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

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