Show simple item record

dc.contributor.author
Revels, Brandi N.
dc.contributor.supervisor
Vance, Derek
dc.contributor.supervisor
Rickli, Jörg
dc.contributor.supervisor
Moura, Candido
dc.contributor.supervisor
Jeandel, Catherine
dc.contributor.supervisor
Burton, Kevin
dc.date.accessioned
2018-11-19T07:46:45Z
dc.date.available
2018-11-16T14:56:47Z
dc.date.available
2018-11-19T07:46:45Z
dc.date.issued
2018-09
dc.identifier.uri
http://hdl.handle.net/20.500.11850/304382
dc.identifier.doi
10.3929/ethz-b-000304382
dc.description.abstract
The transition metals (e.g., Mo, Zn, Ni, Fe, Cu) are integral in surface Earth biogeochemical cycling. Ubiquitous in the environment, their redox sensitivity limits their mobility and gives them central roles in metabolic processes, intimately linking the geosphere with the biosphere. This, coupled with their ability to be archived in the sedimentary record, makes transition metals and their isotopes attractive tracers of biological evolution and oceanic redox in Earth history. Exploitation of this sedimentary archive relies critically on understanding controls of the modern oceanic budgets of these metals and their isotopes. The motivation for this work stems from the observation that, for many transition metals, the dissolved load (<0.45um) of the oceans is isotopically heavier than rivers, themselves isotopically heavier than the upper continental crust (UCC). Assuming this observation describes long-term processes, it gives rise to budgetary problems which necessitate the need for isotopically light sinks in the particulate equivalent of the dissolved phase of both the oceans and rivers, ‘missing’ isotopically heavy sources to rivers and oceans, non-steady state behavior of these systems, or a combination of these. Traditionally, research on the riverine source of transition metals has focused on the dissolved load (<0.45um), as this is the most obvious contribution to the dissolved load of the oceans. However, suspended sediments offer an appealing solution to the above mentioned budgetary problem as the particulate phase dominates the riverine load for most transition metals. A large fraction of this particulate load may be chemically labile, enabling the particulate phase to interact with the dissolved phase as both a source and a sink. This thesis presents results from a detailed study of different phases (truly dissolved, colloidal, and particulate) within the largest river in the world, the Amazon. The dissolved phase was filtered by tangential flow to separate colloidal (>1kDA, <0.45um) from truly dissolved (<1kDa) material, while the particulate phase (>0.45um) was sequentially leached to isolate discrete mineral phases (e.g. organic material and Fe-Mn oxides) within the particle itself. The truly dissolved and colloidal phases of Mo and Zn are isotopically similar to global average rivers, near 0.7‰ and 0.33‰, respectively. Subtle basinal and seasonal variability in Mo and Zn and their isotopes are related to weathering regime. For molybdenum, more intense chemical weathering was associated with lower [Mo] and heavier isotopes, while for Zn increased chemical weathering is associated with higher Zn concentrations and lower d66Zn. Concentrations of molybdenum in the particulate phase are very low throughout the basin, suggesting the complementary light Mo reservoir is likely stored in soils rather than suspended particulates. Particulate zinc is enriched in the oxide phase of suspended sediments, but this phase is not isotopically distinct from the dissolved phase. Furthermore, dissolution of the oxide phase does not affect dissolved phase d66Zn, suggesting it does not hold the complementary heavy Zn reservoir and that this may instead reside in soils. Iron and nickel are enriched in the colloidal phase, which, in association with precipitation of secondary Fe-Mn oxides, controls their mobility and isotopic signatures. For iron, d56Fe of the colloidal and particulate phase is a function of both pH and of the type of colloids present, which are in turn correlated with weathering regime. Those basins characterized by less intense chemical weathering are rich in mineral colloids, are isotopically similar to UCC, and