CEMMNT partner, NPL, has validated the first measurements of sulphur dioxide in Iceland's volcanic ash plume.

Since the 2010 eruption at the Eyjafjallajökull glacier in Iceland, the UK's Facility for Airborne Atmospheric Measurements (FAAM) have been engaged in measurements to characterise the volcanic ash plume using a Dornier 228 aircraft.

*Image courtesy of iStockphoto

After identifying the plume's location by observing high concentrations of sulphur dioxide (using a technique called 'pulsed fluorescence'), NPL calibrated the equipment using its gas dilution facilities. This calibration needs to be performed at frequent intervals, as this type of analyser can drift with time. NPL helped confirm that the elevated concentrations of sulphur dioxide were accurate.

NPL also provided further support by advising FAAM on techniques used to measure airborne particle mass concentration (the total mass of particles per cubic metre of air). The more commonly measured parameter of particle number concentration (the number of particles per cubic metre) is less useful for the volcanic cloud as the result is dominated by the many tiny particles (under 50 nm) which would not be expected to damage an engine. As the volcanic ash particles causing damage to engines are around 1000 nm in size, mass concentration is a better parameter for understanding the cloud's capacity to cause engine problems.

FAAM will incorporate a Tapered Element Oscillating Microbalance (TEOM) from NPL to conduct real-time measurements of particle mass concentration. The TEOM is a well-established instrument that directly monitors airborne particle mass concentration, which could form the basis for determining whether the 2 mg of particles per cubic metre, now used by the Civil Aviation Authority as a safety limit, is being exceeded.

For more information please click here