Looking at cloud formation
Investigating the reactivity of organic aerosol films
Tiny particles in the air known as aerosols play an important role in cloud formation, which in turn has an impact on our planet’s climate. However to date the effect of aerosols on cloud formation remains full of uncertainties. Among these uncertainties is the reactivity of organic films that have been found to coat atmospheric aerosols. Now researchers have turned their attention to studying these using the Surface and Interface Diffraction beamline (I07) at Diamond Light Source.
In work recently published in Atmospheric Environment researchers investigated the reactivity of the organic films found at an aerosol’s surface. After extracting the organic material from atmospheric aerosol samples they placed it on an air-water interface, exposed to ozone gas. Ozone is a common atmospheric oxidant. Through X-ray reflectivity measurements gathered at Diamond’s I07 beamline, they very surprisingly found that the organic samples were inert to oxidation by ozone gas. However, the samples did react when exposed to hydroxyl radicals under the same conditions.
To explain the lack of reaction with ozone, the team propose that the samples collected may contain higher quantities of saturated than unsaturated material. They say that their results indicate that atmospheric aerosols might be less reactive in the atmosphere than previously thought. They now plan to test this theory by investigating further organic samples taken from different types of atmospheric aerosols in order to map their reactivity.
The team extracted the organic matter from samples of atmospheric aerosols before placing the material on an air-water interface and exposing the sample to ozone gas. This was the first time real life samples of the films had been investigated, as previous studies have all used proxies for the organic films.
Jones SH et al. Are organic films from atmospheric aerosol and sea water inert to oxidation by ozone at the air-water interface?, Atmospheric Environment (2017). DOI: 10.1016/j.atmosenv.2017.04.025.