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Environmental problems - Chemical approaches
RESEARCH ARTICLE

Iron isotope composition of aqueous phases of a lowland environment

Stephan Schuth A B C and Tim Mansfeldt A
+ Author Affiliations
- Author Affiliations

A Geographisches Institut, Bodengeographie/Bodenkunde, Universität zu Köln, D-50923 Köln, Germany.

B Institut für Mineralogie, Leibniz Universität Hannover, Callinstraße 3, D-30167 Hannover, Germany.

C Corresponding author. Email address: s.schuth@mineralogie.uni-hannover.de

Environmental Chemistry 13(1) 89-101 https://doi.org/10.1071/EN15073
Submitted: 1 April 2015  Accepted: 7 May 2015   Published: 15 September 2015

Environmental context. Iron (Fe) isotope analysis is a powerful tool to understand the transport of Fe within and from soils to rivers. We determined Fe isotopes and Fe concentrations of soil solutions at different depths and found that the Fe isotope compositions are modified owing to adsorption onto Fe oxides, especially in the subsoil. Hence Fe-rich capillary rising groundwater or seeping Fe-rich surface water are depleted in Fe and potentially other metals in Fe oxide-rich soil horizons.

Abstract. The mobility of iron (Fe) in soils is strongly affected by redox conditions, which also affect Fe input into groundwater and rivers. Stable Fe isotope analyses allow further investigation of Fe translocation processes within, into and out of soils. Soil solutions taken from a Gleysol in a lowland area (NW Germany) at different depths revealed that Fe concentration and isotope ratios strongly varied with abundance of solid Fe oxides. Low δ56Fe values of –1.7 ‰ and minimum Fe concentrations of ~0.2 mg L–1 were recorded in soil solutions of Fe-rich horizons. Soil solutions of a Fe-poor horizon, however, yielded higher δ56Fe values (–0.39 ‰) and Fe concentrations of up to 68 mg L–1. The water of an adjacent drainage ditch featured δ56Fe values of –1.1 ‰, in strong contrast to +0.60 ‰ of short-range ordered Fe oxide deposits in the ditch bed. We attribute the coupled low δ56Fe values and Fe concentrations to combined adsorption and atom exchange between dissolved Fe and Fe oxides. Consequently Fe oxide-poor horizons had higher δ56Fe values and dissolved Fe concentrations. Outflow of Fe-rich groundwater and surface water during rainfall into rivers is responsible for high δ56Fe for Fe-oxide precipitates and low riverine δ56Fe values.


References

[1]  W. Stumm, J. J. Morgan, Aquatic Chemistry: Chemical Equilibria and Rates in Natural Waters 1996 (Wiley: New York).

[2]  B. Zinder, G. Furrer, W. Stumm, The coordination chemistry of weathering: II. Dissolution of FeIII oxides. Geochim. Cosmochim. Acta 1986, 50, 1861.
The coordination chemistry of weathering: II. Dissolution of FeIII oxides.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaL28XlslKjtb8%3D&md5=fde04687ccb8b6c50b5fb7c1e0c2e38eCAS |

[3]  N. Takeno, Atlas of Eh–pH diagrams. Geological Survey of Japan Open File Report 419 2005 (National Institute of Advanced Industrial Science and Technology, Research Center for Deep Geological Environments, Geological Survey of Japan: Tokyo, Japan).

[4]  D. R. Lovley, Dissimilatory FeIII and MnIV reduction. Microbiol. Rev. 1991, 55, 259.
| 1:CAS:528:DyaK3MXltFSjtLY%3D&md5=43dc1620953c864b549fbf2d6ad75097CAS | 1886521PubMed |

[5]  E. E. Roden, J. M. Zachara, Microbial reduction of crystalline iron(III) oxides: influence of oxide surface area and potential for cell growth. Environ. Sci. Technol. 1996, 30, 1618.
Microbial reduction of crystalline iron(III) oxides: influence of oxide surface area and potential for cell growth.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK28XhvVKgt7k%3D&md5=6229842d03dddff4a68fb4a69bbc9753CAS |

