Lead-210 and Beryllium-7 fallout rates on the southeastern coast of Brazil.

ABSTRACT

Total ²¹°Pb and 7Be fallout rates were measured on the coastal region of Niteroi, Brazil. The monthly depositional flux of ²¹°Pb and 7Be varied by a factor of 26, from 1.7 to 43.3 mBq cm⁻² year⁻¹ and ∼27, from 7.5 to 203.5 mBq cm⁻² year⁻¹, respectively. The relatively large oscillations in the depositional flux of ²¹°Pb at this study site were likely due to variations in air mass sources, while the 7Be fluctuations may be driven by a combination of weather conditions. Local geology could support the periodic high fluxes of ²¹°Pb from continental air masses, as shifting oceanic wind sources were affirmed by the uncorrelated ²¹°Pb and 7Be fallout activities and 7Be/²¹°Pb ratios. The ²¹°Pb atmospheric deposition was found to be in agreement with local sediment inventories, an important consideration in geochemical studies that estimate sedimentation processes.