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1.
沐官岛水库是一个拟建的河口海湾水库,库底为富含咸水的潮滩沉积物。这一特殊的地质及水环境条件直接关系到水库未来的水质安全和正常的调度运行,所以必须准确地确定水库水体中盐分空间分布这一关键问题。本文依据现场调查、钻探及室内实验资料,通过垂直方向线性插值技术,建立了沐官岛水库蓄水初期盐分运移准三维模型,模拟了水库蓄水初期在内源盐分释放影响下,库水盐分的演化过程。结果表明:若遇平水年开始蓄水,当蓄水至1.5m时,该层含盐量在平面上的变化范围主要在0.30~1.30g/L之间;当蓄水至4.5m时,该层含盐量在平面上的变化范围主要在0.30~1.55g/L。 相似文献
2.
为了探讨海湾水库蓄水初期单次往复水平密度流的产生与效应,进行砂质斜坡沉积物与水体之间盐分交换的水槽实验。通过沉积物孔隙水与其上覆水的多剖面电导率动态监测,分析盐分的时空分布特征,并计算深水区、浅水区和中心区的边界层单位面积含盐总量。实验结果显示,进水在浅水区沉积物表面产生明显的渗入-溢出现象,浅水区沉积物孔隙水盐分浓度显著低于中心区与深水区同一高度的盐分浓度,深水区初始底边界层含盐量与初始边界层下边界盐分浓度均为最高;这表明进水过程在倾斜沉积物表面产生了前进密度流,水流携带的盐分在坡底累积。水槽进满水后深水区边界层含盐总量与边界层下边界盐分浓度快速降低,并且浅水区表层沉积物孔隙水与深水区同一深度水体之间的盐分快速达到平衡;这表明蓄水初期在两者之间形成了返回密度流,从浅水区表层沉积物冲刷出的盐分在密度流作用下再次进入沉积物。为避免再次进入沉积物的盐分在后期继续影响水库泛咸,建议在蓄水结束后尽快实施坡底咸水排除方案。 相似文献
3.
在野外调查的基础上, 研究不同钠吸附比(SAR)条件下滨海含水层胶体释放规律, 采集天津平原区代表性含水层土样, 采用室内批实验和土柱实验, 研究胶体释放浓度和释放量的动态特征, 识别不同含水介质胶体释放的差异性, 同时分析胶体颗粒释放过程中含水介质渗透性变异特征.结果表明, 在NaCl和CaCl2混合溶液系统中, 含水层含水介质胶体颗粒的释放与地下水溶液所含阳离子价态有关, Ca2+含量越高, SAR越小, 胶体越不容易释放出来, Ca2+对胶体释放的抑制作用越强烈.土柱实验表明不同吸附比情况下粉砂和中砂胶体释放浓度均很小; 当地下水中SAR为0和8时粉土胶体释放很少, 当溶液的SAR为∞时胶体有明显的释放, 释放浓度随孔隙体积数的增加而增加, 在52个孔隙体积数瞬时达到峰值73.76 mg/L, 然后缓慢减少, 最后累积释放量达0.13 mg/g.胶体释放过程中, 粉土、粉砂和中砂渗透性损失分别为98.2%、86.7%和95.9%;含水介质渗透性的降低主要是由于释放的胶体颗粒在空间上重新分布造成的. 相似文献
4.
为预测海湾水库沉积物盐分释放对库水咸化影响的持续时间,建立了描述沉积物孔隙水盐分剖面分布的非稳态数学模型,并优化选取模型的边界条件与关键参数(沉积物孔隙水盐分的扩散系数)。稳态与非稳态条件下沉积物盐分释放的对比分析表明,在计算污染沉积物对其上覆水水质的影响时间时,按非稳态释放更符合实际情况。非稳态盐分释放的计算结果表明,拟建沐官岛海湾水库沉积物中盐分释放对库水咸化的影响时间将大于600年,该影响时间远长于水库的寿命;表明在水库的整个生命周期内,均需要定期监测海湾水库底层水的盐分浓度,并需采取有效措施预防水体的突然泛咸,而不能仅在建库初期关注咸化问题。 相似文献
5.
