硫酸根离子在弱透水层中的迁移行为

通过研究地下水中硫酸根离子通过弱透水层时迁移特征的变异规律及其环境效应作用,分析在不同黏性土壤厚度条件下硫酸根离子浓度的变化及其受pH、Eh、钙离子浓度变化的影响特征,以及在不同pH 值条件下硫酸根离子的浓度变化情况。利用土柱填装及淋滤法,得出地下水中硫酸根离子通过弱透水层时穿透能力很强的结论,并揭示了硫酸根离子浓度随渗透土壤厚度的增大而增大,随淋滤液pH 值增大而减小的规律。     

氨氮在弱透水层中的渗透迁移规律研究

通过渗透试验、吸附试验和高压动态土柱试验对氨氮在弱透水层中的渗透、迁移转化规律进行研究。试验结果表明,弱透水层对氨氮具有很强的吸附能力;弱透水层中生物作用微弱,弱透水层对氨氮的去除主要是非生物作用的结果;硬度或其他交换性离子的作用会影响氨氮在弱透水层的穿透时间和吸附稳定性。此研究对揭示深层地下水的氮污染规律及探索地下水污染修复提供理论支持。     

长江河口地区全新世以来的弱透水层孔隙水地球化学特征及成因分析

弱透水层孔隙水反映了土体沉积时的原始溶液, 对于古气候重建具有重大作用。为了解析长江河口地区全新世以来弱透水层孔隙水的补给及其盐分来源, 采集易溶盐、土工、潜水、近岸海水等样品。采用易溶盐指标结合土工指标(含水率、湿密度、比重)获取了研究区弱透水层孔隙水的水化学特征。采用二端元法、Piper三线图、Gibbs图、离子比值法等解析了孔隙水的补给及其盐分来源。结果表明: 孔隙水矿化度介于1.16~32.79 g/L, 平均值为10.68 g/L, 盐水占比最高, 其次为咸水和微咸水。孔隙水类型以Cl-Na型(85.6%)为主, 其次从高到低依次为Cl-Ca·Mg、HCO3-Ca·Na、HCO3-Ca、Cl-Ca型。当地潜水类型为HCO3-Ca型, 深层孔隙类型为Cl-Na型, 说明深层孔隙水保留了土体沉积时的环境信息。中层与浅层孔隙水受到了大气降水补给、人类活动、蒸发作用等表层作用影响, 孔隙水水化学数据较为离散。孔隙水的δ18O与δD数据说明孔隙水样点受到了海水混合作用与蒸发作用的叠加影响, 蒸发作用较为强烈。孔隙水海水补给比例介于30.2%~87.0%, 大气降水补给比例介于13.0%~69.8%。土体中的盐分主要来自全新世海侵(海源)与蒸发盐岩溶解、长石风化溶解(地壳源)。海水补给深层孔隙水盐分的比例约为37%, 其余盐分主要来自地壳源。     

Hyperfiltration of Nacl Solutions Using a Simulated Clay/Sand Mixture at Low Compaction Pressures

It is widely recognized that clays and shales can demonstrate membrane properties. When a hydraulic head differential exists across a membrane-functioning clay-rich barrier, some of the solute is rejected by the membrane. This process is known as hyperfiltration. Some shallow geologic environments, including aquitards bounding shallow perched aquifers and unconfined aquifers, some river and stream beds, and some lake bottoms contain clay–soil mixes. Many engineering structures such as landfill liners, mixed soil augered barriers, and retention pond liners also consist of soil–clay mixes. No previous testing has been performed to investigate the likelihood that hyperfiltration may occur in such mixed soils. Therefore, we performed five experiments using different mixes of Na-bentonite and glass beads (100, 50, 25, 12 and 0% clay) to determine if any of these mixes exhibited membrane properties and to investigate what effect clay content had upon the membrane properties of the soil. Each mixture was compacted to 345 kPa and the sample mixtures were 0.58–0.97 mm thick. All the experiments used an approximately 35 ppm Cl⁻ solution under an average 103 kPa hydraulic head. Experimental results show that all the simulated clay–sand mixtures do exhibit measurable membrane properties under these conditions. Values of the calculated reflection coefficient ranged from a low of 0.03 for 12% bentonite to 0.19 for 100% bentonite. Solute rejection ranged from 5.2% for 12% clay to a high of over 30% for the 100% clay. The 100% glass bead sample exhibited no membrane properties.     

