The light expansion accelerates the chemical effects on the aerosols


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Aerosols are applied to the air during the day. This light is amplified into aerosol drops and particles, speeding up the effects. ETH researchers were able to demonstrate and compare this result and encourage the enumeration of future examples.

Water droplets and small particles can absorb light – much like the way light is captured between two mirrors. As a result, the intensity of the light inside them is increased. This is done by the finest droplets and solid particles in our air, namely aerosols. Using modern X-ray microscopy, chemists at ETH Zurich and the Paul Scherrer Institute (PSI) have investigated how light increases the photochemical processes that take place in aerosols. . They were able to show that increasing the speed would make these chemical processes two to three times faster than without achieving this result.

Using the Swiss Light Source in PSI, the researchers studied aerosols with small amounts of iron (III) citrate. Exposure to light reduces this compound to iron (II) citrate. X-ray microscopy can separate areas in aerosol particles prepared with iron (III) citrate from those treated with iron (II) citrate to an accuracy of 25 nanometers. In this way, scientists were able to observe and document the high resolution over time of this photochemical effect in individual aerosol particles.

Loss when seen in the light

“For us, iron (III) citrate is a messenger compound that is easy to learn with our method,” said Pablo Corral Arroyo, a postdoc at the group led by ETH Professor Ruth Signorell and an author. of research. Iron (III) citrate belongs to another chemical group that can form in aerosols. Many organic and non -organic compounds are light, and when exposed to light, they can break down into smaller molecules, which can become a gas and thus escape. “Aerosol particles are going to be large in this way, changing their properties,” Signorell explains. Among other things, they scatter the sun in different places, depending on the climate and the nature of the weather. In addition, their features such as condensation nuclei change with the formation of the universe.

Therefore, scientific research has an impact. “The current computer models of earth space chemistry do not reflect this simple expansion effect,” said ETH Professor Signorell. The researchers hope to incorporate the effect into these features in the future.

Response times were not the same across the segments

Now that it has been accurately printed and numbered, the increase in lightness comes through resonance effects. The light is stronger on the side of the area directly facing where the light is shining. “In this hot spot, the photographic effects are ten times faster than the non -resonance effects,” says Corral Arroyo. Average over the whole piece, this gives the speed by the said over two to three. The effects of photochemicals in the atmosphere can take hours or days.

Using data from their experiment, the researchers were able to create a computer model to compare the effect over a variety of other photochemical effects of conventional aerosols in the air. It has been found that the effect is not only related to iron (III) citrate, but also to aerosols – particles or droplets – made with compounds that can be processed easily. These results are two to three times faster on average.

The research is published in Science.

Solid aerosols found in the Arctic atmosphere can affect the formation of clouds and the atmosphere.

More information:
Pablo Corral Arroyo et al, Increasing the light in aerosol particles accelerates in-particle photochemistry, Science (2022). DOI: 10.1126 / science.abm7915.

Directions: Amplification of chemical reactions in aerosols (2022, April 14) retrieved 15 April 2022 from html

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