[6]  B. L. Beard, C. M. Johnson, L. Cox, H. Sun, K. H. Nealson, C. Aguilar, Iron isotope biosignatures. Science 1999, 285, 1889.
Iron isotope biosignatures.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK1MXmtVCnurs%3D&md5=50a11a3e13a9b4144d946901c5a8b8e0CAS | 10489362PubMed |

[7]  S. L. Brantley, L. Liermann, T. D. Bullen, Fractionation of Fe isotopes by soil microbes and organic acids. Geology 2001, 29, 535.
Fractionation of Fe isotopes by soil microbes and organic acids.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3MXks1ansLo%3D&md5=1a9369d5224a4b32de59bdbea016708eCAS |

[8]  H. A. Crosby, E. E. Roden, C. M. Johnson, B. L. Beard, The mechanisms of iron isotope fractionation produced during dissimilatory FeIII reduction by Shewanella putrefaciens and Geobacter sulfurreducens. Geobiology 2007, 5, 169.
The mechanisms of iron isotope fractionation produced during dissimilatory FeIII reduction by Shewanella putrefaciens and Geobacter sulfurreducens.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2sXotVKqu78%3D&md5=0a0dcccbe271e9d8cc022ffe746b4328CAS |

[9]  C. M. Johnson, B. L. Beard, E. E. Roden, The iron isotope fingerprints of redox and biogeochemical cycling in modern and ancient Earth. Annu. Rev. Earth Planet. Sci. 2008, 36, 457.
The iron isotope fingerprints of redox and biogeochemical cycling in modern and ancient Earth.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1cXmvFWmu7s%3D&md5=2ade9f6e98da462daa3f35c39771c0cdCAS |

[10]  B. H. Jeon, B. A. Dempsey, W. D. Burgos, Kinetics and mechanisms for reactions of Fe(II) with iron(III) oxides. Environ. Sci. Technol. 2003, 37, 3309.
Kinetics and mechanisms for reactions of Fe(II) with iron(III) oxides.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3sXksFWgsLs%3D&md5=2862fdfb1a0d0da34adb5a87ae496712CAS | 12966975PubMed |

[11]  G. A. Icopini, A. D. Anbar, S. S. Ruebush, M. Tien, S. L. Brantley, Iron isotope fractionation during microbial reduction of iron: the importance of adsorption. Geology 2004, 32, 205.
Iron isotope fractionation during microbial reduction of iron: the importance of adsorption.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2cXislyhs7s%3D&md5=a88e37f75a027699fa55f88eaf064fd2CAS |

[12]  A. G. B. Williams, M. M. Scherer, Spectroscopic evidence for FeII–FeIII electron transfer at the iron oxide–water interface. Environ. Sci. Technol. 2004, 38, 4782.
Spectroscopic evidence for FeII–FeIII electron transfer at the iron oxide–water interface.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2cXms1Oltrc%3D&md5=d49c2a1f9940ed7f98c0b14b9c49dce8CAS |

[13]  N. Teutsch, U. von Gunten, D. Porcelli, O. A. Cirpka, A. N. Halliday, Adsorption as a cause for iron isotope fractionation in reduced groundwater. Geochim. Cosmochim. Acta 2005, 69, 4175.
Adsorption as a cause for iron isotope fractionation in reduced groundwater.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2MXhtVShtbnK&md5=0af5876945026dc18fc8a049f0ff5cbbCAS |

[14]  P. Larese-Casanova, M. M. Scherer, FeII sorption on hematite: new insights based on spectroscopic measurements. Environ. Sci. Technol. 2007, 41, 471.
FeII sorption on hematite: new insights based on spectroscopic measurements.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD28Xht1yrtrfO&md5=3252ed1519f580e957a87b3c7e9b2af2CAS | 17310709PubMed |

[15]  C. Mikutta, J. G. Wiederhold, O. A. Cirpka, T. B. Hofstetter, B. Bourdon, U. von Gunten, Iron isotope fractionation and atom exchange during sorption of ferrous iron to mineral surfaces. Geochim. Cosmochim. Acta 2009, 73, 1795.
Iron isotope fractionation and atom exchange during sorption of ferrous iron to mineral surfaces.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1MXjtFamsLY%3D&md5=3ac946d6004d9e4ee5015a3c15a1160dCAS |