为了揭示天津滨海地区咸水储能回灌过程中含水层渗透性变化的机制,采用室内土柱试验的方法研究不同温度下咸水储能回灌过程中含水层胶体的释放量、释放速率以及胶体释放对含水层渗透性的影响,同时探讨了胶体释放过程中Ca2+的变化特征。研究结果表明,咸水储能回灌过程中含水层胶体释放是脉冲式的,表现为突然增加,然后缓慢降低,大约20个孔隙体积为一个周期;胶体累积释放量随着孔隙体积数的增加而增加;胶体释放量与孔隙体积数为分段函数,不同阶段胶体累积释放量增长幅度和释放速率发生变化。胶体释放过程中含水层的渗透系数随着孔隙体积数的增加呈“S”型曲线;0℃、10℃和20℃情况下咸水含水层渗透系数分别增加了4.02倍、12.21倍和6.63倍;不同温度下虽然含水层渗透系数开始有差异,但60个孔隙体积数后渗透系数均接近15 cm/d左右。胶体释放过程中也存在着Ca2+-K+、Na+ 阳离子交换作用,不同的温度下这种交换作用动态特征不同。 相似文献
6.
扩散边界层是水环境沉积物与上覆水之间物质交换的必经区。通过无风和有风条件下两组沉积物盐分释放实验,研究海湾水库砂质沉积物-水界面扩散边界层的形成情况,并通过水动力扰动下穿过扩散边界层的实测盐分通量与Fick第一定律理论计算通量的比较,以及扰动与无扰动时通量的比较,探讨扩散边界层对沉积物盐分释放的影响。研究结果表明,在稳定风场条件下,沉积物-水界面处存在厚度约3.5 cm的扩散边界层,有风条件下的界面盐分交换通量略大于无风时的通量;分子扩散是边界层内盐分运移的主要机制,扩散边界层对沉积物盐分释放具有阻滞作用,并且边界层越厚,阻滞效应越显著。另外,由于扩散边界层的存在,限制了水动力对沉积物与上覆水之间物质交换的增强作用,所以海湾水库沉积物中蓄积盐分对上覆水的影响将是长期的过程。 相似文献
7.
在现场调查和钻探的基础上,采集了沐官岛水库库区3种典型底质(粉质粘土、泥质粉沙和中细砂)的原状/扰动土样和地表水样,然后分别采用静水土柱和动水水槽试验测定盐分的时-空变化规律,最后定量计算出不同底质盐分的释放通量,从而为该海湾水库蓄水初期水质的评价和预测提供了科学依据.土柱试验表明,在分子扩散作用下高盐分区主要集中在水-沉积物界面之上7.5 cm的范围内,7.5 cm之上的水体盐分较为均一,底质盐分释放通量按粉质粘土、中细砂、泥质粉沙的顺序递减,盐分释放通量符合负的幂指数形式,而且抽排界面之上高浓度水体对降低水体盐分含量效果显著.根据水槽模拟试验,风的吹拂会影响到界面之上水体盐分的分层,有利于海湾水库中盐分的混合作用. 相似文献
8.
纳米二氧化钛(nTiO2)被广泛应用于去除水体中的重金属。磷酸盐作为水体中普遍存在的无机阴离子,能够对重金属离子在nTiO2上的吸附特征产生影响。本文聚焦磷酸盐存在条件下nTiO2胶体颗粒对典型重金属离子(Zn2+和Cd2+)的吸附行为,以电感耦合等离子体发射光谱法(ICP-OES)测定吸附平衡后水相中重金属离子的浓度。通过批量吸附实验考察不同水化学条件下(离子强度和共存阴离子),磷酸盐对nTiO2胶体颗粒吸附水体中Zn2+和Cd2+特征的影响规律。采用经典吸附等温线模型对实验数据进行拟合,并结合纳米颗粒的Zeta电位和粒径变化等表征手段揭示了相关吸附机制。研究发现：(1)磷酸盐的存在能有效地增强重金属在nTiO2上的吸附,Zn2+和Cd2+的最大吸附量分别由121.1mg/g和84.7mg/g增加至588.3mg/g和434.8mg/g,增加了3... 相似文献
9.