precipitated Fe-Mn oxides have a similar isotope signature. Those basins characterized by intense chemical weathering are rich in organo-colloids which preferentially bind heavy iron d56FeUCC-colloids = ~-0.7‰. The residual light isotopes are then incorporated into the particulate oxide phases d56Feoxide-dissolved = -1.1‰. Colloidal and truly dissolved Ni are not isotopically distinct from each other, but do show contrasts between weathering regimes. Less intense chemical weathering is associated with dissolved fractions similar to average rivers while intense chemical weathering is associated with isotopically light dissolved fractions, similar to average UCC. During the dry season, dissolved load d60Ni is controlled by secondary Fe-Mn oxide precipitation within the river, the magnitude of which is a function of the fraction of Ni precipitated and the pH. At the highest pH of the Amazon, 7.5, the river’s d60Ni reaches 1.4‰, equivalent to the average deep ocean. These findings suggest that the light Mo and heavy Zn reservoirs are not found in suspended sediments, and are instead likely held in soils. Ni fractionation with secondary minerals drives the dissolved load of rivers to heavier values, closer to that of the deep ocean, which may help to close its budgetary problems. Iron’s enrichment in colloidal and oxide phases, each its own unique isotopic signature, may be physiochemically available, ultimately changing the riverine input signature to the oceans. This work has emphasized the importance of the suspended particulate load in controlling the size and isotopic composition of the riverine input to the oceans. The fate of these particulates in estuaries and ocean margins will be key areas for future research as their lability is of critical importance to oceanic budgets.
en_US
dc.format
application/pdf
en_US
dc.language.iso
en
en_US
dc.publisher
ETH Zurich
en_US
dc.rights.uri
http://rightsstatements.org/page/InC-NC/1.0/
dc.subject
Trace metal
en_US
dc.subject
Ocean
en_US
dc.subject
River
en_US
dc.subject
Isotope
en_US
dc.subject
Particulate
en_US
dc.subject
Biogeochemistry
en_US
dc.subject
Isotope geochemistry
en_US
dc.subject
Stable isotope
en_US
dc.subject
geochemistry
en_US
dc.title
The Riverine Delivery of Trace Metals and their Isotopes to Oceans: New Insights from Mo, Ni, Fe, and Zn in the Amazon Basin
en_US
dc.type
Doctoral Thesis
dc.rights.license
In Copyright - Non-Commercial Use Permitted
ethz.size
241 p.
en_US
ethz.identifier.diss
25458
en_US
ethz.publication.place
Zurich
en_US
ethz.publication.status
published
en_US
ethz.leitzahl
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02330 - Dep. Erdwissenschaften / Dep. of Earth Sciences::02725 - Institut für Geochemie und Petrologie / Institute of Geochemistry and Petrology::03956 - Vance, Derek / Vance, Derek
en_US
ethz.leitzahl.certified
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02330 - Dep. Erdwissenschaften / Dep. of Earth Sciences::02725 - Institut für Geochemie und Petrologie / Institute of Geochemistry and Petrology::03956 - Vance, Derek / Vance, Derek
en_US
ethz.tag
trace metal
en_US
ethz.tag
Ocean
en_US
ethz.tag
River
en_US
ethz.tag
Isotope
en_US
ethz.tag
Particulate
en_US
ethz.tag
biogeochemistry
en_US
ethz.tag
geochemistry
en_US
ethz.tag
isotope geochemistry
en_US
ethz.tag
stable isotope
en_US
ethz.date.deposited
2018-11-16T14:56:55Z
ethz.source
FORM
ethz.eth
yes
en_US
ethz.availability
Open access
en_US
ethz.rosetta.installDate
2018-11-19T07:47:11Z
ethz.rosetta.lastUpdated
2018-11-19T07:47:11Z
ethz.rosetta.exportRequired
true
ethz.rosetta.versionExported
true
ethz.COinS
ctx_ver=Z39.88-2004&amp;rft_val_fmt=info:ofi/fmt:kev:mtx:journal&amp;rft.atitle=The%20Riverine%20Delivery%20of%20Trace%20Metals%20and%20their%20Isotopes%20to%20Oceans:%20New%20Insights%20from%20Mo,%20Ni,%20Fe,%20and%20Zn%20in%20the%20Amazon%20Basin&amp;rft.date=2018-09&amp;rft.au=Revels,%20Brandi%20N.&amp;rft.genre=unknown&amp;rft.btitle=The%20Riverine%20Delivery%20of%20Trace%20Metals%20and%20their%20Isotopes%20to%20Oceans:%20New%20Insights%20from%20Mo,%20Ni,%20Fe,%20and%20Zn%20in%20the%20Amazon%20Basin
 Search via SFX

Files in this item

Thumbnail

Publication type

Show simple item record