Does Be10 Underestimate Residence Time of Critical Zones in Acid Environments?

Tuesday, 16 December 2014
Daniel Richter Jr, Duke University, Nicholas School of the Environment, Durham, NC, United States
Meteoric 10Be inventories were coupled with with mass balance of 9Be (bedrock to 18.3 meters soil-saprolite profile) to estimate the soil residence time (SRT) of a biogeomorphically stable Ultisol. We estimate SRT after correcting for observed9Be losses, which indicate that more than half of the 9Be weathered from primary minerals had been leached from the soil and saprolite. Our estimates of minimum SRT range between 1.3–1.4 Ma and between 2.6–3.1 Ma under high and low (2.0 and 1.3 × 106 atoms cm−2 yr−1, respectively) estimates of atmospheric 10Be deposition. Denudation rates of the physiographic region corroborate our residence time estimates. We double to quadruple the pedogenic time constraints of interfluves on the Southern Piedmont, and demonstrate that assumptions of complete meteoric 10Be retention in acidic soil systems need questioning. The results may have far-reaching consequences for soil, sediment, river, and ocean research using meteoric 10Be.