Trawling Through the Murky World of Microplastics
On a recent sticky summer afternoon in Manhattan, a team of scientists took to the Hudson River to trawl for trash. There weren’t any mangled bags, plastic bottles, or other waterlogged debris bobbing on the water’s gray-green surface, but that’s not what the researchers were looking for, anyway—I tagged along as they piled into a boat to skim a fine-mesh net across the top of the water and ensnare the teeny pieces that only come into clear view beneath a microscope.
Microplastics, which are shards measuring less than five millimeters in diameter, can take many forms—they might be pellets, foams, films, lines, or nurdles (the goofy name for plastics made to be melted down into other plastics)—but they’re all pretty hard to spot with the naked eye. Increasingly, researchers are concluding that many waterways are host to a slurry of itty-bitty plastic pieces. Baseline data for microplastics in the Hudson River is pretty sparse, though, and mitigation tactics are still somewhat foggy. The surest way to track microplastics’ sprawl and scope is to collect samples over time. So, we cruised up and down the watery corridor between the New York City and New Jersey skylines at a speed of around five knots, on a mission to scoop them up.
At Pier 40, near Greenwich Village, they measured the water temperature and coordinates, then looked to flags flapping on the shore to see which way the wind was blowing. Since irascible weather and choppy water could affect their collection results, they estimated conditions on the water using the Beaufort scale, where 0 is a mirror-calm day, and 12 indicates hurricane-force winds. This was a 1, said Carrie Roble, the director of science and stewardship at Hudson River Park, and the project’s leader. “A pretty chill day,” she said, and as good as any for collecting nearly invisible trash from the park’s estuarine sanctuary.
We headed south, where the Statue of Liberty towered in the distance; jet skiers bounced past, shooting north, and white sailboats clustered farther afield. All the while, Emma Samstein, a high-school volunteer, sat with a foot on the net, to keep it from splashing up out of the water. (This is a free alternative to rigging up weights, and it’s also “a good thigh workout,” Samstein said.) The goal was to keep the net steady—since plastics float to the surface—without adding turbulence, which could cause them to disperse. As the boat puttered along, water and shards of plastic flowed into the net, which billowed alongside the vessel like a windsock. The trapped debris dropped into a plastic collection cup affixed to the bottom of the net. The irony of using plastic to find plastic, in a crusade against plastic, was not lost on anyone involved.