Ozone heightens atmospheric soot ageing

We are now a step closer to understanding the subtle interplay of gas-soot interactions in the atmosphere thanks to a team of scientists at the Centre National de la Recherche Scientifique and Universit? d’Orl?ans, France.

Well-known as air pollutants, soot aerosols can change the atmosphere’s chemical composition by reacting with important atmospheric trace gases like ozone. Previous calculations supported the belief that soot-ozone interactions were significant enough to explain the damage to ozone levels in the stratosphere at certain latitudes.

Quite a different story has now been unearthed by Yuri Bedjanian and his colleagues. Bedjanian says that his motivation was to ’better define the ageing process of soot in the atmosphere’ and with this in mind his team reacted ozone with soot in the lab ’under real atmospheric conditions’. Previous experiments didn’t properly take account of the soot’s reactivity to time of exposure, and Bedjanian discovered that in fact at first the soot reacts quickly with the ozone, but then rapidly becomes inactive. This ability of ozone to slow down the soot’s reactivity led to the conclusion that ’soot particles have negligible impact on ozone concentration throughout the atmosphere’.

Looking to the future, Bedjanian is hoping to extend his research on gas-soot interactions to ’the physico-chemical transformations of the surface’ and ultimately to replace soot surrogates in the lab with real atmospheric particles.

Stephen Wilkes