Visible ocean plastics just the tip of the iceberg
Simulations find the majority of ocean plastics may be on the seafloor or otherwise difficult to monitor, with vastly more plastic waste likely trapped on land

Date:
March 18, 2022
Source:
Kyushu University
Summary:
Simulating a half century of movement and degradation of plastic
waste in the ocean, a new study estimates that nearly two-thirds
of ocean plastics are outside the reach of current monitoring
methods. Furthermore, the study suggests that the estimated 25.3
million metric tons of total ocean plastics may represent only 5% of
all mismanaged plastic waste to date, with the rest still on land.



FULL STORY ========================================================================== While the billions of tons of plastic products produced in the "Plastic
Age" of the last half-century have drastically changed the way we live
for the better, the plastic waste that has made it into the environment
is posing new challenges for nature.


========================================================================== Seeking to simulate the fate of plastics that have made it into our
oceans, a new study led by Kyushu University estimates that 25.3 million
metric tons of plastic waste has entered our oceans and nearly two-thirds
of that cannot be monitored.

Even more alarmingly, the analysis suggests that this may only be the
tip of the plastic-waste iceberg, with another 540 million metric tons of mismanaged plastic waste -- nearly 10% of all plastic produced so far --
still trapped on land.

While scientists have been surveying the oceans' surfaces and beaches to determine how much plastic waste has made it into the oceans, copious
amounts of ocean plastics are thought to be well below the surface or
on the seafloor, hidden from the reach of scientific observation using
common sampling gear.

"To assess the amount and whereabouts of plastic waste in Earth's oceans,
we have to consider the whole process from their birth to burial,
starting with emission from rivers into the ocean and continuing with
their transportation and fragmentation into pieces," says Atsuhiko Isobe, professor at Kyushu University's Research Institute for Applied Mechanics
and leader of the study.

In the new work, Isobe's team attempted to estimate the amount of
these hidden ocean plastics by creating models that simulate these
processes. They drew on existing studies to derive parameters that
describe how plastics breakdown and age, and used satellite-derived wind
data to incorporate movement of the particles.



==========================================================================
As sources of plastic waste for the simulations, they adjusted recent
estimates of plastic-debris emission in rivers by either the country's
gross domestic product going back to 1961 or predictions of mismanaged
plastic waste generation after 2010. They also added an ocean-based
component from the worldwide fisheries industry, which is said to produce
20% of river plastic emissions.

Their results estimate that large plastics and smaller pieces of so-called microplastics floating on the ocean surface each account for only about
3% of all ocean plastics. While a similar amount of microplastics --
plastic fragments less than five millimeters in size -- was estimated to
be on beaches, 23% of the ocean plastic waste was larger plastic litter
on the world's shores.

However, the simulations suggest that the remaining two-thirds of ocean
plastic may be in locations that make it impossible to monitor. A little
over half of this is heavy plastics that settled on the seafloor because
they are denser than seawater. Half of plastic products today are made
from these heavy plastics, which include polyethylene terephthalate
(PET) and polyvinyl chloride (PVC).

The remainder are old microplastics emitted years and decades earlier
that have since been removed from the ocean surface and beaches and
stored in the ocean floor and elsewhere in the world's oceans.

But compared to ocean plastics, the amount of mismanaged plastic waste
on land that could find its way into ecosystems and the ocean in the
future may be twenty times larger.



==========================================================================
The researchers arrived at their figure for total mismanaged plastic
waste - - which is one tenth of the 5.7 billion metric tons of plastics produced to date -- by combining their estimates for the yearly emission
of plastic waste into the oceans with recent estimates for the total
amount of plastic waste that was not recycled, incinerated, or otherwise properly contained.

Being indecomposable in nature, this half a billion metric tons of
mismanaged plastics will most likely outlive humans on this planet.

"We were able to estimate the budget of ocean plastics, but they are
only the tip of plastic-waste iceberg on Earth," says Isobe. His next
task is to assess the whereabouts of the nearly half a billion metric
tons of mismanaged plastics trapped on land.

"That's going to be a Herculean task. Few advancements have been
made so far in the field of 'terrestrial plastics' due to the lack of observation methods." Undeterred, Isobe recently launched a citizen
science program using crowdsourced photos and AI to assess the mass of
plastic waste dumped in cities and on beaches. At the same time, he is continuing to monitor and develop our understanding of what is happening
to the plastics that make it to our oceans.


========================================================================== Story Source: Materials provided by Kyushu_University. Note: Content
may be edited for style and length.


========================================================================== Related Multimedia:
*
Simulations_of_the_emission_and_subsequent_transport_and_breakdown_of
ocean_plastics ========================================================================== Journal Reference:
1. Atsuhiko Isobe, Shinsuke Iwasaki. The fate of missing ocean
plastics: Are
they just a marine environmental problem? Science of The Total
Environment, 2022; 825: 153935 DOI: 10.1016/j.scitotenv.2022.153935 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220318092128.htm

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