[16]  K. M. Rosso, S. V. Yanina, C. A. Gorski, P. Larese-Casanova, M. M. Scherer, Connecting observations of hematite (α-Fe2O3) growth catalyzed by FeII. Environ. Sci. Technol. 2010, 44, 61.
Connecting observations of hematite (α-Fe2O3) growth catalyzed by FeII.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1MXhsValur3L&md5=0b151dd7a4a55cf64cf2364e46176783CAS | 20039734PubMed |

[17]  P. Zarzycki, S. Kerisit, K. M. Rosso, Molecular dynamics study of FeII adsorption, electron exchange, and mobility at goethite (α-FeOOH) surfaces. J. Phys. Chem. 2015, 119, 3111.
| 1:CAS:528:DC%2BC2MXhtFykurY%3D&md5=0ef063f5e6a91c922940b223153c3c39CAS |

[18]  H. A. Crosby, C. M. Johnson, E. E. Roden, B. L. Beard, Coupled FeII and FeIII electron and atom exchange as a mechanism for Fe isotope fractionation during dissimilatory iron oxide reduction. Environ. Sci. Technol. 2005, 39, 6698.
Coupled FeII and FeIII electron and atom exchange as a mechanism for Fe isotope fractionation during dissimilatory iron oxide reduction.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2MXmsVynsbg%3D&md5=0862c0b9893cc481e5e543aff547c409CAS | 16190229PubMed |

[19]  J.-H. Jang, R. Mathur, L. J. Liermann, S. Ruebush, S. L. Brantley, An iron isotope signature related to electron transfer between aqueous ferrous iron and goethite. Chem. Geol. 2008, 250, 40.
An iron isotope signature related to electron transfer between aqueous ferrous iron and goethite.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1cXkvVemsbw%3D&md5=7c4407d32bb568649239f835be81bd81CAS |

[20]  L. Wu, B. L. Beard, E. E. Roden, C. M. Johnson, Stable iron isotope fractionation between aqueous FeII and hydrous ferric oxide. Environ. Sci. Technol. 2011, 45, 1847.
Stable iron isotope fractionation between aqueous FeII and hydrous ferric oxide.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3MXhsFGnsbs%3D&md5=a34e255d5f21e7fee60817aa7bae4447CAS | 21294566PubMed |

[21]  A. J. Frierdich, B. L. Beard, T. R. Reddy, M. M. Scherer, C. M. Johnson, Iron isotope fractionation between aqueous FeII and goethite revisited: new insights based on a multi-direction approach to equilibrium and isotopic exchange rate modification. Geochim. Cosmochim. Acta 2014, 139, 383.
Iron isotope fractionation between aqueous FeII and goethite revisited: new insights based on a multi-direction approach to equilibrium and isotopic exchange rate modification.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC2cXhtFant7%2FN&md5=24fb3010d0954cd055b4af00000819d4CAS |

[22]  A. M. Jones, R. N. Collins, J. Rose, T. D. Waite, The effect of silica and natural organic matter on the FeII-catalysed transformation and reactivity of FeIII minerals. Geochim. Cosmochim. Acta 2009, 73, 4409.
The effect of silica and natural organic matter on the FeII-catalysed transformation and reactivity of FeIII minerals.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1MXnslKksLc%3D&md5=edc75098ffc692b04251898571d2e791CAS |

[23]  J. G. Wiederhold, Metal stable isotope signatures as tracers in environmental geochemistry. Environ. Sci. Technol. 2015, 49, 2606.
Metal stable isotope signatures as tracers in environmental geochemistry.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC2MXhvV2jurc%3D&md5=9d48312f0e155197c9bc9c36fcbcf060CAS | 25640608PubMed |

[24]  V. B. Polyakov, R. N. Clayton, J. Horita, S. D. Mineev, Equilibrium iron isotope fractionation factors of minerals: reevaluation from the data of nuclear inelastic resonant X-ray scattering and Mössbauer spectroscopy. Geochim. Cosmochim. Acta 2007, 71, 3833.
Equilibrium iron isotope fractionation factors of minerals: reevaluation from the data of nuclear inelastic resonant X-ray scattering and Mössbauer spectroscopy.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2sXnvFOnsL8%3D&md5=fc83975342acbf7b1a3f7f03ee456600CAS |

