排序方式: 共有2条查询结果,搜索用时 0 毫秒
1
1.
Naturally occurring radionuclides and their geochemical interactions at a geothermal site in the North German Basin 总被引:1,自引:1,他引:0
Simona Regenspurg Jörg Dilling Jürgen Mielcarek Frank Korte Uwe-Karsten Schkade 《Environmental Earth Sciences》2014,72(10):4131-4140
The activities of the most common, naturally occurring radionuclides 238U, 226Ra, 210Pb, 228Ra, 228Th, and 40K were measured by gamma-ray spectrometry in samples from reservoir rocks, geothermal fluids, and mineral precipitates at the geothermal research site Groß Schönebeck (North German Basin). Results demonstrated that the specific activity of the reservoir rock is within the range of the mean concentration in the upper earth crust of <800 Bq/kg for 40K and <60 Bq/kg for radionuclides of the 238U and 232Th series, respectively. The geothermal fluid showed elevated activity concentrations (up to 100 Bq/l) for 226Ra, 210Pb, and 228Ra, as compared to concentrations found in natural groundwater. Their concentration in filter residues even increased up to 100 Bq/g. These residues contain predominantly two different mineral phases: a Sr-rich barite (Sr, BaSO4) and laurionite (PbOHCl), which both precipitate upon cooling from the geothermal fluid. Thereby they presumably enrich the radionuclides of Ra (by substitution of Ba) and Pb. Analysis of these precipitates further showed an increased 226Ra/228Ra ratio from around 1–1.7 during the initial months of fluid production indicating a change in fluid composition over time which can be explained by different contributions of stimulated reservoir rock areas to the overall produced fluid. 相似文献
2.
Slavomír Nehyba Daniel Nývlt Uwe Schkade Gerald Kirchner Eva Franců 《Journal of Paleolimnology》2011,45(1):41-55
Facies analysis, magnetic susceptibility, and analysis of grain size, TOC content and isotopes (137Cs, 210Pb, 226Ra, 228Ra, and 238U concentrations) were used to determine the history of the modern deposits of the Brno reservoir. The sedimentary succession
can be subdivided into two main units. The lower unit is formed predominantly by medium- to coarse-grained silty sands and
is interpreted as a fluvial succession deposited before the Svratka River was dammed. The upper unit consists of brownish
planar laminated silts and rarely of clayey or sandy silts and is interpreted as a product of the reservoir deposition. The
concentrations of 238U reflect the history of uranium mining in the upper part of the Svratka River catchment. As a consequence, 210Pb radionuclide concentrations cannot be used for establishing a sediment chronology. Concentrations of 137Cs show two marked peaks, the upper of which is attributed to the Chernobyl reactor accident in 1986, and the lower one is
attributed to the maximum rate of atomic weapons testing in 1963. From these peaks, mean depositional rates of 3.2 cm year−1 for the time period of 1986–2007 and of 3.4 cm year−1 between 1963 and 1986 are calculated. Based on the known age of the reservoir, which was constructed in 1939, we can also
calculate mean depositional rate for the time period of 1939–1963, which is 3.1 cm year−1. 相似文献
1