Lakes with more plastic than in the worst marine sites

Pollution by plastics and microplastics has had an impact on a global scale and has come to affect remote places, where human presence is minimal. A new study confirms for the first time that, in some cases, concentrations of plastic found in some bodies of freshwater are higher than those in some ocean gyres that accumulate large amounts of debris, known as plastic islands.

The research has been carried out by a team made up of, among others, Verónica Nava from the University of Milan-Bicocca in Italy, Rebecca Kessler and Ted Harris from the University of Kansas in the United States, Miguel Matias from the National Museum of Natural Sciences (MNCN) attached to the Higher Council for Scientific Research (CSIC) in Spain, and Miguel Cañedo-Argüelles, from the Institute of Environmental Diagnosis and Water Studies (IDAEA) of the CSIC.

“Lakes are like sentinels of pollution, since they end up accumulating plastic waste that is dispersed through various sources such as reservoirs or the atmosphere. In addition, once they reach their waters, lakes can retain, modify and transport plastic waste through the hydrographic basins towards the oceans” contextualizes Cañedo-Argüelles.

Among the lakes where the greatest contamination by plastic waste has been identified is Maggiore (Italy), Lugano (between Switzerland and Italy), Tahoe (United States), Neagh (United Kingdom) or Pantà de Sau in Catalonia. , one of those that comparatively show higher levels of microplastics. These lakes act as the main sources of drinking water for the populations that surround them. They are also fundamental areas for their respective economies, since numerous recreational activities take place in their surroundings. “The relevance of these results lies in the fact that, in addition to having a negative impact on the drinking water we need, plastic pollution has harmful effects on aquatic organisms and the functioning of ecosystems,” explains Nava.

Rebecca Kessler taking water samples in a lake. (Photo: Ted Harris)

The collaboration of almost 80 researchers has made it possible to take surface water samples, using plankton nets from 38 lakes located in 23 different countries, spread over 6 continents. This diversity has made it possible to represent different environmental conditions. “Once collected, the different teams sent the samples to the University of Milano-Bicocca where, with technologies such as Raman microspectroscopy, an extremely precise analysis was achieved with which we were able to confirm the polymeric composition of the microplastics. Among all that was found, the presence of polyester, polypropylene and polyethylene stands out especially”, says Miguel Matias. “In addition, we have been able to identify determining factors such as population density, urbanization, basin size and water retention times, which explain the vulnerability of lakes and reservoirs to plastic pollution,” he adds.

The long haul of plastics

“Plastic that accumulates on the surface of aquatic systems can promote the release of methane and other greenhouse gases. These residues can interact with the atmosphere, the biosphere and the lithosphere and affect the biogeochemical cycles”, explains Verónica Nava. “The circulation between the different elements of the earth, which go from living matter to inorganic matter through chemical reactions, is still not fully understood and it is necessary to carry out a holistic evaluation of plastic pollution in lakes,” he adds. she.

These results demonstrate the global scale of plastic pollution: no lake, even those furthest away from human activity, can be considered truly pristine: “This should prompt us to review pollution reduction strategies and waste management processes.” concludes Nava.

The project is part of the international Global Lake Ecological Observatory Network, focused on research on the processes and phenomena that are triggered in freshwater environments.

The study is titled “Plastic debris in lakes and reservoirs”. And it has been published in the academic journal Nature. (Source: IDAEA / MNCN / CSIC)