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1.
Roy F. Spalding A.Douglas Druliner Lowell S. Whiteside Arthur W. Struempler 《Geochimica et cosmochimica acta》1984,48(12):2679-2692
Dissolved U concentrations and activity ratios (ARs) of the U isotopes in the 238U decay series were measured in ground and surface waters as part of an investigation to delineate the water quality in a proposed uranium mining area of northwest Nebraska. In oxidizing groundwaters from 67 wells completed in the Tertiary sediments, increasing U concentrations in the direction of groundwater flow generally were associated with a maturation of the formation water as evidenced by evolutionary trends in major ion character. The increased U levels probably are associated with leaching as shown by the positive correlation between U concentrations and total dissolved solids (TDS) (r = +0.83). The inverse relationships between TDS and U ARs (r = ?0.73) and U levels and ARs (r = 0.72) indicate that the decay of excess U-234 is related to maturation of the formation water and to sediment leaching along the flowpath. The data are described by a model which incorporates etching, decay and recoil and suggests that aquifer residence time can be estimated from the TDS level.The levels of soluble U in a reducing uraniferous hydrogeologic unit near Crawford, Nebraska are affected by the proximity of the sample collection to ore. In groundwater samples having similar chemistries (Na-SO4 + Cl type), similar Ehs, and collected from a close-knit pattern, U concentrations ranged from 0.01 to 2,037 μg l?1 and ARs ranged from 0.75 to 12.6. This high variability in U levels and ARs is indicative of uranium ore in small areal studies where low ARs almost always are associated with high U concentrations. 相似文献
2.
Industrial sites present a challenge to the hydrogeological delineation of pollution sources and their impacts. When large-scale
geologic structures such as grabens exist on such sites, these can have a significant impact on the hydrology and water quality
distribution. At the site investigated, geophysical techniques, standard hydrogeological approaches and hydrochemical characterisation
(with methods such as depth-profiling and isotopes) were used to determine the impact of a graben structure and the hydrogeological
properties and consequent water quality distribution. Zones of high conductivity, corresponding with available data, were
identified from the geophysical investigation and subsequent pumping tests in the area. Through hydrochemical characterisation,
including isotopes, it was determined that the fault zone acts as a barrier for groundwater flow and is thus the reason for
the lower levels of pollutants in groundwater beyond this feature. However, the surface water flow is not restricted by these
zones, and contributes significantly to the flow and salt loads at the discharge point. The study showed that graben structures
are important controls on the movement of contaminants, and that the effect of such geological features on groundwater quality
distribution must be investigated using multiple methodologies to construct a feasible conceptual model of the interactions. 相似文献
3.
煤系水矿化度是影响低煤阶煤层气生成、运移和成藏的重要因素之一。以新疆准噶尔盆地南缘地区为研究区,把研究区划分为8个水文地质单元,分析了研究区煤系水矿化度的分布特征及其对产甲烷菌生存的影响。以1 000 m埋深为例,估算了各个水文地质单元内煤系水的甲烷溶解度,据此分析评价了各水文地质单元溶解运移甲烷的能力。通过煤系水的矿化度分布、氯离子浓度和区域地质构造形态分析,综合判断区域内煤系水的大致流向。以准南地区硫磺沟水文地质单元为例,探讨了矿化度与煤层气富集成藏的关系。研究结果表明,研究区矿化度分布具有南北分带、东西分段的特征。后峡水文地质单元、玛纳斯河-呼图壁河水文地质单元的南部、硫磺沟水文地质单元的南端和阜康水文地质单元的西部地区矿化度有利于产甲烷菌的生存和产气。后峡水文地质单元溶解运移甲烷能力最强。地下水的流向大致由南向北,地表水的径流会使地下水流向发生偏转。指出了硫磺沟水文地质单元内高矿化度中心和低水位的汇水洼地是低煤阶煤层气富集成藏的地区。 相似文献
4.
