Spray that again

Aerosols are dangerous. Recent studies have shown that suspensions of pollutant droplets in air are linked with heart attacks and respiratory problems, especially when the droplets are around 2.5 microns across.

But because aerosol particles are so small, they are difficult to analyse - current techniques use filters which collect aerosol particles over 24 hours, in order to obtain a large enough sample.

Researchers from the Georgia Institute of Technology in Atlanta have now developed a device to make the task easier and faster.

Developed by earth scientists Rodney Webber and Douglas Orsini, the Particle-Into-Liquid Sampler (PILS) uses small quantities of steam to form water droplets on individual aerosol particles entering the instrument. The pollutants dissolve in the water droplets, and the resulting solution can be captured and analysed by ion chromatography. The PILS can run for long periods unattended, at ground level or in research aircraft, providing real-time analysis of the aerosol's composition.

The team has configured the PILS to detect nine major chemical species, including sodium, ammonium, nitrates and sulphates. It is 97 per cent efficient at capturing particles between 0.03 and 10microns, and can detect cations at concentrations of 50ng/m3 and anions at 10ng/m3.

'We can make the measurements more quickly than with previous techniques, and with higher sensitivity,' says Weber. 'We no longer have to dissolve these particles in large volumes of water, and don't have to be concerned with contamination during sample handling.'