A comprehensive study of the spread of radioactive contamination in the geological medium near Lake Karachai,Chelyabinsk oblast

The spread of radioactive contamination in the subsurface medium near Lake Karachai is considered. The complexity of this process requires a comprehensive approach to its study. The source of radioactive contamination is overviewed. The map of faults in subsurface medium is considered in order to determine the prevailing direction of contaminated groundwater flow. Photometry in observation wells has been used for structural geological estimation of transport properties of the shallow aquifer, where contaminated groundwater is moving. This study was carried out along with hydrochemical logging, which makes it possible to estimate the dynamics of contamination of subsurface medium and vertical distribution of groundwater contamination. Special attention is paid to transport of radionuclides in the form of radiocolloid particles. Groundwater samples were taken from various depths corresponding to different contamination levels near Lake Karachai. The depth intervals of sampling were determined from the data of hydrochemical logging. Ultrafiltration through membranes with a specific pore size in combination with gamma spectrometry was used to characterize radionuclide transfer with colloidal particles differing in size. The local elemental composition of the radiocolloid surface was studied by Auger spectroscopy. The chemical composition and structure of radiocolloid particles were determined by X-ray photoelectron spectroscopy with consecutive etching of the particle surface by argon ions for a certain depth. The data obtained indicate that radiocolloid particles are heterogeneous and an organic shell consisting of humic and fulvic acids and technogenic organic compounds coat their surface.     

Model of colloidal transportation of radionuclides by groundwater

The transportation of colloidal radionuclides by groundwater was subject to theoretical analysis. The far field of radioactive contamination of the underground environment (liquid waste pumping sites or storage of solidified waste) is dominated by pseudocolloids, i.e., colloidal particles of natural origin contaminated with radionuclides upon contact of groundwater with radioactive materials. Properties of real pseudocolloids were analyzed at sites of radioactive contamination of the underground environment. Based on a probabilistic approach, we developed a mathematical model of pseudocolloid transportation by groundwater, taking into account the difference in size of colloidal particles and the occurrence of nonradioactive natural particles with a similar composition in the groundwater. It is proved that nonuniform dimensions of the particles considerably affect the water transportation rate.     

胶体颗粒在潜流带中沉积过程及机制

潜流带是河流地表水和地下水交混区域,是河流中重要的物质能量交换和水生生物栖息的场所,而胶体颗粒在潜流带中沉积,会改变潜流带中的水动力结构和生态环境。本文利用室内循环水槽实验和多物理场耦合的数值模拟方法,旨在研究胶体颗粒在河流上覆水与潜流带中的迁移过程和胶体颗粒在潜流带中沉积分布特征及其对不同因素的响应规律。结果表明:河流上覆水中胶体会逐渐被河床截留且截留胶体集中于河床浅层;沙波水平方向截留量呈现出迎水面较高、背水面较低的趋势;胶体在潜流带沉积的主要机制是潜流交换、颗粒沉降与河床截留作用。本文能为胶体颗粒在潜流带中的生态环境作用研究提供科学依据,并为河流生态环境修复、河流健康管理提供理论支持。     

Estimation of the emplacement depth of a magmatic intrusive body based on the data for distribution of isogrades in the surrounding metamorphic zoning (Model approximation)

A method of model calculations for the approximate estimation of the emplacement depth of magmatic intrusive body based on data for the distribution of isotherms in the near-intrusive area is proposed. Isotherms are maximums of respective temperatures reached when exocontact rocks are heated at a different time; some of them represent isogrades. The calculations require knowing the form of the intrusive body, the magma composition and initial temperature, the regional geothermal gradient in the Earth’s crust during the magma intrusion, the thermal and physical properties of rocks and melt, and the distribution of isogrades/isotherms in the enclosing rocks. The probable depth of emplacement of the Kharlovo gabbro massif in the northwestern foothill belt of Altai is estimated as an example. It was determined to be 7–8 km. The estimates of depth that are obtained in such a way cannot be absolutely accurate, since they are a result of calculations in a simplified model statement.