弱透水层中有机污染物(菲)的衰减研究

本文以高渗透压渗流试验装置模拟已被污染的浅层地下水越流通过弱透水层污染深层地下水的过程,研究了有机污染物(菲)通过饱和粘性土弱透水层时的自然衰减特征,以及非生物因子-配位体对于弱透水层中菲迁移转化的影响作用。研究表明,菲的衰减曲线明显分为三阶段:初期吸附截留显著期,中期微生物降解旺盛期,后期微生物降解稳定期;溶液中共存离子HCO 3-、Ca2+与菲形成络合物,SO42-参与菲的生物降解;溶液中主要配位体不同时,菲与阴、阳离子之间相互作用的方式也不同,以络合作用为主。渗透水中菲含量有99%以上被衰减,仅有极少量菲穿透弱透水层。     

哈密盆地多层含水系统地下水流数值模拟

对具有多层含水结构的哈密盆地地下水系统, 提出了一类考虑弱透水层弹性释水作用的地下水流耦合数学模型。利用实际资料的数值模拟结果表明, 与忽略弱透水层弹性释水作用的数学模型相比, 其精度提高、更符合实际的水文地质条件, 为定量评价多层越流系统地下水资源提供了一种实用可靠的数值方法。      

土工膜-防渗墙-弱透水层联合防渗的有效性分析

深厚覆盖层坝基往往都是强弱互层结构,坝基中存在弱透水层。弱透水层既是隔水层又是软弱夹层,是否利用其作为控渗依托层关系到工程难度、进度及成本。绝大多数工程都将全封闭式防渗体作为控渗首选方案,保守的设计理念导致采用半封闭式防渗体控渗的工程少之又少。西藏多布水电站采用土工膜-防渗墙-弱透水层三位一体半封闭式联合防渗体,在国内外少见,具有一定代表性,其防渗效果具有重要的参考价值和借鉴意义。本文基于详细的地质构造资料,以非饱和土体渗流、比奥固结理论和土体的非线性流变理论为基础,考虑土体水力学及土力学参数随双场耦合的动态变化关系,借助ADINA建立流固耦合模型,全方位分析多布水电站的渗流场、应力场,以及弱透水层的承载力和液化性。研究表明:土工膜-防渗墙-弱透水层三位一体半封闭式防渗体能有效降低渗透速度、渗流量和抑制渗透坡降,各渗流参量满足控渗要求;大坝及防渗墙的水平位移、沉降和应力相对悬挂式防渗体有一定增大,需提高防渗墙的强度。弱透水层是防渗体系中最重要的部分,经分析弱透水层承载力满足要求,且不会发生液化。对比分析三种防渗体系,多布水电站现采取的土工膜-防渗墙-弱透水层三位一体半封闭式联合防渗体是最佳方案,可减小防渗墙深度近193m。该研究成果对类似工程具有重要的参考价值和借鉴意义。     

多层介质含水系统中石油类污染预测评价：以大庆市纳污湖泡区为例

本文选取大庆贴不贴泡区的多层介质含水系统为研究对象,在分析水文地质条件和研究各层介质渗透规律的基础上,运用地质统计学方法和数值模拟技术建立起此类含水系统中石油类污染运移数值模拟模型,应用所建模型对地下水污染趋势进行了预测,并提出了污染控制措施。     

pH 值对有机磷在弱透水层中迁移转化的试验模拟

为研究渗透水pH 值对有机磷通过弱透水黏土层迁移转化的影响规律,采用黏性土层充压渗透装置模拟污染潜水中有机磷渗透通过弱透水层的迁移转化过程。研究发现,有机磷组分通过弱透水层的迁移能力总体较弱,不同pH 值条件下有机磷的矿化率为93. 5% ～ 99. 95%; 在进水pH 值为5. 5 ～ 8. 5 时,进水pH 值越高,土层中磷酸酶的活性也越高,降解转化有机磷的能力也越强; 黏土对有机磷的阻滞能力也增强。进水pH 值为5. 5 时,迁移率为6. 5%; 当pH 达到8. 5 时,矿化率明显增加,迁移率＜ 0. 05%,使其不易渗入深层地下水引起污染。     

Subsurface hydrology of tile-drained headwater catchments: Compatibility of concepts and hydrochemistry

Concepts and terms used in previous multidisciplinary studies of tile-drained aquitard-dominated catchments (TDADC) are inconsistent and confusing. We provide a well-defined, comprehensive conceptual model of the subsurface hydrology of TDADC by selecting seven mutually compatible and consistent concepts. These concepts are: (1) groundwater as the main source of baseflow in headwater streams, (2) dominance of ‘pre-event’ water in stormflow, (3) importance of both macropores and matrix, (4) changes in flowpaths with rate of stream discharge, (5) dominance of shallow, lateral subsurface flow, (6) interactive nature of subsurface water, (7) transpiration of groundwater. This conceptual model was successfully ‘field-tested’ by examining data collected in a TDADC in a rural area of southern Ontario, Canada. The data consist mainly of chemical and isotopes tracers in water samples (headwater streams, groundwater, precipitation, tile water, soil-surface water), supplemented by water levels and meteorological data.