The Pyrenees is the largest mountain range in southwestern Europe, the border between France and Spain, stretching from the Shore of the Gulf of Biscay in the Atlantic Ocean in the west to the Mediterranean coast in the east, with a length of about 435 kilometers and an altitude of mostly above 2,000 meters. (Oriental IC/Photo)
(This article was first published in Southern Weekend on June 6, 2019)
A growing body of evidence shows that plastic pollution is worse than we think: it's not just found in drinking water, creeping into our food chain, and even in the most inaccessible natural environments on Earth.
You've probably heard that microplastics have found their way into our soils, oceans, drinking water, and even human waste. Now, scientists have found that these tiny pieces of plastic can even float in the air, landing in the most desolate corners of the planet with the help of wind and rain and snow.
A recent study published in Nature Geoscience showed that in the French Pyrenees, which have long been thought to still preserve a pristine ecology, scientists have found tiny pieces of plastic that fall from the air like artificial dust. These microplastics can be carried with the wind, efficiently passing through the atmosphere and reaching the most remote areas on Earth, such as the Pyrenees. Scientists think this is just the beginning, that free-rider particles like this could travel thousands of miles, and that the threat they pose is twofold: Atmospheric transport enables microplastics to be transferred from sources of pollution to other clean environments, and long trips by microplastics take pollutants where they go, while animals, including humans, inhale the gases.
<h3>Microplastics that drift with the wind</h3>
Microplastics are plastic particles with a particle size of less than 5 mm and consist of a variety of complex polymers and added chemicals. Microplastics were originally found in the ocean, but scientists are gradually realizing that they are also found in freshwater systems, soils and atmospheres.
In the latest study, published on April 15, 2019 in Nature Geoscience, researchers installed two types of atmospheric sediment collectors at the Bernaduz Weather Station in the Pyrenees to study the air conditions in the Pyrenees. From November 2017 to March 2018, scientists took samples about once a month and then analyzed the collected particles. The results found that there was a large amount of microplastics in the air in the area, and the study estimated that on average, 249 fragments, 73 layers of film and 44 fibers were deposited in the area per square meter per day. Using a technique called air mass trajectory analysis, they calculated that the transport distance for these microplastics was 59 miles (95 kilometers). Researchers speculate that the microplastic rain in the Pyrenees may have been carried by wind blowing from big cities like Barcelona.
Only two previous studies have looked at the presence of microplastics in the air, one in Paris, France, and the other in Dongguan, China. The size and type of microplastics found in the Pyrenees are different from those measured in previous studies of atmospheric sediment microplastics in Paris or Dongguan. The main particles deposited in the air in Paris and Dongguan are elongated fibers of more than 100 microns, composed of polypropylene or polyethylene terephthalate (PET), which is usually derived from clothing or other textiles. In the Pyrenees, however, most plastic fragments are smaller than 25 microns and consist mainly of polystyrene and polyethylene fragments, which are commonly found in many packaging materials. According to the results of the study, polystyrene is particularly susceptible to weathering or ultraviolet degradation from the sun, making worn debris more susceptible to being blown away by the wind.
With this discovery, the researchers revealed a new horror of plastic pollution. Scientists already know that microplastics can be suspended in the air in big cities like Paris and Dongguan, China, but no one has yet shown how far these things can go. What's less clear yet is how different types of plastics— from polystyrene to polyethylene to polypropylene —spread throughout the atmosphere depending on their material properties. Another aspect, considering the unique properties of plastic decomposition. As microplastics decompose, their properties theoretically change. For example, one fiber may split into two fibers, resulting in new parts with new aerodynamic properties. Little is also known about the shape of microplastics, whether it is films, fibers or fragments, and it is not very clear how the shape of microplastics affects their movement. So scientists want to use 3D models to simulate how far microplastics can travel in the air.
The scientists involved in the study plan to expand the scope of the study and collect more detailed samples from other remote areas more frequently. "It's not just local pollution, it's not just happening in cities," said Steve Allen, an atmospheric and environmental scientist and co-author of the study. ”
<h3>Visitors from remote areas</h3>
The microplastics found in the Pyrenees are not unique. In many areas where humans have not yet set foot, microplastics have quietly arrived and become the main "residents" of the local area.
