Short-term soil mixing quantified with fallout radionuclides

Research Article| March 01, 2007 Short-term soil mixing quantified with fallout radionuclides James M. Kaste; James M. Kaste 1Department of Earth Sciences, Dartmouth College, Hanover, New Hampshire 03755, USA Search for other works by this author on: GSW Google Scholar Arjun M. Heimsath; Arjun M. Heimsath 1Department of Earth Sciences, Dartmouth College, Hanover, New Hampshire 03755, USA Search for other works by this author on: GSW Google Scholar Benjamin C. Bostick Benjamin C. Bostick 1Department of Earth Sciences, Dartmouth College, Hanover, New Hampshire 03755, USA Search for other works by this author on: GSW Google Scholar Author and Article Information James M. Kaste 1Department of Earth Sciences, Dartmouth College, Hanover, New Hampshire 03755, USA Arjun M. Heimsath 1Department of Earth Sciences, Dartmouth College, Hanover, New Hampshire 03755, USA Benjamin C. Bostick 1Department of Earth Sciences, Dartmouth College, Hanover, New Hampshire 03755, USA Publisher: Geological Society of America Received: 12 Sep 2006 Revision Received: 24 Oct 2006 Accepted: 27 Oct 2006 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2007) 35 (3): 243–246. https://doi.org/10.1130/G23355A.1 Article history Received: 12 Sep 2006 Revision Received: 24 Oct 2006 Accepted: 27 Oct 2006 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation James M. Kaste, Arjun M. Heimsath, Benjamin C. Bostick; Short-term soil mixing quantified with fallout radionuclides. Geology 2007;; 35 (3): 243–246. doi: https://doi.org/10.1130/G23355A.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Soil mixing plays a significant role in contaminant transport, carbon sequestration, and landscape evolution, yet the rates and driving mechanisms are poorly constrained. Here we use depth profiles and advection-diffusion modeling of fallout nuclides to quantify differences in short-term (<100 yr) physical soil mixing across contrasting landscapes. We constrain advection in soils using the distribution of cosmogenic 7Be and weapons-derived isotopes, and quantify mixing with a steady-state model of vertical 210Pb transport. On a forested landscape in the Bega Valley in southeastern Australia and on grasslands in Marin County, California, where bioturbation is documented as the dominant sediment transport mechanism, we calculate diffusion-like mixing coefficients of 1–2 cm2 yr−1. In montane forest soils of northern New England, we observe little field evidence of short-term mixing, and find that the traditional advection-diffusion model fails to describe 210Pb profiles. Because nuclide profiles here can be described with a simple model of litterfall, organic matter decay, and radioactive decay, we argue that diffusion-like processes are barely active on short time scales, and that the advection-diffusion model overestimates diffusion-like transport. While animal bioturbation and soil freezing cycles have little effect on the fate of elements in New England, physical soil mixing drives transport at Bega Valley and Marin County. We suggest that the absence of soil stirring that we quantify in New England forests may explain the slow physical erosion here (∼0.2 cm/k.y.) relative to the actively bioturbated soils of Bega Valley and Marin County (5–10 cm/k.y.). You do not have access to this content, please speak to your institutional administrator if you feel you should have access.