Rivers are one of the major pathways for the transportation of microplastics (MPs) from land-based sources to the ocean. However, there are only a few studies on MPs in freshwater environments, particularly in Asian countries. In this study, MP contamination in the Chao Phraya River in selected locations distributed throughout Bangkok, Thailand was investigated. MPs were collected using a Manta net with a mesh size of 335 μm. After digestion and distinction based on density, MPs were observed using a stereomicroscope, and polymer types were identified using Fourier Transform Infrared Spectroscopy. MP concentrations detected in the five sampling locations of the river water from upstream to downstream were 11, 35, 40, 15, and 4 particles/m³, with an average concentration of 21±16 particles/m³. Most MPs were identified as either fragments or sheets/films. Polypropylene was the dominant polymer type. The number of MPs increases as their size decreases. Potential sources of MPs may include the degradation of single-use plastic products, especially containers and plastic packaging. MP concentrations and characteristics varied for different locations, indicating different sources and pathways of MPs in urban contexts. Further investigation on the different pathways of the transportation of MPs to river water from land-based sources is required.

河流是将微塑料 (MPs) 从陆源运输到海洋的主要途径之一。然而，关于淡水环境中 MPs 的研究很少，特别是在亚洲国家。在这项研究中，调查了分布在泰国曼谷的选定地点的湄南河 MP 污染。使用网眼大小为 335 μm 的 Manta 网收集 MP。根据密度进行消化和区分后，使用立体显微镜观察 MP，并使用傅里叶变换红外光谱识别聚合物类型。河水从上游到下游5个采样点检测到的MP浓度分别为11、35、40、15、4个/m ³，平均浓度为21±16个/m ³. 大多数国会议员被确定为碎片或片材/胶片。聚丙烯是主要的聚合物类型。MP 的数量随着其规模的减小而增加。MPs 的潜在来源可能包括一次性塑料产品的降解，特别是容器和塑料包装。不同地点的 MP 浓度和特征不同，表明城市环境中 MP 的不同来源和途径。需要进一步研究 MPs 从陆源运输到河水中的不同途径。