Do microplastics float or sink?

What are the main components of microplastics?

The new study identifies points on the peninsular coastline with maximum concentrations of up to 500,000 microplastics per square kilometer (mp /km2), a value much higher than the average value, which is 100,000 mp / km2. “These results are consistent with studies done in other regions of the Mediterranean, a marine ecosystem that is considered one of the largest floating microplastic sinks in the world,” notes William P. de Haan.

In the coastal waters of Murcia and Almeria, the variety of polymers is greater – especially nylon, polyurethane or polyethylene terephthalate – than that observed in Catalan waters, and the denser microplastics, which sink more easily, predominate. As for colors, the most abundant are opaque white (46% in Murcia and 54% in Almeria) and dark colors (20% and 12%, respectively). On these coasts, the marine dynamics – with the arrival of surface water from the Strait of Gibraltar – could favor the irruption of microplastics from the Atlantic Ocean.

Microplastics in food

The fact that plastic contaminants are reaching the oceans more frequently than before is well documented. However, until now, there has been little information about how much of the waste generated makes its way into the ocean, or information about how much of it is already in the sea, particularly microplastics.

Of the total CO2 emissions produced by humans, approximately 30-40% dissolves in oceans, rivers and lakes. This causes a drop in the pH of the water, a process known as ocean acidification, which affects all marine life and the ecosystem in general.

Some studies have shown, for example, that marine organisms (from oysters to whales) that depend on filtration systems for food are especially vulnerable because they can ingest the microplastics, which in turn can clog these systems, affecting their tissue. In addition to this, plastic has a great capacity to absorb other chemical contaminants that are also found in the sea, such as pesticides or polychlorinated biphenyls. An additional problem is that microplastics can act as vehicles for other contaminating compounds, since marine organisms can ingest these plastics and be affected by the aforementioned chemical compounds.

How plastic becomes microplastic

We found up to 1.9 million pieces of microplastic in a 5-cm-thick layer covering just one square meter, the highest levels of microplastics yet recorded on the ocean floor.

Now we have discovered how a global network of deep-sea currents transports microplastics, creating plastic hotspots within large sediment drifts.  By taking a ride on these currents, microplastics can accumulate where marine life abounds.

We examined an area of the Mediterranean off the west coast of Italy, known as the Tyrrhenian Sea, and studied bottom currents flowing near the seafloor.  These currents are driven by differences in water salinity and temperature as part of an ocean circulation system that spans the globe.

In the lab, we separated microplastics from the sediment and counted them under microscopes, analyzing them by infrared spectroscopy to find out what types of plastic polymers were present.

Microplastic problems

Aware of this reality, a team of 12 engineering students from the University of Sherbrooke in Quebec (Canada) invented a revolutionary vacuum cleaner capable of absorbing microplastics from beaches without getting clogged with sand.

How did they do it? Simple. By creating a machine that sucks up both plastic and sand. Both get into a tank of water, the sand sinks and the microplastics float away. Does it work? Beautifully!

The revolutionary Canadian idea has spread around the world, and what started as a student project is now projected as an export product to be used by coastal communities to combat the microplastics that wash up on beaches.