Major plastic pollution hidden beneath the surface of rivers •

The scene of plastic pollution in rivers is unfortunately familiar to everyone. Images of bottles bouncing on the surface or plastic bags hanging from branches symbolize the growing environmental crisis. However, the problem goes much deeper – literally.

A significant portion of the plastic pollution in our rivers is invisible to the naked eye, consisting of microplastics and fragments that sink below the surface.

This hidden reality has a significant impact on our understanding of the problem and our ability to address it effectively.

Microplastics and nanoplastics lurk beneath

While large plastic items like bottles and bags are easily visible and recognizable as pollutants, the vast majority of plastic pollution takes less obvious forms. Microplastics, tiny particles less than 5 millimeters in size, are a major contributor to this problem.

These particles originate from a variety of sources, including the degradation of large plastic debris over time, microbeads intentionally added to personal care products, and fibers released from synthetic clothing during laundry.

Due to their small size, microplastics often escape detection and can accumulate within the food chain and be easily ingested by aquatic organisms.

Large plastic debris sinks into river bed

Large plastic items can also become submerged, posing a hidden threat to aquatic ecosystems. This happens due to many factors.

The density of the plastic material itself plays a role, with denser plastics sinking more easily. The shape of an object also affects its buoyancy, as irregular shapes can trap air and temporarily prevent it from sinking.

Additionally, the presence of biofilms can significantly alter the fate of plastic debris. Biofilms are complex communities of microorganisms that can colonize plastic surfaces, increasing their weight and causing them to sink.

Once submerged, these plastics can interact with the benthic environment, potentially affecting sediment composition, oxygen levels, and organisms living on the river bottom.

Additionally, submerged plastic can release harmful chemicals into the water, compromising water quality and ecological balance.

plastic pollution in rivers

PHD. A study led by James Lofty. Researchers from Cardiff University's School of Engineering have shed new light on the behavior of plastic sinking in rivers.

Lofty and his team conducted a series of experiments in which they released more than 3,000 plastic objects into large water channels designed to simulate real-world river conditions.

Using high-resolution cameras, they tracked the activity of these plastics, revealing surprising findings. Contrary to previous beliefs, plastic fragments do not always sink in a uniform manner.

Their orientation may change as they descend, having a significant impact on their sinking speed and ultimately their distribution within the river.

“In our study, we demonstrate how plastic sinks in different directions. This significantly changes how fast a particle sinks. “It was previously thought that plastic always found a constant sinking direction and therefore sank at a constant speed,” explained Mr Lofty.

“However, we have shown that this is not the case for plastics that are fragmented and fragmented. This is important, because the sinking rate of a plastic particle is essential to understanding its transport. “This discovery significantly changes our understanding of how plastic flows through rivers,” Lofty added.

This new understanding has far-reaching implications for how we measure and manage plastic pollution in our waterways.

Tracking invisible plastic pollution in rivers

The research team took advantage of their experimental findings to further their understanding of the dynamics of plastic pollution in rivers.

They integrated their newly acquired knowledge about the different sinking behavior of different types of plastics into established physics-based equations that were initially designed for sediment transport prediction.

This integration included adapting equations to take into account the unique characteristics of plastic debris, such as its density, size, and shape distribution.

By incorporating these plastic-specific parameters, the researchers developed a sophisticated model that can measure the transport and distribution of submerged plastic pollution in rivers with high accuracy.

This model provides a valuable tool to assess the extent of plastic pollution in aquatic environments and inform targeted mitigation strategies. “Our method can be used in any river because this very well-known equation is also used for sediment,” Mr Lofty said.

This innovative approach overcomes the limitations of previous methods, such as underwater cameras and sonar, which are impractical for widespread use in rivers.

road ahead

The study's findings underline the importance of taking a comprehensive approach to tackling plastic pollution. We can no longer focus only on the debris visible floating on the surface. The invisible plastic hidden beneath also attracts our attention.

By understanding the full scope of the problem, we can develop more targeted and effective solutions. This includes not only cleaning up existing pollution but also preventing more plastic from entering our rivers in the first place.

This will require a multi-pronged approach, encompassing everything from better waste management practices to innovative materials and technologies that reduce our reliance on single-use plastics.

Lafey and his team's research is an important step in this ongoing fight. By revealing the hidden world of sinking plastic, they have empowered us with the knowledge and tools needed to protect our rivers and the delicate ecosystems they support.

This study has been published in the journal water research,


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