[25]  L. Wu, B. L. Beard, E. E. Roden, C. B. Kennedy, C. M. Johnson, Stable Fe isotope fractionation produced by aqueous FeII–hematite surface interactions. Geochim. Cosmochim. Acta 2010, 74, 4249.
Stable Fe isotope fractionation produced by aqueous FeII–hematite surface interactions.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3cXnvFGrurg%3D&md5=1cc21045231ed7f6d5a96f4f972974d7CAS |

[26]  M. S. Fantle, D. J. DePaolo, Iron isotopic fractionation during continental weathering. Earth Planet. Sci. Lett. 2004, 228, 547.
Iron isotopic fractionation during continental weathering.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2cXhtVCqtLvN&md5=5f1522534b1632e685dfce83b95fcbdfCAS |

[27]  A. Thompson, J. Ruiz, O. A. Chadwick, M. Titus, J. Chorover, Rayleigh fractionation of iron isotopes during pedogenesis along a climate sequence of Hawaiian basalt. Chem. Geol. 2007, 238, 72.
Rayleigh fractionation of iron isotopes during pedogenesis along a climate sequence of Hawaiian basalt.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2sXitFShsr4%3D&md5=bc009956de90ca3cd94c2908e2f9c891CAS |

[28]  J. G. Wiederhold, N. Teutsch, S. M. Kraemer, A. N. Halliday, R. Kretzschmar, Iron isotope fractionation during pedogenesis in redoximorphic soils. Soil Sci. Soc. Am. J. 2007, 71, 1840.
Iron isotope fractionation during pedogenesis in redoximorphic soils.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2sXhtl2ru7rI&md5=0d90d3b93605b12e3ef89fa1c211624aCAS |

[29]  J. G. Wiederhold, N. Teutsch, S. M. Kraemer, A. N. Halliday, R. Kretzschmar, Iron isotope fractionation in oxic soils by mineral weathering and podzolisation. Geochim. Cosmochim. Acta 2007, 71, 5821.
Iron isotope fractionation in oxic soils by mineral weathering and podzolisation.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2sXhtlWnsrrJ&md5=444c1219aadb4f2b44ecc3b0358dbd02CAS |

[30]  T. Mansfeldt, S. Schuth, W. Häusler, F. E. Wagner, S. Kaufhold, M. Overesch, Iron oxide mineralogy and stable iron isotope composition in a Gleysol with petrogleyic properties. J. Soils Sediments 2012, 12, 97.
Iron oxide mineralogy and stable iron isotope composition in a Gleysol with petrogleyic properties.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC38XksVOmtQ%3D%3D&md5=5a6b39ec8c5888447722d537627cfcb6CAS |

[31]  Z. Fekiacova, S. Pichat, S. Cornu, J. Balesdent, Inferences from vertical distribution of Fe isotopic compositions on pedogenetic processes in soils. Geoderma 2013, 209–210, 110.
Inferences from vertical distribution of Fe isotopic compositions on pedogenetic processes in soils.Crossref | GoogleScholarGoogle Scholar |

[32]  S. A. Liu, F. Z. Teng, S. Li, G. J. Wei, J. L. Ma, D. Li, Copper and iron isotope fractionation during weathering and pedogenesis: insights from saprolite profiles. Geochim. Cosmochim. Acta 2014, 146, 59.
Copper and iron isotope fractionation during weathering and pedogenesis: insights from saprolite profiles.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC2cXhsleltr%2FE&md5=3f91d9587042169e616ac831a0bf9b98CAS |

[33]  A. Thompson, O. A. Chadwick, D. G. Rancourt, J. Chorover, Iron oxide crystallinity increases during soil redox oscillations. Geochim. Cosmochim. Acta 2006a, 70, 1710.
Iron oxide crystallinity increases during soil redox oscillations.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD28XisFChsrg%3D&md5=82f60a5017e9c09904906063cee2a845CAS |

[34]  A. Thompson, O. A. Chadwick, S. Boman, J. Chorover, Colloid mobilization during soil iron redox conditions. Environ. Sci. Technol. 2006b, 40, 5743.
Colloid mobilization during soil iron redox conditions.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD28Xot1Cgsr4%3D&md5=28e0e5c4b939b73efda8ccd4a465fb8eCAS | 17007135PubMed |

