Beryllium‐7 wet deposition variation with storm height, synoptic classification, and tree canopy state in the mid‐Atlantic USA. Issue 1 (22nd July 2015)

• Record Type: Journal Article
• Authors: Karwan, D. L.; Siegert, C. M.; Levia, D. F.; Pizzuto, J.; Marquard, J.; Aalto, R.; Aufdenkampe, A. K.
• Is Part Of: Hydrological processes. Volume 30:Issue 1(2016)
• Page Start: 75
• Page End: 89
• Publication Date: 2015-07-22
• Subjects: beryllium‐7 -- wet deposition -- precipitation -- sediment fingerprinting -- throughfall -- storm type; Hydrology -- Periodicals; Hydrology -- Research -- Periodicals; Hydrologic models -- Periodicals; Hydrological forecasting -- Periodicals; 631.432
• DOI: 10.1002/hyp.10571
• Languages: English
• ISSNs: 0885-6087

Abstract

Abstract: Short‐lived fallout isotopes, such as beryllium‐7 ( 7 Be), are increasingly used as erosion and sediment tracers in watersheds. 7 Be 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 7 Be 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 7 Be activity concentrations up to 5.0 Bq l −1 in precipitation and 4.7 Bq l −1 in throughfall, while single‐event wet depositional fluxes reached 168 Bq m −2 in precipitation and 103 Bq m −2 in throughfall. Storms originating from the continental USA were associated with lower 7 Be activity concentrations and single‐event wet depositional fluxes for precipitation (0.7–1.2 Bq l −1 and 15.8–65.0 Bq m −2 ) and throughfall (0.1–0.3 Bq l −1 and 13.5–98.9 Bq m −2 ). Tropical systems had relatively low activity concentrations, 0.2–0.5 Bq l −1 in precipitation and 0.2–1.0 Bq l −1 in throughfall, but relatively high single‐event depositional fluxes due to large rainfall volumes, 32.8–67.6 Bq m −2 in precipitation and 25.7–134 Bq m −2 in throughfall. The largest sources of 7 Be depositional variation were attributed to storm characteristics including precipitation amount and maximum storm height. 7 Be activity associated with fluvial suspended sediments also exhibited the highest concentration and variability in summer (175–1450 Bq kg −1 ). We conclude the dominant source of variation on event‐level 7 Be deposition is storm type. Our results illustrate the complex relationships between 7 Be deposition in precipitation and throughfall and demonstrate event‐scale relationships between the 7 Be in precipitation and on suspended sediment. Copyright © 2015 John Wiley & Sons, Ltd.