Uranium depositional controls at the Prairie Flats surficial uranium deposit, Summerland, British Columbia 总被引：1，自引：0，他引：1
A hydrological and geochemical investigation of the Prairie Flats surficial uranium deposit in Summerland, BC was undertaken to identify the principal controls on uranium deposition. A network of piezometers was installed and used to measure the hydraulic conductivities of the host sediments as well as the general flow direction and aqueous geochemistry of the resident groundwaters. Two hydrostratigraphic units were identified: a peat and clay unit overlying a sand and gravel unit. Measured hydraulic conductivities were on the order of 10-7 and 10-5 m/s, respectively, and the vertical hydraulic gradients indicate significant groundwater discharge upward into the peat and clay unit. Prairie Flats groundwaters are neutral to alkaline in pH, enriched in Ca2+ and HCO3-, and have dissolved uranium concentrations ranging from 10 to nearly 1,000 µg/l. Groundwater flow and geochemistry data were used to estimate the flux of uranium in groundwater at the site. A major fraction of the uranium is taken up by adsorption to organics. There is also evidence for subsequent desorption by the formation of soluble complexes with bicarbonate. Uranium that is not held by adsorption is most likely precipitated as uraninite, UO2(c). Reducing conditions in the peat and clay unit (Eh<0.1 V) relative to the underlying sand and gravel unit (Eh>0.2 V) may explain the high concentrations of uranium nearer ground surface. The current flux of uranium into the flats is significantly smaller than that calculated from the size and age of the deposit, which may be an indication of changing rates of deposition in response to varying climatic and hydrogeologic conditions over time. 相似文献
5.
The South Alligator uranium deposits are located in the Northern Territory, Australia, south-west from the recent discoveries of Nabarlek, Ranger, Koongarra and Jabiluka. All five deposits occur in intensely folded Early Proterozoic rocks around the perimeter of the Kombolgie Formation, a flatlying Middle Proterozoic sandstone unit. It is proposed that during reconstitution (weathering or diagenesis) of acid volcanic rocks, groundwaters leached uranium and percolated down into the groundwater system of the permeable sandstone and conglomerate unit at the base of the sequence. Uranium as uranyl ion was stable in relatively high Eh groundwater conditions and was carried in solution until active reducing conditions were met with which resulted in reduction of uranyl ion to insoluble UO2. Reduction occurred where faulting had brought underlying carbonaceous shales up against the sandstone aquifer, or where groundwater could percolate down permeable fault zones into the carbonaceous shales. These structural, chemical traps were sites of uranium accumulation. 相似文献
6.
Complex flow circulation patterns are likely to be present in fault‐controlled groundwater flow systems, such as carbonate aquifers. Nevertheless, not much information is available for faults in carbonates, and their hydrogeological behaviour is often neglected in conceptual and numerical models. The understanding of this aspect of subsurface fluid flow has been improved in a carbonate aquifer, where hydrogeological investigations at site scale demonstrated the existence of fault zones that act as barriers. The hydraulic conductivity of the fault core is as low as that of siliciclastic rocks that represent the regional aquitard of the carbonate aquifer. Despite the lower permeability, the fault zones allow a significant groundwater flowthrough and a good interdependence of piezometric heads upgradient and downgradient of the faults. Because of this discontinuous heterogeneity, the aquifer looks like a basins‐in‐series system, where seasonal springs can be detected along some fault zones, as a function of groundwater level fluctuations. 相似文献
7.
