Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, College of the Environment and Ecology, Xiamen University, Xiamen, Fujian 361102, China.
Fujian Key Laboratory of Coastal Pollution Prevention and Control, College of the Environment and Ecology, Xiamen University, Xiamen, Fujian 361102, China.
Water Res. 2024 Dec 1;267:122463. doi: 10.1016/j.watres.2024.122463. Epub 2024 Sep 17.
Microplastics (MPs) pollution in coastal wetlands has attracted global attention. However, few studies have focused on the effect of soil properties and structure on MP transport in coastal wetlands. Salinity is one of the most pivotal environmental factors and varies in coastal wetlands. Here, we conducted column experiments and employed fluorescent labeling combined with Derjaguin-Landau-Verwey-Overbeek (DLVO) theoretical calculations to reveal the vertical transport behavior of MPs. Specifically, we investigated the influence of five salinity levels (0, 0.035, 0.35, 3.5, and 35 PSU) on MP transport in different coastal wetlands soils and a sand through the X-ray photoelectron spectroscopy and nondestructive computed tomography technique. The results indicated that the migration capability of MPs in soils is significantly lower than in quartz sand, and that the migration capability varies depending on the soil type. This variability may be due to soil minerals and microporous structures providing numerous attachment sites for MPs and may be explained by the DLVO energy barrier of MP-Soil (6568-7767 KT) and MP-sand (5250 KT). Salinity plays a crucial role in modifying the chemical properties of pore water (i.e., zeta potential) as well as altering the soil elemental composition and pore structure. At 0 PSU, the maximum C/C0 of MPs through the sand, Soil 1, and Soil 2 transport columns were 37.86 ± 2.36 %, 23.96 ± 1.71 %, and 3.94 ± 0.68 %, respectively. When salinity increased to 3.5 PSU, MP mobility decreased by over 20 %. Additionally, a salinity of 35 PSU may alter the soil pore distribution, thereby changing water flow paths and velocities to constrain the migration of MPs in soils. These findings could provide valuable insights into understanding the environmental behavior and transport mechanisms of MPs, and lay a solid scientific basis for accurately simulating and predicting the fate of MPs in coastal wetland water-soil systems. We highlight the effect of salinity on the fate of MPs and the corresponding priority management of MPs risks under the background of global climate change.
微塑料（MPs）污染在沿海湿地引起了全球关注。然而，很少有研究关注土壤性质和结构对沿海湿地中 MPs 迁移的影响。盐度是最关键的环境因素之一，在沿海湿地中变化较大。在这里，我们进行了柱实验，并采用荧光标记结合德加古因-兰德奥弗贝克（DLVO）理论计算来揭示 MPs 的垂直输运行为。具体来说，我们研究了五个盐度水平（0、0.035、0.35、3.5 和 35 PSU）对不同沿海湿地土壤和砂中 MPs 迁移的影响，使用了 X 射线光电子能谱和无损计算机断层扫描技术。结果表明，MPs 在土壤中的迁移能力明显低于石英砂，且迁移能力取决于土壤类型。这种变异性可能是由于土壤矿物和微孔结构为 MPs 提供了众多的附着位点，可以用 MP-土壤（6568-7767 KT）和 MP-砂（5250 KT）的 DLVO 能量障碍来解释。盐度在改变孔隙水的化学性质（即 ζ 电位）以及改变土壤元素组成和孔隙结构方面起着至关重要的作用。在 0 PSU 时，MPs 通过砂、土壤 1 和土壤 2 运输柱的最大 C/C0 分别为 37.86±2.36%、23.96±1.71%和 3.94±0.68%。当盐度增加到 3.5 PSU 时，MP 的迁移性降低了 20%以上。此外，35 PSU 的盐度可能会改变土壤的孔隙分布，从而改变水流路径和速度，限制 MPs 在土壤中的迁移。这些发现可以为深入了解 MPs 的环境行为和迁移机制提供有价值的见解，并为准确模拟和预测沿海湿地水-土系统中 MPs 的命运奠定坚实的科学基础。我们强调了盐度对 MPs 命运的影响，以及在全球气候变化背景下对 MPs 风险进行优先管理的必要性。