[35]  T. Yesavage, M. S. Fantle, J. Vervoort, R. Mathur, L. Jin, L. J. Liermann, S. L. Brantley, Fe cycling in the Shale Hills Critical Zone Observatory, Pennsylvania: an analysis of biogeochemical weathering and Fe isotope fractionation. Geochim. Cosmochim. Acta 2012, 99, 18.
Fe cycling in the Shale Hills Critical Zone Observatory, Pennsylvania: an analysis of biogeochemical weathering and Fe isotope fractionation.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC38Xhs12ks7vK&md5=9416eee2c6fcd68799cca94563dd0357CAS |

[36]  R. M. Handler, B. L. Beard, C. M. Johnson, M. M. Scherer, Atom exchange between aqueous FeII and goethite: an Fe isotope tracer study. Environ. Sci. Technol. 2009, 43, 1102.
Atom exchange between aqueous FeII and goethite: an Fe isotope tracer study.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1MXpsl2iug%3D%3D&md5=906833d94def66264b6523236992eefcCAS | 19320165PubMed |

[37]  B. L. Beard, R. M. Handler, M. M. Scherer, L. Wu, A. D. Czaja, A. Heimann, C. M. Johnson, Iron isotope fractionation between aqueous ferrous iron and goethite. Earth Planet. Sci. Lett. 2010, 295, 241.
Iron isotope fractionation between aqueous ferrous iron and goethite.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3cXmsVemtb0%3D&md5=c9cd36cbd8bf2201f944eecb0efeebddCAS |

[38]  T. Mansfeldt, M. Overesch, Arsenic mobility and speciation in a Gleysol with petrogleyic properties – a field and laboratory approach. J. Environ. Qual. 2013, 42, 1130.
Arsenic mobility and speciation in a Gleysol with petrogleyic properties – a field and laboratory approach.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3sXhtFOjsL%2FJ&md5=bfa27f77c581c0eac477bc0f6649a34aCAS | 24216364PubMed |

[39]  S. Schuth, J. Hurraß, C. Münker, T. Mansfeldt, Redox-dependent fractionation of iron isotopes in suspensions of a groundwater-influenced soil. Chem. Geol. 2015, 392, 74.
Redox-dependent fractionation of iron isotopes in suspensions of a groundwater-influenced soil.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC2cXhvF2qsrjP&md5=a561120201bc67f17734dbb8fe5a0798CAS |

[40]  A. Banning, W. G. Coldewey, P. Göbel, A procedure to identify natural arsenic sources, applied in an affected area in North Rhine–Westphalia, Germany. Environ. Geol. 2009, 57, 775.
A procedure to identify natural arsenic sources, applied in an affected area in North Rhine–Westphalia, Germany.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1MXivFyrurw%3D&md5=c94f45e9a5c236067c4482d591cb4b65CAS |

[41]  A. Banning, T. Rüde, B. Dölling, Crossing redox boundaries – aquifer redox and effect on iron mineralogy and arsenic availability. J. Hazard. Mater. 2013, 262, 905.
Crossing redox boundaries – aquifer redox and effect on iron mineralogy and arsenic availability.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3sXjtFOr&md5=2750458ce2875b1383827915090df59fCAS | 23280400PubMed |

[42]  H. Dahm-Ahrens, Entstehung der Eisenschwarten in den Kreidesanden Westfalens. Fortschritte Geol. Rheinld. u. Westf. 1972, 21, 133.

[43]  K. Skupin, Erdgeschichte – Tertiär, in Geologie im Münsterland (Ed. H. D. Hilden) 1995, pp. 66–70 (Geologisches Landesamt Nordrhein–Westfalen: Krefeld, Germany).

