Beryllium-7 Wet Deposition in Open Precipitation and Canopy Throughfall

Short-lived cosmogenic isotopes, such as beryllium-7 (7Be), are increasingly used in forested watersheds as tracers of erosion and sediment movement. Beryllium-7 is produced in the atmosphere and is delivered to Earth's surface primarily in precipitation. However, relatively little published data are available to document the influence of tree canopy on the 7Be activity that reaches the soil surface. We have collected open precipitation, canopy throughfall, and soils in two forested, headwater catchments associated with the Christina River Basin Critical Zone Observatory. On average, there was no significant difference between the 7Be activity in open precipitation and throughfall over a one-year period, although differences do occur in individual events. Deposition activity in all samples was higher during late summer storms that followed a dry period, with a disproportionate increase in the open precipitation. In the soil, the 7Be activity is concentrated in the litter layer and organic material of the O horizon.