【作者】 梁春；

【导师】 郑西来；

【作者基本信息】 中国海洋大学 ， 环境工程， 2011， 博士

【摘要】 随着世界对石油需求的不断增长,石油类已成为地下水-土环境中一类重要的有机污染物。特别是轻质石油制品(如各种燃料油、润滑油等),由于其粘滞系数较低,在土壤中的迁移能力较强,因此轻质石油的泄漏对地下水-土环境具有更大的污染潜力。本文以淄博重大石油化工区为研究背景,以标准石英砂及该区典型砂土、壤土作为代表性含水介质,以CD15W-40机油、0#柴油、93#汽油作为代表性轻质石油制品,系统研究了石油污染含水介质的水动力特性,探讨了石油污染对含水介质表面润湿性、毛细特性和水-盐动力学特性的影响机制,为石油污染场地的治理、修复等提供科学理论依据。通过一系列的试验研究,主要取得了以下几个方面的新认识和结论:(1)改进了石油污染含水介质含水量和含油量的测定方法。通过引入油烘干损失系数,改进了测定含水量的传统烘干法和测定含油量的萃取-紫外分光光度法,并提出了相应的新计算公式,解决了由于油、水相互干扰,难以简单、准确测定石油污染含水介质中油、水含量的难题,为后续理论研究提供了准确的数据支持。采用改进后的方法测定石油污染含水介质中含水量和含油量准确可靠,测定误差均仅为0.5%左右,主要产生于不可避免的仪器误差,且适用范围广,不受石油种类和挥发性的影响。(2)弄清了石油污染含水介质的表面润湿性变异规律。采用测定土壤斥水性的方法,研究了不同含油量下机油和柴油污染含水介质的湿润性变化规律。结果显示,随着石油污染程度的提高,介质斥水性显著提高。当介质中含油量达到一临界值时,介质表面润湿性开始发生变异,由亲水性变为疏水性。试验测得石英砂和粗砂产生斥水性的临界机油含量分别为0.3%、0.5%左右,临界柴油含量则分别为20%、14%左右;亚粘土产生斥水性的临界机油含量约为8%,而柴油污染对亚粘土斥水性的影响不显著。介质组成和油品组成对含水介质润湿性变化特征具有重要影响。(3)研究了石油污染含水介质表面的润湿反转特征。当油污介质中的含水量达到某一临界值时,介质表面润湿性可再次发生反转,由疏水表面变回亲水表面,斥水性消失。对于油污砂性土,较低的含水率即能使其润湿性再次发生改变,润湿反转的含水量阈值约为0.4~0.8%;对于机油污染亚粘土,其临界含水量随含油率的升高而增大,且两者在数值上近似相等。(4)系统研究了毛细水上升动力学和毛细带水分垂向分布规律。随着石油含量的增加,含水介质中毛细水上升高度和赋水能力显著降低,主要是由于石油污染含水介质的表面被油分吸附,使界面润湿接触角增大,表面疏水性增强,且由于油分填充在介质颗粒之间,堵塞了毛细水上升的通道。与柴油污染相比,机油污染对介质毛细性的影响更为强烈,而石油污染对粗砂毛细性的影响远大于对亚粘土的影响(5)建立了毛细水上升高度和速率的动力学表达式。不同机油、柴油含量下,砂土和亚粘土的毛细水上升高度和时间的对数关系分别可用二次多项式关系和线性关系拟合,据此推导得到毛细水上升速率的动力学表达式。砂性土和粘性土的毛细水稳定高度与石油含量分别成乘幂和二次多项式关系。(6)系统研究了石油污染含水介质的水-盐动力学特性。通过室内一维水动力弥散试验,得到了不同含油砂土渗透性、有效孔隙度、弥散系数和弥散度的变化规律。柴油污染对砂土有效孔隙度、渗透性的影响比机油更加显著。随着石油含量的增加,石英砂、粗砂和粉砂的有效孔隙度均呈线性减小,而渗透性的降低趋势则逐渐变缓。相同含油率条件下,粉砂的渗透系数比石英砂和粗砂的渗透系数低2至3个数量级,主要是由于粉砂中水的流速较小,使得机械弥散作用相对较弱。相对于石油污染,含水介质的固有性质对其水-盐动力学特性的影响更显著。更多还原

