共查询到20条相似文献，搜索用时 140 毫秒
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为查明有机质微生物降解过程对地下水系统中碘迁移富集的影响,以大同盆地为研究区,对区内22组地下水样品进行了水化学和生物标志物研究。水化学分析结果表明,地下水碘质量浓度为5～1 212μg/L,其中,56.52%的地下水样品中碘质量浓度超过饮用水标准限定值150μg/L。地下水样品生物标志物分析结果显示,可提取饱和烃中存在大量"未分辨组分(UCM)";CPI_1和CPI_2分别为0.38～1.03和0.27～1.19;低相对分子质量正构烷烃无明显奇偶优势。上述生物标志物特征表明,含水层中有机质经历了强烈的微生物降解。有机质微生物降解产生的HCO_3~-通过竞争吸附,导致沉积物中吸附态碘的解吸附并在地下水中富集。此外,有机质的微生物降解有利于迁移能力强的低相对分子质量有机质或有机胶体的形成,该类有机物通过吸附或螯合作用进一步促进碘在地下水中的富集。 相似文献
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根据野外调查及取样分析,文章分析了某中小城市生活垃圾场区地下水污染组分特征,建立了研究区污染组分CODcr和Cl-的数学迁移模型,进行了CODcr、Cl-污染因子在地下水中的迁移模拟。模拟结果与实测值基本一致,证明建立的数学模型是合理的,并解释了类似Cl-的较为稳定的污染组分和类似于CODcr的易降解吸附污染组分在该区地下水中的迁移规律。 相似文献
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在分析废旧金属拆解场地浅层地下水中芘的检出和分布特征的基础上,对地下水中芘的污染来源、污染途径和污染控制因素进行了探讨.研究结果表明,场地中心和地下水下游2km范围内芘污染明显,垂直于地下水流向芘迁移距离较小,一般小于0.5km.芘在地下水中的迁移转化受地下水中pH、Eh及DO等因素的控制,弱酸性或中性环境以及厌氧强还原条件下,芘易于检出和迁移,一般难以生物降解. 相似文献
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本文根据国内外对于地下水系统中有机物质的行为特征的研究现状,综合介绍有机物质在地下水系统中的吸附-解吸作用,对重金属迁移的制约作用、对流-弥散迁移作用。为认识和了解有机物质在地下水中的行为特征提供一点资料。 相似文献
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在收集查阅国内外已有研究资料的基础上,对地下水中胶体稳定性、迁移机制以及模拟预测方法进行了详细归纳和总结。研究表明,胶体稳定性主要受自身理化性质和水文地球化学条件的影响,其受控于胶体粒径、形态、电势电位以及地下水的pH、离子强度等条件。胶体在多孔介质中的迁移机制主要表现为胶体沉积和形变阻塞,其中针对胶体稳定性的差异性,胶体沉积过程分别表现为表面封阻和过滤熟化。目前有关胶体在地下水中迁移的模拟技术已发展得日益成熟,但结合多孔介质非均质性和胶体化学性质非均质性的数学模型还需进一步探讨。 相似文献
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镎是放射性废物中的关键核素,研究镎在地下水中的存在形态及影响因素,可为今后研究镎在地质介质中的迁移行为及迁移规律,提供必要的资料支持和指导。这里运用PHREEQC模拟软件计算了镎在西北某区钻孔地下水中的存在形态,并讨论了水温、pH值以及pe值对镎存在形态的影响。结论是镎的存在形态受pH值及pe值的影响较大,但温度对镎存在形态的影响较小。 相似文献
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《Applied Geochemistry》1991,6(5):565-574
Natural colloids (1–450 nm) and suspended particles (>450 nm) were characterized in groundwaters of the Whiteshell Research Area of southern Manitoba to evaluate their potential role in radionuclide transport through fractured granite. Data on particle concentrations, size distributions, compositions and natural radionuclide content were collected to predict radionuclide formation and to provide a database for future colloid migration studies. The concentrations of colloids between 10 and 450 nm ranged between 0.04 and 1 mg/l. The concentrations of suspended particles, which require higher groundwater velocities for transport, varied from 0.04 to 14 mg/l. Colloid (10–450 nm) concentrations as low as these observed in Whiteshell Research Area groundwater would have a minimal effect on radionuclide transport, assuming that radionuclide sorption on colloids is reversible. If radiocolloid formation is not reversible, and radionuclide-containing colloids cannot sorb onto fracture walls, the importance of natural colloids in radionuclide transport will depend upon particle migration properties. 相似文献
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《Applied Geochemistry》1993,8(6):605-616
The Cigar Lake U deposit is located in northern Saskatchewan in the eastern part of the Athabasca Sandstone Basin, and consists of a high-grade ore body (up to 55% U) located at a depth of ∼430 m. As part of a study to evaluate the analog features of this deposit with respect to a disposal vault for waste nuclear fuel, colloids (1–450 nm) and suspended particles (450nm) in groundwater have been investigated to evaluate their effect on element transport through the U deposit. Tangential-flow ultrafiltration was used to concentrate particles from 501 groundwater samples in order to characterize the size distribution, concentration, composition and natural radionuclide content of particles in representative parts of the U deposit. Although Cigar Lake groundwaters contain particles in all sizes ranging from 10 nm to slightly larger than 20 μm, most samples contained a relatively high concentration of colloids in the 100–400 nm size range. Particle compositions are similar to the composition of minerals in the sandstones and ore body, suggesting that particles in groundwater are generated by the erosion of fracture-lining