Reaching up High – Aerosol Concentrations at EGU 2013

For those with a keen eye, you may have spotted a red balloon soaring high above the EGU Centre this week. The little white box attached underneath is the Light Optical Aerosol Counter (LOAC), a device that has been measuring the aerosols it the air around the conference.

LOAC hangs from the red balloon outside the EGU. Picture Courtesy: Eric Hamonou.

Aerosols are air borne particles that can be liquid or solid, natural or manmade. Salt, fog, sand, plaster and carbon are common aerosols found in the air.

Studies have shown particles less than 2.5 micrometres (mm) and 10 mm can be detrimental to human health as they are small enough to get into your lungs and enter your cells. An average human hair for example is about 200 mm. Regulations set thresholds for the amount of a particular particle size that should be in the air we breathe.

LOAC is an optical instrument that sends a beam of light through particles and the way the light scatters determines the size and shape. From this, the scientists can work out if the aerosol is carbon, mineral or liquid.

EGU GeoLog reporters managed to catch up with Jean-Baptiste Renard to explain his experiment this week…

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So what did you find in the air around the EGU?

Indoor air pollution was worse than outside. On Wednesday as it was too windy outside to fly; we flew the balloon in the exhibition hall. Particle levels sized10 mm (the dangerous kind) were at least five times more inside, almost reaching the threshold of alert levels.

Results from the indoor flight – minerals are reaching threshold levels. Graphs: Jean-Baptiste Renard.

These particles come from our clothes, in our hair, the dirt we scuff on the floor, is all lifted back up into the air. We are full of dust!

Outside, the concentration changed a lot during the day. In the morning there was a lot of carbon measured, possibly from the traffic that you would expect in a big city or the direction of the wind.

Measurements in the afternoon showed more mineral particles. This may be because of all of the building work going on in the towers on the right of the conference centre entrance. Every time someone uses a saw or hammer, tiny particles are produced and we can measure them in the air.

In the morning there is more carbon, and in the afternoon more minerals. Graphs: Jean-Baptiste Renard.

But won’t they measure the same – on the ground or in the sky?

No – the ground level concentration of aerosols can be completely different to 100 meters in the air. The higher you are, the greater more mixture of aerosols you find because up there, the particles that have been transported from elsewhere. At ground level, it is much more localised and the aerosols present are specific to what is close by.

Is that what’s so great about LOAC, you can put it on a balloon?

The key to LOAC is that it is airborne. As it is so small and lightweight, it can be attached to any kind of balloon. Before, the instruments had to be attached to planes or much larger balloons. Now, we can accurately trace if particles are locally produced or if the conditions in a small area, say on a specific street, are reaching an unhealthy threshold.

Being able to measure particles less than 1 mm is also totally new. We can distinguish between aerosols too. Before LOAC, instruments had to be set to detect a certain particle in the air, say salt. You would need to calibrate to look for salt. If there were no particles in the air, there would be no results, but now we can use one piece of equipment for multiple measurements, we can always collect data!

 by Becky Summers, City University, London

video by Sue Voice, University of Otago


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