What is DOAS?
DOAS is short for Differential Optical Absorption Spectroscopy. DOAS instrumentation operates on a well-established scientific principle, Beer-Lambert's absorption law, which relates the quantity of light absorbed to the number of gas molecules in the light path. This technology is used in instruments that can measure a number of different pollutants along a single light beam which may be up to 800 metres long.
The EPA currently uses DOAS technology at the Brisbane
CBD and Springwood
sites in Brisbane, and Targinie
near Gladstone. This ‘long path’ monitoring system is at the cutting
edge of air pollution monitoring technology.
How it works
A DOAS system has three major parts - an emitter, receiver and analyser.
The emitter sends a beam of light to the receiver. The light beam contains a
range of wavelengths, from ultraviolet to visible. Different pollutant molecules
absorb light at different wavelengths along the path between the emitter and
receiver. The receiver is connected to the analyser which measures the intensity
of the different wavelengths along the entire light path and converts this into
concentrations for each of the gaseous pollutants being monitored.
The DOAS system installed in 1998 at the Brisbane CBD site was the first of its type in Australia. The emitter, located at the Brisbane Convention Centre, sends a beam of light across the Brisbane River and South East Freeway to the receiver at the Sciencentre in George Street, Brisbane.
So, if you’re at Brisbane’s Southbank to enjoy a fireworks
show, look for a bright light coming from the roof of the Convention Centre
— that's the DOAS and it is probably measuring the sulfur dioxide produced
by the fireworks!
Last updated: 15 February 2007
