Plastic in the sea can be seen from space, the test in the Mediterranean

The images were taken by the Sentinel-2 satellites of the European Union's Copernicus program

ROME - Satellites currently in orbit can be used to monitor the state of marine plastic pollution.This is what was highlighted by an international research in which the Institute of Marine Sciences of the National Research Council of Lerici (Cnr-Ismar) participated, as reported by the Cnr in a press release.Using a series of 300,000 satellite images taken every three days for six years, with a spatial resolution of 10 meters, Thousands of waste strips have been identified, some more than a kilometer long and some up to 20 km.These data have allowed us to create the most complete map to date of floating marine waste pollution in the Mediterranean.

To be detectable by existing satellites, plastic and other floating debris must aggregate into dense zones at least ten meters long.These floating formations, known as windrows, patches, stripes or swaths, often take the form of filaments, resulting from the convergence of currents on the sea surface. The presence of a waste strip indicates a high level of pollution in a specific place and time.Through research it has been seen that the abundance of these patches is sufficient to map pollution and reveal trends over time. The images were taken by the Sentinel-2 satellites of the European Union's Copernicus programme, whose sensors, however, are not designed for waste detection, and therefore have a rather limited capacity for plastic detection.“Searching for multi-meter waste aggregates on the sea surface is like searching for needles in a haystack– explains Stefano Aliani, research director and oceanographer of Cnr-Ismar – Despite the unspecialized satellites, we managed to identify the most polluted areas and their main changes over the course of weeks or years.For example, aWe have observed that a lot of waste enters the sea when there are storms“.

The analysis of satellite images, carried out with supercomputers and advanced algorithms, has made it possible to understand that these accumulations in the coastal windrows are mainly due to the emissions of terrestrial waste in the immediately preceding days.Knowing this aspect therefore makes these trainings particularly useful for the surveillance and management of plastic pollution, demonstrating the applicability of the study to real cases.“This tool is ready to be used in different contexts:We are convinced that it will teach us a lot about the waste phenomenon, including identifying sources and routes to the ocean– comments Giuseppe Suaria, researcher at the Cnr-Ismar of Lerici – Furthermore, Our detection ability would improve enormously if we put dedicated plastic observation technology into orbit.The implementation of a high-resolution sensor specifically dedicated to the detection and identification of floating objects of one meter in size could also be useful in other relevant issues such as monitoring oil spills, cargo losses from ships or research activities and rescue at sea”.

The work was funded by the Discovery Element of the European Space Agency (ESA) and the consortium is made up of multinational space companies and research institutes from six countries.The study was coordinated by Andrés Cózar of the University of Cadiz (Spain) and Manuel Arias of the Institute of Marine Sciences, Csic (Spain).In addition to the contribution of the Cnr-Ismar, the international group that conducted the research is made up of researchers from:University of Cadiz and Csic in Spain, European Space Agency (ESA), Argans France, Universitat Politècnica de Catalunya (Spain), Technical University of Crete (Greece), Argans Ltd.(UK), Airbus Defense and Space (France), Joint Research Center (JRC) of the European Commission, The Ocean Cleanup (Netherlands) and Acri-St (France).The study was funded by the European Space Agency (ESA) and the Spanish Ministry of Science and Innovation;he also received contributions from the Mur with the PRIN EMME 2017WERYZP_006 project and the SCOR FLOTSAM-IMDOS project, and from the European Union with the EUROqCHARM and NAUTILOS projects.