MOSCOW — The vast and ancient Lake Baikal in Russia has a rich history, providing a home for thousands of plants and animal species and sustaining the nearby Buryat tribes going back millennia. It’s the world’s deepest and oldest lake, and has survived for some 25-30 million years. But its depths bury a dark secret: a growing layer of microplastic pollution that threatens the health of Lake Baikal.
A new study looking at microplastics was conducted in the southeastern coast of the lake and the Small Sea in Southern Siberia. These places are not the most populated on the Baikal shore; no more than several hundred people live there permanently. But the water sampling areas were chosen not by chance: all of them are touristic areas, so they are considered to have a significant human impact.
Olesya Ilyina, head of the expedition to Baikal, says, “In terms of water surface area, the concentration of particles corresponds to a high level of plastic pollution and is comparable to their content in man-made freshwater bodies, such as the North American Great Lakes.”
The chemical composition of the plastic microparticles is not much different from particles found by colleagues of Russian scientists many years ago in other lakes, oceans and seas. Lake Baikal is filled with polyethylene, polypropylene and polystyrene, the decay products of various household packaging materials.
Pollution from trash, industrial waste and fishing nets
Dr. Maxim Timofeev, director of the Research Institute of Biology at Irkutsk State University, says that microplastic particles get into Baikal waters in different ways: Plastic is largely carried by the Selenga River that goes from Mongolia to Russia and flows into the lake. The second source of pollution is spontaneous garbage dumps and the third is the sewage treatment plants.
“Fragments, films and foam are products of the breakdown of plastic into small particles in the coastal zone,” Timofeev explains. “Fibers have a different origin: This type of microplastic particle comes from washing the synthetic clothing worn by much of the planet’s population.”
Abandoned fishing nets are a breeding ground for harmful substances, and a place where fish die
Another way for plastic to get into Baikal waters is through cheap Chinese-made polymer fishing nets. According to local ecologists, they cling to the rocky bottom and tear, and no one brings them back up to the surface.
Abandoned fishing nets have long been a breeding ground for harmful substances and a place where fish die. Local ecologists and scientists from federal research institutes of the Russian Academy of Sciences are trying to solve this problem. They recently established a regional public organization, Responsibility Depth, in Irkutsk.
According to Alexander Krasovsky, Responsibility Depth president, past generations were more responsible. Further, the nets were woven by hand and were stronger; if they broke, they weren’t abandoned. New polymer nets are hardly toxic, although their chemical compounds haven’t been fully studied. Over time they too undergo degradation, disintegrating into microscopic polymer fibers and settling on the muddy bottom.
Krasovsky says that now, few fishermen who lose a net are concerned about retrieving it: “Why do it when you can buy a new cheap Chinese net at the nearest market? And it all starts again.”He explains that often, nets lay on the sea floor, start to grow algae and rot. This process is accompanied by the consumption of oxygen, resulting in decreased water quality and fish death.
“In general, the net becomes overgrown with algae, and over time they produce toxins that are bad for fish and people,” he says.
The harm of decomposing plastic
Although, the damage caused by these nets has not been sufficiently studied, harm is also being done by those other external sources: rivers flowing into Lake Baikal, waste dumps and garbage thrown by tourists. And the quality of plastic depends on its source.
The main source of synthetic fibers in the water is simple laundry.
Dr. Timofeev highlights the differences in microplastic pollution in Baikal and Lake Khuvsgul in Mongolia. The composition of Baikal water pollutants is dominated by synthetic fibers, while in Khubsugul, it’s fragments of microplastics. Dr. Tomofeev says this difference tells us about the sources of the main pollution and determines the priority tasks: The source of plastic micro- and macro-fragments is precisely the coastal trash that gets into the water.
“Therefore, in the case of Lake Khubsugul, it is enough to establish a system of removing garbage accumulated on its shores to solve the problem of such pollution,” he says. “The situation in Baikal, on the other hand, is more complicated.”
It is known that the main source of synthetic fibers in the water is simple laundry. The dominance of synthetic fibers in the pollution of Lake Baikal is a marker of an ineffective or even non-existent system of treating sewage from settlements. Dr. Tomofeev says that “Therefore, the highest priority is the urgent installation of modern treatment facilities, both directly in the populated areas on the lakeshore and in its tributaries.”
A global look at microplastics
The ratio of plastic particle size groups in Baikal is not significantly different from the Pacific garbage patch. According to biologists, in Baikal, microplastic particles make up 34.3%; in the North Ocean garbage patch it’s 52.5% and in the Atlantic, Pacific and Indian Oceans it’s 34.9%. At the same time, larger-sized pollutants — from 1.01 to 4.75 mm — in the waters of Lake Baikal make up 56.2% of particles, almost as much as was found in the three oceans: 57.5%.
Philip Sapozhnikov, a senior researcher at the Institute of Oceanology at the Russian Academy of Science, says that polluting often includes colonial diatom algae that form large branching colonies of biopolymer (matrix) threads with their cells sitting at the ends. Sapozhnikov explains, “The colonies are heavy and overgrown microplastics — even with their own buoyancy, which is close to neutral — easily go to the bottom and are buried in the ground.”
In addition, many particles of plastic are, in principle, heavier than water and sink under their own weight. The thin layer of microplastics that is gradually gathering at the bottom of Lake Baikal can be used in the near future to mark our era of super consumption, using the geological profiles of sedimentary rocks. The loose sediments at the bottom of Lake Baikal already contain many microparticles of plastic forming a centimeter-thick layer. At this rate, scientists will have to admit that it’s no longer possible to remove all microplastics from Baikal water.
