Influences of atmospheric transport pathways on radionuclide activities in aerosol particles from over the North Atlantic

Data for Be-7 (produced in the upper troposphere and lower stratosphere (UT/LS)) and Pb-210 (a tracer of continental emissions) activities in daily aerosol samples from over the North Atlantic were combined with meteorological information to investigate how the composition of aerosol particles varied in relation to transport pathways and precipitation scavenging. The strongest UT/LS influences (highest Be-7/Pb-210 ratios) occurred in winter, but differences in nuclide activities among sites reflect heterogeneity over the basin. High values for a radionuclide loading index (RLI) at Bermuda were matched to northwesterly air mass trajectories, while low RLIs, due at least in part to precipitation scavenging, occurred under easterly flow. The activities of both nuclides and the RLI at Bermuda were lower on rainy versus non-rainy days, but there was no evidence that a day-of-the-week cycle was imposed on radionuclide activities by precipitation scavenging. (Author)