Ozone depletion in tropospheric volcanic plumes

We measured ozone (O 3 ) concentrations in the atmospheric plumes of the volcanoes St. Augustine (1976), Mt. Etna (2004, 2009) and Eyjafjallajökull (2010) and found O 3 to be strongly depleted compared to the background at each volcano. At Mt. Etna O 3 was depleted within tens of seconds from the crater, the age of the St. Augustine plumes was on the order of hours, whereas the O 3 destruction in the plume of Eyjafjallajökull was maintained in 1–9 day old plumes. The most likely cause for this O 3 destruction are catalytic bromine reactions as suggested by a model that manages to reproduce the very early destruction of O 3 but also shows that O 3 destruction is ongoing for several days. Given the observed rapid and sustained destruction of O 3 , heterogeneous loss of O 3 on ash is unlikely to be important.