Harmful environmental impact of microplastics adsorbing Zinc Oxide from sunscreens and microbeads from cleansers indicated
Results confirm that mixtures of Zn-aggregates/micro-polymers were naturally leached/released from the commercial products, revealing worrying environmental implications for fish and other aquatic organisms in the food chain.
IMAGE: SCANNING ELECTRON MICROSCOPY (SEM) ANALYSIS FOR THE ZNO NANOMATERIALS STABILISED IN TAP-WATER FOR 7 DAYS, AND FURTHER INCUBATED WITH MICROPLASTICS FOR 24 HOURS. THE LEFT SEM IMAGE IS A LOW-MAGNIFICATION VIEW, WITH THE MIDDLE IMAGE ZOOMING IN THE REGION SUBSEQUENTLY QUANTIFIED. THE ZN-SIGNAL FROM THE ENERGY DISPERSIVE X-RAY SPECTROSCOPY (EDX) IS DISPLAYED AT THE RIGHT AFTER APPLYING A DIFFERENT COLOUR MAP AND ADJUSTING THE HISTOGRAM ACCORDINGLY. view more
CREDIT: ALL THE IMAGES ARE AN ADAPTATION OF THE PUBLISHED PAPER AT: HTTPS://ONLINELIBRARY.WILEY.COM/DOI/FULL/10.1002/GCH2.202300036.
A new study by a research team from Diamond Light Source looks at how microplastics wastes may interact with Zinc Oxide (ZnO) nanomaterials in freshwater and seawater scenarios. It also evaluated, a ZnO-based sunscreen and an exfoliating cleanser with microbeads in its composition under the same conditions. Their results confirm that mixtures of Zn-aggregates/micro-polymers were naturally leached/released from the commercial products revealing worrying environmental implications for fish and other aquatic organisms in the food chain which could swallow these microplastics and ingest zinc particles at the same time.
Called “Toward understanding the environmental risks of combined microplastics/nanomaterials exposures: Unveiling ZnO transformations after adsorption onto polystyrene microplastics in environmental solutions” the work was published on 5 July in Global Challenges https://doi.org/10.1002/gch2.202300036 . The team from the UK’s national synchrotron, included a student, Tatiana Da-Silva Ferreira, who was at Edinburgh University on Diamond’s 12 week 'Summer Placement' scheme. This allows undergraduate students studying for a degree in Science, Engineering, Computing or Mathematics (who expect to gain a first or upper-second class honours degree) to gain experience working in a number of different teams at Diamond. Lead author, Miguel Gomez Gonzalez, Diamond Beamline Scientist, praised Tatiana, now studying for a PhD in Switzerland, for her key contribution to the start of this environmental project.
Explaining the impetus for the research, Miguel said that they had all seen how in recent decades, there has been a dramatic increase in the manufacture of engineered nanomaterials (tiny, tiny particles about 1000 times thinner than a human hair), which has inevitably led to their environmental release. Similarly, Zinc oxide (ZnO) is among the more abundant nanomaterials fabricated due to its advantageous use in electronics, semiconducting, and for antibacterial purposes. At the same time, plastic waste has become ubiquitous and may break down into smaller pieces called microplastics. These also are tiny, but ~100 times bigger than the nanomaterials. Because both these elements are getting disposed more often, they decided to study their fate when they are potentially being combined in freshwater and oceans and to help make environmental risk assessments more accurate.
To make their study more relevant to the real world, the team tested a sunscreen containing zinc oxide which is commonly used to block UV-radiation. They let the sunscreen incubate in the different environmental solutions for a week and then added the microplastics for a day. The objective was to check if the zinc oxide could come out of the sunscreen and stick to these microplastics. They also followed the same procedure with a facial scrub containing tiny plastic beads. The results clearly showed that the zinc oxide (either pure or leached from the sunscreen) did stick to the microplastic in both cases (Fig. 2), revealing that it could potentially happen in our rivers and oceans too.
