Environmental scientists in the UK are improving the understanding of how compounds that form ground-level ozone, which can damage crops and affect human health, relate to sunlight and pollution.

Claire Reeves of the University of East Anglia and collaborators have refined a technique that turns the very low atmospheric concentrations of ozone-creating peroxy radicals into something measurable. 'Peroxy radicals are very short-lived molecules thus their concentrations vary a lot both in time and in space,' Reeves said. 

Unfortunately, the amplification technique relies on subtracting a noisy background signal from the amplified signal. Reeves said 'we therefore developed a dual channel instrument which allows both the background and amplification signals to be monitored continuously, thus increasing the frequency of measurement and reducing the noise.'

Dwayne Heard, an atmospheric chemist at the University of Leeds, UK, appreciates Reeves' findings. 'Achieving shorter averaging times yet maintaining good signal-to-noise the instrument shows clearly the relationships between concentrations of peroxy radicals, sunlight intensity and levels of pollution,' said Heard.

The instrument will be flown over West Africa this summer, an area believed to be responsible for major emissions of biogenic compounds, according to Reeves. The air sampled by a fast-moving aircraft can change greatly over a short time. 

'The new dual channel instrument has thus allowed us to collect good peroxy radical data with low signal to noise ratios that would have been impossible with our previous single channel instrument,' said Reeves. Future challenges include producing small, lightweight, automated instruments that can be deployed on commercial aircraft, thus increasing coverage, she added.

Colin Batchelor