A modified DRASTIC model for groundwater vulnerability assessment (abbreviated as DRARCH model by combining the first letters
of its six assessment indices) was proposed. It is essentially the specific application of DRASTIC model rather than a new
model. Both natural hydrogeological conditions that prevent groundwater from contamination and important intrinsic hydrogeochemical
properties of sediments in vadose zone that are related to the retardation of contaminants were considered as vulnerability
indices. The DRARCH model consists of six indices: (1) Depth to the water table, (2) net Recharge, (3) Aquifer thickness,
(4) Ratio of cumulative thickness of clay layers to total thickness of vadose zone, (5) Contaminant adsorption coefficient
of sediment in vadose zone, and (6) Hydraulic conductivity of aquifer. The rating values and the weights of these vulnerability
indices were obtained by contaminant transport simulation and factor analysis method respectively. Furthermore, the DRARCH
model was applied to evaluate the groundwater vulnerability to arsenic contamination in Taiyuan basin, northern China, where
groundwaters with high arsenic concentration occur in some localities. GIS-based mapping of groundwater vulnerability using
this model indicates that the distribution of very high and high-vulnerability areas corresponds well to that of high-arsenic
groundwaters. The DRARCH model is therefore reliable and useful for guiding groundwater environment management. 相似文献
8.
Groundwater flow and radionuclide decay-chain transport modelling around a proposed uranium tailings pond in India 总被引：1，自引：0，他引：1
L. Elango K. Brindha L. Kalpana Faby Sunny R. N. Nair R. Murugan 《Hydrogeology Journal》2012,20(4):797-812
Extensive hydrogeological investigations followed by three-dimensional groundwater flow and contaminant transport modelling were carried out around a proposed uranium tailings pond at Seripalli in Andhra Pradesh, India, to estimate its radiological impact. The hydrogeological parameters and measured groundwater level were used to model the groundwater flow and contaminant transport from the uranium tailings pond using a finite-element-based model. The simulated groundwater level compares reasonably with the observed groundwater level. Subsequently, the transport of long-lived radionuclides such as 238U, 234U, 230Th and 226Ra from the proposed tailings pond was modelled. The ingrowths of progenies were also considered in the modelling. It was observed that these radionuclides move very little from the tailings pond, even at the end of 10,000 y, due to their high distribution coefficients and low groundwater velocities. These concentrations were translated into committed effective dose rates at different distances in the vicinity of the uranium tailings pond. The results indicated that the highest effective dose rate to members of the public along the groundwater flow pathway is 2.5 times lower than the drinking water guideline of 0.1?mSv/y, even after a long time period of 10,000 y. 相似文献
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10.
地下水流数值模拟是高放废物处置库选址中水文地质评价的重要内容.水文地质概念模型是地下水流数值模拟的基础和前提.在北山预选区水文地质分析基础上,利用DEM数据生成了研究区地表水系,据此确定了模拟范围;借助GMS软件,建立了研究区三维水文地质结构模型;再通过边界条件、流场特征、地下水均衡项和水文地质参数的分析和描述,建立了北山地区水文地质概念模型. 相似文献
11.
Uraniferous Holocene sediments occur in the Carson Range of Nevada and California, U.S.A., between Lake Tahoe and Carson Valley. The hosts for the uranium include peat and interbedded organic-rich sand, silt, and mud that underly valley floors, fens, and marshes along stream valleys between the crest of the range and the edge of Lake Tahoe. The known uranium accumulations extend along the Carson Range from the area just southeast of South Lake Tahoe northward to the area just east of Carson City; however, they almost certainly continue beyond the study area to the north, west, and south. Due to the young age of the accumulations, uranium in them is in gross disequilibrium with its highly radioactive daughter products. These accumulations have thus escaped discovery with radiation detection equipment in the past. The uranium content of these sediments approaches 0.6 percent; however, the average is in the range of 300–500 ppm. Waters associated with these sediments locally contain as much as 177 ppb uranium. Modest levels of helium and radon also occur in these waters.Uraniferous waters are clearly entering the private and public water supply systems in some parts of the study area; however, it is not known how much uranium is reaching users of these water supplies. Many of the waters sampled in the study area exceed the published health effects guidance level of the Environmental Protection Agency. Regulatory standards for uranium in waters have not been published, however.Much uranium is stored in the sediments along these stream valleys. Estimates for a marsh and a fen along one drainage are 24,000 and 15,000 kg, respectively. The potential effects of man-induced environmental changes on the uranium are uncertain. Laboratory studies of uraniferous sediment rich in organic matter may allow us to evaluate the potential of liberating uranium from such sediments and creating transient increases in the level of uranium moving in water in the natural environment. 相似文献
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13.