minerals. As a result, particle concentrations in groundwater are affected by the integrity of the host rock. In some piezometers the high initial concentrations of suspended particles, which may have been drilling artifacts, decreased during the collection of the first 350 1. Although colloid concentrations fluctuated during sampling, there are no indications that these concentrations will be permanently reduced by continued groundwater pumping. The observed colloid and suspended particle concentrations in the deep groundwaters are too low to have a significant impact on radionuclide migration, provided that radionuclide sorption is reversible. If radionuclides are irreversibly sorbed to particles they cannot sorb to the host rock and their migration can only be evaluated with an understanding of particle mobility. The data for dissolved and particulate U, Th and Ra were used to calculate field-derived distribution ratios (Rd) between particles and groundwater. The wide range of observed Rd values indicates that these radionuclides in particulate form are not in equilibrium with groundwater. U-series isotope data indicated that most of the U and Ra on particles was derived from groundwater. Some particles could have retained their U for as long as 8000 a. The U and Ra contents of particles in the ore and surrounding clay zones are significantly higher than in particles from sandstone, suggesting that the clay has been an effective barrier to particle migration. 相似文献
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为了对地下水系统中天然胶体与Ni2+的共迁移特征进行研究,通过静态吸附实验和石英砂模拟含水层介质柱实验研究了土壤胶体对Ni2+在地下水中运移的影响,以及pH、离子强度（IS）、有机质等对土壤胶体吸附Ni2+的影响。结果表明：随着pH值升高,土壤胶体对Ni2+的吸附量增加;离子强度的增加会显著地降低土壤胶体吸附Ni2+的能力;腐殖酸（HA）的存在会增强胶体对Ni2+的吸附能力;在有胶体的情况下,Ni2+穿透砂柱的时间会缩短,吸附能力增强,吸附量增加,但当离子强度增加时,虽然Ni2+穿透砂柱的时间也被缩短,但是吸附量却降低。 相似文献
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Rachid Ait Akbour Jamaâ Douch Mohamed Hamdani Philippe Schmitz 《Comptes Rendus Geoscience》2002,334(13):981-985
To evaluate the risk of contaminant transport by mobile colloids, it is necessary to understand how colloids and associated pollutants behave during their migration through uncontaminated soil or groundwater. In this study, we investigated the influence of aggregation induced by Ca2+ and trace metals (Pb2+, Cu2+) concentrations on the transport of humic-coated kaolinite colloids through a natural quartz sand at pH=4. Adsorbed divalent cations reduce the colloids surface charge and thereby induce aggregation and deposition in porous media. To cite this article: R. Ait Akbour et al., C. R. Geoscience 334 (2002) 981–985. 相似文献
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Compacted bentonite has been considered as a candidate buffer material in the underground repository for the disposal of high-level radioactive waste. An erosion of bentonite particles caused by a groundwater flow at the interface of a compacted bentonite and a fractured granite was studied experimentally under various geochemical conditions. The experimental results showed that bentonite particles could be eroded from a compacted bentonite buffer by a flowing groundwater depending upon the contact time, the flow rate of the groundwater, and the geochemical parameters of the groundwater such as the pH and ionic strength.
A gel formation of the bentonite was observed to be a dominant process in the erosion of bentonite particles although an intrusion of bentonite into a rock fracture also contributed to the erosion. The concentration of the eroded bentonite particles eroded by a flowing groundwater was increased with an increasing flow rate of the groundwater. It was observed from the experiments that the erosion of the bentonite particles was considerably affected by the ionic strength of a groundwater although the effect of the pH was not great within the studied pH range from 7 to 10. An erosion of the bentonite particles in a natural groundwater was also observed to be considerable and the eroded bentonite particles are expected to be stable at the given groundwater condition.
