Satellites track microplastic hotspots in the ocean
Image credit: nasa
A new technique allows microplastics to be easily tracked from space using satellites, University of Michigan researchers have found.
The satellites are able to track soapy or oily residue in seas and oceans which have been shown to carry microplastics.
Microplastics – tiny flecks that can ride ocean currents hundreds or thousands of miles from their point of entry – can harm sea life and marine ecosystems, and they’re extremely difficult to track and clean up.
But the researchers believe satellites could offer day-by-day timelines of where microplastics enter the water, how they move and where they tend to collect, for prevention and clean-up efforts.
Data recorded by the Cyclone Global Navigation Satellite System (pictured) showed less surface roughness – that is, fewer and smaller waves – in areas of the ocean that contain microplastics, compared to clean areas.
In preliminary testing, they used the technique to spot suspected microplastic releases at the mouth of China’s Yangtze River and to identify seasonal variations in the Great Pacific Garbage patch, a convergence zone in the North Pacific Ocean where microplastics collect in massive quantities.
A new study shows that the anomalies in wave activity are caused not by the plastics themselves, but by surfactants – soapy or oily compounds that are often released along with microplastics and that travel and collect in similar ways once they’re in the water.
Professor Chris Ruf, author of the study, said that a satellite-based tracking tool would be a major improvement over current tracking methods, which rely mainly on spotty reports from plankton trawlers that net microplastics along with their catch.
“But we need to be cautious and fully understand the system’s limitations before putting it into widespread use,” he added.
Using the facility’s wave tank, the researchers measured the effects of surfactants and microplastic pellets on waves generated both mechanically and by wind from a fan.
They found that, in order for microplastics to affect surface roughness, their concentrations had to be much higher than those typically found even in polluted areas of the ocean.
The researchers found that surfactant-laden water required more wind to generate waves of a given size, and that those waves dissipated more quickly than they would in clean water.
“We can see the relationship between surface roughness and the presence of microplastics and surfactants,” said corresponding author on the paper Yulin Pan. “The goal now is to understand the precise relationship between the three variables.”
They plan to use a combination of water sampling, satellite observations and computer modelling to build that understanding. Ultimately, they hope to develop a system that governments, clean-up organisations and others can use to both spot existing microplastics and predict how they’re likely to travel through waterways.
Sign up to the E&T News e-mail to get great stories like this delivered to your inbox every day.