【作者】 周骏；

【导师】 郑西来；

【作者基本信息】 中国海洋大学 ， 环境工程， 2010， 博士

【摘要】 随着经济的发展和人口的增加,滨海地区水资源日益紧缺。由于地下水的过量开采,导致海水入侵现象日趋严重。目前,对于海水入侵的修复方法主要是人工回灌含水层。但在回灌过程中,由于水文地球化学和水动力学的扰动,会引起咸-淡水界面和水-气界面的胶体颗粒释放、絮凝、迁移-沉积等一系列过程。这一系列胶体过程,会导致含水层结构的破坏和渗透性的突变,进而降低含水层修复效率。本文在系统分析、测定研究区(青岛大沽河下游)含水介质、胶体、水样的物理化学性质的基础上,通过室内批量试验、砂柱试验、显微镜切片试验、微型玻璃柱等方法,从微观和宏观尺度上对咸-淡水界面和水-气界面上的胶体过程及其影响效应进行了研究。通过批量和砂柱试验对咸淡水界面在咸-淡水界面胶体过程及其影响效应进行了定量研究。研究发现,(1)通过批量和砂柱试验证实粘土颗粒的临界释放浓度(CSC)和临界絮凝浓度(CFC)存在明显差异,临界絮凝浓度低于临界盐浓度。试验确定了粘土颗粒对于NaCl溶液和海水/河水混合溶液的临界盐浓度分别为60mmol/L和6800μs/cm,临界絮凝浓度分别为40mmol/L和4800μs/cm。释放出来的颗粒的絮凝对渗透性降低具有显著作用。(2)盐浓度突变和渐变试验结果显示,盐浓度突变试验中渗透性的降低幅度比盐浓度渐变试验时要大。盐浓度突变过程中大量被释放的颗粒引起的孔隙阻塞、中断是渗透性降低的主要原因。而盐度渐变过程中颗粒是逐步释放的,颗粒浓度较低,堵塞孔隙的可能性降低,孔隙堵塞作用对渗透性的影响比突变试验要小。因此,除了堵塞作用以外,粘粒的膨胀和被释放粘粒的絮凝、沉积对渗透性降低的作用显得更加重要。(3)通过定水头试验和定流速试验发现,定水头试验中渗透性的降低程度比定流速条件时渗透性的降低程度大,颗粒的累计流出量分别为138mg和236mg。在本试验条件下,粘土颗粒的运移速度均处于稳流态,佩克列数(Pe)比较大。根据颗粒佩克列数与无量纲的堵塞参数γ之间的回归方程分析可以发现,在本试验条件下,颗粒的堵塞现象比较轻。沉积颗粒引起的水动力阻力很小,水动力阻力主要是多孔介质造成的。通过显微镜切片和微型玻璃柱试验,利用激光共聚焦扫描电镜和ImageJ软件计算对水-气界面上胶体颗粒释放进行了定量研究。(1)胶体颗粒在水-气界面上存在明显的释放。绝大部分的颗粒释放都发生在第一次界面移动过程中。疏水胶体比亲水胶体更易被水-气界面所吸附,因此更易释放。对于疏水胶体来说,不论带正电还是带负电的胶体,颗粒的释放率都比较高,且差别不大；而亲水的胶体颗粒,带负电胶体颗粒的释放率明显高于带正电的胶体颗粒。(2)胶体颗粒的释放率随着界面移动速度的加快而降低。在相同流速下,带负电胶体颗粒释放率更高,带正电胶体的释放对水-气界面的移动速度更敏感。在本试验条件下,水-气界面移动速度较低(0.4-400cm/h),胶体颗粒的释放率均比较高,胶体颗粒的释放与界面移动速度成非线性关系。(3)前进接触角和后退接触角对于胶体颗粒在水-气界面上释放的影响存在明显差异。从激光共聚焦扫描电镜图像中看出,在界面移动速度相同的条件下,前进接触角为实际接触角时,水-气界面上的胶体颗粒含量明显高于后退接触角为实际接触角时界面上的胶体颗粒含量。两者的释放差值最大可达到58.8%左右,两者的差值随着流速的增加而减小。(4)在不同盐浓度条件下,水-气界面上均有胶体颗粒释放。当盐浓度高于临界离子强度(6000μm/cm)时,胶体颗粒的释放量基本不变；离子强度低于该值时,界面上的颗粒浓度随盐浓度的降低而升高。更多还原

【Abstract】 With the economic development and population increase, the shortage of water resource is increasingly serious in the coastal region. The excessive exploitation of groundwater leads to seawater intrusion. Nowadays, the main recovery method of seawater intrusion is artificial recharge. However, the disturbance effects of hydro geochemistry and hydrodynamic lead to a series of processes as colloids release, flocculation, transport and deposition on the sea-fresh water interface and air-water interface These processes can lead to the destruction of aquifer and the sudden change of permeability, which in turn can render restoration efforts ineffective. Adopting batch experiments, packed column experiment, microscope slide experiment, minisize glass column, taking the aquifers sample containing minim clay mineral (mainly illite) in Dagu River aquifer, this paper studies the series colloids behavior and it effect on permeability.(1) Using both batch and packed column experiment, we find the difference in critical solution concentration (CSC) and critical flocculation concentration (CFC). For NaCl solution, the critical solution. concentration and critical flocculation concentration are 60mmol/L and 40mmol/L; for seawater and freshwater mixed solution, the critical solution concentration and critical flocculation concentration are 6800μs/cm and 4800μs/cm. Colloids flocculation is an important factor for permeability decrease. (2) The result of abrupt salinity change experiments and gradual salinity change of experiments show that the permeability in the abrupt salinity change decreased by 60%, but in the gradual salinity change reduced only 50%. Abrupt changes in salinity can lead to a flush of particle release, which in turn then leads to pore clogging due to a jamming effect and then to a reduction of permeability. A gradual change in salinity, on the other hand, leads to a more gradual particle release and there is less chance for pore jamming. So flocculation and swelling is very important for permeability decrease in during gradual salinity change. (3)The permeability decreased more during constant head than during constant flux, Indeed, the total amount of particles flushed from the constant-flux column was 236 mg, but only 168 mg from the constant-head column. The flow regime for particle transport in all our experiments was dominated by advection. The particle Peclet numbers were large. Based on a regression equation relating the particle Peclet number to a dimensionless clogging parameter y. We can find that there was little hydrodynamic drag imposed on the flow by deposited particles, and that most drag was imposed by the collector.We use microscope slide and minisize glass column to study the colloids release on the air-water interface. The colloids release is visualized using confocal laser scanning microscopy and quantified by image analysis. The result show that there are many colloids released on the air-water interface. Most of colloids are release in the first interface movement. The hydrophobic colloids detached in larger amounts than did the hydrophilic colloids. For the hydrophilic colloids, detachment of the positively-charged colloids is significantly less than of the, negatively-charged colloids. For the hydrophobic colloids, no significant difference in detachment between positively-and negatively-charged colloids. Removal of colloids increase with decreasing velocity of the air-water interface. The positively-charged colloids were more sensitive to interface velocity than the negatively-charged colloids. However, Under this experiment condition (0.4-400cm/h), the relationship between detachment and velocity was not linear. Under advancing contact angle condition, the amount of released colloids is larger than under advancing contact angle condition, the difference of rate of detachment colloids can be up to 58.8%. When the salt concentration is high than critical solution concentration, the concentration on the air-water interface is similar. However, when the salt concentration is lower than critical solution concentration, the colloids concentration increase with the salt concentration decrease.更多还原