This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Plastics are accumulating in ecosystems around the world, and their tiny fragments can collect and carry chemical pollutants and pathogens into plants, animals and people. When fishermen in Cambodia's Mekong River became alarmed about the amounts of plastic they were hauling up with each catch, they reached out to scientists for help.
To investigate and measure the problem, DRI researchers joined a river expedition with Wonders of the Mekong—a project focused on applied research, capacity building and outreach to solve conservation and development challenges along Southeast Asia's longest river. Now, their results are available in a new study that demonstrates the role of waste collection services in rural communities along the river. The research can help inform improvements in waste management on a river that is critical to livelihoods in China, Myanmar, Thailand, Lao PDR, Cambodia and Vietnam.
The research, published in the journal npj Emerging Contaminants, was led by Rachel Kozloski and her colleagues with DRI's Microplastics and Environmental Chemistry Lab and the University of Nevada Reno. They sampled plastics and microplastics along the Cambodian stretch of the Mekong River during the wet and dry seasons in 2022. Their findings showed that where communities lacked waste collection services, microplastics concentrations immediately downstream were much higher.
By modeling the observed relationship, they showed that improving waste collection services in rural riverside communities could result in a substantial reduction in downstream microplastic concentrations. The research is critical for improving water quality in a river that 66% of Cambodians rely on for subsistence fishing or employment. "Our research shows that there's a pretty strong link between what you do with your trash in those riparian areas and the microplastic concentration in the river just downstream of that," Kozloski said.
"Of course, our data is from 2022, and we know that the Cambodian government has been working to improve waste collection services in the years since. Our hope is that our data can highlight strategic locations where waste collection would make the biggest impact and help limited resources go further." The research team also examined more than 3,000 plastic particles collected from the surface of the Mekong River and identified their chemical compositions. They found a notable shift in the types and sizes of plastics collected in the dry season compared to the wet season, when high monsoonal flows flush larger plastics from the river bottom and the surrounding landscape.
A wide variety of polymers was identified during the dry season, with the single largest category identified as an assortment of uncommon plastics. During the wet season, the dominant plastics were polypropylene, polyterephthalates (PET) and polyethylene. Although the concentration of microplastics was about the same (between 3 and 4 microplastics per liter of water), the average daily load increased by an order of magnitude in the wet season because the higher flows mobilized more trash.
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