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PubMed2004

239+240Pu, 90Sr and 137Cs inventories in surface soils of Vietnam.

Fallout 239+240Pu, 238Pu, 90Sr and 137Cs inventories in surface soils were measured for 20 locations in northern Vietnam yielding the mean values (+/- standard error) of 26.5+/-3.8 Bq m(-2) for 239+240Pu, 1048+/-143 Bq m(-2) for 137Cs and 212+/-28 Bq m(-2) for 90Sr. The concentrations of 137Cs and plutonium isotopes strongly correlate with each other resulting in a stable 239+240Pu/137Cs inventory ratio of 0.025+/-0.002. Among soil parameters, organic matter and fulvic acids strongly correlate with caesium and plutonium isotopes, especially in the 0-10 cm layer. 137Cs and 239+240Pu are distributed rather similarly over the 0-10 cm and 10-20 cm layers. At locations with high contents of sand (82-93%) along the South China Sea coast, the downward percolation by rainwater results in a higher accumulation of 239+240Pu and 137Cs in the 10-20 cm layer. The mean 137Cs/ 90Sr inventory ratio is 9.3+/-2.2, and the correlation is weak between these isotopes.

Environmental Monitoring↗
PubMed2003

Soil-to-grain transfer of fallout 137Cs for 28 winter wheat cultivars as observed in field experiments.

In order to find wheat cultivars with a minimum soil-to-grain transfer of fallout (137)Cs, 28 winter wheat cultivars were investigated at 3 different sites with different soil types in Bavaria, Germany. Each cultivar was grown on an area of 10 m(2) and harvested in August 1999. The soil-to-grain concentration ratios (C(r)) of (137)Cs varied by a factor of up to 3 from cultivar to cultivar at a given site and from site-to-site for a given cultivar. The mean C(r) values at the three sites, 4.2 x 10(-4), 4.9 x 10(-4) and 7.5 x 10(-4), differed significantly. The fact that no cultivar showed similar C(r) values at the three sites indicates a strong influence of the soil on C(r). The cultivars Flair, Kornett and Previa showed a minor uptake of (137)Cs compared with the mean of all cultivars at each site. Unlike (137)Cs, the (40)K concentrations in the wheat grains varied only within a small range (122-190 Bq kg(-1)) at each site, which is due to the potassium regulation by the plants. For both radionuclides, the differences between the root uptake characteristics of the cultivars may not only be explained by an inter-cultivar variability due to genetic differences between the cultivars, but also by an intra-cultivar variability due to different soil conditions.

Cesium Radioisotopes↗
PubMed1971

The behavior of 137Cs and other fallout radionuclides on a Michigan dairy farm.

The behavior of the fallout radionuclides 137Cs, 54Mn, 14Ce-Pr and 90Sr in the milk-food chain was studied at a commercial dairy farm near Tecumseh, Michigan during 1964 and 1965. The main purpose of the study was to develop mathematical models to describe the movement of radionuclides from air to milk. Three models are presented: the first predicts the total deposition on precipitation collectors given the air concentration and rainfall rate; the second predicts the concentration in forage from air concentration, rainfall rate, and the rates at which the forage grows and is consumed by the dairy herd; the third predicts the milk concentration from the concentration in each type of feed and the rate at which each feed type is consumed by the dairy herd. The first two models are applicable to all four radionuclides but the milk model is valid only for 137Cs. Milk concentrations for the other three radionuclides are treated individually. The model for deposition on precipitation collectors was developed independently and is shown to predict weekly deposition rates to within a factor of three (95% of the time). This uncertainty is reduced as the time span for the prediction is increased. Development of the other two models was based in part on data from the Tecumseh study; both still require independent verification. The forage model fits the weekly experimental data to within a factor of 2.2. The milk model fits the weekly measurements of 137Cs concentrations to within a factor of 1.5. The error of the latter 2 models also decreases as the time span for the prediction is increased.