     

Composition and sources of clastic material in conglomerates from Precambrian metamorphic rocks of Kola Peninsula

Precambrian conglomerates, generally metamorphosed with concomitant loss of form, orientation, structure, and texture, are often regarded as fault breccias, mylonites, and even porphyroblastic formations. Study of the Precambrian of the Kola Peninsula has revealed that Proterozoic conglomerates are common, and although many original rock features have been obliterated by metamorphism, detailed study has led to the conclusion that valuable stratigraphic and petrologic data are discernible. The distribution of various metamorphosed conglomerates, their stratigraphic position and relationship to the enclosing rocks, their structure, the nature and location of source rocks, and the probable modes of transportation and environments of deposition were determined for many metamorphosed Proterozoic conglomerates of the eastern Kola Peninsula. This study shows that valuable information on the pre-metamorphic history of Precambrian areas can be obtained by careful analysis of metasedimentary rocks.—R. D. DeRudder     

The origin of fluoride in the granitic aquifer of Porto Alegre, Southern Brazil

The Porto Alegre region, Southern Brazil, comprises a fractured aquifer system constituted by pre-Cambrian granitic and gneissic rocks, and a porous aquifer system formed by Cenozoic muddy–sandy to sandy sediments. A model is presented for the origin of the fluoride in the groundwater of the fractured aquifer system, based on ionic interrelations, a statistical analysis of physicochemical parameters and geochemical modeling. The fluoride is present at levels of up to 6.13 mg/L in groundwater and it arises due to the dissolution of secondary fluorite filling fractures in the granitic and gneissic rocks. The dissolution of fluorite occurs at the same time as calcite and dolomite solubilization. The statistical analysis identified three chemically distinct groups (named 1, 2 and 3) and two subgroups (1A and 1B) of groundwater in the fractured aquifer. The most significant differences between these groups are the different concentration ranges of fluoride, calcium, bicarbonate, magnesium, total dissolved solids and chloride and pH values, as well as the correlations between them. The compositional evolution of each groundwater group is governed mainly by how much high-salinity groundwater from the porous aquifer system is mixed with them and the different thermodynamic equilibrium conditions of calcite, dolomite and fluorite.     

关中盆地地下水系统分析与地下水资源可持续开发利用对策

关中盆地是一个完整的、相对独立的地下水系统,按含水介质的结构组合与空间分布以及地下水循环特 征,文章将关中盆地地下水系统进一步划分为黄土台塬孔隙$C裂隙含水系统、冲积平原孔隙含水系统、秦岭山前洪 积平原孔隙含水系统、渭北岩溶含水系统及基岩裂隙含水系统共5个亚系统和26个更次一级的子系统。在研究 各子系统水文地质特征、分析水资源开发利用现状的基础上,认为区内地下水资源开发利用中存在的问题有:地下 水资源污染与浪费严重,重复利用率低;不合理开采地下水,出现负环境效应;行政区块限制,水资源宏观调配不 够;地下水人工调控力度不够,不能有效地促进生态环境良性循环;对地下水资源的研究、规划和管理滞后等方面。 并针对存在的主要问题,提出了5项水资源可持续开发利用对策,包括节水对策、开源对策、改水对策、增补对策以 及管理对策。     

Mass Transfer, Oxygen Isotopic Variation and Gold Precipitation in Epithermal System: A Case Study of the Hishikari Deposit, Southern Kyushu, Japan

