The effectiveness of most in situ remedial technologies, including nanoremediation, lies on successful delivery of reagents to a subsurface target treatment zone. Targeted delivery of engineered nanoparticles (NPs) to treat petroleum hydrocarbons present in the unsaturated zone requires an understanding of their transport behaviour in these systems. A series of column experiments explored the effect of initial water saturation, flowrate, input dosage, and porous medium texture on the transport of iron oxide or cobalt ferrite NPs coated with an amphiphilic co-polymer, as well as their targeted attachment to a crude oil zone. As the initial water content increased with a concomitant reduction in air saturation, the degree of tailing present in the NP breakthrough curves (BTCs) reduced, and the mass of NPs recovered increased. Air saturation is positively correlated with the magnitude of air-water interfaces, which provide additional NP retention sites. At a lower injection flow rate, NP retention increased due to a longer residence time and comparatively high air saturation. NP transport behaviour was not sensitive to NP injection dose over the range tested. Increased retention and retardation of the NP BTC was observed in sediments with a higher clay and silt content. NPs coated with a lower concentration of a Pluronic block co-polymer to promote binding were preferentially retained within the crude oil zone. To simulate the asymmetrical NP breakthrough curves observed from the unsaturated systems required the use of a model that accounted for both mobile and immobile flow regions as well as NP attachment and detachment with nonlinear Langmuirian blocking. This model allowed examination of attachment and detachment rate coefficients which captured NP interaction with the porous medium and/or crude oil. It was found that the initial water saturation and flow rate did not have an appreciable impact on the NP attachment rate coefficient, while it increased by ~10× with increasing clay and silt content, and by ~100× in the presence of crude oil, indicating preferential NP attachment within the crude oil zone. As a result of the lower NP polymer concentration coating used to promote increased attachment to crude oil, higher retention was observed near the column inlet and was captured quantitatively by adding a depth-dependent straining term to the model. This retention behaviour represents a combination of irreversible attachment at the air-water interfaces and straining near the column inlet enhanced by the formation of NP aggregates. The detachment rate coefficient decreased with a lower initial water saturation and flowrate, but increased with higher clay and silt content. The findings from this study contribute to our understanding of the transport and binding behaviour of Pluronic-coated NPs in unsaturated conditions and, in particular, the role of initial water content, flowrate and porous medium texture. Demonstrated delivery of NPs to a target zone is an important step towards expanding the utility of NPs as treatment reagents.

大多数原位修复技术（包括纳米修复）的有效性取决于成功地将试剂输送到地下目标处理区。工程纳米粒子 (NPs) 的靶向递送以处理存在于不饱和区的石油烃需要了解它们在这些系统中的传输行为。一系列柱实验探讨了初始含水饱和度、流速、输入剂量和多孔介质质地对涂有两亲共聚物的氧化铁或钴铁氧体纳米粒子的传输以及它们与原油的靶向附着的影响区。随着初始含水量随着空气饱和度的降低而增加，NP突破曲线中存在的拖尾程度(BTCs) 减少，并且回收的 NPs 的质量增加。空气饱和度与空气-水界面的大小呈正相关，这提供了额外的 NP 保留位点。在较低的注入流速下，由于较长的停留时间和较高的空气饱和度，NP 保留增加。在测试范围内，NP 转运行为对 NP 注射剂量不敏感。在粘土和淤泥含量较高的沉积物中观察到 NP BTC 的保留和阻滞增加。涂有较低浓度的 Pluronic 嵌段共聚物以促进结合的 NP 优先保留在原油区域内。为了模拟从不饱和系统中观察到的不对称 NP 突破曲线，需要使用一个模型，该模型同时考虑了流动和固定流动区域以及具有非线性 Langmuirian 阻塞的 NP 附着和脱离。该模型允许检查捕获 NP 与多孔介质和/或原油相互作用的附着和脱离速率系数。发现初始含水饱和度和流速对 NP 附着率系数没有明显影响，而随着粘土和粉砂含量的增加，它增加了 ~10 倍，在原油存在下增加了 ~100 倍，表明原油区域内的优先 NP 附着。由于用于促进增加对原油的附着力的较低 NP 聚合物浓度涂层，在色谱柱入口附近观察到更高的保留，并通过在模型中添加与深度相关的应变项进行定量捕获。这种保留行为代表了空气-水界面处的不可逆附着和由于 NP 聚集体的形成而增强的柱入口附近的应变的组合。滑脱率系数随着初始含水饱和度和流量的降低而降低，但随着粘土和粉砂含量的增加而增加。这项研究的结果有助于我们理解 Pluronic 涂层 NP 在不饱和条件下的传输和结合行为，特别是初始含水量、流速和多孔介质质地的作用。向目标区域展示 NPs 是扩大 NPs 作为治疗试剂的效用的重要一步。