Microplastics once appeared in the Arctic, where the process of sea ice freezing and melting transports plastic particles. Microplastics have also recently been found in Switzerland's Forni glacier, confirming the widespread pollution of natural resources by plastics. The study speculates that 40 percent of the microplastics in the glaciers may have been blown from nearby settlements and towns; the other 40 percent could have come from outdoor clothing designed to adapt to harsh climates. Most outdoor clothing for hikers traveling to the area is designed for low temperatures and high altitudes, and the material of the clothing is a mixture of synthetic and natural fibers. The researchers found 75 particles in the glacier sediment samples and speculated that there might be 162 million plastic particles in the entire Fernie Glacier. The study, conducted by Dr. Roberto Sergio Azzoni and his team at the University of Milan, was recently presented at the European Geoscience Union conference in Vienna, Austria.
Not only that, but microplastics have also been found in the deepest part of the earth that humans can reach. The Mariana Trench is considered the closest sea to the mantle that humans can reach, at a depth of 11,034 meters below sea level, and several assessments have reported that plastic has reached this area. In February 2019, researchers from Newcastle University's School of Natural and Environmental Sciences published in the Royal Society Open Science that they were in the Mariana Trench and five other trenches with a depth of more than 6,000 metres (the Peruvian-Chile Trench in the southeast Pacific, the New Hebrides Trench and the Kmadeke Trench in the southwest Pacific, Japan Trench and Izu Ogasawara Trench in the northwest pacific ocean) captured and analyzed marine animal samples and found that in all six trenches, foot segments were found to ingest microplastics, and the closer they were to the seabed for feeding, the more microplastics they ingested. In 2017, china's manned submersible Jiaolong brought back marine organisms from the depths of the ocean was also analyzed, and microplastics were detected in marine organisms living at a depth of 4500 meters.
Microplastics are more far-reaching than the human footprint, and they have preempted the areas that humans have not yet widely explored in different ways.
<h3>Plastic Petri dishes</h3>
Ubiquitous microplastic pollution is no longer just an environmental concern, they easily absorb toxic chemicals (such as pesticides and heavy metals) during their spread, and may also carry harmful bacteria. Researchers at the National University of Singapore found in a study that more than four hundred species of bacteria were found on 275 pieces of microplastics collected from local beaches, including those that cause gastroenteritis and wound infections in humans, as well as those linked to coral reef bleaching. Scientists are beginning to worry about the potential health effects of microplastics.
When microplastics enter the organism, humans need to worry about more than just the plastic itself. Previous studies have shown that mussels are harmed by these toxins when they eat microplastics, and that the toxins filtered out of the microplastics cause the mussel larvae to grow in an abnormal way. A 2018 study suggests another way in which plastic can harm marine life: Microplastic pollution disrupts the relationship between predators and prey, which can disrupt the entire food chain. The study, published in November 2018 in Biology Letters, looked at the common jade snail, which feeds on algae and crabs as its predators. The central position of the snail in the food chain makes it a key species on the beach and is widely eaten by people. When a crab approaches a snail, chemical signals usually cause the shellfish to take evasive actions, such as hiding in a shell or under a rock. But in the lab, when these snails were placed in water along with microplastics (the concentrations of microplastics used in the experiments were similar to those on the beach), they did not respond. Microplastics are known to absorb heavy metals and persistent organic pollutants, so the study's researchers believe that the release of this chemical mixture interferes with the snail's senses. After eating the jade snail contaminated with microplastics, what kind of harm will be caused to human health is still unknown. But in ecosystems like coral reefs, plastic has been shown to be a vector for disease. A piece of plastic is like a small Petri dish that can hold all kinds of bacteria, including pathogens. As they move along the reef, they come into contact with one type of coral and another and spread disease.
Currently, the world produces about 370 million tons of plastic each year, equivalent to the weight of 2.5 million blue whales. More than 90% of the products produced by humans are not recycled. Scientists have been documenting plastic pollution for decades, but a growing body of evidence shows that plastic pollution is worse than we think: Not only does it exist in our water, creeping into our food chain, but it also drifts with the wind in our most pristine natural environment. Filling the earth with plastic is a huge gamble, and it is foreseeable that without intervention and allowing things to continue, humanity will undoubtedly lose in this game.
Southern Weekend contributed to Zhu Yehua