含单裂隙非饱和带中轻非水相流体修复的数值模拟

Numerical simulation oflight non-aqueous phase liquids remediation in the unsaturated zone with single fractures

针对非饱和带中油类污染物时空分布的研究,室内实验很难定量分析运移机理,野外检测成本高且破坏地层。数值模拟法作为一种应用广且成熟的方法,可以用来分析油类污染物在非饱和带中的运移规律。为了研究单井抽提及原位冲洗修复时,含单裂隙非饱和带中轻非水相流体(Light non-aqueous phase liquids,LNAPL)的时空变化规律,建立了数值模型,分析不同条件下LNAPL的修复效果及时空变化规律。模拟结果发现,LNAPL注入时优先流入裂隙,停止注入时优先流出裂隙。单井抽提修复模拟表明,抽提流量越大,修复效率越高。原位冲洗技术能有效补充地下水,防止产生新的环境问题;注水井起到“冲洗”及稀释污染物的作用,模拟最优方案修复面积达到96%,修复率达到75%,LNAPL饱和度控制在约0.05;对比分析发现,注水井布设在污染物范围的上边界时修复效果最好,能有效“冲洗”污染物并携带至抽提井中抽出地表。该研究为受轻油污染的土壤及地下水修复提供了科学的理论依据及有效的评估方法。

For the study of the spatial and temporal distribution of oil pollutants in unsaturated zones,it is difficult to quantitatively analyze the migration mechanism in laboratory and field tests are costly and damages the foundation.Numerical simulation,as a widely used and mature method,can be used to analyze the movement of oil pollutants in unsaturated zones.In order to examine the spatial and temporal distribution law of LNAPL(light non-aqueous phase liquids)in the unsaturated zone with single fractures during the single-well extraction and in-situ flushing remediation,in this paper a numerical model is established to analyze the effect under different conditions.The results show that LNAPL preferentially flows into fractures when injected,and preferentially flows out of the fractures when the injection is stopped.The single well extraction remediation simulation show that the larger the extraction flow,the higher the remediation efficiency.The in-situ flushing technology can effectively replenish groundwater and prevent new environmental problems.The injection wells play the role of“flushing”and diluting pollutants.Under the optimal scheme,the remediation area reaches 96%,the remediation rate reaches 75%,and the LNAPL saturation is controlled at 0.05.The comparative analysis indicates that the water injection wells have the best effect when placed on the upper boundary of the pollutant,and can effectively“flush”the pollutants and carry them to the extraction well and to the land surface.The research conclusions provide a scientific theoretical basis and effective assessment methods for the remediation of soil and groundwater contaminated by light oil.