Spatial variability of 7Be fallout for erosion evaluation

The uniformity of beryllium-7 (7Be) fallout is a basic assumption for the validity of the method that uses the fallout redistribution analysis to estimate the rates of soil erosion and sediment deposits. However, this topic has not yet been intensively investigated and the information available in the literature is scarce. This paper presents results of the 7Be fallout spatial variability in rainfall events that occurred on a relatively small experimental area within the city of Piracicaba, Brazil. Rainwater taken from 24 rainfall events was collected at twelve sampling points, and five of these events were selected for the variability study. Activity concentrations of 7Be in rainwater ranged from 0.26 to 1.81 Bq L−1. The spatial variability of 7Be fallout can be considered as moderate to high when considering the coefficient of variation, but some events presented certain uniformity along the study area. The influence of 7Be fallout spatial variability in soil erosion measurements was also evaluated and it shows how important this uniformity is for the 7Be erosion model accuracy.

► We evaluate the spatial variability of 7Be fallout by measuring 7Be in rainwater.
► We discuss the effects of 7Be fallout variability for the 7Be erosion model accuracy.
► The spatial variability of 7Be fallout shows to be high for isolated events of rain.
► The 7Be erosion model accuracy is highly affected by 7Be fallout variability.