Though we know millions of metric tons of plastic flow into the ocean each year, there is plenty of room for improvement in how we track its distribution throughout the seas. The Ocean Cleanup project has been experimenting with a new technique to fill in some of the blanks and has, what it says, is the first proof of concept for using a form of infrared imagery to quantify marine plastic pollution.

Around two years ago, the Ocean Cleanup Project conducted an aerial research expedition of the Great Pacific Garbage Patch to better understand the magnitude of the problem. This involved two slow flyovers at a speed of 140 knots and altitude of 400 m (1,312 ft) in a C130 Hercules aircraft, scanning the surface with LiDAR sensors, human eyes and a Short-Wave Infrared (SWIR) imaging system.

Where earlier research expeditions involving large fleets of vessels had given some insights into the problem, the goal of the aerial expedition was to survey larger chunks of plastic trash that couldn't be measured from the ocean surface.

But there were still some unknowns around how enlightening different elements of the survey would be. For example, the aerial photography taken aboard the C130 Hercules revealed larger chunks, but the team found it difficult to distinguish some pieces of plastic from the glistening sun, chips of wood and other pieces of marine debris.

Now the team has published scientific results concerning the effectiveness of the SWIR imaging technology. Plastic had previously been found to offer distinctive features when viewed in infrared in the lab, but how it would present in the vast, swirling ocean from that height and at that speed was still unknown.

The team picked out the 30 largest plastic items identified in its aerial photos and then examined those items through the lens of the SWIR imagery. It was able to glean certain spectral features common to the plastic pieces and not to the other debris, opening up some exciting new possibilities in efforts to better understand and tackle this huge problem.

"We have just published the first study exploring the SWIR spectra of ocean plastics in-situ," tweeted Julia Reisser, Oceanographer at the Australian Institute of Marine Science and author on the paper. "Our research highlights the potential of hyperspectral sensors to remotely quantity marine plastic pollution."

The Ocean Cleanup Project has towed its first system out toward the Great Pacific Garbage Patch, and is currently conducting a series of final tests in the North Pacific. It will look to build on this breakthrough by adapting the remote sensing technology for use on drones, which it will deploy to monitor the effectiveness of its first system as it goes to work on the patch next month.

The paper was published in the journal Environmental Science & Technology.

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