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

Abstract:

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.