The cleanest place on earth is dirty

From November 30 to December 2, 2019, in order to confirm the distribution of microplastics in Antarctica, researchers collected 19 samples from various locations on Ross Island in Antarctica, and a total of 109 particles were confirmed to be microplastics; especially at the scientific base adjacent to Ross Island, Scott Base and Antarctica's largest McMurdo Station, the density of microplastics was almost three times higher. Researchers at the University of Canterbury in New Zealand discovered microplastics for the first time in new snowfall in Antarctica .

A paper published in the journal The Cryosphere said the particles contained 13 types of plastic, including PET, the most common type used to make beverage bottles and clothing, and the researchers believe the microplastics could pose a risk to the Antarctic food chain.

The ocean is the world's largest gathering place for plastic waste, and fish and birds often mistake microplastics for food.

01

Microplastics leave no land untouched

From November 30 to December 2, 2019, in order to confirm the distribution of microplastics in Antarctica, researchers collected 19 samples from various locations on Ross Island in Antarctica, and a total of 109 particles were confirmed to be microplastics; especially in the scientific base adjacent to Ross Island, Scott Base and Antarctica's largest McMurdo Station, the density of microplastics was almost three times higher.

This is the first time a study of this scale has been conducted in Antarctica, but during two expeditions in 2018 and 2019 with the research vessel Polarstern, researchers collected 34 surface water samples and 79 groundwater samples. In total, they filtered about 8 million liters of seawater and found microplastics in it.

Early studies of microplastics in Antarctica were conducted at research stations, in areas with high levels of shipping traffic and people, and more recent studies and citizen science projects in the Southern Ocean have reported microplastics in deep-sea sediments and surface waters; one foundation found microplastics in four samples collected using trawl nets in the Southern Ocean.

The research team led by Professor Patricia Holm (University of Basel) and Dr. Gunnar Gerdts (AWI) assumed that the concentration of microplastics in the remote Weddell Sea would be significantly lower. However, their measurements showed that the concentrations were only partially lower than in other parts of Antarctica. Image source: Internet

Microplastics are already present in large quantities in marine ecosystems around the world, from the tropics to Arctic sea ice and now in the Southern Ocean.

(A) Major Antarctic coastal facilities operated by the National Antarctic Program have recorded microplastics and macroplastics found in surface waters, beaches, and sediments south of the polar front. Plot boundaries: average location of the polar front. Red dots are research stations and facilities. Yellow crosses indicate records of macroplastics. Green crosses indicate records of microplastics. Purple arrows indicate the direction of major ocean currents.

(B) Average number of vessels (including fishing, tourist and scientific research vessels) within a 1°×1° spatial grid cell from November 2009 to January 2010.

(C) Near-surface drifter trajectories (1989-2015). The figure shows all drifters found south of 48°S; those deployed north of the average position of the polar front (thick black line) and crossing the polar front to the south are highlighted with red/orange shading. The deployment locations of these latter drifters are indicated by black circles. Image source: Internet

How do microplastics achieve their “global travel”?

Microplastic particles enter the ocean through two channels, one of which is wastewater.

For example, in Antarctic waters, microplastics are found in wastewater discharged from scientific research stations and expedition vessels, fishing boats and tourist ships.

Conventional wastewater treatment, including tertiary treatment technologies such as microfiltration, may not be able to completely remove microplastics, a situation that may be exacerbated in remote polar regions where operational difficulties may reduce treatment efficiency.

Light blue represents the total amount of plastic produced, dark blue represents the amount of mismanaged plastic waste, gray represents plastic waste entering the hydrosphere, and red represents plastic waste entering the ocean. This pattern is called a plastic funnel. 400 million tons of plastic economy has turned into 1 million tons of marine plastic problem. Image source: Ocean Cleanup Foundation

This wastewater treatment method is already very backward. A report found that 52% of the 71 research stations in Antarctica did not even have a wastewater treatment system, which made the pollution even worse.

The other is through the decomposition of large plastics into microplastics, which then enter the ocean.

Numerous studies have shown that microplastic particles persist in the marine system, accumulating in ocean circulation, including surface and deep sea waters and deep-sea sediments, and eventually entering deep and deep-sea sediments and animals around the world.

Research has found that marine microplastic pollution has primary and secondary sources.

