Distribution Of 137Cs In Sediments Research Articles

Distributions of 137Cs in sediments of a crater lake: results from Baengnokdam of Mt. Halla, Jeju Island

Vertical and horizontal distributions of 137Cs were investigated in sediment cores of the crater lake, Baengnokdam of Mt. Halla, Korea. The activities of 137Cs in sediments were in the range of minimum detectable activity 0.2–214 Bq kg−1 in the 0–100 cm layer. The inventories of 137Cs were in the range of 7.4–29.7 kBq m−2. The higher total inventories of 137Cs were observed in the middle of Baengnokdam of Mt. Halla, indicating that higher 137Cs in soil sediments of the middle of Baengnokdam of Mt. Halla can be strongly adsorbed on mud.

Post‐deposition diffusion of 137Cs in lake sediment: Implications for radiocaesium dating

AbstractPeak activities of radiocaesium (137Cs) in lake sediments have frequently been used to infer the ages of sediments deposited in the 1960s (137Cs derived from nuclear bomb testing) or in 1986 (Chernobyl derived 137Cs). Records of the vertical distribution of 137Cs in sediments can thus be used to provide accurate dates for a critical period in which palaeoecological reconstructions often overlap contemporary monitoring data. However, knowledge regarding how the distribution of 137Cs in sediments is affected by post‐depositional processes is limited to interpretations based on the 137Cs distribution in sediments sampled at a single given date. This study assesses the extent to which the 137Cs record in annually laminated (varved) lake sediments is affected by post‐depositional diffusion, using 11 archived sediment cores sampled between 1986 and 2007. The sediment record reveals how Chernobyl 137Cs incorporated into the 1986 varve diffused downwards in the core at a decreasing rate over time, whereas the surface sediments continued to receive inputs of 137Cs mobilized from the catchment soils or lake margin. In spite of these processes, all cores post‐dating the Chernobyl accident had a clear and well‐resolved peak in the 1986 varve, justifying the use of this feature as a fixed chronostratigraphic feature. Because of the very high levels of Chernobyl fallout at this site, downwards migration of Chernobyl 137Cs has, however, completely masked the nuclear weapons 137Cs fallout peak that had been clearly preserved in the 1964 varve of a pre‐Chernobyl core sampled just three weeks before the Chernobyl accident. In consequence, the weapons fallout marker is likely to be of little use for determining 137Cs dates in areas strongly affected by high levels of Chernobyl fallout.

96/01547 The distribution of 137Cs in sediments of the littoral zone of a former reactor cooling pond

96/01547 The distribution of 137Cs in sediments of the littoral zone of a former reactor cooling pond

The distribution of 137Cs in sediments of the littoral zone of a former reactor cooling pond

Previous studies in Pond B, a 12-m deep, 82-ha reservoir that once served as a reactor cooling pond, had (i) suggested the preferential accumulation of 137Cs in sediments at a water depth of 3m within the littoral zone and (ii) attributed this accumulation to the effects of either macrophyte vegetation or sediment slope. To test for the preferential accumulation of 137Cs at intermediate depths within the littoral zone, sediment cores were taken at water depths of 0.5, 1, 2, 3, 4 and 5 m along 6 transects in Pond B. The sediment structure was similar at all water depths in the littoral zone with a surface layer of 0.02–0.04 m of plant debris and fine sediments over a base of sandy sediments. The 137Cs was largely restricted to the surface layer of fine sediments, and there was no indication of preferential accumulation of fine sediments or 137Cs at water depths of 3 m. There was no apparent relationship between sediment slope and 137Cs content. Although the 137Cs entered Pond B more than 20 years ago, its prevalence in the surface layers of littoral zone sediments resembles the pattern observed for 134Cs deposited in European lakes from the recent Chernobyl accident.