[44]  T. Mansfeldt, In situ long-term redox potential measurements in a dyked marsh soil. J. Plant Nutr. Soil Sci. 2003, 166, 210.
In situ long-term redox potential measurements in a dyked marsh soil.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3sXjsFSrsb8%3D&md5=7f892c4e7812a358eaa8aa8444d4d075CAS |

[45]  T. Mansfeldt, Redox potential of bulk soil and soil solution concentration of nitrate, manganese, iron, and sulfate in two Gleysols. J. Plant Nutr. Soil Sci. 2004, 167, 7.
Redox potential of bulk soil and soil solution concentration of nitrate, manganese, iron, and sulfate in two Gleysols.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2cXhslOjsrw%3D&md5=07b1f3841712c76d3df115ecb0d79da5CAS |

[46]  E. Viollier, P. W. Inglett, K. Hunter, A. N. Roychoudhury, P. Van Capellen, The ferrozine method revisited: FeII/FeIII determination in natural waters. Appl. Geochem. 2000, 15, 785.
The ferrozine method revisited: FeII/FeIII determination in natural waters.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3cXhsVWhsLc%3D&md5=5c4f84783612af82bfe5c4033eb223b2CAS |

[47]  G. L. Arnold, S. Weyer, A. D. Anbar, Fe isotope variations in natural materials measured using high-mass-resolution multiple-collector ICPMS. Anal. Chem. 2004, 76, 322.
Fe isotope variations in natural materials measured using high-mass-resolution multiple-collector ICPMS.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3sXpsFyht7c%3D&md5=701fb261490f83fa726450c05d511c94CAS | 14719878PubMed |

[48]  N. Teutsch, M. Schmid, B. Muller, A. N. Halliday, H. Burgmann, B. Wehrli, Large iron isotope fractionation at the oxic–anoxic boundary in Lake Nyos. Earth Planet. Sci. Lett. 2009, 285, 52.
Large iron isotope fractionation at the oxic–anoxic boundary in Lake Nyos.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1MXptVCqurg%3D&md5=2c29b0204de29336da826915dc3f1ed7CAS |

[49]  M. Kiczka, J. G. Wiederhold, J. Frommer, A. Voegelin, S. M. Kraemer, B. Bourdon, R. Kretzschmar, Iron speciation and isotope fractionation during silicate weathering and soil formation in an Alpine glacier forefield chronosequence. Geochim. Cosmochim. Acta 2011, 75, 5559.
Iron speciation and isotope fractionation during silicate weathering and soil formation in an Alpine glacier forefield chronosequence.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3MXhtFWltLrJ&md5=6f3ff01cf9ce6d2dbb502e0a907f6eceCAS |

[50]  L. Zhi-Guang, Oxidation–reduction potential, in Physical Chemistry of Paddy Soils (Ed. Y. Tian-ren) 1985, pp. 1–26 (Springer: Berlin, Germany).

[51]  J. Casanova, F. Bodénan, P. Négrel, M. Azaroual, Microbial control on the precipitation of modern ferrihydrite and carbonate deposits from the Cézallier hydrothermal springs (Massif Central, France). Sediment. Geol. 1999, 126, 125.
Microbial control on the precipitation of modern ferrihydrite and carbonate deposits from the Cézallier hydrothermal springs (Massif Central, France).Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK1MXlt1SgtLs%3D&md5=eb005c4762cae5cf904f0281ea6cc54dCAS |

[52]  T. Hiemstra, W. H. Van Riemsdijk, A surface structural model for ferrihydrite I: sites related to primary charge, molar mass, and mass density. Geochim. Cosmochim. Acta 2009, 73, 4423.
A surface structural model for ferrihydrite I: sites related to primary charge, molar mass, and mass density.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1MXnslKksb8%3D&md5=aa5a4d354e22bb00880b2c46d397afe2CAS |

[53]  C. A. J. Appelo, M. J. J. van der Weiden, C. Tournassat, L. Charlet, Surface complexation of ferrous iron and carbonate on ferrihydrite and the mobilization of arsenic. Environ. Sci. Technol. 2002, 36, 3096.
Surface complexation of ferrous iron and carbonate on ferrihydrite and the mobilization of arsenic.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD38XktlChtbw%3D&md5=81ce16fda95bd4f841525cc16d642ea5CAS |

[54]  F. M. M. Morel, J. G. Hering, Principles and Applications of Aquatic Chemistry 1993 (Wiley: New York).

