[1] Pb 210 is a well known tracer of particle dynamics in the marine environment. Geochemical models partially rely on the knowledge of its atmospheric input. Unfortunately, this is poorly known in the western Mediterranean Sea, especially regarding long-term records. In this work we have evaluated the , and were strongly correlated (R 2 = 0.95) with mean annual rainfall. This provides the possibility to determine 210 Pb fluxes in a given location if the mean annual rainfall is well known, a useful outcome for both marine biogeochemical and soil erosion studies in this region. We have also estimated the mean annual atmospheric flux of 210 Pb due to Saharan dust events registered in total deposition north of Barcelona during the last 17 years, yielding a value of 20 Bq m À2 yr À1 . This flux represents a fraction of about 16% of the total atmospheric deposition of 210 Pb in this area, but it could be up to 50% in sites with lower rainfall.

Inventories of radionuclides commonly used to study environmental processes, especially in erosion research, were determined in soil cores from two distant river basins in northern Spain. Results showed that 210Pb atmospheric fluxes correlate very well with mean annual rainfall across the region, and this is also the case for 137Cs inventories but only on the basin scale. Therefore we suggest that 210Pb is a better candidate as a radiotracer for soil erosion studies. In this region, the equation 210Pb flux (Bq m(-2) yr(-1)) = (0.19 +/- 0.02) x rainfall (mm yr(-1)) - (24 +/- 17) can be used as a calibration to estimate input 210Pb fluxes, a key parameter in soil erosion studies and models, when mean annual rainfall is known.