A new study from researchers in the US is adding to the understanding of the chromium cycling in the aquatic environment. The new results have important implications for the Cr isotope system as a paleoceanographic redox proxy.
Background:The reconstruction of redox conditions in ancient oceans is a major challenge in Earth systems science. Redox conditions, commonly described in terms of the abundance of molecular oxygen relative to dissolved sulfide, are controlled by weathering reactions, volcanic emissions, biological processes, and ocean mixing. Therefore, redox reconstructions over geological timescales trace the evolution of oceanic and atmospheric chemistry and of the connections between the biosphere, hydrosphere, and geosphere. Earth’s redox state (the oxidation of the planet’s atmosphere and ocean) has played an important role in the evolution of life and, ultimately, Earth’s habitability. Therefore, understanding redox over various timescales throughout our planet’s history is an important step in determining how the Earth came to support the diversity of life we see today.
Isotopes of redox-sensitive metals have provided key information about past redox conditions at the Earth’s surface. Cr also has the potential to provide constraints on redox conditions in the oceans and atmosphere because Cr isotopes are fractionated during redox reactions, and a number of recent studies have attempted to use this system to trace changes in the level of O2 in the atmosphere in the Archaean and Neoproterozoic. The simplest application of Cr isotopes as a paleoredox proxy relies on the basic idea that variability of δ53Cr in sedimentary rocks requires mobile Cr(VI) on Earth’s surface and that the oxidation of Cr(III) to Cr(VI), via Mn oxides, requires free oxygen.
The use of Cr isotopes as a redox proxy is limited for now because scientists haven’t built up a clear understanding of the global mass balance of Cr isotopes. Many geological reservoirs and isotope fractionation processes are still not well understood.
Photo:
Satellite image of the Connecticut River depositing silt into Long Island Sound (NASA Earth Observatory, Public domain)
The new study:One environment in which this mass balance is little-understood is in estuaries. The new study now addresses this gap in knowledge by focusing on the Connecticut River estuary, collecting samples over a gradient from fresh to salty water. The study provides the first Cr isotope dataset for this type of environment. The team of scientists examined Cr-containing particulates in the water as well as dissolved Cr. Their results suggest that particles lose Cr as salinity increases, a finding that could have implications for interpreting Cr isotope data from the sedimentary rock record of the Earth. The authors conclude that interpreting δ53Cr in the sedimentary record requires taking multiple processes into consideration.
The work was supported by NASA Astrobiology through the Exobiology Program.
The cited study:
Zeyang Sun, Xiang-li Wang, Noah Planavsky,
Cr isotope systematics in the Connecticut River estuary, Chem. Geol., 506 (2019) 29-39.
DOI: 10.1016/j.chemgeo.2018.12.034 
Used techniques and instrumentation:
Related studies (newest first):
Simone B. Moos, Edward A. Boyle,
Determination of accurate and precise
chromium isotope ratios in seawater samples by MC-ICP-MS illustrated by
analysis of SAFe Station in the North Pacific Ocean, Chem. Geol., 2018.
DOI: 10.1016/j.chemgeo.2018.07.027
M.G. Babechuk, I.C. Kleinhanns, E. Reitter, R. Schoenberg,
Kinetic stable Cr isotopic
fractionation between aqueous Cr (III)-Cl-H2O complexes at 25 °C:
implications for Cr (III) mobility and isotopic variations in modern and
ancient natural, systems. Geochim. Cosmochim. Acta 222 (2018) 383–405.
DOI: 10.1016/j.gca.2017.10.002
Juraj Farkaš, Jirí Frýdad, Cora Paulukat, Ed C. Hathorne, Šarka
Matoušková, Jan Rohovec, Barbora Frýdová, Michaela Francová, Robert
Frei,
Chromium isotope fractionation between modern seawater and
biogenic carbonates from the Great Barrier Reef, Australia: Implications
for the paleo-seawater δ53Cr reconstruction, Earth Planet. Sci. Lett.,
498 (2018) 140–151.
