HE feldspar a mineral ubiquitous and in fact it makes up about half of the earth’s crust. But it has truly unexpected properties beyond soil. In the Earth’s atmosphere, feldspars play a surprisingly important role:They help create clouds.
When the fine dust of this material is carried in the air, it affects the formation of clouds. And this water molecules adhere to feldspar powder better than other particles. Tiny grains of this mineral floating in the atmosphere become perfect ‘seeds’ to which water molecules adhere and freeze, eventually forming a cloud.
It is not clear why feldspar has this remarkable ability to bind water efficiently and allow cloud formation, and it has been the subject of recent scientific research.
Using a highly sensitive atomic microscope, researchers from the Technical University of Vienna (TU Wien) showed that: The unique geometry of the feldspar surface provides an excellent attachment point for the OH groups of hydrogen and oxygen and subsequently water.
Atomic resolution images
“Researchers have been considering various ideas as to why feldspar is such an effective nucleation seed,” says Professor Ulrike Diebold from the Institute of Applied Physics at the Technical University of Vienna, who led the project. “This may be due to the potassium atoms contained in the feldspar or to some defects in its crystal structure.”
To find out, TU researchers They used a very sensitive atomic microscopeThe glass surface is scanned point by point. The force between the tip and the surface produces a high-resolution image in which the position of each atom can be precisely determined.
“We placed a piece of feldspar in the vacuum chamber of the microscope and cut it in half to obtain a flawless, clean surface,” says Giada Franceschi, first author of the study. “We were stunned by the results: “Surface images looked different than predicted by general theories.”
Optimum connection: hydroxyl layer
The reason was quickly discovered: The culprits were small water crusts on the rock. When the stone is broken, some water vapor is released. This vapor adheres to the newly separated surface and water molecules break apart to form hydroxyl (OH) groups. “Under the microscope you see not the surface of the feldspar, but a surface covered with hydroxyl groups,” explains Giada Franceschi. “In nature, the surface of feldspar is also covered with a hydroxyl layer.”
Due to the geometry of the feldspar crystal These hydroxyl groups are positioned in a way that makes them ideal attachment points for water molecules. capable of bonding to hydroxyl groups, such as building blocks that fit perfectly together. Thus, the hydroxyl layer forms the perfect link between the feldspar and the water adhering in the form of ice.
“The union is set up very easily and quickly and is also very stable” says Ulrike Diebold. “To remove the hydroxyl layer from feldspar, it needs to be heated to high temperatures.” Computer simulations also support this finding.
The results provide insight into why certain crystals in our atmosphere are particularly suitable as cloud-forming nucleation seeds. It is important to better understand the physics of cloud formation, especially in the face of climate change. And sometimes it is necessary to delve deeper into the world of atoms, as the research project at the Technical University of Vienna has shown.”
Reference work: https://pubs.acs.org/doi/10.1021/acs.jpclett.3c03235#
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