我国江苏北部连云港地区海相软土蒙脱石族矿物含量相对较高,且在海陆交互环境中沉积形成,沉积过程中具有孔隙水盐分较高的特点,但在后沉积过程中由于地表和地下淡水入侵,会使孔隙水盐分发生变化,而相应的次固结行为的变化规律尚不明晰,因此需要深入了解矿物成分、孔隙水盐分在软黏土次固结行为中的作用机制。由于天然软黏土的矿物成分、孔隙水成分差异较大,试验材料采用矿物成分均一的商用高岭土与膨润土组成的人工黏土作为研究对象,配制不同浓度的NaCl溶液作为孔隙水,模拟孔隙水盐分变化。通过常规固结试验,发现对于含蒙脱石矿物的人工黏土,压缩指数Cc随着盐分浓度的增加而减小,主固结完成时间随盐分的增加而提前,且同一应力水平下和孔隙比下,次固结系数随着盐分的增加而减小。在同样的上部荷载下,次固结系数与压缩指数的比值Cα/Cc不再保持为经验常数,而是随着孔隙水盐分的增加而偏离经验值,主要原因为盐分对水膜蠕变的影响。但是,对于主要由高岭石矿物构成的人工黏土,孔隙水盐分浓度则未对其次固结参数产生明显的影响。因此,如果场地的黏性土蒙脱石含量较高且孔隙水含盐量较高,则需要考虑孔隙水盐分的变迁对地基长期变形的影响。 相似文献
10.
冻结盐渍砂土单轴强度特性研究 总被引：5，自引：3，他引：2
通过对兰州盐渍砂土重塑土添加不同量的盐分来模拟不同含盐量的盐渍土, 并对其进行单轴抗压试验, 分析其在不同含盐量、不同温度及不同速率的应变加载情况下, 冻结盐渍砂土的单轴抗压强度的变化规律, 重点讨论了盐分对土体力学参数的影响以及弹性模量与含盐量、温度的关系. 结果表明: 易溶盐含量的增加会导致单轴抗压强度逐渐降低, 试验温度越低抗压强度会越大; 应变加载速率的增加会增大土体的单轴抗压强度, 同时会缩短土体达到应力峰值的时间; 土体含盐量越大弹性模量越小, 温度越低弹性模量越大. 相似文献
11.
《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
12.
针对中国北方海湾水库间歇来水、连续取水和沉积物动态释盐的特点,建立水量与盐分耦合的数学模型,以青岛拟建的沐官岛水库为例,探讨水位变化条件下混合型海湾水库库水盐分的影响因素、超标风险与达标条件。模拟结果表明,在水库水位连续降低条件下,毫米量级的日蒸发量对库水盐分的累积效应显著。在不利水文条件下,受沉积物释盐、水分蒸发与人工取水的影响,混合型海湾水库长期存在盐分超标的风险。与水位不变时相反,水位降低时库水盐分浓度随着取水量的增大而升高;因此,当库水盐分存在超标风险时,可以通过减少日取水量实现库水盐分达标。为保障安全供水,在海湾水库设计与运营管理阶段,均需要综合考虑水量-盐分因素进行水库的日取水量调算。 相似文献
13.
The first geological materials impacted by oil field wastes released into near-surface environments in southern Louisiana, USA, are typically clays and silts. Clay minerals within these siliciclastic sediments have the potential for altering the composition of produced water wastes through cation exchange. The general relations between the composition of adsorbed cations and interstitial water salinity in brine-contaminated samples from a site in southeastern Louisiana are consistent with previous studies of multicomponent exchange in groundwater systems of varying salinity. The divalent cations Ca and Mg dominate as adsorbed cations at low salinities (<1200 mg/L), but Na is dominant at moderate to high salinities (up to 53,000 mg/L). The change in the proportions of adsorbed cations is a non-linear function of salinity, and the transition from Ca-dominated adsorption to Na-dominated adsorption occurs over a narrow range of salinities. 相似文献
14.
