Meteoric Beryllium-10 as a Tracer of Erosion Due to Postsettlement Land Use in West-Central Minnesota, USA

Meteoric beryllium-10 (¹⁰Be_m, t^1/2 = 1.4 Myr) is a cosmogenic radionuclide that remains largely underutilized for deriving hillslope-scale estimates of erosion on uplands under conditions of land use change. We applied two different models for estimating erosion rates from observed ¹⁰Be_m concentrations (a one-dimensional model predicting vertical profiles of ¹⁰Be_m within hillslope soils [loss only, diffusion only, LODO] and a two-dimensional model predicting the concurrent evolution of hillslope topography and ¹⁰Be_m distributions via bioturbation, chemical mobility, and surface erosion [Be2D]). Both models were used to derive pre-European and post-European settlement erosion rates (E_nat and E_post, respectively) across paired cultivated and uncultivated hillslopes in west-central Minnesota, USA. E_post estimates from ¹⁰Be_m were compared to E_post estimates derived from ¹³⁷Cs inventories and the process-based Water and Tillage Erosion Model (WaTEM). The results from these models suggest that erosion rates from upper positions on the cultivated hillslope have increased from an average of 0.047 mm/year under natural conditions to E_post values of 3.09 mm/year. The Be2D and LODO models, on average, produced E_post estimates that were similar in magnitude to WaTEM and ¹³⁷Cs conversion models. This numerical convergence does not imply absolute ¹⁰Be_m model accuracy, particularly when considering the uncertainties inherent in each approach, but it does suggest that the orders of magnitude increase in estimated erosion rates from E_nat to E_post is robust. Additionally, the pattern of E_post estimates produced using ¹⁰Be_m conversion models is supported by the distribution of soil inorganic carbon at the study site. Our results demonstrate that ¹⁰Be_m can provide reasonable estimates of both predisturbance and postdisturbance erosion rates in landscapes that have undergone extensive human modification.