基于TOUGH2/EOS9nT模拟饱和双区介质砂柱中纳米颗粒的运移

The simulation of nanoparticles transport in saturated dual-permeable media using TOUGH_2/EOS9nT

随着纳米材料的大量生产和广泛应用,纳米颗粒不可避免地进入环境中,对地下水系统和人体健康产生潜在影响,研究纳米颗粒在地下水中的迁移规律具有重要意义.采用TOUGH2/EOS9nT模块,基于多重相互作用连续体(MINC)概念和胶体过滤理论,数值分析示踪剂KNO_3和纳米氧化石墨烯在一维非均质砂柱中的运移.研究结果表明:1MINC方法能够有效模拟双重非均质介质,非均质介质渗透系数的差异是造成出流穿透曲线双峰和拖尾特征的主要原因之一;随溶液离子强度增大,纳米氧化石墨烯在饱和非均质介质中的迁移能力下降;基于EOS9nT模块中的线性平衡过滤模型可有效模拟低离子强度下双重非均质介质中纳米颗粒运移,但即使采用动态过滤模型仍无法精确模拟高离子强度下纳米颗粒的运移;2通过双渗模型中渗透率的敏感性分析发现:随渗透率比值增大,裂隙区穿透曲线峰值提前,基质区曲线峰值推后,穿透曲线双峰现象更明显;3比较三重介质和双重介质,发现总穿透曲线受三重区域各自曲线叠加时刻影响,也表现出峰值/拖尾的增强或削弱,在合适的渗透率比值下,可能出现三个峰值和拖尾.

The increase in the production and application of nanomaterial inevitably makes the exposure of the nanoparticles in environment,which causes potential hazards to the groundwater,as well as to public health. It is therefore of great significance to study the transport of nanoparticles in groundwater.In this study,the transport of tracer KNO3 and Nano Graphene Oxide（ GO） in heterogeneous porous media was numerically simulated and analyzed using the TOUGH2/EOS9nT module based on the MINC method and colloid filtration theory. Simulation results were also compared with observed data in the laboratory sand column experiments. Results show that 1MINC method could effectively simulate the heterogeneous porous medium with high efficiency.The difference in hydraulic conductivities of heterogeneous media was one of the main reasons for the double peaks and tailings in the breakthrough curves（BTCs）. The mobility of Nano-GO in saturated heterogeneous medium decreased with increasing ionic strength（ IS） of solution. The transport of nanoparticles in dual-permeable medium at low IS could be efficiently simulated by the linear equilibrium filtration process from the EOS9nT module,however it was hard to accurately simulate the transport at high IS even using the linear kinetic filtering model.2With increase in the permeability ratio of dual-permeable medium,the peak of the BTCs from fracture zone was achieved earlier while it was the opposite for that from matrix zone,resulting in amore obvious double-peak behavior.3Similar to dual-permeable medium,the BTCs of a triple-permeable medium also show an enhanced or weakened peak/tail due to the superposition of curves from three different media. As a result,there may be up to three peaks/tails with a proper permeability ratio.