Abstract: Transportation of various kinds of elements occurred in wall rocks (Quaternary andesites) during the hydrothermal alteration accompanied by the Hishikari epithermal gold mineralization. For example, K₂O and MgO contents of wall rocks decrease away from the gold-quartz veins, while (CaO+Na₂O) content increases, and SiO₂ content is variable near the veins. Hydrothermal alteration zoning and bulk compositional variations in wall rocks suggest that the mixing of hydrothermal solution and acidic groundwater took place an important role as the cause for the hydrothermal alteration and bulk compositional variations. The relationship between dissolved silica concentration and temperature of hydrothermal solution mixed with groundwater is obtained based on precipitation kinetics-fluid flow–mixing model, and the computed results are compared with the distribution of SiO₂ minerals (quartz and cristobalite) in the hydrothermal alteration zones. This comparison suggests that the most reasonable flow rate of fluids migrating through hydrothermal alteration zones, and A/M (A: surface area of rocks interacting with fluid, M: mass of fluid) are estimated to be ca. 10^-4.2 m/sec, and ca. 0.10 m²/kg, respectively. The mixing of two fluids (hydrothermal solution and acidic groundwater) can also explain δ¹⁸O zoning in the altered country rocks, hydrothermal alteration zoning from K-feldspar through K-mica to kaolinite from the center (veins) to margin, and deposition of gold.     

鄂尔多斯盆地南缘彬县地区水文地球化学及铀成矿作用特征

水文地质作用是砂岩型铀矿成矿过程中不可缺少的重要作用之一。通过陕西彬县地区水文地质条件和水文地球化学环境分析,将中新生代地层地下水划分为松散岩类孔隙水、碎屑岩类孔隙裂隙水和碎屑岩类裂隙水3种类型。根据地下水的补给、径流、排泄条件,划分出水交替强烈带、水交替缓慢带和水交替滞缓带3个不同的水动力分带。不同类型地下水的含铀性、不同分带铀的运移和富集特征,以及酸、碱性地下水对围岩蚀变与铀成矿的作用表明,中侏罗统直罗组砂岩含矿含水层中铀成矿主要经历了沉积成岩时期铀的预富集作用、古地下水的后生改造叠加成矿作用和深部油田水的还原成矿作用,铀成矿作用为复合成因类型。     

Stability assessment and characterization of colloids in coastal groundwater aquifer system at Kalpakkam

Natural colloids have a potential role in facilitating the transport of radionuclides in groundwater. To assess the role of mobile colloidal phases in radionuclide transport, characterization of colloids for size, size distribution, zeta potential, surface charge and elemental composition is required. Groundwater samples were collected from 12 borewells in the study area and were characterized with respect to physicochemical parameters. Water quality parameters such as pH, temperature, specific conductance, TDS and dissolved O₂ were measured in situ. Based on salinity, two groundwater types were identified in the study area: (1) freshwater type and (2) brackish type. Laboratory and field-scale turbidity measurements in addition to quantitative analysis of major ions were carried out. It was observed that the colloid concentrations are reduced at higher salinity. Zetasizer, particle size analyzer, scanning electron microscopy, energy dispersive X-ray analysis and X-ray diffraction techniques were used to characterize the colloidal particles in groundwater. Colloids were present in all the groundwater samples, the concentration varying between 0.05 and 6 mg/L. Colloid concentration was greater in wells with low ionic strength and the number of colloidal particles varied between 3 × 10⁹ and 4 × 10¹¹ particles/L. The average colloid size varied between 200 and 350 nm for various samples. The zeta potential of the colloidal particles varied between −25.5 and –34.0 mV. SEM analysis of colloidal particles revealed the presence of clays particularly kaolinite and that the mineral composition of colloids reflects the mineralogy of the aquifer. For proper risk assessment and remediation studies, the role of colloids in radionuclide transport assumes greater importance. This study highlights the need for, and relevance of, detailed colloid characterization to assess its role in the migration of radionuclides from near surface disposal facilities.     