Miguel comments; “The ability of zinc oxide, both pure nanomaterials and those released from a sunscreen, to stick to very small pieces of plastic has big implications. These plastics can even come from everyday items like exfoliating facial cleansers. In this study, we found the microplastics can carry even smaller particles of zinc from place to place. As a consequence, fish or other aquatic organisms could swallow these microplastics, ingesting zinc particles at the same time.”
“We need to understand how this engineered zinc oxide changes when it gets into freshwaters and how much of it can stick to small plastic wastes. This is important for making everyone aware, from people who make these products to those who regulate them, about the potential harm they could do to our environment. Better rules for managing waste are needed, especially related to tiny particles like these. As we continue to produce more and more of these micro- and nanoparticles, their effect on our environment is going to keep growing. Because they are so long-lasting, they can pose a risk to different organisms, and ultimately even make their way into our food. This is something we simply cannot afford to ignore.”
Talking about the contribution of 2021 Summer Placement Student Tatiana Miguel highlighted the huge opportunities afforded to students by Diamond study programmes. “Tatiana did a great job in optimising the conditions for the 7-days stabilisation of nanomaterials, followed by the 24-hours incubation of microplastics and nanomaterials. In addition, she improved the filtering protocol and isolation of the microplastics after the incubation period. Likewise, she performed the very preliminary scanning electron microscopy analysis which revealed nanomaterials adsorption into the plastic surfaces. Therefore, her contribution was key for the overall success of this environmentally relevant project,” he added. She thanked Miguel and Diamond saying; “This experience really deepened my interest in environmental chemistry and academic research. It also gave me enough background and confidence to pursue my Masters and now my PhD. I’m really happy I got to work on such an interesting project, and even happier you chose to look deeper into it.”
The team took some pure zinc oxide particles (ranging from 80 to 200 nm size) and incubated them in different kinds of environmental solutions for a week, allowing their natural stabilisation. They then mixed them with small polystyrene microspheres (~900 mm diameter, about the size of a grain of sand) and stirred them together for a day. After washing and rinsing the microplastics, they found that the zinc oxide got adsorbed to the plastic surfaces. This was seen by scanning electrical microscopy, using a very powerful microscope (Fig. 1). This confirmed that microplastics and zinc oxide can interact in our water bodies, which might affect how they impact the environment.
The team then examined these zinc oxide-covered microplastics using X-rays generated at Diamond Light Source, an electron accelerator facility. Diamond’s I14 beamline can shape the X-rays into a nanometric size, making it one of the best in the world for this kind of detailed work. Fast scanning of the samples around the nanometric X-rays beam, enabled detailed pictures of each element contained in their samples to be captured by the fluorescence detector. Alongside this work, another X-ray technique called X-ray absorption near-edge structure spectroscopy (XANES) was applied to check what kind of chemical changes had happened to the zinc oxide when adsorbing to the microplastics and after a week’s incubation in freshwaters.
Miguel adds’ “We found out that the zinc oxide had transformed into different types of zinc-related particles. Some of these new particles (Zn-sulfide) were formed quickly, while others formed more slowly but were more stable (Zn-phosphate) (Fig. 3). This reveals valuable information about how zinc oxide behaves when it is in the environment.”
. X-ray fluorescence (XRF, left) maps (100 nm pixel size) for the Zn signal and differential phase contrast (DPC, right) image for morphological inspection of the adsorbed structures measured at the hard X-ray nanoprobe (I14 beamline). Zn-particles from the sunscreen were deposited on the pristine microplastics after incubation in seawater (top row) while ZnO nanomaterials were deposited on the microplastics leached from the exfoliating cleanser after incubation in seawater as well (bottom row).
Principal component analysis [left image] and cluster analysis [middle] performed on the ZnO nanomaterials adsorbed into the microplastics surfaces after incubation in seawater. The averaged XANES spectra from the violet cluster (1) and from the red cluster (2) were subsequently analysed by linear combination fitting (red-dashed line) against the well-known standards to interrogate the Zn speciation, revealing a mixture of Zn-sulfide and Zn-phosphate species.
