Beryllium-7 wet deposition variation with storm height, synoptic classification, and tree canopy state in the mid-Atlantic USA

Short-lived fallout isotopes, such as beryllium-7 (⁷Be), are increasingly used as erosion and sediment tracers in watersheds. ⁷Be is produced in the atmosphere and delivered to the Earth's surface primarily in precipitation. However, relatively little has been published about the variation in ⁷Be wet deposition caused by storm type and vegetation cover. Our analysis of precipitation, throughfall, and sediments in two forested, headwater catchments in the mid-Atlantic USA indicates significant variation in isotope deposition with storm type and storm height. Individual summer convective thunderstorms were associated with ⁷Be activity concentrations up to 5.0Bql^-1 in precipitation and 4.7Bql^-1 in throughfall, while single-event wet depositional fluxes reached 168Bqm^-2 in precipitation and 103Bqm^-2 in throughfall. Storms originating from the continental USA were associated with lower ⁷Be activity concentrations and single-event wet depositional fluxes for precipitation (0.7-1.2Bql^-1 and 15.8-65.0Bqm^-2) and throughfall (0.1-0.3Bql^-1 and 13.5-98.9Bqm^-2). Tropical systems had relatively low activity concentrations, 0.2-0.5Bql^-1 in precipitation and 0.2-1.0Bql^-1 in throughfall, but relatively high single-event depositional fluxes due to large rainfall volumes, 32.8-67.6Bqm^-2 in precipitation and 25.7-134Bqm^-2 in throughfall. The largest sources of ⁷Be depositional variation were attributed to storm characteristics including precipitation amount and maximum storm height. ⁷Be activity associated with fluvial suspended sediments also exhibited the highest concentration and variability in summer (175-1450Bqkg^-1). We conclude the dominant source of variation on event-level ⁷Be deposition is storm type. Our results illustrate the complex relationships between ⁷Be deposition in precipitation and throughfall and demonstrate event-scale relationships between the ⁷Be in precipitation and on suspended sediment.