DOI: 10.1016/j.epsl.2018.06.032
D.E. Canfield, S. Zhang, A.B. Frank, X. Wang, H. Wang, J. Su, Y. Ye, R. Frei,
Highly
fractionated chromium isotopes in Mesoproterozoic-aged shales and
atmospheric oxygen. Nat. Commun. 9 (2018) 2871.
DOI:
10.1038/s41467-018-05263-9
D.B. Cole, S. Zhang, N.J. Planavsky,
A new estimate of detrital
redox-sensitive metal concentrations and variability in fluxes to marine
sediments. Geochim. Cosmochim. Acta 215 (2017) 337–353.
DOI:
10.1016/j.gca.2017.08.004
X.L. Wang, N.J. Planavsky, P.M. Hull, A.E. Tripati, H.J. Zou, L. Elder,
M. Henehan,
Chromium isotopic composition of core-top planktonic
foraminifera, Geobiol., 15/1 (2017) 51-64.
DOI: 10.1111/gbi.12198
Weihua Wu, Xiangli Wang, Christopher T. Reinhard, Noah J. Planavsky,
Chromium isotope systematics in the Connecticut River, Chem. Geol., 456
(2017) 98-111.
DOI: 10.1016/j.chemgeo.2017.03.009
E.M. Saad, X. Wang, N.J. Planavsky, C.T. Reinhard, Y. Tang,
Redox-independent chromium isotope fractionation induced by
ligand-promoted dissolution. Nat. Commun. 8 (2017) 1590.
DOI:
10.1038/s41467-017-01694-y
J. D'Arcy, N.G. Babechuk, L.N. Dřssing, C. Gaucher, R. Frei,
Processes controlling the chromium isotopic composition of river water: constrains from basaltic river catchments. Geochim. Cosmochim. Acta, 186 (2016) 296–315.
DOI: 10.1016/j.gca.2016.04.027
Cora Paulukat, Geoffrey J. Gilleaudeau, Pavel Chernyavskiy, Robert Frei,
The Cr-isotope signature of surface seawater — A global perspective,
Chem. Geol., 444 (2016) 101-109.
DOI: 10.1016/j.chemgeo.2016.10.004
Xiangli Wang, Noah J. Planavsky, Christopher T. Reinhard, Huijuan Zou,
Jay J. Ague, Yuanbao Wu, Benjamin C. Gill, Esther M. Schwarzenbach,
Bernhard Peucker-Ehrenbrink,
Chromium isotope fractionation during
subduction-related metamorphism, black shale weathering, and
hydrothermal alteration, Chem. Geol., 423 (2016) 19-33.
DOI:
10.1016/j.chemgeo.2016.01.003
D.B. Cole, C.T. Reinhard, X. Wang, B. Gueguen, G.P. Halverson, T.
Gibson, M.S. Hodgskiss, N.R. McKenzie, T.W. Lyons, N.J. Planavsky,
A
shale-hosted Cr isotope record of low atmospheric oxygen during the
Proterozoic. Geology 44 (2016) 555-558.
DOI: 10.1130/G37787.1
David M.Semeniuk, Maria T. Maldonado, Samuel L. Jaccard,
Chromium uptake
and adsorption in marine phytoplankton – Implications for the marine
chromium cycle, Geochim. Cosmochim. Acta, 184 (2016) 41-54.
DOI:
10.1016/j.gca.2016.04.021
David M.Semeniuk, Maria T. Maldonado, Samuel L. Jaccard,
Chromium uptake
and adsorption in marine phytoplankton – Implications for the marine
chromium cycle, Geochim. Cosmochim. Acta, 184 (2016) 41-54.
DOI:
10.1016/j.gca.2016.04.021
Bleuenn Gueguen, Christopher T. Reinhard, Thomas J. Algeo,
The chromium
isotope composition of reducing and oxic marine sediments, Geochim.
