LAQN Pollution Episodes

Pollution Notification released on 17/03/2014

Pollution incident notification 12th to 14th March 2014.

London and South East England were affected by a widespread pollution episode that affected much of north-west Europe, including England, northern France (including Paris), Belgium, Luxemburg and the Netherlands. A high pressure system slowed the circulation of air across this area and cold, foggy nights that further hampered pollution dispersion.

From the UK perspective the episode first impacted here on Wednesday 12th March with widespread moderate particle concentrations across London and south east England. Further feeds of ground level continental air caused the episode to intensify on Thursday 13th March with PM2.5 reaching "very high", the top level of the UK air quality index, across eastern parts of London; through Greenwich and in Bexley.

"High" PM10 and PM2.5 concentrations continued on Friday 14th March before a return to a westerly airflow pushed the polluted air eastwards and began to disperse this over Europe on Saturday 15th March. "High" was measured in networks beyond London including Sussex, west Kent, Essex and Hampshire.

This is the worst PM10 episode to affect London for two years; the mean background PM10 in London reached its greatest concentrations since 15th March 2012. Tracing back London’s air during this episode shows that air flowed across northern Germany, the Netherlands and Belgium before reaching us. This is reflected in the composition of particles measured by real-time aerosol mass spectrometers in London which showed a dominance of nitrate and organic particles, consistent with distant traffic emissions that have been chemically aged in the atmosphere.

During this episode 3.5 million pollution notifications were sent out to users of our smart phone apps across London and Sussex.