地下水系统中胶体的形成机理及其对污染物迁移的影响

胶体能有效地吸附地下水中的污染物并对其迁移距离及速度产生显著的影响 ,因此 ,研究胶体在地下水中的性质具有重要的意义。鉴于这一研究工作所存在的困难 ,叙述了在地下水中胶体的取样方法及分析技术 ,且以分析胶体在地下水系统中的形成机理为基础 ,对胶体的迁移与富集规律的定量模拟预测作了简要的介绍。     

A numerical simulation of impact of groundwater seepage on temperature distribution in karst collapse pillar

This paper presents an investigation of the impacts of groundwater seepage on temperature distribution in the karst collapse pillar (KCP). A thermal mathematic model with groundwater seepage was proposed, and a numerical model was established to describe the impacts of groundwater seepage on the temperature distribution in the KCP. The results show that the groundwater seepage velocity improved with the increasing permeability of porous medium in the KCP. The increasing seepage velocity improves thermal convection and then improves thermal conduction in the porous medium. As a result, the heat in the deep Ordovician limestone groundwater gradually diffuses. The seepage velocity occurred differently in different locations of KCP, and the heat exchange was also different, resulting in temperature differences for different locations. This temperature divergence in the surrounding rocks can reach 5~9°C at distances less than 50 m to the KCP. These findings can be used to protect the mine from water inrush by monitoring temperature changes in the surrounding rocks of KCP.     

冻融循环作用下节理岩体锚固性能退化机理和模式

岩土锚固的长期性能和耐久性是当前岩土工程界普遍关注的热点问题,也是影响锚固工程长期安全性的关键问题之一。节理岩体存在不同尺度、程度的损伤和缺陷,为地下水的存储和运移提供场所和通道。当达到孔隙水和裂隙水的冻结温度时,岩体中产生冻胀,并伴随着水分迁移,影响锚固系统的锚固性能,在冻融循环作用下,引起锚固系统长期性能和耐久性的退化。依据孔隙介质的冻结理论,建立了砂浆、岩石、砂浆-钢筋和砂浆岩石接触面静水压力学模型,分析其冻结机理。在总结岩石冻融损伤劣化研究成果基础上,深入系统地分析了节理岩体锚固系统的冻融损伤劣化机理及其影响因素,并建立冻融循环作用下节理岩体锚固性能退化的6种模式及其数学模型。     

隐伏矿地气地球化学勘查方法的影响因素及其作用方式

在介绍隐伏金属矿床地气勘查方法的基础上,探讨了上覆岩石、地层、土壤、地下水和近地表大气等地质体及采样方法对揭示隐伏金属矿床的地球化学异常特征的影响,认为地气异常是多成因的,主要来自隐伏矿床所行成的纳米级物质,同时受到隐伏矿床上覆岩石、地层、土壤、地下水和近地表大气等地质要素影响。其作用方式是幔源气对隐伏矿床上覆岩体与地层造岩及微量元素的迁移,土壤固相组分对气体中矿致异常纳米物质吸附与固定及土壤反应脱有机气体,土壤对大气或污染大气对土壤的物质扩散,而地气采集装置和方法对元素含量改变也有影响。     

烃源岩生排烃组分法模型研究与应用

本文提出了一种新的烃源岩生排烃组分法模拟模型。组分法生烃模型根据热模拟实验得到的组分产率曲线模拟烃源的生烃史。排烃模型包括开放体系模型和间歇开放体系模型，分别用于模拟以压实作用为主要动力的孔隙排烃和以异常高压为主要动力的微裂缝排烃。这一模型根据孔隙温度、压力和烃类组成，采用热力学方法模拟孔隙体系流体体积和相态的变化、不同组分在各相中的分布，并由此求出各组分的排出量和总排烃量。对陕甘宁盆地古生界源岩生排烃史的模拟结果表明，该模型具有实用价值。     

Column experiments to investigate transport of colloidal humic acid through porous media during managed aquifer recharge