The erosion of the bentonite particles by a flowing groundwater did not significantly reduce the physical stability and thus the performance of a compacted bentonite buffer. However, it is expected that an erosion of the bentonite particles due to a groundwater flow will generate bentonite particles in a given groundwater condition, which can serve as a source of the colloids facilitating radionuclide migration through rock fractures. 相似文献
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Polychlorinated biphenyls (PCBs) are the main constituents of clophen (the liquid of the electric transformers and capacitors)
and have been characterized as potential human carcinogens. PCBs can be a hazardous contaminant of soil and groundwater. We
used the mathematical model variably saturated 2D flow and transport (VS2DT model) to simulate the transport of PCBs from
the soil surface to groundwater for a time period of 30 years. We also used a mathematical model to simulate the colloid-facilitated
PCB transport, under saturated flow conditions. The results showed that PCBs dissolved in water cannot be transported to large
depths in unsaturated soils, because of their strong sorption onto soil and low solubility in water. For soils with very low
or no organic matter content, PCB transport is much faster and the probability of groundwater contamination is much higher.
PCBs can partition to colloids originating from dissolved organic matter in groundwater. Colloid-facilitated PCB transport
is faster compared to PCB transport in aqueous solution with no colloids present. 相似文献
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《Applied Geochemistry》2001,16(14):1653-1662
Strontium-90 (90Sr) is one of the major radioactive contaminants found in DP Canyon at Los Alamos, New Mexico, USA. Radioactive surveys found that 90Sr is present in surface water and shallow alluvial groundwater environments in Los Alamos National laboratory (LANL). Colloids may influence the transport of this radionuclide in surface and groundwater environments in LANL. In this study, the authors investigated the sorption/desorption behavior of radioactive Sr on Ca-montmorillonite and silica colloids, and the effect of ionic strength of water on the sorption of Sr. Laboratory batch sorption experiments were conducted using 85Sr as a surrogate for 90Sr. Groundwater, collected from Well LAUZ-1 at DP Canyon and from Well J-13 at Yucca Mountain, Nevada, and deionized water, were used. The results show that 92–100% of the 85Sr was rapidly adsorbed onto Ca-montmorillonite colloids in all three waters. Adsorption of 85Sr onto silica colloids varied among the three waters. The ionic strength and Ca2+ concentration in groundwater significantly influence the adsorption of 85Sr onto silica colloids. Desorption of 85Sr from Ca-montmorillonite colloids is slower than from silica colloids. Desorption of 85Sr from silica colloids was faster in LAUZ-1 groundwater than in J-13 groundwater and deionized water. The results suggest that clay and silica colloids may facilitate the transport of Sr along potential flowpaths from DP Canyon to Los Alamos Canyon. 相似文献
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Stability assessment and characterization of colloids in coastal groundwater aquifer system at Kalpakkam 总被引：1，自引：0，他引：1
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. 相似文献
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To establish when the presence of colloids can favour contaminant migration is a critical task for the performance assessment of a high level radioactive waste repository. In this study, the effects of the presence of bentonite colloids on the migration of highly sorbing elements, such as Eu and Pu, in a granite environment were investigated. Special efforts were made to quantify the filtration of bentonite colloids in this medium and to determine the experimental uncertainties that could bias the interpretation of the results. 相似文献
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《Applied Geochemistry》2000,15(2):171-179
The origin and mobility of humic colloids in the Gorleben aquifer system have been examined. For this purpose, the distribution of humic colloids and relevant hydrological and geochemical parameters were examined. An investigation area was selected where sediments have been disturbed by salt dome uplift and glacial events. It is shown that, on a local scale, considerable groundwater movement and intermixing takes place from the surface down to the salt dome. Consequently no effective separation of groundwater layers occurs. Two different humic colloid sources are identified: influx from the humus horizon with recharge water and continuous in situ generation via mineralization of sedimentary organic carbon (SOC). The in situ generation leads to groundwaters with humic colloid concentrations approaching 0.4 g/L, compared to concentrations of less than 0.005 g/L in recharge waters. Young groundwaters (no 14C decay detected) between approximately 50 and 200 m depth exhibit these highly elevated humic colloid concentrations. At greater depth, salt brines are found with low humic colloid concentrations. This can be attributed to precipitation of humic acid and/or hampering of the in situ generation process due to the high salt content. There is no indication of retention or decomposition of humic colloids. The fate of in situ generated humic colloids cannot be precisely evaluated due to analytical limitations and insufficient understanding of groundwater movement. 相似文献