Cosmochim. Acta, 184 (2016) 1-19.
DOI: 10.1016/j.gca.2016.04.004
Xiangli Wang, Christopher T. Reinhard, Noah J. Planavsky, Jeremy D.
Owens, Timothy W. Lyons, Thomas M. Johnson,
Sedimentary chromium
isotopic compositions across the Cretaceous OAE2 at Demerara Rise Site
1258, Chem. Geol., 429 (2016) 85–92.
DOI: 10.1016/j.chemgeo.2016.03.006
X.L. Wang, N.J. Planavsky, C.T. Reinhard, H. Zou, J.J. Ague, Y. Wu, B.C.
Gill, E.M. Schwarzenbach, B. Peucker-Ehrenbrink,
Chromium isotope
fractionation during subduction-related metamorphism, black shale
weathering, and hydrothermal alteration. Chem. Geol., 429 (2016) 19–33.
DOI: 10.1016/j.chemgeo.2016.01.003
X.L. Wang, T.M. Johnson, A.S. Ellis,
Equilibrium isotopic fractionation
and isotopic exchange kinetics between Cr (III) and Cr (VI). Geochim.
Cosmochim. Acta, 153 (2015) 72–90.
DOI: 10.1016/j.gca.2015.01.003
A. Rodler, N. Sánchez-Pastor, L. Fernández-Díaz, R. Frei,
Fractionation
behavior of chromium isotopes during coprecipitation with calcium
carbonate: Implications for their use as paleoclimatic proxy, Geochim.
Cosmochim. Acta, 164 (2015) 221-235.
DOI: 10.1016/j.gca.2015.05.021
Andri Stefánsson, Ingvi Gunnarsson, Hanna Kaasalainen, Stefán Arnórsson,
Chromium geochemistry and speciation in natural waters, Iceland, Appl.
Geochem., 62 (2015) 200-206.
DOI: 10.1016/j.apgeochem.2014.07.007
K. Scheiderich, M. Amini, C. Holmden, R. Francois,
Global variability of
chromium isotopes in seawater demonstrated by Pacific, Atlantic, and
Arctic Ocean samples. Earth Planet. Sci. Lett., 423 (2015) 87–97.
DOI:
10.1016/j.epsl.2015.04.030
J. Shen, J. Liu, L. Qin, S.J. Wang, S. Li, J. Xia, S. Ke, J. Yang,
Chromium isotope signature during continental crust subduction recorded
in metamorphic rocks. Geochem. Geophys. Geosyst., 16 (2015) 3840-3854.
DOI: 10.1002/2015GC005944.
C.T. Reinhard, N.J. Planavsky, X. Wang, W.W. Fischer, T.M. Johnson, T.W.
Lyons,
The isotopic composition of authigenic chromium in anoxic marine
sediments: a case study from the Cariaco Basin. Earth Planet. Sci.
Lett. 407 (2014) 9–18.
DOI: 10.1016/j.epsl.2014.09.024
P. Bonnand , R.H. James, I.J. Parkinson, D.P. Connelly, I.J. Fairchild,
The chromium isotopic composition of seawater and marine carbonates, Earth Planet. Sci. Lett., 382 (2013) 10–20.
DOI: 10.1016/j.epsl.2013.09.001
J. Farkaš, V. Chrastny, M. Novak, E. Cadkova, J. Pasava, R. Chakrabarti, S.B. Jacobsen, L. Ackerman, T.D. Bullen,
Chromium isotope variations (δ53/52Cr) in mantle-derived sources and their weathering products: Implications for environmental studies and the evolution of δ53/52Cr in the Earth's mantle over geologic time. Geochim. Cosmochim. Acta, 123 (2013) 74–92.
DOI: 10.1016/j.gca.2013.08.016
Anirban Basu, Thomas M. Johnson,
Determination of Hexavalent Chromium
Reduction Using Cr Stable Isotopes: Isotopic Fractionation Factors for
Permeable Reactive Barrier Materials, Environ. Sci. Technol., 46/10
(2012) 5353–5360.
