Scientists Find Three Worried Causes of American Microplastic Pollution

Microplastic You can think of it as garbage that never disappears. This new study of seemingly invisible pollution shows how durable it is from land to sea, to the air, and back again.

Every day, microplastics (often smaller than the head of the sewing machine needle) penetrate Our sea,our seafood, And ourselves body. Scientists now say the problem is more extreme than previously recognized.

To Research Published on Monday Minutes of the National Academy of Sciences, Researchers propose atmospheric microplastics — Fibers and fragments In the air — Even if you have already settled on land or in your body of water, you may re-enter the atmosphere.

Three impressive discoveries are:

• 84% of the atmospheric microplastics in the western United States come from road dust.
• The maximum concentration of microplastics in the atmosphere is estimated to be at sea.
• Antarctica does not contribute to the emission of microplastics, but it is still contaminated with microplastics.

what’s new – Co-author Natalie Mahowald He is a professor at Cornell University and specializes in earth and atmospheric sciences.Previous studies have shown that microplastics can reach remote areas far from the origin of the Earth, but this study provides new and amazing data, says Mahowald. Inverse..

“Our paper suggests that microplastics not only reach remote areas, but are also resuspended in the atmosphere from oceans, agricultural areas, or roads,” says Mahwald. I will.

In addition, Mahowald et al. Discovered the presence of approximately 1 gigagram (Gg) of microplastics in the atmosphere of the western United States. In context, 1 gigagram is equivalent to 1,000,000 kilograms.

The research team discovered three causes that contributed to the spread of microplastics in the atmosphere of the western United States: dust from roads, the sea, and agricultural production.

• Roads were the largest contributor to microplastics (84 percent)
• The second highest contributor was the ocean (11 percent)
• The last and least contributed source was agricultural dust (5%)

On average, this study suggests that particles remain in the atmosphere for various periods in the range of 1 hour to 6.5 days. This depends on the size and source of the microplastic.

How they did it — To measure the abundance of microplastics, the team obtained information collected by data stations in the western United States for 14 months.

Armed with this data, scientists modified the atmospheric model to identify where microplastics in the atmosphere came from, how long they spent in the atmosphere, and where they accumulated on the surface of the Earth.

They also examined the size of the microplastics and divided them into large, medium, and small particles (although they used medium size particles as a reference baseline).

Small particles were difficult to track and measure, so they contained only fine particles larger than 4 μm (micrometers). 4 micrometers is 0.004 millimeters.

For comparison Sewing machine needle head The range is 0.5 mm to 1 mm, so the particles can actually be very small.

Finally, scientists have applied the model to a global context to understand the greater impact of microplastics in the atmosphere.

Delve into the details — Previous studies have already found microplastics Enter the Earth’s atmosphere, This data provides new insights into a variety of sources that contribute to the spread of pollution.

“Our model and data combination suggests that these microplastics may come not only from road sources, but also from agricultural dust and the ocean,” says Mahwald.

Importantly, roads may not make a significant contribution to atmospheric microplastics. Instead, it is important that plastic particles are carried by wind or other means and deposited on roads, including roads far from human cities.

Tires on these roads break down plastic particles (otherwise too large to rise into the atmosphere) into finer microplastics that allow them to be released into the atmosphere.

However, research claims that the important role that the ocean plays in circulating microplastics cannot be understated. “Most continents are net importers of plastics from the marine environment, emphasizing the cumulative role of legacy pollution in the airborne load of plastics,” scientists write.

Important reason — Eventually, the team discovered that microplastics could move far away from their original dumping site. Studies have shown that the maximum concentration of plastic in the atmosphere is at sea, and Antarctica has its own microplastic pollution, albeit far from the actual production of microplastics.

“The idea that microplastics are resuspended means that any unmanaged plastic we accidentally dump into the sea or land can end up in other remote areas. “Mahowald says.

In addition, Mahowald’s research suggests an increase in microplastic contamination.And recent research has discovered microplastics in the placenta. Foetation, It is not yet known how microplastics affect health.

“Given these preliminary findings, the accumulation and transport of microplastics in the natural environment can have a negative impact on ecosystems and human health, with still unknown consequences,” the research team said. writing.

What’s next- Researchers write that their research “leads to more questions than it definitively answers.”

Some of these questions relate to data constraints. This survey relies on data from the western United States. In short, there is considerable uncertainty about the global application of these findings. As the author of the study states, “Plastic now swirls the earth.”

For example, the authors suggest that plastics are used more in road materials in Europe and Asia than in the United States. This can change the amount of plastic that enters the atmosphere from the road. Researchers also assume that Africa and Asia are the largest global sources of plastics, so further research is needed, especially on these continents.

Various agricultural practices around the world, such as the growing use of plastic mulch in China’s agricultural sector, could increase the release of microplastics into the atmosphere in these regions. On the other hand, coastal areas can have high atmospheric concentrations of microplastics from marine sprays. Changes in ocean currents can also affect the distribution of microplastics.

Ultimately, the team argued that our “relative ignorance” should drive us to improve the management of plastic waste and the technology that can capture and remove plastic from the ocean. I will.

Overview: Plastic pollution is one of the most pressing environmental and social problems of the 21st century. Recent research has highlighted the role of the atmosphere in transporting microplastics to remote locations. Allen et al., Nut. Geosci.12, 339 (2019) and J. Brahney, M. Hallerud, E. Heim, M. Hahnenberger, S. Sukumaran, Science368, 1257–1260 (2020)]. Here, we test the hypothesis of the most probable sources of atmospheric plastics using in-situ observations of microplastic deposits that combine atmospheric transport models with optimal estimation techniques. Results suggest that atmospheric microplastics in the western United States come primarily from secondary re-emission sources such as roads (84%), oceans (11%), and agricultural soil dust (5%). .. Using the best estimates of plastic sources and modeled transportation routes, most continents are net importers of plastics from the marine environment and play a cumulative role in legacy pollution in the airborne load of plastics. I emphasized. This effort uses high-resolution spatial and temporal deposition data and some hypothesized sources to constrain plastics in the atmosphere. Similar to the global biogeochemical cycle, plastics are now swirling around the world with well-defined atmospheric, marine, cryosphere, and terrestrial dwell times. Although the production of biodegradable polymers is advancing, our data suggest that existing non-biodegradable polymers continue to circulate in the Earth’s system. Due to limited observation and understanding of the source process, great uncertainty remains in the transport, deposition, and source attribution of microplastics. Therefore, we prioritize the direction of future research to understand the plastic cycle.