S.K. Acharyya 《Gondwana Research》2005,8(1):55-66
Late Quaternary stratigraphy and sedimentation in the Ganga Alluvial Plain and the Bengal Basin have influenced arsenic contamination of groundwater. Arsenic contaminated aquifers are pervasive within lowland organic rich, clayey deltaic sediments in the Bengal Basin and locally within similar facies in narrow, entrenched river valleys within the Ganga Alluvial Plain. These were mainly deposited during early-mid Holocene sea level rise. Arsenic was transported from disseminated sources as adsorbed on dispersed phases of hydrated-iron-oxide. These were preferentially entrapped as sediment coatings on organic-rich, fine-grained deltaic and floodplain sediments. Arsenic was released later to groundwater mainly by reductive dissolution of hydrated-iron-oxide and corresponding oxidation of sediment organic matter. Strong reducing nature of groundwater in the Bengal Basin and parts of affected middle Ganga floodplains is indicated by high concentration of dissolved iron (maximum 9-35 mg/l). Groundwater being virtually stagnant under these settings, released arsenic accumulates and contaminates groundwater. The upland terraces in the Bengal Basin and in the Central Ganga Alluvial Plain, made up of the Pleistocene sediments are free of arsenic contamination in groundwater. These sediments are weakly oxidised in nature and associated groundwater is mildly reducing in general with low concentration of iron (<1 mg/l), and thus incapable to release arsenic. These sediments are also flushed free of arsenic, released if any, by groundwater flow due to high hydraulic head, because of their initial low-stand setting and later upland terraced position. 相似文献
15.
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
16.
Adams公式和Couch公式是利用沉积物中硼元素浓度对沉积水体古盐度进行定量恢复的常用方法,但由于两种方法的恢复结果经常存在较大差异,古盐度的计算结果常难以让人信服。为了验证Adams公式和Couch公式的可靠性,本次研究采集了青海湖布哈河口区不同沉积环境的表层沉积物和底层水体样品,处理后分别分析了沉积物中硼元素浓度、总有机碳（TOC）含量及矿物组成,同时对水体盐度及其硼浓度进行了测量,结果表明:湖泊水体中硼浓度与盐度存在极好的线性正相关性,但沉积物中硼元素的浓度与沉积水体中硼的浓度并无直接联系。根据沉积物中硼的浓度及黏土矿物含量和组成,分别采用Adams公式和Couch公式对水体盐度进行计算,盐度计算值均远高于水体盐度实测值,其中Adams公式的计算结果与实测值差别最大,盐度计算值与沉积物中硼含量呈正相关关系。沉积物中的硼元素主要由继承自母岩的硼、黏土矿物吸附硼和有机质中富集的硼三部分组成,只有黏土矿物中的吸附硼能够反映水体盐度。青海湖布哈河口区沉积物富含有机质,有机质对硼强烈的富集作用是导致Adams公式和Couch公式盐度恢复结果失效的重要原因,同时不同类型黏土矿物对硼吸附能力的差异也对恢复结果有重要影响:黏土矿物在盐水中的浸泡试验表明蒙脱石对硼的吸附能力最强,次为伊利石,高岭石吸附能力最差,推翻了Couch关于伊利石对硼吸附能力最强的认识。原Adams公式和Couch公式仅没有考虑有机质对硼的影响,对不同类型黏土矿物吸附能力的认识有误,不适合陆相沉积物沉积水体古盐度的恢复。沉积物黏土矿物中吸附硼浓度仍是反映沉积水体盐度的可靠指标,古盐度的恢复首先必须消除沉积物中有机质对硼的影响,然后根据一系列的浸泡试验确定不同类型黏土矿物对硼的吸附系数,并建立新的计算公式。 相似文献
17.
宁夏宁东煤田东北部地下水矿化度较高,且具有分布不均和变化较大的特点。通过分析地下水矿化度的空间分布特征,结合区域地质构造、地下水补给径流条件,借助Piper三线图、Gibbs图、离子比例系数等手段,深入研究高矿化度地下水的形成机制。结果表明,宁东煤田东北部地下水矿化度为0.30~23.56 g/L,平均值为5.84 g/L,淡水、微咸水、咸水、盐水所占比例分别为3.16%、50.00%、33.68%、13.16%。水平方向上,基岩裂隙水矿化度由东向西逐渐降低,在鸳鸯湖矿区南部形成高矿化度异常带。此外,在研究区西部及南北部的零星地区出现矿化度较高区。矿化度整体较高与石膏、盐岩及黄铁矿溶解和地下水长期滞流有关,而矿化度由东向西逐渐降低则受鄂尔多斯台地逆冲推覆构造前缘坳陷影响。鸳鸯湖矿区南部位于鄂尔多斯台地南北冲断体系的过渡带,褶曲较完整,地下水环境相对封闭,形成高矿化度异常带。垂直方向上,从Ⅰ含水层至Ⅴ含水层深部含水层的矿化度比浅部高,主要与深部地下水环境封闭,更新较慢有关。该研究将为相似矿区地下水资源开发与利用提供理论依据。 相似文献