Colloids act as vectors for pollutants in groundwater, thereby creating a series of environmental problems. While managed aquifer recharge plays an important role in protecting groundwater resources and controlling land subsidence, it has a significant effect on the transport of colloids. In this study, particle size and zeta potential of colloidal humic acid (HA) have been measured to determine the effects of different hydrochemistry conditions. Column experiments were conducted to examine the effects on the transport of colloidal HA under varying conditions of pH (5, 7, 9), ionic strength (<0.0005, 0.02, 0.05 M), cation valence (Na⁺, Ca²⁺) and flow rate (0.1, 0.2, 0.4 ml/min) through collectors (glass beads) to model the properties and quality of artificial recharge water and changes in the hydrodynamic field. Breakthrough curves showed that the behavior of colloidal HA being transported varied depending on the conditions. Colloid transport was strongly influenced by hydrochemical and hydrodynamic conditions. With decreasing pH or increasing ionic strength, a decrease in the peak effluent concentration of colloidal HA and increase in deposition could be clearly seen. Comparison of different cation valence tests indicated that changes in transport and deposition were more pronounced with divalent Ca²⁺ than with monovalent Na⁺. Changes in hydrodynamic field (flow rate) also had an impact on transportation of colloidal HA. The results of this study highlight the need for further research in this area.     

An overview of phosphate rocks and their mining impact on groundwater,Eastern Desert,Egypt

The Eastern Desert of Egypt represents a remote arid area which is scarce in water resources. The area is characterized by many mining sites to exploit the phosphate deposits; thus, these activities can generate groundwater contaminants. The main objective of the present study is discussing the effect of the mining activities and phosphate bearing rocks on groundwater. The obtained results pointed out that the water bearing formations can be distinguished as Quaternary alluvial, Oligocene sandstone, Campanian phosphate limestone (Duwi Formation), and Precambrian basement rocks. Some of the investigated groundwater shows relatively high concentrations of trace elements compared to other samples, such as Pb, Zn, Cu, Cr, Ni, and Sr. This is consistent with the analyses of phosphate rocks which are also enriched in the same trace elements. The high groundwater salinity is due to evaporation, limited re-charge, and leaching of salts in rocks. The results of speciation modeling reveal that majority of groundwater samples are supersaturated with calcite, aragonite, and dolomite, and some samples are also at equilibrium or supersaturated with hydroxyapatite. The groundwater quality in the study area evaluated for human drinking, livestock and poultry domestic, and industrial purposes is not suitable in most wells. It is obvious that the groundwater contamination occurs when drilling wells penetrate the phosphate bearing beds and not only at mining activity sites. Therefore, it is recommended to avoid any groundwater exploration from the Duwi Formation and also select the drilling sites outside the mining areas.     

Groundwater Systems and Resources in the Ordos Basin, China

The Ordos Basin is a large-scale sedimentary basin in northwestern China.The hydrostratigraphic units from bottom to top are pre-Cambrian metamorphic rocks,Lower Paleozoic carbonate rocks,Upper Paleozoic to Mesozoic clastic rocks and Cenozoic deposits.The total thickness is up to 6000 m.Three groundwater systems are present in the Ordos Basin,based on the geological settings,i.e.the karst groundwater system,the Cretaceous clastic groundwater system and the Quaternary groundwater system.This paper describes systematically the groundwater flow patterns of each system and overall assessment of groundwater resources.     

Analysis of colloidal transfer of strontium-90 with groundwater

The colloidal fractions of various particle sizes were separated from the samples of groundwater in the area of radioactive contamination nearby Obninsk (Kaluga region, Russia). The primary component of the radioactive contamination is ⁹⁰Sr isotope. The colloidal particles were separated from the samples of groundwater by means of ultrafiltration through membranes of 200, 100, and 25 nm pore sizes. The chemical composition of particle surfaces in each of the fractions was determined using X-ray photoelectron spectroscopy. The structure of particles was determined by the changes in the surface composition after the removal of outer layers of particles by etching with argon ions to a depth of 100 Å. It was found that the particles are constituted by inorganic cores mainly of montmorillonite and iron metahydroxide and a broken covering of humic acids. It was shown that about 50% of ⁹⁰Sr is transferred by groundwater with colloidal particles of over 25 nm in size.