37
Miguel commented: “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, fi sh 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.”
The Diamond team included a student, Tatiana Da-Silva Ferreira, who at the time of research was attending Edinburgh University and was part of Diamond’s 12- week Summer Placement scheme. The popular programme allows undergraduate students studying for a degree in science, engineering, computing or mathematics to gain experience working in a number of different teams at Diamond.
Diamond Beamline scientist, Miguel Gomez Gonzalez
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), or the microbeads from the facial scrub, and stirred them together for a day. The sunscreen was also incubated in the environmental solutions for a week and then added the microplastics for a day. The objective was to check if the zinc oxide could leach out of the sunscreen and adhere to the microplastics.
After washing and rinsing the microplastics, it was found that the zinc oxide was adsorbed to the plastic surfaces. This was observed by scanning electron microscopy (SEM), (Figure 1). This confi rmed 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 at the Hard X-ray Nanoprobe beamline. Here X-rays are focused to a nanometre scale beam (50nm) and a technique called nano- X-ray Fluorescence (n-XRF) is used to build a map of different elements as a sample is scanned through the beam. This was used to create a nanometre scale map of the distribution of the Zinc on the surface of the microplastics (Figure 2). An advantage of using the nanoprobe beamline is the ability to combine information from different techniques, here the n-XRF could be combined with differential phase contrast imaging to show the morphology of the adsorbed nanomaterials
A further X-ray technique called X-ray absorption near-edge structure spectroscopy (XANES) was applied at I14 to investigate spatially resolved chemical changes and transformations that may have occurred to the zinc oxide following adsorption to the microplastics and incubation in a freshwater solution.
Miguel concluded,: “We found that the zinc oxide had transformed into different types of zinc-related particles. Some of these new particles (Zn-sulphide) were formed quickly, while others formed more slowly but were more stable (Zn-phosphate) (Figure 3). This reveals valuable information about how zinc oxide behaves when it is in the environment.”
Some of the scientists within Diamond’s Imaging and Microscopy Group on the I14 beamline. From left to right; Julia Parker, Eunyoung Choi, Jessica Walker, Miguel Gomez Gonzalez, David Mahoney
Miguel praised Tatiana, who is now studying for a PhD in Switzerland, for her key contribution to the start of this environmental project. “Tatiana did a great job in optimising the conditions for the seven days stabilisation of nanomaterials, followed by the 24-hours incubation of microplastics and nanomaterials. In addition, she improved the fi ltering 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.”
Figure 3: 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-sulphide and Zn-phosphate species.
Images are an adaptation of the published paper at:
https://onlinelibrary.wiley.com/doi/full/10.1002/gch2.202300036.
Julia Parker, Imaging and Microscopy Science Group Leader, Diamond
WWW.LABMATE-ONLINE.COM
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44
