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Ocean modelling engineer Philippe Delandmeter and chemist Ramon Oord from Utrecht ľ�ϸ���Ӱ�� are both interested in very small particles of ocean plastics, however from totally different angles. Delandmeter is modelling trajectories of microplastics through the ocean water and Oord wants to analyze the composition of ocean plastics at the nanoscale. Both boarded the research vessel the Pelagia, of the Netherlands Institute of Sea Research (NIOZ). With UU’s strategic partner, they made a scientific cruise to the South Atlantic Ocean.

Count particles by hand

In three weeks, the Pelagia cruised from Cape Town at 18° East to the South Atlantic Subtropical Gyre – close to the Mid Atlantic Ridge - at 15.3° West, and back, covering a total of more than 6000 km. Led by chief scientist , Delandmeter and Oord took water samples at varying depths, together with the crew and other scientists from different disciplines. For the collection of microplastic at the surface, they used so-called manta trawl nets. Delandmeter: “We pulled such a net into the water for half an hour, and then counted the number of plastic particles by hand in our on board lab. In the gyre, there were several hundreds of tiny parts of plastic in a net.”

Platform with 24 bottles

The deeper microplastic samples and the samples of nanoplastics were taken in a different way. Oord: “We used a platform with 24 bottles that could be closed at any depth you want. The platform was fitted with several sensors that – apart from the depth - measured the water temperature, salinity, pressure, density and the amount of chlorophyll. Once drawn in, other scientists filtered the microplastics out and after that, I concentrated the nanoplastic samples from the remaining water for further analysis in our Utrecht ľ�ϸ���Ӱ�� lab.”

Molecular buildup of plastics

Ramon Oord works for the Utrecht ľ�ϸ���Ӱ�� hub of , the institute for sustainable chemistry in the Netherlands. He explains how ARC CBBC hopes to contribute to research on ocean plastics: “In Utrecht, we’ve got a brand new lab, with equipment for advanced spectroscopy, which will provide knowledge into the molecular buildup of these nanoparticles. It enables us to analyze the compositions and types of plastics like PE, PP, or PVC, in such a remote part of the ocean. One of the questions is where all the plastics in the ocean ends up. We can only find one percent of all plastics that goes into the ocean, meaning 99 percent is missing. By analyzing our nanoplastic samples, we hope to answer many questions related to plastics waste in the ocean.”

3D map

The Institute for Marine and Atmospheric Research Utrecht (IMAU) is specialized in making models of past, present and future climates. IMAU postdoctoral researcher Philippe Delandmeter studies the anthropogenically-induced problem of ocean plastic from a new angle. “We want to make a model and a 3D map of the three-dimensional dispersion of microplastics in the ocean, as part of our .” For that, Delandmeter first needs to know more about the way and places ocean water moves from the surface to the bottom and vice versa. “We don’t have insight into the vertical dynamics of those small particles yet. They move up and down through the water column. I want to know where plastic sinks, how it sinks and where it ends up.’