Microplastic contamination on the lower Chao Phraya: Abundance, characteristic and interaction with heavy metals

While a large number of studies on microplastics (MPs) in the western hemisphere have been performed, few studies are available in the eastern hemisphere, especially in Southeast Asia. In this study, the abundance of MPs in water and sediment samples from the Chao Phraya River at the Tha Pra Chan area, Thailand, was investigated. Water samples were collected by a manta trawl, and sediment samples were collected by a Van Veen grab sampler. The average number and concentration of MPs in water samples were 80 ± 65 items/m³ and 53.3 ± 58.4 mg/m³, respectively. The average number and concentration of MPs in sediment samples were 91 ± 13 items/kg and 4.9 ± 3.4 mg/kg, respectively. The main morphologies of MPs were fragments and fibers, mostly white. Polypropylene (PP) was the dominant polymer type found in both water and sediment. Moreover, the content of heavy metals (Cr, Cu, Ni, and Pb) on MPs was extracted by aqua regia solution and analyzed by ICP-OES. Results show high concentrations of Pb and Cu adsorbed on MPs in the study area. In brief, this study suggests that there are high levels of MPs in the water and sediments of the Chao Phraya River at the Tha Pra Chan area. [Display omitted] •MPs were found in water and sediment of Chao Phraya River at Tha Pra Chan.•MPs in water were detected at 80 ± 65 items/m³ and 53.3 ± 58.4 mg/m³.•MPs in sediment were detected at 91 ± 13 items/kg and 4.9 ± 3.4 mg/kg.•Most MPs were PP, PE and PS with the dominant size of 0.05–0.5 mm.•Heavy metals were found with high concentration of Pb and Cu adsorbed on MPs.