Jeong Hwang Sang-Ho Moon Edward M. Ripley Yang Ho Kim 《Environmental Earth Sciences》2014,72(10):4035-4046
Korea has suffered from high U concentrations in some groundwater, especially in Daejeon near the central Ogcheon metamorphic belt. However, clear explanation has not been yet reported for the uranium sources in groundwater. This study is focused on identifying the potential uraniferous host rocks and finding the exact U-minerals serving as uranium sources in groundwater near Daejeon, Korea. For this work, we performed an in situ gamma ray spectrometer survey and a laboratory microscopic study with electron micro-probe analysis. The measurements for radioactive element content did not show any prominent K- and Th-anomaly spots, but they did result in several observations of considerable U-anomalies in pegmatite and hydrothermally altered granite, in which uraninite, coffinite and uranophane were found by electron micro-probe analysis. The occurrences of U-minerals are the first such discovery except in the low-grade U deposits of the Ogcheon metamorphic belt in Korea. All observed U-minerals were intimately associated with hydrothermal alteration. The remarkably low Th/U ratios in the studied uraniferous rocks also suggest that the U enrichment was genetically related to a post-magmatic hydrothermal process. However, many of the uraniferous parts were controlled by a reducing environment and occurred near the border between graphite-rich mica-schist and Jurassic leucocratic granite. The findings on these uraniferous rocks can be used in elucidating the source of highly enriched U groundwater in granite aquifers as well as in understanding the occurrence of igneous U-minerals, which has not been previously reported in Korea. 相似文献
14.
《Chemical Geology》2006,225(1-2):156-171
Groundwater samples were collected along a groundwater flow path in the Carrizo Sand aquifer in south Texas, USA. Field measurements that included pH, specific conductivity, temperature, dissolved oxygen (DO), oxidation–reduction potentials (Eh in mV), alkalinity, iron speciation, and H2S concentrations were also conducted on site. The geochemistry (i.e., concentrations, shale-normalized patterns, and speciation) of dissolved rare element elements (REEs) in the Carrizo groundwaters are described as a function of distance along a flow path. Eh and other redox indicators (i.e., DO, Fe speciation, H2S, U, and Re) indicate that redox conditions change along the flow path in the Carrizo Sand aquifer. Within the region of the aquifer proximal to the recharge zone, groundwaters exhibit both highly oxidizing and localized mildly reducing conditions. However, from roughly 10 km to the discharge zone, groundwaters are reducing and exhibit a progressive decrease in redox conditions. Dissolved REE geochemical behavior exhibits regular variations along the groundwater flow path in the Carrizo Sand aquifer. The changes in REE concentrations, shale-normalized patterns, and speciation indicate that REEs are not conservative tracers. With flow down-gradient, redox conditions, pH and solution composite, and adsorption modify groundwater REE concentrations, fractionation patterns, and speciation. 相似文献
15.
Groundwaters in contact with hidden ore deposits may acquire chemical compositions that offer a guide for exploration, if the chemistry of the waters can be properly interpreted. Hydrogeochemical computer models allow significant progress to be made in the interpretation of the chemistry of all types of natural waters. The computer program, WATEQFC, an expansion and restructuring of WATEQF, is directed toward geochemical exploration for uranium and base metals. The expanded program can now solve the simultaneous equilibria involved in the aqueous geochemistry of 47 chemical elements, represented by approximately 540 minerals and solid compounds and 650 aqueous species.Calibration of the model with groundwaters from known deposits of uranium ore suggests that hidden ore bodies may be revealed by the state of saturation of the waters with respect to a suite of potential ore and gangue minerals. The saturation index (SI) is a reliable predictor of the presence of uranium ore from known deposits in Texas, Wyoming, and Czechoslovakia. The use of groundwater for regional reconnaissance strongly suggests that uranium mineralization is present in the subsurface near Colorado City, Colorado, whereas a similar modeling of groundwaters from a large area of Triassic sandstones in England virtually eliminates that area from consideration as a host for hidden uranium ore. 相似文献
16.
