Probably all lakes in the world are polluted with these particles

According to new research, in which Polish scientists also took part, about 14 million tons of plastic end up in the oceans every year, but the problem of pollution also applies to freshwater. The researchers found microplastics in every lake they sampled.

Even those reservoirs that were previously considered untouched by human activity are not free from pollution.

The study, published in the scientific journal Nature, was conducted as part of the Global Network of Lake Ecology Observatories (GLEON). In total, 79 scientists from around the world took part in it, including Poles: dr inż. Marcin Biernaczyk and dr hab. Eng. Katarzyna Stepanowska from the West Pomeranian University of Technology in Szczecin, dr hab. Beata Messyasz from the University of Adam Mickiewicz in Poznań, dr hab. Agnieszka Pociecha from the Institute of Nature Conservation of the Polish Academy of Sciences and dr hab. Edyta Zawisza from the Institute of Geological Sciences of the Polish Academy of Sciences.

They found that the concentration of plastic in freshwater environments is actually higher than in so-called garbage patches in the oceans. “Some of these lakes are considered clean, beautiful places. But we found that even in these lakes the human influence is clearly visible” – the authors of the publication stressed.

Plastic pollution is one of the challenges of our time. Marine environments are considered to be the main recipients of synthetic waste and it is them that the majority of research on this phenomenon focuses on. However, as the authors of the paper in Nature point out, the emphasis on marine systems has overshadowed the role of freshwater as vital components of global plastics pathways. Meanwhile, it is these waters that accumulate plastic pollution at a rate similar to or even higher than the seas and oceans.

According to experts, global research on plastic waste in inland waters has not been carried out so far for two main reasons. The first is to focus on a limited number of freshwater systems in certain geographic regions. The second is the lack of standardized sampling methods, which prevents direct quantitative comparisons between individual experiments.

‘Until now, results from studies on plastics in lakes and other freshwater have been compared through meta-analyses and reviews that acknowledged that the comparability was limited due to inconsistent methods used across studies. global, nor has an attempt been made to identify and quantify the factors that cause plastic pollution in lake systems at this scale.

Experts united in the GLEON network have designed the first-ever large-scale study. The methodology was quite simple: freshwater tanks in the area were examined by dipping special nets with very small meshes into them and filtering the water for about two minutes. The samples were then sent to the coordinating center for analysis.

In total, the scientists collected samples from the surface waters of 38 lakes and other reservoirs, located in various geographic zones and with various limnological characteristics. Plastic contamination was detected in all of them.

‘Basically, our paper shows that the more people there are, the more plastic there is,’ the authors noted. Lakes located in areas with a relatively low population density were characterized by a relatively low content of microplastics, while reservoirs over which large human settlements are located were the most polluted.

‘Some of these lakes are seemingly pristine and beautiful, but microplastics were also present in them,’ they added.

According to them, many of the plastic particles polluting lakes come from such a seemingly harmless source as bathing clothes. “Such a trivial activity as entering the water in costumes made of artificial fibers leads to the fact that microplastics get everywhere” – they pointed out.

The study identified two types of reservoirs that are particularly susceptible to plastic pollution: lakes in densely populated and urbanized areas, and lakes with increased areas of deposition (the process of moving and deposition of loose materials), long water retention times, and high levels of anthropogenic impact.

The authors also remind us that although microplastics cannot be seen with the naked eye, the scale of microplastic pollution is as large as the conspicuous bottles and bags that create huge ocean garbage patches. “Hearing about plastic pollution, we imagine large objects floating on the surface, and we forget about all these particles. On a lake, even the most polluted one, we do not see giant patches of garbage (…) Only under a microscope, with a magnification of 40,000 times, we can see the enormous of these particles.”

According to the authors of the study, the most important conclusion from the study is that microplastics can be found in all lakes. ‘Of course, they are present in different concentrations, but they are literally everywhere. And the most important contributor to these pollutants is human interaction with lakes.’

The researchers emphasized that since plastic was found in all the samples analyzed, probably no lake in the world is free of it. Freshwater ecosystems can be considered to play a key role in the plastic pollution cycle.