LAWS of chemistry accepted for 100 years do not work when applied to the chemical reactions that take place in the turbulent atmosphere. This realisation has stunned chemists and throws predictions about the size of the ozone hole into doubt.
The bombshell was dropped by Adrian Tuck, an atmospheric scientist from the US National Oceanic and Atmospheric Administration鈥檚 Aeronomy Laboratory in Boulder, Colorado. He found that pressure fluctuations concentrate chemicals in some parts of the atmosphere, making reactions there happen more quickly. This confirms his earlier predictions that the equations chemists use to describe the rates of reactions may be too simple to apply to the fluctuating atmosphere.
David Roberts of the UK鈥檚 Hadley Centre for Climate Prediction and Research in Bracknell, Berkshire, says the research is some of the most surprising he has ever seen. 鈥淚t implies quite a revolution,鈥� he says.
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Tuck used data on turbulence gathered by aircraft flying over Antarctica to calculate how pressure varies in the lower stratosphere, which begins 15 kilometres above the ground and is where the protective ozone layer normally lies.
The aircraft also measured changes in the concentration of ozone, and the chlorine that destroys it. The ozone was disappearing faster than simple rate equations would predict. But Tuck was able to explain the effect by considering the pressure fluctuations. When the pressure is higher, molecules are closer together and so the chlorine free radicals are more likely to collide with ozone molecules, triggering the reaction.
Overall, the regions of high and low pressure average out to produce a faster reaction rate. This will affect not only the rate at which 鈥渙zone dances its macabre dance with chlorine鈥�, says Tuck, but all reactions in the atmosphere. 鈥淭his is a general problem for atmospheric chemistry.鈥�
鈥淚鈥檝e been banging on about this stuff for ages, but that was modelling. This is based on observations,鈥� said Tuck at the Royal Meteorological Society Conference in Norwich, UK, last week. His work will be published in the Journal of Geophysical Research (vol 108, p 4451).