Arable land can have a negative impact on air quality

Dust source activation on March 23 11:00 UTC over the southern Ukraine (arrow). Click here for more information.

Tracking down a mystery

In Germany, people in the Erz Mountains were not a little surprised when the sky took on a slightly yellow sheen. The controllers from the state air monitoring network also realised very quickly that something unusual had happened. Their filters were a much browner colour than usual, which meant that there must have been a lot more dust in the air. In the offices of the particulate experts at the Leibniz Institute for Tropospheric Research the phones were ringing. Dr Wolfram Birmili has for years been investigating the long-distance transport of particulates in the troposphere, i.e. the lower few kilometres of the atmosphere. He and his colleagues quickly ruled out the classic air pollutants, such as coal-fired power stations and forest fires, because their measuring instruments showed unusually high levels of coarse-grained particles (larger than 0.001 mm) in the dust plume. The relatively low carbon monoxide and carbon dioxide concentrations also seemed to rule out industrial sources and biomass combustion. Dust from the Sahara Desert had caused a stir in Germany several times in the past. But the Sahara was not a possibility either, because the weather conditions were wrong – the wind was coming from the east. So where was the dust coming from" The detective work began.

Spatio-temporal evolution of the dust plume in Central Europe on March 24, 2007. The map is based on time series of PM10 mass concentration at over 360 government monitoring stations... Click here for more information.

Satellite pictures solve the riddle