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1.
Natural radioactivity in sediment of Wei River,China 总被引：1，自引：0，他引：1
The concentrations of natural radionuclides in sediment of Wei River of China were measured using γ-ray spectrometry with
the aim of estimating the radiation hazard as establishing a database for radioactivity levels of river sediment of China.
The activity concentrations of 226Ra, 232Th and 40K in sediment samples ranged from 10.4 to 39.9 Bq kg−1, 15.3 to 54.8 Bq kg−1 and 514.8 to 1,175.5 Bq kg−1, respectively. The concentrations of these radionuclides were compared with the typical world values and the average activities
of Chinese soil and Shaanxi soil. Radium equivalent activity (Raeq), external hazard index (H
ex) and representative level index (I
γr) were calculated for the samples to assess the radiation hazards arising due to the use of these sediment samples in the
construction of dwellings. All the sediment samples have Raeq lower than the limit of 370 Bq kg−1, H
ex less than unity and I
γr close to 1 Bq kg−1. The overall mean outdoor terrestrial gamma dose rate is 64.8 nGy h−1 and the corresponding outdoor annual effective dose is 0.079 mSv. None of the studied location is considered a radiological
risk and sediment can be safely used in construction. 相似文献
2.
Georadiochemical evidence to weathering of mining residues of the Mansfeld mining district,Germany 总被引：1，自引：0，他引：1
Mining heaps are used as archives for the investigation of weathering processes. Aim of this work was to investigate the different
weathering behavior of heap materials derived from Kupferschiefer mining with respect to environmental hazard. For this purpose,
Kupferschiefer and slag material of two heaps of different age were examined regarding to the radionuclide distribution and
geochemical composition. By measuring of the local dose rate, performing digital autoradiography and gamma spectrometry the
radiological load of the heaps and the heap materials was determined. The geochemical characterization of the samples was
performed by XRF, ICP–OES and ICP–MS. The results show a clear higher radionuclide load of the younger slag heap. A depletion
of chalcophile and lithophile elements in the older slag was determined. Apart from a homogeneous radionuclide distribution,
considerable radionuclide enrichments in fossil fragments could be proven. The results reveal a different weathering behavior
of slag material in comparison to the Kupferschiefer depending on the chemical binding of the elements on organic and inorganic
species. Natural organic matter as well as apatite in Kupferschiefer act as retention barrier for some metals. 相似文献
3.
A significant criterion in evaluating disposal strategies for high-level nuclear waste is the assessment of the isolation capacity for the most radiotoxic radionuclides, the actinides. Important processes pertinent to potential mobilization from the waste forms, retention in secondary phases and migration of actinides in the geochemical environment of the near field of disposal locations are summarized. Criteria are formulated for assessing engineered barrier performance as a geochemical barrier for actinide long-term retention. 相似文献
4.
Arid karst landscapes that have been degraded by human activities provide a challenge for rehabilitation and an opportunity
to test ideas about the stability and resilience of limestone ecosystems. The Nullarbor Plain is the largest arid karst area
in Australia (220 000 km2) and is divided into extensive closed karstic depressions separated by low rocky ridges, while the dominant vegetation is
chenopod shrubland. Since European settlement there has been considerable change in the vegetation, with significant reduction
in shrub and grass cover over large areas of the plain. These changes are related to a state and transition model of vegetation
dynamics which incorporates climatic variability, fire history and grazing pressure from sheep, kangaroos and rabbits. A partial
sediment budget using 137Cs inventories reveals local and regional patterns of soil redistribution within this arid karst landscape. Rehabilitation
of eroded soil in pastoral lands has been accomplished at several sites but is labour intensive and vulnerable to climatic
fluctuations. Given the low stock numbers, limited number of people involved, and poor economic returns, it would be sensible
to make pastoral activities on the Nullarbor secondary to conservation priorities. This would necessitate a change in land
ethic to stewardship, with emphasis on rehabilitation and control of feral animals. Management of increased numbers of visitors
to the caves and karst also requires that resource inventories and management plans for each area be drawn up and used.
Received: 1 June 1995 · Accepted: 4 December 1995 相似文献
5.
6.
