The fact that microplastics can accumulate and transfer organic pollutants from the environment has been known for some time. What is new, however, is that metals can also be transported in this way. In addition, the smaller the particles, the more metal builds up on the plastic. This has been demonstrated by scientists at Helmholtz-Zentrum Hereon in a new study. The results are now published in Hazardous Materials Letters Magazine.
Scientists around the world have already demonstrated the alarming environmental presence and longevity plastic grains. The size of the particles is between one and a half micrometers. They develop in part when larger plastic components break down in the sea or end up in rivers and then directly into the ocean from land sewage. Microplastics are toxic in very high concentrations. In addition, they can also accumulate, transport and release other pollutants. While the data has already been published on organic pollutants In this context, little is known about the interactions between microplastic particles It floats in water and dissolved minerals. That is why scientists from the Institute of Coastal Environmental Chemistry at Helmholtz-Zentrum Hereon have systematically studied these reactions in the laboratory.
The team, which includes first author Dr Lars Hildebrandt, studied the accumulation of fifty-five different metals and semimetals on the polyethylene and polyethylene terephthalate particles, whose size ranges from 63 to 250 micrometers. “In terms of plastic-contaminated water, the two types of plastic we studied play a vital role,” says environmental chemist Hildebrandt. This is due to its wide range of applications and the large production volume associated with it. Most shopping bags, for example, are made of polyethylene (recycling code 4, LDPE), and plastic drinking bottles almost without exception are made of polyethylene terephthalate (recycling code 1, PET). “
Says co-author Dr. Head of the Department of Environmental Inorganic Chemistry at Hereon. Some metals, or more precisely their ions, such as chromium, iron, tin and rare earths, attach themselves almost entirely to microplastics. While others, such as cadmium, zinc and copper, showed almost no build-up on the plastic during the entire testing period. In addition, the polyethylene particles showed significantly greater accumulation than the polyethylene terephthalate particles.
Metals are almost completely released again
In the second phase of testing, the Hereon scientists can show that the metal- or semi-metal-laden particles completely released almost all of them. metal Again under chemical conditions, such as those prevailing in the gastrointestinal tract. “The in vitro test setup was really simplistic and without living models. However, the results provide important evidence that microplastics, when absorbed by the body, act as a kind of metal trojan and that these metals can be introduced into living organisms largely by this method. The method, says Lars Hildebrandt, drew his preliminary conclusion.
Further studies are now being conducted to determine how other plastics frequently found in the environment behave and what influences particle age and weathering conditions on accumulation and release processes.
more information: Hildebrandt et al., Microplastics as a Trojan horse for trace metals, Hazardous Materials Letters Magazine (2021). DOI: 10.1016 / j.hazl.2021.100035
its source Phys.org