210Po, 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.