Li Wang, Brunetti Giuseppe, Bolshakova Anastasiia, Stumpp Christine
University of Natural Resources and Life Sciences, Vienna, Department of Water, Atmosphere and Environment, Institute of Soil Physics and Rural Water Management, Muthgasse 18, 1190 Vienna, Austria.
University of Calabria, Department of Civil Engineering, Rende, Italy.
Sci Total Environ. 2024 Jul 20;935:173429. doi: 10.1016/j.scitotenv.2024.173429. Epub 2024 May 22.
The occurrence and persistence of microplastics (MPs) in natural environments are of increasing concern. Along with this, the transport of MPs in sediments has been investigated mainly focusing on the effect of plastic size and shape, media size effect, and solution chemistry. Yet, the influence of particle density is only partially understood. Therefore, column experiments on the transport of variably buoyant MPs in saturated natural sediments and glass beads were conducted, and transport parameters were quantified using a two-site kinetic transport model with a depth-dependent blocking function (the amount of retained MPs does not decrease at a constant rate with increasing depth, the majority of MPs were retained near the column inlet). Neutral, sinking, and buoyant MPs within the same size range were selected, with stable water isotope applied as conservative tracer to explore water and MP movement in the tested sediments. The results showed that 95.5 ± 1.4% of sinking MPs remained in columns packed with gravel, followed by buoyant and neutral MPs, thus indicating that particle density does affect MP mobility. Similar recovered amounts of MPs were found in columns packed with glass beads, indicating that tested sediment types do not affect the deposition behavior of MPs. The breakthrough curves of MPs were accurately described by the selected model. However, the simulated retention profiles overestimated the observed MP amount in layers closest to the column inlet. The coupled experimental and modeled results suggest an enhanced retention of sinking MPs, while neutrally and buoyant MPs exhibit a higher mobility in comparison. Thus, neutral or buoyant MPs can potentially pose a higher contamination risk to subsurface porous media environments compared to sinking MPs. Discrepancies between observed and simulated retention profiles indicate that future model development is needed for advancing the MP deposition as affected by particle density.
微塑料（MPs）在自然环境中的出现和持续存在日益受到关注。与此同时，对沉积物中微塑料的迁移研究主要集中在塑料尺寸和形状的影响、介质尺寸效应以及溶液化学方面。然而，颗粒密度的影响仅得到部分理解。因此，进行了关于可变浮力微塑料在饱和天然沉积物和玻璃珠中迁移的柱实验，并使用具有深度依赖阻滞函数的双位点动力学迁移模型（保留的微塑料量不会随着深度增加以恒定速率减少，大多数微塑料保留在柱入口附近）对迁移参数进行了量化。选择了相同尺寸范围内的中性、下沉和漂浮微塑料，并应用稳定水同位素作为保守示踪剂来探索测试沉积物中的水和微塑料运动。结果表明，95.5±1.4%的下沉微塑料保留在装有砾石的柱中，其次是漂浮和中性微塑料，这表明颗粒密度确实会影响微塑料的迁移率。在装有玻璃珠的柱中发现了类似的微塑料回收量，表明测试的沉积物类型不会影响微塑料的沉积行为。所选模型准确地描述了微塑料的突破曲线。然而，模拟的保留剖面高估了最靠近柱入口层中观察到的微塑料量。实验和模拟结果相结合表明下沉微塑料的保留增强，而中性和漂浮微塑料相比之下具有更高的迁移率。因此，与下沉微塑料相比，中性或漂浮微塑料可能对地下多孔介质环境构成更高的污染风险。观察到的和模拟的保留剖面之间的差异表明，未来需要开发模型来推进受颗粒密度影响的微塑料沉积研究。
