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The Inertia

Have you ever wondered how scientists even begin to study things like patterns in ocean pollution and movements of microplastics? Better yet, you can probably imagine the people working the hardest to fight these problems could benefit from useful information like being able to track where a majority of microplastics come from in the first place? Surprisingly, initial methods to keep tabs on such things rely on reports from plankton trawlers, according to a new report from the University of Michigan, and those same researchers have introduced the use of some far more advanced machinery for their work: satellites.

The new tracking method employed by the UM team is taking data from a system of eight micro-satellites that were launched in 2016 to track storms. Creating measurements for what they’re calling “ocean surface roughness,” they were able to find a correlation between radar measurements used to track wind speed and the existing data from plankton trawlers and ocean current models already used to predict the movement of microplastics.

“Areas of high microplastic concentration, like the Great Pacific Garbage Patch, exist because they’re located in convergence zones of ocean currents and eddies. The microplastics get transported by the motion of the water and end up collecting in one place,” says Chris Ruf, the Frederick Bartman Collegiate Professor of Climate and Space Science at UM. “Surfactants behave in a similar way, and it’s very likely that they’re acting as sort of a tracer for the microplastics.”

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One of the team’s headline-making findings with this new tracking method is that concentrations of microplastics in a body of water can vary by season. For example, the Great Pacific Garbage Patch shrinks to its smallest size in January, the thick of the Northern Hemisphere winter. Six months later, microplastic concentrations are at their highest in the exact same region come summer. Meanwhile, the same cycle is flipped in the Southern Hemisphere. The researchers’ hope is that straightforward data like this can direct an organization like the Ocean Cleanup, helping them know when and where to deploy their resources. The same discovery also helped UM researchers narrow down some of the greatest sources of microplastic flow into the ocean, like China’s Yangtze River.

“It’s one thing to suspect a source of microplastic pollution, but quite another to see it happening,” Ruf said. “The microplastics data that has been available in the past has been so sparse, just brief snapshots that aren’t repeatable.”

Next up, the researchers are testing hypotheses from their findings and conducting experiments in a wave-generating tank to learn the relationship between surface roughness and the presence of microplastics. Small wins that they hope add up to big gains in fighting a gigantic environmental problem.

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