Aurélien van Welden Christian Beck Jean-Louis Reyss Salvatore Bushati Rexhep Koci François Jouanne Jean-Louis Mugnier 《Journal of Paleolimnology》2008,40(2):619-633
Lake Shkodra (northern Albania, southern Montenegro) is a large (45 km length, 15 km width) and shallow (5 m mean depth) lake,
developed on a mainly karstic carbonate substratum. Its recent sedimentary fill (mixed calcareous/siliciclastic clayey silts)
was analysed through short gravity cores representing five centuries of environmental archive. A combination of high resolution
texture analysis (particle size), magnetic susceptibility, carbon content, and radionuclide activity profiles (210Pb, 137Cs, 241Am) permitted us to detect and date environmental changes, such as the Little Ice Age and the 1962–1963 catastrophic floods.
Anthropogenic influences on the watershed, such as damming of the Drin River in the late 1970s, also appear to be recorded.
Impacts of known strong earthquakes (1905, 1979), however, could not be clearly detected in the sediment record. The potential
of the Shkodra lacustrine archive for paleoseismic investigations on long time intervals (such as Holocene) is discussed.
This paper is a preliminary contribution to Shkodra Lake’s Holocene paleolimnology. 相似文献
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J. Val KLUMP David N. EDGINGTON James T. WAPLES Donald C. SZMANIA Bruce E. BROWN Kent A. ORLANDINI 《国际泥沙研究》2003,(2)
1 INTRODUCTION Sediment resuspension, particularly in response to episodic storm events, is a common characteristic of coastal and nearshore environments. The resulting 揵enthic storms?may play a significant role in the dynamics of benthic systems, including structuring the physical characteristics of the bottom, providing a mechanism for the recycling of biogeochemically important materials to the water column, and driving horizontal and cross margin transport of suspended particulates … 相似文献
9.
Visnja Orescanin Delko Barisic Ivanka Lovrencic Luka Mikelic Martina Rozmaric-Macefat Gordana Pavlovic Stipe Lulic 《Environmental Geology》2005,49(1):53-64
The objective of this study was chemical and radiological characterization of Kastela Bay sediments exposed to numerous anthropogenic sources like deposition of fly and bottom ash enriched in radionuclides and heavy metals, chemical plant, cement plant, iron plant, shipyard, electroplating facility, untreated industrial and domestic waste waters as well as heavy traffic. Totally, 33 samples of the mixture of fly and bottom ash, 12 sediment cores ranging from 0 to 40 cm and nine surface sediment samples were analyzed. Enrichment in heavy metals in the mixture of fly and bottom ash was ranging from 1.5 to 36 times compared to flysch soil while 226Ra and 238U were up to 50 times enriched compared to average activities characteristic for surrounding soils developed on the Middle and Upper Eocene flysch. Maximum 238U activity was approximately 32 times higher and 226Ra approximately 40 times higher in the Kastela Bay sediment compared to mean value determined for Adriatic sediments. The highest enrichment in sediment cores compared to background values were found for Zn (35.6 times), Pb (16 times), Cr (9.1 times) and Ni (4 times) 相似文献
10.
Characterizing the dynamics of fluvial sediment sources over space and time is often critical in identifying human impacts on fluvial systems. Upland interfluve and subsoil sources of suspended sediment at Loco Bayou, Texas, were distinguished using 226Ra/232Th, 226Ra/230Th and, 228Ra/232Th. Source contributions were apportioned at three stations during within-bank and flood flows. 137Cs and 210Pbxs (excess 210Pb) were used to determine floodplain sedimentation; suspended sediment 210Pbxs/137Cs data mirrored results of Ra/Th, showing dominance of subsoil sources during within-bank flows, changing to interfluve sources during flood. This trend corresponds spatially to influx of sediment from ephemeral tributaries, reflecting mobilization of stored interfluvial sediments during flood stage. Upper basin sedimentation was similar but markedly less at the lowermost station. These results indicate (1) modified ephemeral tributaries store sediment derived from sheet wash, discharging them during flood, and (2) southernmost Loco Bayou is episodically re-worked, resulting in significantly reduced local rates of sedimentation. 相似文献