LNAPL在砂质含水层中动态迁移的电阻率法监测试验研究

在海滨潮间带采集细砂,通过室内柴油泄漏模拟试验,利用自制电阻率监测系统对轻非水相液体在砂土-地下水系统垂向渗透过程进行电阻率变化动态监测;通过配制不同含油率砂土测定其静态电阻率变化规律,探讨电阻率变化的影响因素;最后取样分析测定污染含水介质稳定后含水率及含油率,对监测结果有效性进行了验证;并利用显微成像法对污染砂土进行了微观形态分析.结果表明,柴油污染砂土微观形态上胶结现象明显;柴油渗透海滨砂土过程电阻率大小同含水饱和度,比电阻率和含油饱和度之间存在良好的相关性,均可用Archie公式拟合,n值分别为2.36和0.15;通过电阻率测定可以有效估算柴油透镜体厚度;电阻率随深度的变化可以反映含油率和含水率的垂向分布.本研究为轻质油品储罐或者海上油品输运过程泄露造成的海滨砂土地下污染扩散过程监测及机制研究提供了一种有效的方法,也可为其他典型石油泄漏污染场地的电阻率法探测或监测提供参考.

LNAPL Migration Monitoring in Simulated Sand Aquifer Using Resistivity Method

Laboratory model tests of diesel spillage were performed on the beach sand samples collected from intertidal zone in Qingdao. The dynamic resistivity changes during the diesel infiltration in sand-water system were monitored by the self-made Resistivity Monitoring System. The impact factors on resistivity were discussed by preparing sand samples with different oil contents. The water content and oil content were measured by sampling after the simulation experiment to verify the monitoring data. The micro-structure of contaminated sand was tested by image technique using microscope. It shows that cementation is evident from the micro-structure of contaminated sand. The resistivity closely relates with the water saturation, and the specific resistivity with oil saturation, both fitted with Archie equation, the n values are 2.36 and 0.15 separately. Through electrical resistivity measurements, the thickness of diesel lens was effectively estimated. The vertical distribution of oil content and water content could be reflected by resistivity changes with depths. It provides an effective way for in-situ monitoring of light non-aqueous phase liquid (LNAPL) contaminating processes and mechanism research in beach sand after underground tank leakage or oil spillage during transport by seas. It can also supply reference to contamination detection or monitoring of typical petroleum contaminated sites using resistivity method.