling procedures used by five laboratories for the determination of radiocaesium in vegetation and peaty soil was carried out at two locations in Cumbria. The multiple sampling has given information on the homogeneity of the parameters studied at each location. The parameters comprise soil bulk densities, total deposition of 137Cs, deposition of 137Cs in three soil layers, biomass densities, concentrations of 137Cs in pasture, and activity ratios ( 134Cs/ 137Cs) in soil and vegetation. The determination of total deposition of 137Cs gave no indication of differences between the laboratories. The results from the soil profiles do indicate significant differences between laboratories. One laboratory using a coring technique observed difficulties during sampling due to compression of the soil. The coring technique should thus be avoided or applied with extreme care for the sampling of depth profiles in peaty soil. The results from the sampling of pasture show no indication of differences between the laboratories. For the parameters studied the observed variabilities across soil depths and locations range from 10% to 81% in terms of relative standard deviations. A comparison across all results at the two locations indicate a 50% higher field variability at one of the sites relative to the other. 相似文献
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