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PubMed1990

Modeling transfer of 137Cs fallout in a large Finnish watercourse.

In the Finnish environment, lakes provide very important transfer pathways for various pollutants. In this study, a large watercourse was modeled using the dynamic compartment model DETRA. The model includes a fish model for roach, nonpredatory and predatory perches, and pike. Transfer of 137Cs fallout deposited onto the Kymijoki drainage area after the Chernobyl accident was calculated using the model. In the model, fallout was assumed to consist of a soluble and insoluble component, behaving differently in the environment. Model predictions were compared with measured concentrations. Lake Päijänne, the largest lake of the watercourse, was studied most extensively. Calculated concentrations in lake water were consistent with measured concentrations. However, calculated concentrations in fish were lower than measured concentrations. To test the model by using additional experimental data, transfer of nuclear weapons testing fallout was also calculated. The processes that cause the rather rapid removal of 137Cs from lake water need to be studied further using more detailed data. In the long term, runoff and resuspension of sedimentary material were considered to be important in causing concentrations in lake water.

Accidents↗
PubMed2006

A gradient of radioactive contamination in Dolon village near the SNTS and comparison of computed dose values with instrumental estimates for the 29 August, 1949 nuclear test.

Spatial distributions of soil contamination by 137Cs (89 sampling points) and 239+240Pu (76 points) near and within Dolon village were analyzed. An essential exponential decrease of contamination was found in Dolon village: the distance of a half reduction in contamination is about 0.87-1.25 km (in a northwest-southeast direction from the supposed centerline of the radioactive trace). This fact is in agreement with the available exposure rate measurements near Dolon (September 1949 archive data): on the basis of a few measurements the pattern of the trace was estimated to comprise a narrow 2 km corridor of maximum exposure rate. To compare computed external doses in air with local dose estimates by retrospective luminescence dosimetry (RLD) the gradient of radioactive soil contamination within the village was accounted for. The computed dose associated with the central axis of the trace was found to be equal to 2260 mGy (calculations based on archive exposure rate data). Local doses near the RLD sampling points (southeast of the village) were calculated to be in the range 466-780 mGy (averaged value: 645+/-70 mGy), which is comparable with RLD data (averaged value 460+/-92 mGy with range 380-618 mGy). A comparison of the computed mean dose in the settlement with dose estimates by ESR tooth enamel dosimetry makes it possible to estimate the "upper level" of the "shielding and behavior" factor in dose reduction for inhabitants of Dolon village which was found to be 0.28+/-0.068.

Body Burden↗
PubMed2004

Use of 137Cs measurements to estimate changes in soil erosion rates associated with changes in soil management practices on cultivated land.

Intensification of agricultural production in south-central Chile since the 1970s has caused problems of increased soil erosion and associated soil degradation. These problems have prompted a shift from conventional tillage to no-till management practices. Faced with the need to establish the impact of this shift in soil management on rates of soil loss, the use of caesium-137 (137Cs) measurements has been explored. A novel procedure for using measurements of the 137Cs depth distribution to estimate rates of soil loss at a sampling point under the original conventional tillage and after the shift to no-till management has been developed. This procedure has been successfully applied to a study site at Buenos Aires farm near Carahue in the 9th region of Chile. The results obtained indicate that the shift from conventional tillage to no-till management has caused net rates of soil loss to decrease to about 40% of those existing under conventional tillage. This assessment of the impact of introducing no-till management at the study site must, however, be seen as provisional, since only a limited number of sampling points were used. A simplified procedure aimed at documenting the reduction in erosion rates at additional sampling points, based solely on measurements of the 137Cs inventory of bulk cores and the 137Cs activity in the upper part of the soil has been developed and successfully tested at the study site. Previous application of 137Cs measurements to estimate erosion rates has been limited to estimation of medium-term erosion rates during the period extending from the beginning of fallout receipt to the time of sampling. The procedures described in this paper, which permits estimation of the change in erosion rates associated with a shift in land management practices, must be seen as representing a novel application of 137Cs measurements in soil erosion investigations.

Agriculture↗
PubMed1984

Distribution of fallout cesium-137 in Hawaii.

The concentration of 137Cs was determined by gamma spectrometry in soils and surface-deposited volcanic sublimates from various climatic locations on the islands of Hawaii, Oahu and Maui. A distinct pattern of higher concentrations on the wetter windward sides of the islands and a correlation between 137Cs concentration and amount of rainfall were observed, which confirm the source of the 137Cs as atmospheric fallout. In the soils, the concentrations measured (to 1.93 pCi/g) are within the range reported for the continental United States and other mid-latitude locations in the northern hemisphere. In the basaltic lavas, the concentration of 137Cs was found to be variable but was overall very low, and is apparently controlled by the porosity and permeability of the lavas in addition to rainfall.

Cesium Radioisotopes↗
PubMed2006

Surface ground contamination and soil vertical distribution of 137Cs around two underground nuclear explosion sites in the Asian Arctic, Russia.

Vertical distributions of 137Cs have been determined in vegetation-soil cores obtained from 30 different locations around two underground nuclear explosion sites--"Crystal" (event year - 1974) and "Kraton-3" (event year - 1978) in the Republic of Sakha (Yakutia), Russia. In 2001-2002, background levels of 137Cs surface contamination densities on control forest plots varied from 0.73 to 0.97 kBq m(-2) with an average of 0.84+/-0.10 kBq m(-2) and a median of 0.82 kBq m(-2). 137Cs ground contamination densities at the "Crystal" site ranged from 1.3 to 64 kBq m(-2); the activity gradually decreased with distance from the borehole. For "Kraton-3", residual surface contamination density of radiocaesium varied drastically from 1.7 to 6900 kBq m(-2); maximal 137Cs depositions were found at a "decontaminated" plot. At all forest plots, radiocaesium activity decreased throughout the whole vertical soil profile. Vertical distributions of 137Cs in soil for the majority of the plots sampled (n=18) can be described using a simple exponential function. Despite the fact that more than 20 years have passed since the main fallout events, more than 80% of the total deposited activity was found in the first 5 cm of the vegetation-soil cores from most of the forested landscapes. The low annual temperatures, clay-rich soil type with neutral pH, and presence of thick lichen-moss carpet are the factors which may hinder 137Cs transport down the soil profile.

Arctic Regions↗