Animals↗
PubMed1999

Soil to plant uptake of fallout 137Cs by plants from boreal areas polluted by industrial emissions from smelters.

To study the impact of industrial pollution on the soil-to-plant uptake of fallout-radiocesium in a boreal forest ecosystem, four study sites were selected at distances of 7, 16, 21 and 28 km from the large copper-nickel smelter at Monchegorsk on the Kola Peninsula (Russia). At each site, soil and selected plant species were sampled from five plots and analysed separately for 137Cs and 40K. The data show that the root-uptake of 137Cs, as characterised by the median aggregated transfer-factor T(ag), decreased significantly (P < 0.05) with decreasing distance from the smelter for the plants Vaccinium myrtillus (from 0.023 to 0.007 m2 kg-1) and Empetrum nigrum (from 0.015 to 0.007 m2 kg-1), but increased for Deschampsia flexuosa (from 0.013 to 0.031 m2 kg-1). For Vaccinium vitis-idaea a significant trend for the T(ag) was not observed. The median 40K activity concentrations in these plants also decreased significantly (P < 0.001) with decreasing distance from the smelter for Vaccinium myrtillus (from approx. 140 to 20 Bq kg-1 dry wt.), Empetrum nigrum (from approx. 90 to 40 Bq kg-1 dry wt.), and also for Deschampsia flexuosa (from approx. 270 to 40 Bq kg-1 dry wt.). For Vaccinium vitis-idaea such a continuous significant trend was not observed. The results for the Cu-Ni polluted soils thus show: (1) that the soil-to-plant transfer of radiocesium can be significantly modified; (2) that these modifications are quite specific; and (3) that modifications of the uptake of potassium do not always correspond to those of radiocesium.

Biological Transport, Active↗
PubMed2003

Liming as a method to remedy lakes contaminated by radiostrontium.

This work has identified the characteristics regulating lake sensitivity to 90Sr-contamination and why certain lakes are likely to respond positively to lake liming (Ca-treatment) and when this would not be a feasible or economic remedial measure to lower 90Sr-levels in fish. The results demonstrate that liming would work best in (1) small, (2) low-productive, (3) oligohumic, (4) acid lakes with (5) low initial Ca-concentrations. It is important to start the liming as soon as possible after the fallout. The liming model discussed in this work can be used to calculate the changes in lake Ca-concentrations and the duration of the liming. The Sr-model can be used to calculate changes in Sr-levels in water, sediments and fish. At best, these simulations indicate that it is realistic to expect that lake liming can reduce peak levels of 90Sr in fish by 25-40%.

Animals↗
PubMed1990

Overview of the National Cancer Institute's activities related to exposure of the public to fallout from the Nevada Test Site.

The Department of Health and Human Services (DHHS) was directed by Congress to assess the risk of thyroid cancer from 131I associated with fallout from the atmospheric testing of nuclear weapons at the Nevada Test Site. The National Cancer Institute (NCI) was requested by DHHS to address Public Law 97-414, Section 7 (a), which directs DHHS to "(1) conduct scientific research and prepare analyses necessary to develop valid and credible assessments of the risks of thyroid cancer that are associated with thyroid doses of Iodine 131; (2)...develop...methods to estimate the thyroid doses of Iodine 131 that are received by individuals from nuclear bomb fallout; (and) (3)...develop...assessments of the exposure to Iodine 131 that the American people received from the Nevada atmospheric nuclear bomb tests." In addition, the University of Utah, under contract with the NCI, is carrying out a study to determine if the incidence of thyroid disease and leukemia among identified populations in Utah may be related to exposure from fallout originating at the Nevada Test Site.

Environmental Exposure↗
PubMed1989

Cesium-137 in Montana soils.

