Dahms Heinrich Theodor Jacob, Greenfield Richard
Department of Zoology, University of Johannesburg, Kingsway Campus, Auckland Park, South Africa.
Institute for Alpine Environment, Eurac Research, Bolzano, Italy.
Environ Monit Assess. 2025 Mar 4;197(4):351. doi: 10.1007/s10661-025-13800-5.
Microplastics have been studied in rivers worldwide with far-reaching implications for aquatic ecosystems. What is less understood is how microplastics distribute through rivers, as microplastics do not distribute ubiquitously through a river system. This study described the microplastic profile of the Nyl, Mogalakwena and Limpopo Rivers in South Africa. The study aimed to determine the driving environmental factors of microplastic distribution in a river system over multiple seasons. The study discovered relationships between flow and microplastics in sediment. This relationship allowed microplastics to have significantly (p < 0.05) different distributions over seasons. Seasons with reduced flow had higher mean microplastic abundances in water (1436 ± 4492 particles.m) and sediment (1710 ± 4951 particles.kgdw), which decreased in both water (59 ± 46 particles.m) and sediment (17 ± 11 particles.kgdw) during the high flow season. Although microplastic abundances decreased with increased flow, a more homogenous distribution was detected through the entire system in the high flow period. The results suggest that microplastics could become trapped and increase significantly during reduced flow but become more evenly distributed during high flow seasons. The microplastics had also become bioavailable, being found in benthic macroinvertebrates in the river system at varying concentrations with a mean of 29 ± 33 particles.gww, which could not be related to environmental matrices. Significant differences (p < 0.05) were determined between microplastic polymers found in water compared to sediment in all seasons. The study is the first in this transboundary river system, which impacts multiple African nations and a RAMSAR accredited wetland of international importance.
世界各地的河流都对微塑料进行了研究，这对水生生态系统具有深远影响。人们对微塑料如何在河流中分布了解较少，因为微塑料并非在整个河流系统中普遍存在。本研究描述了南非尼勒河、莫加拉克韦纳河和林波波河的微塑料概况。该研究旨在确定河流系统中多个季节微塑料分布的驱动环境因素。该研究发现了流量与沉积物中微塑料之间的关系。这种关系使得微塑料在不同季节的分布存在显著差异（p < 0.05）。流量减少的季节，水中（1436 ± 4492个/立方米）和沉积物中（1710 ± 4951个/千克干重）的微塑料平均丰度较高，而在高流量季节，水中（59 ± 46个/立方米）和沉积物中（17 ± 11个/千克干重）的微塑料丰度均下降。尽管微塑料丰度随流量增加而降低，但在高流量期整个系统中检测到更均匀的分布。结果表明，微塑料在流量减少时可能会被困住并显著增加，但在高流量季节会分布得更均匀。微塑料也具有生物可利用性，在河流系统的底栖大型无脊椎动物中被发现，其浓度各不相同，平均为29 ± 33个/克湿重，这与环境基质无关。在所有季节中，水中和沉积物中发现的微塑料聚合物之间存在显著差异（p < 0.05）。这项研究是在这个跨界河流系统中首次进行的，该河流系统影响多个非洲国家以及一个具有国际重要性的拉姆萨尔认证湿地。
