Temporal variations of atmospheric depositional fluxes of ⁷Be and ²¹⁰Pb over 8 years (2006–2013) at Shanghai, China, and synthesis of global fallout data

Abstract 7 Be and 210 Pb, two atmospherically delivered radionuclides, have been broadly applied to study the processes including air mass transport, soil erosion, and particle cycling in aqueous systems. These studies require temporal variations of their depositional fluxes. In the present work, monthly atmospheric bulk depositional fluxes of 7 Be and 210 Pb were measured over 8 years (December 2005 to December 2013) at Shanghai, China. The bulk depositional fluxes of 7 Be and 210 Pb varied from 17.9 to 421 Bq m −2 month −1 and 6.8 to 82.1 Bq m −2 month −1 , respectively. The volume‐weighted activities ranged from 0.20 to 8.06 Bq L −1 for 7 Be and 0.05 to 3.40 Bq L −1 for 210 Pb. There were strong seasonal variations in the depositional fluxes of these nuclides. The seasonal fraction of depositional fluxes was >30% of the total annual depositional fluxes of 210 Pb in winter and 7 Be in spring. The lowest depositional fluxes were found in summer for both radionuclides, with precipitation‐normalized enrichment factor ( α ) values of <1.0. The results from the synthesis of global fallout data indicate that there are latitudinal variations in the maximum depositional fluxes and volume‐weighted activities of 7 Be, both values increase with latitude from the equator to the midlatitudes. The 210 Pb depositional fluxes increase with the distance from the coast in inland regions (distance from the coast >50 km) and increase with the amount of precipitation in onshore region (distance from the coast ≤50 km). We also report that Shanghai, China, has the second highest bulk depositional fluxes of 210 Pb in literature.