两相流条件下微纳塑料颗粒迁移及滞留机理研究

doi:10.13745/j.esf.sf.2025.10.9

摘要/Abstract

摘要： 微纳塑料(micro/nano-plastics,M/NPs)在多孔介质中的迁移与滞留机制是土壤与地下水污染领域的重要问题,然而受当前可视化技术的限制,两相流条件下M/NPs迁移与滞留过程的细观机理尚不明确。本研究基于三维可视化实验平台,直接观测并量化了渗吸条件下M/NPs在孔隙空间中的分布特征,重点分析了驱替结束后其在多孔介质骨架颗粒接触区、固相表面及液-液界面的滞留规律,探究了M/NPs粒径与驱替流量对其空间分布的控制机制。结果表明:M/NPs粒径通过改变M/NPs-固相表面与M/NPs-流体界面间的相互作用能来主导其滞留位点的选择;而M/NPs间的相互作用能大小是决定其能否聚集成团簇并滞留在孔隙空间的关键因素;驱替流量则通过改变固相-湿润相界面面积影响其滞留总量。此外,M/NPs滞留在多孔介质中不同点位的主导机制不同,其在多孔介质骨架颗粒接触区的滞留主要受筛分作用控制,而在固相表面与液-液界面处的滞留则主要依赖于界面吸附作用。在高剪切条件下滞留在固相表面的M/NPs可能会脱落,而骨架颗粒接触区作为低速区,其聚集团簇数量随流速增大而增加。本研究揭示并量化了M/NPs粒径与流速对其迁移滞留的作用机制,可为预测土壤和地下水等多相流体环境中污染物的迁移与归宿提供重要的理论依据。

关键词: 微纳塑料, 多孔介质, 两相流, 滞留机理, 分布特性

Abstract:

The transport and retention of micro/nano-plastics (M/NPs) in porous media is a critical concern in soil and groundwater contamination. However, limitations in visualization techniques have hindered a deeper understanding of the microscopic mechanisms governing M/NP transport under two-phase flow conditions. Using a three-dimensional visualization apparatus, we directly observed and quantified the distribution characteristics of M/NPs within pore spaces, with a specific focus on their retention at grain-grain contacts, solid surfaces, and fluid-fluid interfaces during imbibition. The effects of M/NP size and imbibition rate on their spatial distribution were further investigated. Our results reveal that M/NP size predominantly governs the selection of retention sites by altering the M/NP-solid and M/NP-fluid interface interaction energies. Conversely, the magnitude of interaction energy between M/NPs determines their potential to form aggregated clusters. The flow rate primarily influences the overall retention by altering the solid-wetting phase interfacial area. Moreover, distinct mechanisms govern retention at different locations: straining dominates at grain-grain contacts, while interfacial adsorption prevails at solid surfaces and fluid-fluid interfaces. Under high flow rates, M/NPs retained on solid surfaces can be readily detached due to enhanced shear forces. In contrast, the size of aggregated M/NP clusters at grain-grain contacts increases with flow velocity. This study elucidates the synergistic mechanisms by which M/NP size and flow velocity govern M/NP migration and retention, providing a theoretical basis for predicting the transport and fate of contaminants in multiphase subsurface environments.

Key words: micro/nano plastics, porous medium, two-phase flow, retention mechanism, distribution characteristics

中图分类号:

刘启明, 杨志兵, 吴婷. 两相流条件下微纳塑料颗粒迁移及滞留机理研究[J]. 地学前缘, 2026, 33(1): 222-235.

LIU Qiming, YANG Zhibing, WU Ting. Transport and retention mechanisms of micro/nano plastics during two-phase flow[J]. Earth Science Frontiers, 2026, 33(1): 222-235.

图/表 10

图1 三维可视化实验系统 (a)—实验装置示意图;(b)—不同深度下二维图像,其中红色区域为非湿润相流体,蓝色为M/NPs颗粒,黑色为玻璃微珠;(c)—三维重构图。

Fig.1 3D visualization experimental system

图2 M/NPs间、M/NPs-两相界面和M/NPs-固相表面之间的DLVO相互作用能

Fig.2 DLVO interaction energy between M/NPs, between M/NPs and the two-phase interface, and between M/NPs and the solid surface for M/NPs (a)—d=0.5 μm;(b)—d=1 μm;(c)—d=5 μm。

图3 不同粒径(d)M/NPs在不同驱替流量(Q)下多孔介质中非湿润相与M/NPs的分布

Fig.3 Distribution of the nonwetting liquid and M/NPs of different diameters (d) in porous media and displacement flow rates (Q) (a)-(c)—d=0.5 μm,Q=1、50和500 μL/min;(d)-(f)—d=1 μm,Q=1、50和500 μL/min;(g)-(i)—d=5 μm,Q=1、50和500 μL/min。比例尺代表100 μm。

图4 不同粒径M/NPs团簇的体积分布 (a)—d=0.5 μm;(b)—d=1 μm;(c)—d=5 μm;(d)—聚集的M/NPs团簇总体积。

Fig.4 Volume distribution of M/NPs clusters with different diameters

图5 残余饱和度与界面面积随流量的变化 (a)—残余非湿润相饱和度随流量大小变化;(b)—固-液界面以及湿润-非湿润两相界面面积变化。

Fig.5 Variation of residual saturation and interfacial area with flow rate

图6 M/NPs团簇聚集点位示意图与显微实拍图像 ①骨架颗粒接触区;②固相表面;③液-液界面。

Fig.6 Schematic diagram and microscopy image showing M/NPs clusters accumulation at: (1) grain-grain contact area, (2) solid surfaces, and (3) fluid-fluid interfaces

图7 驱替流量Q=500 μL/min时粒径为5 μm的M/NPs颗粒在典型聚集位置的局部3D重构图像 (a)—玻璃微珠、非湿润相和M/NPs团簇局部3D重构图;(b)-(d)—驱替结束后在骨架颗粒接触区、固相表面及液-液界面处聚集的M/NPs团簇。为了清晰展示聚集在不同点位的M/NPs团簇,(b)和(c)去掉了非湿润相,(d)去掉了玻璃微珠。图中灰色区域为玻璃微珠,红色为残余非湿润相,蓝色为M/NPs团簇。

Fig.7 Local 3D reconstruction of 5 μm M/NPs clusters at typical accumulation sites after displacement at Q=500 μL/min

图8 粒径为0.5 μm的M/NPs颗粒在典型聚集位置的体积分布统计图 (a)-(d)分别展示了驱替流量Q=1、10、100和500 μL/min时典型聚集位置的M/NPs团簇的体积分布以及局部三维重构图。

Fig.8 Volume distribution with local 3D reconstructions of 0.5 μm M/NPs clusters at typical accumulation sites

图9 粒径为1 μm的M/NPs颗粒在典型聚集位置的体积分布统计图 (a)-(d)分别展示了驱替流量Q=1、10、100和500 μL/min时典型聚集位置的M/NPs团簇的体积分布以及局部三维重构图。

Fig.9 Volume distribution with local 3D reconstructions of 1 μm M/NPs clusters at typical accumulation sites

图10 粒径为5 μm的M/NPs颗粒在典型聚集位置的体积分布统计图 (a)-(d)分别展示了驱替流量Q=1、10、100和500 μL/min时典型聚集位置的M/NPs团簇的体积分布。

Fig.10 Volume distribution of 5 μm M/NPs clusters at typical accumulation sites

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