Quantitative Analysis of Groundwater Flow near a Partially Penetrating River under Riverside Pumping
WANG Bingchen ZHENG Xilai QIAN Hui LIN Guoqing XU Qian Comprehensive Institute of Geotechnical Survey Beijing Institute of Environmental Science Engineering China Ocean University Qingdao Shandong Department of Water Resources Chang''an University Xi''an Shaanxi 《《地质学报》英文版》2004,78(3):820-824
According to practical geological and hydrogeological conditions of riverside water-supply well fields in northwestern China, an ideal hydrogeological model has been generalized and a three-dimensional mathematical model has been set up. A finite difference method was applied to simulating groundwater flow near a partially penetrating river under riverside pumping, and to analyzing the effects of river width, partial penetration and permeability of riverbed sediments on groundwater recharges. Results show that riverside pumping may cause groundwater to flow beneath the partially penetrating river, and that river width, penetration and riverbed permeability obviously influence flows from the partially penetrating river and constant-head boundaries. However, the pumping output is mainly from the partially penetrating river. 相似文献
17.
开鲁盆地铀矿水文地球化学找矿研究 总被引：2，自引：0，他引：2
本文从基础地质条件出发 ,界定了开鲁盆地的发展历史 ,全面分析了研究区的水文地质条件、水文地球化学特征及地下水的含铀性 ,确定了在整体坳陷期形成的姚家组和四方台组区域承压含水层的找矿意义。同时 ,从水文地质构造层、渗入渗出体系的划分及浅层地下水和深部地下水化学异常显示等方面入手 ,较详细地阐述了开鲁盆地水文地质条件和水文地球化学特征及其对层间氧化带发育条件的影响 ,预测了两处可地浸砂岩型铀矿的成矿远景地段 ,并指出道德庙是本区最具找矿前景的地区。 相似文献
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19.
中国碳硅泥岩型铀矿床时空演化规律 总被引：3，自引：0，他引：3
中国海相碳硅泥岩建造空间分布上受控于陆缘裂谷体系、陆缘裂陷体系、陆缘盆地体系及陆缘活动带断陷台沟体系,而大规模铀成矿作用与陆缘裂谷、陆缘裂陷环境下由海底喷流作用和海底火山喷发而沉积形成的热水沉积硅质岩、硅质磷块岩和碳硅质泥岩组成的含铀海相碳硅泥岩建造密切相关。铀矿床的空间分布受热液叠加改造驱动力条件制约,受红盆边缘断裂沟通效应影响。铀矿体的空间定位受切穿碳硅泥岩含铀建造的深大断裂及其派生的次级断裂、层间破碎带和联合断裂型复合带的控制。铀成矿时代则与形成热液叠加改造驱动力源的构造岩浆活化期相一致。 相似文献
20.
《Applied Geochemistry》1994,9(3):271-278
The North and South Platte Rivers contribute sigficant concentrations of dissolved uranium to the Platte River system from the weathering of uraniferous rocks at their headwaters in Colorado and Wyoming. Uranium isotopes measured in three groups of samples collected from the Platte River and its major tributaries exhibted a wide range of concentrations (0.27–31.7 μg/l) and activity ratios (1.03–1.72) reflecting variations in the contributions of different sources under differing flow conditions. Locally elevated uranium concentrations and higher activity ratios were associated with groundwater sources during low flow periods. Uranium concentrations in surface runoff were lower than in baseflow and correlated significantly with dissolved solids. Uranium activity ratios in runoff were closer to equilibrium values than those in baseflow suggesting that dissolved uranium in runoff is less affected by disequilibrium processes. Mixing calculations using uranium concentrations and activity ratios indicate considerable variations in longitudinal and transverse mixing of tributary water with Plate River water, and temporal variations of groundwater contributions (baseflow and irrigation return flow) in the Plate River system. 相似文献