The Eyjafjallajökull eruption has been occurring since March 2010. In April, the eruption had 2 distinct stages: first was between 14/04 and 18/04 during which the large ash cloud was formed and explosive mixing between the glacial lake and the lava occurred. The second phase was characterised by a less explosive plume. This second phase is still continuing and intermittently the plume has passed over the UK at varying altitudes.
Volcanoes are a major natural source for mercury and it can be found in the gas phase and associated with volcanic ash. The graph below shows the most recent 5 days of mercury measurements. This data is updated daily.
Normal air concentrations at remote UK sites are between 1.4 -1.5 ng/m3. Higher concentrations can be seen if air has passed over a coal-burning power station, a crematorium, an industrial source of mercury or a volcano before reaching the site. If the plume from Eyjafjallajökull reached the ground we would expect to see a significant increase in concentration. When elevated mercury levels are observed, to verify the origin of the mercury links to the source, e.g. the volcano, would then need to be made by following the path of the air prior to reaching the measurement site. Even at concentrations several times larger than the norm, elemental mercury in air poses no threat to human health.