DOI: 10.1021/es204086y R. Frei, C. Gaucher, L.N. Dřssing, A.N. Sial,
Chromium isotopes in
carbonates — A tracer for climate change and for reconstructing the
redox state of ancient seawater, Earth Planet. Sci. Lett., 312/1–2
(2011) 114-125.
DOI: 10.1016/j.epsl.2011.10.009
P. Bonnand, I.J. Parkinson, R.H. James, A.-M. Karjalainen, M.A. Fehr,
Accurate and
precise determination of stable Cr isotope compositions in carbonates
by double spike MC-ICP-MS. J. Anal. At. Spectrom., 26 (2011) 528–535.
DOI: 10.1039/c0ja00167h
L.N. Dřssing, K. Dideriksen, S.L.S. Stipp, R. Frei,
Reduction of
hexavalent chromium by ferrous iron: A process of chromium isotope
fractionation and its relevance to natural environments, Chem. Geol.,
285 (2011) 157-166.
DOI: 10.1016/j.chemgeo.2011.04.005
R. Schoenberg, S. Zink, M. Staubwasser, F. von Blanckenburg,
The stable
Cr isotope inventory of solid Earth reservoirs determined by double
spike MC-ICP-MS, Chem. Geol., 249 (2008) 294–306.
DOI:
10.1016/j.chemgeo.2008.01.009
D.P. Connelly, P.J. Statham, A.H. Knap,
Seasonal changes in speciation
of dissolved chromium in the surface Sargasso Sea. Deep-Sea Res. I
Oceanogr. Res. Pap. 53 (2006) 1975–1988.
DOI: 10.1016/j.dsr.2006.09.005
E. Schauble, G.R. Rossman, H.P. Taylor Jr.,
Theoretical estimates of
equilibrium chromium-isotope fractionations, Chem. Geol., 205 (2004)
99–114.
DOI: 10.1016/j.chemgeo.2003.12.015
A.S. Ellis, T.M. Johnson, T.D. Bullen,
Using chromium stable isotope ratios to quantify Cr (VI) reduction: lack of sorption effects. Environ. Sci. Technol., 38 (2004) 3604–3607.
DOI: 10.1021/es0352294
Andre S. Ellis, Thomas M. Johnson, Thomas D. Bullen,
Chromium Isotopes
and the Fate of Hexavalent Chromium in the Environment, Science,295/5562
(2002) 2060-2062.
DOI: 10.1126/science.1068368
K. Barbeau, KE.L. Rue, K.W. Bruland, A. Butler,
Photochemical cycling of
iron in the surface ocean mediated by microbial iron (III)-binding
ligands. Nature, 413 (2001) 409–413.
DOI: 10.1038/35096545
Monica Rotaru, Jean Louis Birck & Claude J. Allčgre,
Clues to early
Solar System history from chromium isotopes in carbonaceous chondrites,
Nature, 358 (1992) 465-470:
DOI: 10.1038/358465a0
L. Edmond Eary, Dhanpat Rai,
Kinetics of chromium(III) oxidation by reaction with manganese dioxide, Environ. Sci. Technol., 21 (1987) 1187-1193.
DOI: 10.1021/es00165a005
W.S. Broecker, T. Peng,
Tracers in the Sea, Columbia University (1982). available from:
https://www.ldeo.columbia.edu/~broecker/Home_files/TracersInTheSea_searchable.pdf R. Cranston, J. Murray,
Chromium species in the Columbia River and estuary, Limnol. Oceanogr. 25 (1980) 1104–1112.
DOI: 10.4319/lo.1980.25.6.1104 R. Cranston, J. Murray,
The determination of chromium species in natural waters. Anal. Chim. Acta, 99 (1978) 275-282.
DOI: 10.1016/S0003-2670(01)83568-6
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