There are many sources of primary microplastics, such as personal care products such as toothpaste, shampoo and shower gel, and fibers from laundries may release microplastic fibers into wastewater.

Studies have shown that a polyester fleece jacket can release more than 1,900 fibers each time it is washed, of which about 90% of microplastics may be retained in sewage treatment plants. Microplastics can "pass smoothly" through sewage treatment facilities and be released into the nearshore marine environment in a basically unchanged state.

Secondary microplastic pollution, including particles and fibers, resulting from the breakdown of macroscopic marine plastic fragments, is also common in oceans around the world.

About half of discarded plastic floats in seawater and is therefore potentially subject to degradation by ultraviolet (UV) radiation and decomposition. Several comprehensive studies evaluating oceans near densely populated areas found that primary and secondary microplastics contribute most to overall microplastic levels in the marine environment from secondary sources.

Secondary microplastics are known to be present in the ocean surface and deep waters, as well as in deep-sea sediments in all the world's oceans. A recent global assessment suggests that about 6.4 million tonnes of plastic enter the ocean each year, with about 5 million pieces of solid waste thrown from ships or dropped from boats.

Antarctic microplastic pollution is never an isolated case, but it exposes the seriousness of this pollution.

02

Plastic waste goes around in circles

The major current systems in the Southern Ocean include the eastward-flowing Antarctic Circumpolar Current, the westward-flowing Antarctic Coastal Current, and the clockwise-flowing Weddell and Ross Currents.

The polar front in the circulation was once considered by researchers to be a hope for preventing the spread of microplastic pollution because it can block the exchange of materials from low latitudes.

But in reality, the polar front creates eddies that transfer material southward . In areas like the western Antarctic Peninsula, the polar front is close to the Antarctic continent, allowing seawater from lower latitudes to be transferred to the nearshore environment via a shorter route.

Material south of the polar front can be transferred to the Antarctic continent by southward-flowing branches of the regional circulation, for example in the Weddell and Ross Seas, where interaction with the Antarctic Coastal Current may lead to further dispersal.

This will affect four habitats in the Southern Ocean: the pelagic zone, benthic zone, nearshore zone and intertidal zone. The food webs here are fluid, unstable, and have a rapid turnover, and are all affected to varying degrees by microplastics.

Based on experiments using high concentrations of microplastics, filter feeders are expected to ingest a large proportion of food in zooplankton communities because their feeding method is to filter food from large volumes of water, and microplastics may disrupt the biological processes of zooplankton and affect Antarctic krill, which form the basis of the continental food chain.

Antarctic krill is an ecologically important filter feeder whose population distribution is uneven in both space and time, with about 25% of its biomass concentrated in 10% of its total habitat area, namely the Scotia Sea and Drake Passage.

The Scotia Sea is one of the areas with high shipping traffic in the region and may be a key area for microplastic ingestion by krill. Evidence from the Northern Hemisphere suggests that microplastics may cause toxicological impacts in pelagic ecosystems via keystone species at the base of the food chain and through the food chain. These processes may negatively impact higher predators such as fish, seabirds, seals and whales.

Just from the point of marine life, it is not difficult to understand why microplastics can be on human tables and ingested. It is imperative to control microplastic pollution, not only to eat less plastic, but also to purify the marine environment. For example, a study published in the journal Microbial Genomics found that the common mealworm (Zophobas morio, also known as the "super mealworm") can devour polystyrene (a colorless and transparent thermoplastic) with the help of a bacterial enzyme in its intestine. "The mealworm is like a small recycling factory, tearing up polystyrene with its mouth and then 'feeding' it to the bacteria in the intestine." This worm with an "appetite" for polystyrene may be the key to large-scale recycling of plastics. Scientists hope that this "upgraded" biological cycle can bring new ways to recycle plastic waste, thereby reducing the amount of landfill.

Each of us is working hard to protect the marine environment, prevent the "plastic plague" from spreading, and make the white earth clean again.

References:

[1]https://www.sciencedirect.com/science/article/pii/S0048969717308148?via%3Dihub

[2]http://www.stdaily.com/index/kejixinwen/202206/0f5ac84114734c59b3e594a6d599f0b7.shtml·https://tv.cctv.com/2022/06/10/VIDEznP0t1fR8tH6ebEYlXQt220610.shtml

[3] "Environmental Sciences and Technology" magazine

Source: China National Geographic BOOK