氯代烃污染土壤修复过程中相间非平衡态空间迁移机理研究

Chlorinated organics are commonly found at contaminated sites. These compounds have drawn much attention due to their mobility and persistence in the underground environment. The non-equilibrium transport of chlorinated organics has been found to affect the tailing and secondary emission during the remediation of soils contaminated by this group of compounds. However, there are no established theories and models that can quantify these effects. In this project, we plan to collect soil and soil gas samples from different depths at a real contaminated site, in order to obtain site characteristics and to determine the soil physiochemical properties and environmental factors that affect the partitioning and transport of chlorinated organics. Based on site investigation results, we will construct one-dimensional soil column and three-dimensional soil chamber, to explore how various perturbation may introduce non-equilibrium states and how they affect the transport of chlorinated organics, and subsequently to identify the underlying factors and mechanisms. Lastly, we will build a numerical model to simulate the tailing and secondary contaminant emission, using soil chamber data to validate the model, and ultimately to explain the non-equilibrium transport of chlorinated organics during remediation processes. Based on results from this project, we can provide new theoretical guidance for technological innovation in addressing tailing, and we can also provide technical support for improving engineering practice, mitigating secondary emission, and promoting green and sustainable remediation.

氯代烃普遍存在于污染场地，因其易迁移和难降解性而被广泛关注。氯代烃相间非平衡态空间迁移是影响氯代烃污染土壤修复过程中拖尾和二次污染物释放的重要因素。本项目拟采集氯代烃污染场地中不同深度土壤和土壤气样品，了解污染场地氯代烃迁移环境的基本特征，确定土壤理化性质以及环境因素对氯代烃相间分配和空间分布的影响。依据污染场地特征的研究成果，构建氯代烃一维和三维空间迁移的物理模型，研究氯代烃在多种相间非平衡态诱导因素影响下的空间迁移特征，提出相间非平衡态空间迁移的原理和影响因子。建立数值模型模拟修复过程中氯代烃污染物的拖尾现象和二次污染物释放现象，使用物理模型获取数据来验证数值模型，进一步阐明修复过程中的相间非平衡态空间迁移机理。本项目研究结果将为氯代烃修复技术创新和解决拖尾问题提供新的理论依据，并且为精细化施工、二次污染物减排及绿色可持续污染土壤修复的开展提供技术支持。

氯代烃普遍存在于工业污染场地，因其易迁移性和难降解性而受到广泛关注。本研究通过场地实验、土壤柱实验、沙箱实验和数学建模等多个角度，明确土壤理化性质和环境因素对实际污染场地土壤氯代烃分布特征的影响，阐明自然过程和修复过程中的相间非平衡态空间迁移机理，为氯代烃修复技术创新和解决拖尾及二次污染物释放问题提供理论依据和技术支持。.通过场地实验，分析了污染场地的土壤理化特征和氯代烃总浓度分布，发现土壤氯代烃总浓度在不同的深度差异很大，在0.75 m处达到浓度的最大值。土壤中氯代烃浓度与土壤总有机碳含量和湿度成正相关，而与土壤颗粒的平均粒径成负相关。土壤气中的氯代烃浓度随着气象条件的变化而呈现大幅波动的状态，其与大气压力和降雨量成负相关，但气温昼夜波动的影响并不显著。.通过土壤填充柱实验和相间非平衡态空间迁移建模，发现相较于平衡态模型，相间非平衡态空间迁移模型能更好解释大气压波动、地下水波动和降雨对氯代烃相间迁移的影响。大气压的升高、地下水水位的下降和降雨均能导致氯代烃逸出通量的下降，而长期的地下水波动会显著增加氯代烃的逸出通量。土壤有机碳的含量越高，氯代烃的亨利常数越小，其在土壤中的分配系数越大，则相间非平衡态空间迁移所造成的通量越大。.通过沙箱实验，定量探究了氯代烃相间非平衡态空间迁移对机械通风、土壤挖掘、气相抽提和热脱附联用修复技术的影响，发现在这些修复过程中均能产生较为显著的拖尾现象和二次污染物释放现象，同时在修复结束后会产生反弹现象。其中，氯代烃相间非平衡态空间迁移对抽提修复效率影响最大。因此，进一步构建了基于相间非平衡态空间迁移的多相抽提数学模型，并利用实际场地修复数据验证了该模型的正确性。通过模型计算，发现在多相抽提过程中，相间非平衡态空间迁移导致了通过气相和水相抽提去除的氯代烃通量显著小于平衡态模型计算值，从而限制了多相抽提的修复效率。.

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