Fractionation of Fe isotopes by soil microbes and organic acids

Research Article| June 01, 2001 Fractionation of Fe isotopes by soil microbes and organic acids Susan L. Brantley; Susan L. Brantley 1Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania 16802, USA Search for other works by this author on: GSW Google Scholar Laura Liermann; Laura Liermann 1Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania 16802, USA Search for other works by this author on: GSW Google Scholar Thomas D. Bullen Thomas D. Bullen 2U.S. Geological Survey, Menlo Park, California 94025, USA Search for other works by this author on: GSW Google Scholar Geology (2001) 29 (6): 535–538. https://doi.org/10.1130/0091-7613(2001)029<0535:FOFIBS>2.0.CO;2 Article history received: 05 Sep 2000 rev-recd: 26 Feb 2001 accepted: 06 Mar 2001 first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Susan L. Brantley, Laura Liermann, Thomas D. Bullen; Fractionation of Fe isotopes by soil microbes and organic acids. Geology 2001;; 29 (6): 535–538. doi: https://doi.org/10.1130/0091-7613(2001)029<0535:FOFIBS>2.0.CO;2 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 Small natural variations in Fe isotopes have been attributed to biological cycling. However, without understanding the mechanisms of fractionation, it is impossible to interpret such variations. Here we show that the δ56Fe of Fe dissolved from a silicate soil mineral by siderophore-producing bacteria is as much as 0.8‰ lighter than bulk Fe in the mineral. A smaller isotopic shift is observed for Fe released abiotically by two chelates, and the magnitude of the shift increases with affinity of the ligand for Fe, consistent with a kinetic isotope effect during hydrolysis of Fe at the mineral surface. Fe dissolved abiotically without chelates shows no isotopic shift. The δ56Fe of the exchange fraction on soil grains is also lighter by ∼0.6‰–1‰ than Fe from both hornblende and iron oxyhydroxides. The kinetic isotope effect is therefore preserved in open systems such as soils. When recorded in the rock record, Fe isotopic fractionation could document Fe transport by organic molecules or by microbes where such entities were present in the geologic past. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.