[55]  Y. K. Henneberry, T. E. C. Kraus, P. S. Nico, W. R. Horwath, Structural stability of coprecipitated natural organic matter and ferric iron under reducing conditions. Org. Geochem. 2012, 48, 81.
Structural stability of coprecipitated natural organic matter and ferric iron under reducing conditions.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC38Xot1Cisrc%3D&md5=55d185ed969cd0c50de3a1c5e56f867cCAS |

[56]  V. B. Polyakov, S. D. Mineev, The use of Mössbauer spectroscopy in stable isotope geochemistry. Geochim. Cosmochim. Acta 2000, 64, 849.
The use of Mössbauer spectroscopy in stable isotope geochemistry.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3cXhtl2rtrw%3D&md5=c6220f71ee0e4eb844a74a5ab1ad87c3CAS |

[57]  J. R. Rustad, W. H. Casey, Q. Z. Yin, E. J. Bylaska, A. R. Felmy, S. A. Bogatko, V. E. Jackson, D. A. Dixon, Isotopic fractionation of Mg2+(aq), Ca2+(aq), and Fe2+(aq) with carbonate minerals. Geochim. Cosmochim. Acta 2010, 74, 6301.
Isotopic fractionation of Mg2+(aq), Ca2+(aq), and Fe2+(aq) with carbonate minerals.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3cXht12gt7fE&md5=4a3fb8d79213c847f301f38d9e9ffa58CAS |

[58]  R. Henderson, N. Kabengi, N. Mantripragada, M. Cabrera, S. Hassan, A. Thompson, Anoxia-induced release of colloid- and nanoparticle-bound phosphorous in grassland soils. Environ. Sci. Technol. 2012, 46, 11727.
Anoxia-induced release of colloid- and nanoparticle-bound phosphorous in grassland soils.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC38XhsVWmsLnI&md5=00c8816ed7a9468362a691313d2f6ad2CAS | 23017121PubMed |

[59]  S. M. Ilina, F. Poitrasson, S. A. Lapitskiy, Y. V. Alekhin, J. Viers, O. S. Pokrovsky, Extreme iron isotope fractionation between colloids and particles of boreal and temperate organic-rich waters. Geochim. Cosmochim. Acta 2013, 101, 96.
Extreme iron isotope fractionation between colloids and particles of boreal and temperate organic-rich waters.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC38XhvVKgu7nL&md5=5c8e7fdaed5fe0bfad8a73c34f4d76f5CAS |

[60]  J. N. Ryan, T. H. Illangasekare, M. I. Litaor, R. Shannon, Particle and plutonium mobilization in macroporous soils during rainfall simulations. Environ. Sci. Technol. 1998, 32, 476.
Particle and plutonium mobilization in macroporous soils during rainfall simulations.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK1cXjsVKgsg%3D%3D&md5=4c3f3f4b7eef5bde4f7a1d0325edfc85CAS |

[61]  J. Ingri, D. Malinovsky, I. Rodushkin, D. C. Baxter, A. Widerlund, P. Andersson, Ö. Gustafsson, W. Forsling, B. Öhlander, Iron isotope fractionation in river colloidal matter. Earth Planet. Sci. Lett. 2006, 245, 792.
Iron isotope fractionation in river colloidal matter.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD28XkvVCrtrw%3D&md5=c82f54758afba4d245c69574007b84b7CAS |

[62]  R. A. Bunn, R. D. Magelky, J. N. Ryan, M. Elimelech, Mobilization of natural colloids from an iron oxide-coated sand aquifer: effect of pH and ionic strength. Environ. Sci. Technol. 2002, 36, 314.
Mobilization of natural colloids from an iron oxide-coated sand aquifer: effect of pH and ionic strength.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD38XhsVWitg%3D%3D&md5=1e953944e8147cf315e68c36a40617e2CAS | 11871543PubMed |

[63]  C. J. Tadanier, M. E. Schreiber, J. W. Roller, Arsenic mobilization through microbially mediated deflocculation of ferrihydrite. Environ. Sci. Technol. 2005, 39, 3061.
Arsenic mobilization through microbially mediated deflocculation of ferrihydrite.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2MXit12jurk%3D&md5=c31a582d210489a066f75d103e77e6ecCAS | 15926553PubMed |

