RWTH: Plastic pollution is becoming a global problem

Plastic particles can be found all over the world: in deserts, on mountain peaks, in the depths of the oceans and in arctic snow. In a review article in the journal Science, an international team of scientists warns that long-lived plastic waste not only exacerbates climate change, but could also have consequences for ecosystems and biodiversity that cannot be reversed. In order to contain this global threat, the massive input of plastic into the environment must be drastically reduced.

Between nine and 23 million tons of plastic were washed into oceans, rivers and lakes around the world in 2016, and 13 to 25 million tons ended up in terrestrial ecosystems – amounts of waste that will double by 2025 if nothing changes in the use of plastic . Only in a few, mostly very easily accessible places can humans still remove plastic waste from the environment, for example by cleaning beaches. Plastic ingress becomes a problem in particular due to its longevity and because the plastic is broken down into the finest particles, often only micrometers or nanometers in size, through physical, chemical and biological weathering processes, it emits free chemicals and is therefore hardly visible to the human eye in ecosystems around the world distributed.

“The problem in the oceans is that plastic waste is deposited in those places that are hardly accessible to humans: in deep water layers of the open oceans, on the sea floor or on remote coasts. Plastic can hardly be removed there, ”says co-author Professor Annika Jahnke, environmental chemist at the Helmholtz Center for Environmental Research (UFZ) and professor for exposure analysis at RWTH Aachen University. Another factor is that plastic, once it has sunk to the sea floor and is no longer exposed to weathering as a result of solar radiation or higher temperatures, has a long lifespan. “In the dark and cold deep sea, plastic will only weather extremely slowly,” she says.

The persistent persistence of plastic in the environment creates numerous problems, not just because the plastic particles continually release chemicals that are harmful to the environment. The particles also exacerbate the consequences of climate change, for example, because they disrupt the biological carbon pump in the oceans. This natural mechanism actually ensures that carbon dioxide from the atmosphere is bound by blue-green algae and phytoplankton and sinks into the depths after they die. However, small plastic particles in the upper layers of the oceans, the habitat of blue-green algae and phytoplankton, can inhibit their growth – for example due to restricted food intake or increased cloudiness of the water. That would have the consequence that less carbon dioxide would be bound from the atmosphere and fewer nutrients would end up in the deep sea. Sinking plastic particles, on the other hand, increase the transport of carbon in deep-sea sediments, but their food content for deep-sea organisms is presumably very low.

Plastic waste in the oceans also has an impact on biodiversity. “Researchers were able to detect plastic waste in more than 2,600 animal and plant species as well as microorganisms. Hundreds of studies have described the negative effects on marine organisms such as toxicity, mortality, changes in behavior, mobility or oxygen consumption, ”says co-author Mine Tekman, Alfred Wegener Institute Helmholtz Center for Polar and Marine Research (AWI) Reference to the AWI online portal LITTERBASE, where scientific studies on the subject of marine litter are compiled. For example, plastic slings and fishing nets lost during fishing are the second most common causes of death for the rare Mediterranean monk seal, of which only 600 to 700 individuals still exist.

Plastic pollution increases the stress on the oceans, which are already exposed to rising temperatures, acidification, overfishing and eutrophication. “If the long-lasting plastic ends up in the oceans, weathering will inexorably produce smaller and smaller plastic particles over time, and chemicals will be released that can cause toxic effects that cannot be reversed and which also damage the oceans. If these emissions cannot be drastically reduced, global plastic pollution could soon reach a tipping point, ”says Annika Jahnke.

Because it is particularly difficult to sample and detect small plastic particles in the vastness of the oceans or on the ocean floor, which is often several thousand meters deep, there is usually a lack of data with which the development of plastic pollution in the oceans can be predicted more precisely. That is why researcher Annika Jahnke is coordinating the MICRO-FATE project. As part of this, she crossed the Pacific with the entire project team and other scientists on board the German research vessel “Sonne” in 2019 to find out more about the whereabouts and occurrence of microplastics. “So far, estimates have mainly been based on computer models, individual data and observations from the air. In order to further refine the models, we are investigating what happens to the plastic in the ocean and what effects microplastics have on the environment, ”she explains.

More research is one approach to better understanding the negative effects of plastic waste on the environment. Nevertheless, enough knowledge is already known about the problems of plastic in the environment to drastically reduce the consumption of plastic. “What is needed are measures such as limiting the production of new plastics in order to increase the value of recycled plastic, or an export ban on plastic waste to countries that do not have good recycling infrastructures,” says AWI researcher Mine Tekman. Above all, it is important to act as quickly as possible in order to drastically reduce plastic pollution.

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