- 1Aix-Marseille University, CNRS, LCE, Laboratoire Chimie Environnement, Aix-en-Provence, France (thi-thao.nguyen@univ-amu.fr)
- 2Department of Water-Environment-Oceanography, University of Science and Technology of Hanoi (USTH), Vietnam Academy of Science and Technology (VAST), 18 Hoang Quoc Viet, Cau Giay, Hanoi 100000, Vietnam
- 3Université de Toulouse, LEGOS (CNES/CNRS/IRD/UPS), Toulouse, France
- 4Land-Ocean-Atmosphere regional coupled system study center (LOTUS), University of Science and Technology of Hanoi (USTH), Hanoi, Vietnam
Global plastic production in 2023 reached 400.3 million metric tons (MMT)1. After being released into the environment, plastics degrade into secondary plastic – a major source of microplastics due to environmental factors. Microplastics (MPs), defined as plastic particles smaller than 5 mm, are ubiquitous across marine, freshwater and atmospheric environments2. Given their widespread dissemination and persistence, MPs have emerged as a notable environmental threat. Vietnam would rank 4th of the top 20 countries most polluted by plastic waste, with approximately 3.1 MMT of mismanaged plastic waste discharged in 20223. Despite this, research on MPs within the Association of Southeast Asian Nations (ASEAN) remains limited, accounting for only 5% of global studies, with Vietnam’s contribution of just 0.6%3.
This work aimed to examine the occurrence of MPs in superficial sediment samples collected at the 3 largest Vietnamese rivers from downstream parts to the sea: the Red River (RR, n=25 sampling points), Saigon River (SG, n=16), and Mekong River (MK, n=13) during the rainy season 2024. The analytical procedure involved digestion by hydroperoxide 20% (v/v), flotation by potassium carbonate (d=1.5 g.cm-3), and filtration (pore size 13 to 5000 µm). The filters were analyzed by µ-FTIR to determine the abundances and composition.
The results showed the concentrations of MPs in sediments ranged from 653 to 8069 items.kg in RR, from 2978 to 32151items.kg-1 in SG, and from 3173 to 15216 items.kg-1 dry weight in MK. The results underlined the previously observed link between MP input and vicinity to urban/densely populated areas since the highest concentrations were found close to the urban areas along the three rivers (i.e. Hanoi, Ho Chi Minh City, and Can Tho City). As expected, the trend showed MP dilution at the rivers’ mouths. The particle size of 13–200 µm represented the major size class, accounting for 72.4%, 90.7%, and 85.1% in RR, SG, and MK, respectively. Polyethylene, polypropylene, polyethylene terephthalate, and polyvinyl chloride (PVC) were the major polymers, accounting for a total of 82.4%, 78.3%, and 87.5% in RR, SG, and MK, respectively. The risk was assessed and represented high degrees of pollution load index, hazard index, and potential ecological risk index. High ecological risks were primarily linked to polymer hazards, particularly PVC, rather than pollution load. All the stations presenting a high polymeric risk also posed a high potential ecotoxicological risk. However, the station containing a large number of MPs does not necessarily present the highest potential ecological risk. This must be carefully considered in future regulations. The outcomes of this study will contribute todocumenting the quality status of the aquatic environment and support improved management and conservation of aquatic resources not only in Vietnam but also in ASEAN countries, where plastic production, consumption, and recycling activities are rapidly increasing.
References
[1] PlasticsEurope, 2023
[2] Sambandam et al., 2022, https://doi.org/10.1016/j.chemosphere.2022.135135
[3] Gabisa et al., 2022, https://doi.org/10.1016/j.marpolbul.2022.114118
How to cite: Nguyen, T. T., Bui, V. H., Fauvelle, V., Ouillon, S., Wong-Wah-Chung, P., and Malleret, L.: Abundances and characteristics of sedimentary microplastics in the three main Vietnamese Rivers, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9806, https://doi.org/10.5194/egusphere-egu25-9806, 2025.
