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The Pew Charitable Trusts research centre estimates that every year sees the world ocean get further polluted with more than 10 million tons of plastic produced using additives harmful to marine ecosystems: persistent organic pollutants, adsorbed toxic metals, residuals of catalysts and solvents for polymerisation. As a result of exposure to water, plastic disintegrates into microplastics. In order to produce a correct estimate of the impact of microplastics on living organisms, one has to track the polymer disintegration process.
This was the purpose of the study performed by the GEOKhI scientists, who analysed three types of plastics: biodegradable, “non-biological” and naturally aged (collected on the shore of the Mediterranean). Plastic samples were placed into seawater for three months, during which the scientists recorded changes in their composition through mass spectrometry (measuring atomic mass based on the motion of their ions in electric and magnetic fields) and ultrafiltration (a process wherein water is pushed under pressure through a semipermeable membrane).
“In our study, we used the method of isotope mass spectrometry of light elements, which allowed us to estimate the degree of degradation in plastics that stay in seawater over time. Microplastic particles were separated via ultrafiltration. We used the method of mass spectrometry with inductively coupled plasma to estimate the sorption of metals on the surface of plastics,” Olga Kuznetsova, senior researcher at the GEOKHI carbon geochemistry laboratory, is quoted as saying by the GEOKhI of the RAS.
By observing the process of microelement accumulation on the plastics, the scientists were able to make two main conclusions. Firstly, some plastic materials contain large amounts of metals even before they react with seawater; secondly, plastics in seawater start accumulating metals, which happens especially quickly with polymers of plant origin, including polymers of potato starch, soybean and corn.
