210 Po, an atmospheric tracer of long-range transport of volcanic plumes

With the aim of testing the ability of 210Po to be a tracer of volcanic aerosol plumes, we collected air samples during an oceanographic cruise around the Indonesian arc and measured the radioactivity of 210Po. Owing to the atmospheric circulation pattern and geographical distribution of 210Po sources around the sampling site, the origin of 210Po of the samples could be determined by calculating 5-day backward air mass trajectories. It is shown that the signature of 210Po originating from volcanic emissions is distinct from that of 222Rn decay, even though these processes are the 2 major sources of atmospheric 210Po. Moreover, the proportion of 210Po in a given air parcel is conservative during the transport: as other aerosols, 210Po aerosols are very sensitive to the atmospheric removal processes and the production and the loss of 210Po by radio decay within an air parcel is negligible. Our results confirm that 210Po is a good tracer for aerosols emitted by volcanoes.