Ozone depletion in tropospheric volcanic plumes

We measured ozone O₃ concentrations in the atmospheric plumes of the volcanoes St. Augustine (1976), Mt. Etna (2004, 2009) and Eyjafjallajökull (2010) and found O₃ to be strongly depleted compared to the background at each volcano. At Mt. Etna O₃ was depleted within tens of seconds from the crater, the age of the St. Augustine plumes was on the order of hours, whereas the O₃ destruction in the plume of Eyjafjallajökull was maintained in 1-9 day old plumes. The most likely cause for this O₃ destruction are catalytic bromine reactions as suggested by a model that manages to reproduce the very early destruction of O₃ but also shows that O₃ destruction is ongoing for several days. Given the observed rapid and sustained destruction of O₃, heterogeneous loss of O₃ on ash is unlikely to be important.