【Abstract】 With the growing demand for oil around the world, petroleum has become an important kind of organic pollutants in groundwater system. Oil pouring or leaking occurs inevitably during petroleum exploitation, refining, transportation and utilization, which can result in serious pollution in the underground water and soil environment. Especially for the low-density oil (e.g. fuel oil, lubricating oil), its migration ability is stronger due to the low viscosity coefficient, which has greater pollution potential once leaked into underground environment.This study is based on petrochemical area of Zibo City. Standard sand and typical soils in this area were taken as representative aquifer medium. CD15W-40 oil, 0 # diesel and 93 # gasoline were taken as representative low-density oil products. The changing rugulations and influence mechanism of surface wettability, capillary characteristics and water-salt dynamics characteristic of oil-contaminated aquifer medium were researched systematically, which can provide important references for evaluation, control and in-situ rehabilitation of oil-polluted sites. The main new understandings and conclusions obtained in this research were shown as follows:(1) Determination method of water and oil content of oil-polluted aquifer medium were established. The traditional drying method for water content and extraction-ultraviolet spectrophotometry for oil content were improved by measuring oil drying loss coefficient and new calculating formulas were also put forward. The new methods can solve the problems caused by mutual interference of oil and water, which can support the subsequent theoretical research with accurate data. Inspection test results showed that, the measuring error of these new methods was just about 0.5%, which mainly result from inevitable instrument errors. Therefore, these improved methods are proeved to be accurate and reliable. In addition, it won’t be influenced by oil types or volatility and thus have wide application range. (2) The surface wettability of oil-contaminated aquifer medium variation rule was obtained. The water repellency of oil- contaminated aquifer medium with different engine oil and diesel oil contents was determined. Results showed that the water repellency level increased dramatically, with the increase of oil pollution degree. Once the oil content reaches a certain critical value, the wettability will begin to change from hydrophilic into hydrophobic. The critical engine oil content of quartz sand and coarse sand is respectively around 0.5% and 0.3%, while their critical diesel oil content is respectively around 20% and 14%. The critical engine oil content of clay is about 8%, while diesel pollution hasn’t significant influence on clay. In addition, composition of medium and oil both have important influence on the variation characteristics of wettability of aquifer medium.(3) The wettability reversal feature of oil-contaminated aquifer medium was also studied, and the critical water content of wettability reversal was obtained. The results showed that when the water content reaches a certain critical value, the surface wettability will change again, from hydrophobic surface to hydrophilic surface, and the repellency of medium is disappeared. Low water content can reverse the wettability of oil-contaminated sand, the threshold value of which is about 0.4~0.8%. With the increase of oil content, the critical water content of engine oil-contaminated clay increases, and the value of water and oil contents is equal approximately.(4) The capillary water rising dynamics and capillary zone water vertical distribution rule were studied systematically. The results showed that, with the increase of oil content, both the capillary water rising height and water storage capacity reduced significantly. The reason is problebly that some oil was absorbed on the aquifer medium surface, which can increase the interface wetting contact angle and enhance the surface hydrophobicity. Besides, some oil can exsit among the medium particles and thus block the effective capillary water rising channels. In addition, compared with diesel pollution, engine oil pollution has stronger influence on medium capillarity, and the influence of oil pollution on coarse sand is much stronger than clay. (5) The mathematical expressions of capillary water rising height and rate were established as well. Under different conditions of engine oil and diesel contents, logarithmic relationship between capillary water rising height of sand and time can be expressed by quadratic polynomial, and that of clay can be expressed by linear relationship. Accorading to logarithmic relationship between capillary water rising height and time, the relationship between capillary water rising rate and time can also be deduced. The relationships between capillary water stability height and oil content of sand and clay were power and quadratic polynomial respectively.(6) The water-salt dynamics of porous media polluted by oil were studied. Through hydrodynamic dispersion experiment, permeability, effective porosity, diffusion coefficientand and dispersion variation were obtained. The results showed that the effect of diesel pollution on sand effective porosity and permeability was more significant than that of engine oil. With the increase of oil content, effective porosities of quartz sand, coarse sand and silt showed linear decreases. Permeability decreased gradually with a sluggish tendency and permeability coefficient of clay was two or three orders of magnitude lower than that of quartz sand and coarse sand with the same oil content. Dispersion had no apparent change. Hydrodynamic dispersion coefficient of oily silt was one order of magnitude lower than that of oily quartz sand and coarse sand, because pore water velocity in silt was lower and the role of mechanical dispersion was smaller. Relative to oil pollution, the inherent properties of porous media had a more significant influence on its water-salt dynamics.更多还原