CREDIT
All the images are an adaptation of the published paper at: https://onlinelibrary.wiley.com/doi/full/10.1002/gch2.202300036
JOURNAL
Global Challenges
METHOD OF RESEARCH
Imaging analysis
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
“Toward Understanding the Environmental Risks of Combined Microplastics/Nanomaterials Exposures: Unveiling ZnO Transformations after Adsorption onto Polystyrene Microplastics in Environmental Solutions”
Oceans release microplastics into the atmosphere
Study determines composition and sources of the microplastics
Peer-Reviewed PublicationIMAGE: DURING STORMY WEATHER, SEA SPRAY CAN CARRY MICROPLASTICS INTO THE AIR. THE PHOTO WAS TAKEN DURING A TRIP OF THE RESEARCH VESSEL HEINCKE OFF THE NORWEGIAN COAST IN JUNE 2021. view more
CREDIT: PHOTO: ALVISE VIANELLO
Microplastic particles are present in the marine atmosphere even in remote parts of the world. These tiny particles come from land sources but are also re-emitted into the atmosphere from the sea, a study by a team of German and Norwegian researchers led by Dr Barbara Scholz-Böttcher of the University of Oldenburg has shown. The scientists analysed air samples taken from various sites along the Norwegian coast all the way up to the Arctic region. The results have now been published in the scientific journal Nature Communications.
"With our study, we present data on the mass load of different types of plastic in the marine atmosphere for the first time," said Isabel Goßmann, a doctoral candidate at the University of Oldenburg's Institute for Chemistry and Biology of the Marine Environment (ICBM) and first author of the paper. The research team collected the samples during an expedition with the Research Vessel Heincke in 2021. The northernmost destination was Bear Island, the most southerly island of the Svalbard archipelago which lies halfway between the mainland and the archipelago's largest island, Spitsbergen. The team used two different devices to collect air samples. The devices actively pumped in air and were mounted on the bow of the research vessel at a height of twelve metres.
Different types of plastics identified
The scientists analysed the air samples using pyrolysis-gas chromatography-mass spectrometry. With this method they were able to identify and quantify the different types of plastics in the atmosphere through thermal degradation and selective analysis. They then performed model calculations and reconstructed the sources and distribution paths of the particles, each of which is just a few thousandths of a millimetre in size.
The analysis revealed the omnipresence of polyester particles. Polyethylene terephthalate particles, which presumably entered the atmosphere in the form of textile fibres, were detected in all samples. Other plastic types were also present, including polypropylene polycarbonate and polystyrene. Tire wear particles, the tiny debris abraded from tires during driving and especially braking, were identified as another major source of microplastics. The researchers measured concentrations of up to 37.5 nanograms (one nanogram = one-billionth of a gram) of microplastics per cubic metre of air. "These pollutants are ubiquitous. We find them even in remote polar regions," Goßmann stressed.
Until now, little was known about microplastics pollution levels including tire wear particles in the marine atmosphere. "There are only a handful of studies on the concentration of these pollutants in the air," said team leader Scholz-Böttcher. "Our model calculations indicate that the microplastics in the marine atmosphere come from direct sources on the land as well as from the sea," she added. The team posits that plastic particles floating near the sea surface enter the atmosphere via sea spray and bursting air bubbles produced during stormy weather, for example.
Ships are also a source of microplastics
Microplastics find their way into seawater via rivers, but also through the atmosphere – particles are washed out of the atmosphere by rain, for example. Another potential source is ship traffic: in an earlier study, a team led by Scholz-Böttcher demonstrated that in the open North Sea, the paint and coatings used on ships is the main source of microplastics. In the current study, chemicals such as polyurethanes and epoxy resins typically used in paints and coatings for ships were also found in the air samples.
In addition to researchers from the ICBM, scientists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) in Bremerhaven, the Technische Universität Berlin, the Norwegian Institute for Air Research (NILU) and the Norwegian Institute of Public Health (NIPH) were also part of the research team.
JOURNAL
Nature Communications
METHOD OF RESEARCH
Observational study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Occurrence and backtracking of microplastic mass loads including tire wear particles in northern Atlantic air
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