Fallout 137Cs levels in soil were measured at 11 diverse sites throughout Montana. Concentrations in near-surface samples ranged from 20-200 mBq g-1 (0.51-5.41 pCi g-1). Most of the 137Cs was in the top 10 cm of soil. Deeper occurrences were attributed to disturbances by animals and to interstitial flow of small sediment particles within saturated soils. The areal concentrations ranged from 130-748 mBq cm-2 (3.6-20.2 pCi cm-2) and were highly correlated with annual precipitation.

Cesium Radioisotopes↗
PubMed1987

Forecasting radiation rates and exposure from multi-aged fallout.

A graphical method for forecasting radiation exposure rates from multi-aged fallout is extended to include a nomogram method. A simple method for forecasting accumulated radiation exposure is also presented. It is shown mathematically that these methods can provide estimates of radiation exposure rates or cumulative exposures for intervals of a few days to a few weeks in the future to within +/- 30% from assumed actual radiation exposure rates or accumulated exposures for fallout that decays according to t-n, where n is any number from 0.8 to 1.6. Because of the self-adjusting feature of the method which results in an estimated effective age for the fallout, it is not necessary to attempt to subtract contributions from separate fallouts with different ages. The method can be applied to composite fallout without knowledge of the previous history of the various-aged contributions.

Biometry↗
PubMed2002

Estimates of doses from global fallout.

This paper summarizes information about external and internal doses resulting from global fallout and presents preliminary estimates of doses resulting from intermediate fallout in the contiguous United States. Most of the data on global fallout were extracted from the reports of the United Nations Scientific Committee on the Effects of Atomic Radiation, in which the radiation exposures from fallout have been extensively reviewed at regular intervals. United Nations Scientific Committee on the Effects of Atomic Radiation estimated the average effective doses received by the world's population before 2000 to be about 0.4 mSv from external irradiation and 0.6 mSv from internal irradiation, the main radionuclide contributing to the effective dose being 137Cs. Effective doses received beyond 2000 result mainly from the environmentally mobile, long-lived 14C and amount to about 2.5 mSv summed over present and future generations. Specific information about the doses from fallout received by the United States population is based on the preliminary results of a study requested by the U.S. Congress and conducted jointly by the Centers for Disease Control and Prevention and the National Cancer Institute. Separate calculations were made for the tests conducted at the Nevada Test Site and for the high-yield tests conducted mainly by the United States and the former Soviet Union at sites far away from the contiguous United States (global tests). The estimated average doses from external irradiation received by the United States population were about 0.5 mGy for Nevada Test Site fallout and about 0.7 mGy for global fallout. These values vary little from one organ or tissue of the body to another. In contrast, the average doses from internal irradiation vary markedly from one organ or tissue to another; estimated average thyroid doses to children born in 1951 were about 30 mGy from Nevada Test Site fallout and about 2 mGy from global fallout.

Nevada↗
PubMed1999

Vertical and horizontal fluxes of plutonium and americium in the western Mediterranean and the Strait of Gibraltar.

New data on the vertical distributions of plutonium and americium in the waters of the western Mediterranean and the Strait of Gibraltar are examined in terms of the processes governing their delivery to, transport in and removal from the water column within the basin. Residence times for plutonium and americium in surface waters of approximately 15 and approximately 3 years, respectively, are deduced, and it is shown that by the mid 1990s only approximately 35% of the 239,240Pu and approximately 5% of the 241Am deposited as weapons fallout still resided in the water column. Present 239,240Pu inventories in the water column and the underlying sediments are estimated to be approximately 25 TBq and approximately 40 TBq, respectively, which reconcile well with the time-integrated fallout deposition in this zone, taken to be approximately 69 TBq. The data show that there are significant net outward fluxes of plutonium and americium from the basin through the Strait of Gibraltar at the present time. These appear to be compensated by net inward fluxes of similar magnitude through the Strait of Sicily. Thus, the time-integrated fallout deposition in the western basin can be accounted for satisfactorily in terms of present water column and sediment inventories. Enhanced scavenging on the continental shelves, as evidenced by the appreciably higher transuranic concentrations in shelf sediments, supports this contention.

Americium↗

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