Munkhbat Dolgormaa, Battulga Batdulam, Oyuntsetseg Bolormaa, Kawahigashi Masayuki
Department of Geography, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo, 192-0397, Japan.
Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Tokai, Ibaraki, 319-1195, Japan.
Environ Sci Pollut Res Int. 2024 Dec;31(57):65548-65558. doi: 10.1007/s11356-024-35584-w. Epub 2024 Nov 26.
Plastic pollution in river environments has become an emerging global concern. However, the migration of plastic and changes in its properties between river compartments are less understood. This study demonstrates the plastic debris aging and the dynamics between floodplain, surface water, and sediment compartments of the Tuul River, Mongolia. Plastic occurrence is evaluated in terms of their abundance, size, shape, polymer type, and photodegradation in each compartment. Photodegradation stages were calculated using the carbonyl index (CI). Plastic abundance was 5.46 ± 3.53 items m in the floodplain, 155 ± 100.7 items m in the surface water, and 128.4 ± 76.3 items kg in the sediment. Microplastics dominated in the size category in all compartments, while macro- and megaplastics were found only in the floodplain. Polyethylene and polypropylene dominated the surface water and sediment, while polystyrene was the predominant plastic in the floodplain. A positive correlation was found between the distributed polymer types in the surface water and sediment compartments. The similar composition in size and polymer type suggests vertical plastic migration from water to sediment. Although CI values showed that the plastic aging was significantly different between water and sediment (water, 0.61 ± 0.26, and sediment, 0.90 ± 0.68), the dominance of low-density plastics with high CI in the sediment suggests that the aged plastic density changed during the vertical transport in the river system.
河流环境中的塑料污染已成为一个新出现的全球关注问题。然而，塑料在河流不同区域之间的迁移及其性质变化却鲜为人知。本研究展示了蒙古图勒河漫滩、地表水和沉积物区域之间塑料碎片的老化及动态变化。根据各区域中塑料的丰度、尺寸、形状、聚合物类型和光降解情况对塑料的存在进行评估。使用羰基指数（CI）计算光降解阶段。漫滩中塑料丰度为5.46±3.53个/平方米，地表水中为155±100.7个/平方米，沉积物中为128.4±76.3个/千克。所有区域中微塑料在尺寸类别上占主导，而宏观和巨型塑料仅在漫滩中被发现。地表水和沉积物中聚乙烯和聚丙烯占主导，而聚苯乙烯是漫滩中主要的塑料。地表水和沉积物区域中分布的聚合物类型之间存在正相关。尺寸和聚合物类型的相似组成表明塑料从水到沉积物的垂直迁移。尽管CI值表明水和沉积物中塑料老化存在显著差异（水为0.61±0.26，沉积物为0.90±0.68），但沉积物中具有高CI值的低密度塑料占主导，这表明老化塑料密度在河流系统的垂直输送过程中发生了变化。