[64]  O. Dellwig, T. Leipe, C. März, M. Glockzin, F. Pollehne, B. Schnetger, E. V. Yakushev, M. E. Böttcher, H. J. Brumsack, A new particulate Mn–Fe–P-shuttle at the redoxcline of anoxic basins. Geochim. Cosmochim. Acta 2010, 74, 7100.
A new particulate Mn–Fe–P-shuttle at the redoxcline of anoxic basins.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3cXhsVCmsLrF&md5=fa093ff62936b8be35c82359ca3dbd8bCAS |

[65]  G. M. dos Santos Pinheiro, F. Poitrasson, F. Sondag, G. Cochonneau, L. Cruz Vieira, Contrasting iron isotopic compositions in river suspended particulate matter: the Negro and the Amazon annual river cycles. Earth Planet. Sci. Lett. 2014, 394, 168.
Contrasting iron isotopic compositions in river suspended particulate matter: the Negro and the Amazon annual river cycles.Crossref | GoogleScholarGoogle Scholar |

[66]  D. I. Kaplan, P. M. Bertsch, D. C. Adriano, W. P. Miller, Soil-borne mobile colloids as influenced by water flow and organic carbon. Environ. Sci. Technol. 1993, 27, 1193.
Soil-borne mobile colloids as influenced by water flow and organic carbon.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK3sXitF2hsbk%3D&md5=96366e6b6c1290b3865420f1b10aaab7CAS |

[67]  R. Escoube, O. J. Rouxel, E. Sholkovitz, O. F. X. Donard, Iron isotope systematics in estuaries: the case of North River, Massachusetts (USA). Geochim. Cosmochim. Acta 2009, 73, 4045.
Iron isotope systematics in estuaries: the case of North River, Massachusetts (USA).Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1MXmvVynsLY%3D&md5=83a5d1b0303f2d9e62f07f5e803e167eCAS |

[68]  T. D. Bullen, A. White, C. W. Childs, D. V. Vivit, M. S. Schulz, Demonstration of significant abiotic iron isotope fractionation in nature. Geology 2001, 29, 699.
Demonstration of significant abiotic iron isotope fractionation in nature.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3MXmtVOqsbs%3D&md5=504754c1aa5f4a23dbb2ae00ad9d5b98CAS |

[69]  T. Hiemstra, Surface and mineral structure of ferrihydrite. Geochim. Cosmochim. Acta 2013, 105, 316.
Surface and mineral structure of ferrihydrite.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3sXivVGrtrc%3D&md5=aa38f1b55ee551f8d1119b1cfee6354eCAS |

[70]  J. G. Wiederhold, S. M. Kraemer, N. Teutsch, P. M. Borer, A. N. Halliday, R. Kretzschmar, Iron isotope fractionation during proton-promoted, ligand-controlled, and reductive dissolution of goethite. Environ. Sci. Technol. 2006, 40, 3787.
Iron isotope fractionation during proton-promoted, ligand-controlled, and reductive dissolution of goethite.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD28XkslWlsbo%3D&md5=9019bfbedbada45dcfe7647460eaaf49CAS | 16830543PubMed |

[71]  D. Langmuir, Aqueous Environmental Geochemistry 1997 (Prentice Hall: Upper Saddle River, NJ, USA).

[72]  S. V. Golubev, P. Bénézeth, J. Schott, J. L. Dandurand, A. Castillo, Siderite dissolution kinetics in acidic aqueous solutions from 25 to 100 °C and 0 to 50 atm pCO2. Chem. Geol. 2009, 265, 13.
Siderite dissolution kinetics in acidic aqueous solutions from 25 to 100 °C and 0 to 50 atm pCO2.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1MXptVygu7o%3D&md5=197539db88f070f7694e4dd523d1fea6CAS |

[73]  R. E. Criss, Principles of Stable Isotope Distribution 1999 (Oxford University Press: New York).

[74]  M. Guelke, F. von Blanckenburg, R. Schoenberg, M. Staubwasser, H. Stuetzel, Determining the stable Fe isotope signature of plant-available iron in soils. Chem. Geol. 2010, 277, 269.
Determining the stable Fe isotope signature of plant-available iron in soils.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3cXht1Sntb%2FP&md5=19788522df55e498ee68ae7fb9f70216CAS |