ひ沼におけるフォールアウト核種の移行挙動に関する研究 （Ｉ）

Deposition of 134Cs, 137Cs and other fallout nuclides was observed at PNC O-arai Engineering Center in May 1986 after Chernobyl accident. The fallout radionuclides, especially 90Sr and 137Cs in lake water, sediments and fish have been measured in Lake Hinuma located 2km north-west of the Center since 1986 in order to investigate migration behavior of these nuclides in lake ecosystem. In August 1986, the 137Cs in sediments was irregularly distributed at each sampling point in Lake Hinuma. It was different from distributions of 239, 240Pu and 241Am, which showed that concentrations at center of the lake were higher than that near the shore in 1986. Horizontal distributions of 137Cs in sediments then shifted to similar distribution of 239, 240Pu by 1989. The 137Cs concentrations in sediment showed a tendency to increase slightly in 1987 and 1988 and then to decrease. An apparent half-life of 137Cs in sediment was derived from field data as approximately 3 years. Distribution coefficient (Kd) for 90Sr in sediments, a ratio of the concentration of 90Sr in dry sediment to that in water, was approximately 90(l/kg) as 50% value in cumulative probability distribution of observed KdS. Concentration Factors (CFs) for 90Sr were from 4 to 45(l/kg) in edible parts of fishes (Haze, Ugui and Wakasagi).

Application of Radioactive Fallout Cesium‐137 for Measuring Soil Erosion and Sediment Accumulation Rates and Patterns: A Review

AbstractRadioactive fallout 137Cs (cesium‐137) deposited across the landscape from atmospheric nuclear tests is strongly absorbed on soil particles limiting its movement by chemical and biological processes. Most 137Cs movement in the environment is by physical processes; therefore, 137Cs is a unique tracer for studying erosion and sedimentation. Cesium‐137 loss from a watershed has been shown to correlate strongly with soil loss calculated by the Universal Soil Loss Equation (USLE) or measured from small runoff plates. By measuring spatial patterns of 137Cs in vertical and horizontal planes across the landscape, rates of soil loss or deposition can be measured for different parts of a watershed. Even within landscape units, redistribution of soil can be mapped and erosion or deposition rates for different parts of individual fields measured and mapped. Sediment accumulation rates can be measured by comparing the vertical distribution of 137Cs in sediments with the temporal deposition of fallout 137Cs from the atmosphere to locate sediment horizons. Using these dated sediment horizons, sediment accumulation rates can be measured. Interpretations about the location of these dated horizons must consider particle size of the sediments, reworking of deposited sediments, diffusional movement of 137Cs, and time rates of physical process in the sedimentation process. The 137Cs technique can be used to determine sediment accumulation rates in a wide variety of depositional environments including reservoirs, lakes, wetlands, coastal areas, and floodplains. The bibliography shows that 137Cs has been used widely for studying erosion and sedimentation in many different environments around the world.

Physical and chemical parameters affecting transport of 137Cs in arid watersheds

The occurrence and amount of fallout 137Cs were determined in 12 watersheds in the arid southwestern United States. The factors believed to influence the distribution of 137Cs in the watershed soils and in the reservoir sediments were investigated by using stepwise regression techniques. Seventeen parameters, in the case of soils, and 21 parameters, in the case of sediments, were used in the study. Ninety percent of the variation in the 137Cs content of soils, per unit weight, could be predicted in terms of the percentage of soil nitrogen, the R factor (rainfall intensity) of the universal soil loss equation, the percentage of sand in the soils, and the soil cation exchange capacity. Also, 90% of the variation in the content of 137Cs in the watershed soils, per unit area, could be predicted in terms of the fallout intensity, the percentages of silt and clay, and the cation exchange capacity. For reservoir sediments the equivalent predictors of 137Cs accumulation in the sediment profile, per unit weight, were the soil cation exchange capacity, the January–March average precipitation, and the soil contents of total P and N. The distribution Of 137Cs in sediments per unit area was similarly predicted by watershed area, percentage of total soil C, reservoir surface area, areal concentration of 137Cs in the watershed soils, and soil organic matter.