http://lod.bco-dmo.org/id/dataset/767208
eng; USA
utf8
dataset
Highest level of data collection, from a common set of sensors or instrumentation, usually within the same research project
Biological and Chemical Oceanography Data Management Office (BCO-DMO)
Unavailable
508-289-2009
WHOI MS#36
Woods Hole
MA
02543
USA
info@bco-dmo.org
http://www.bco-dmo.org
Monday - Friday 8:00am - 5:00pm
For questions regarding this resource, please contact BCO-DMO via the email address provided.
pointOfContact
2019-05-09
ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data
ISO 19115-2:2009(E)
Experimental determination of Fe isotope effect for reduction from Fe(III) to Fe(II)
2019-05-09
publication
2019-05-09
revision
BCO-DMO Linked Data URI
2019-05-09
creation
http://lod.bco-dmo.org/id/dataset/767208
Seth G. John
University of South Carolina
principalInvestigator
Biological and Chemical Oceanography Data Management Office (BCO-DMO)
Unavailable
508-289-2009
WHOI MS#36
Woods Hole
MA
02543
USA
info@bco-dmo.org
http://www.bco-dmo.org
Monday - Friday 8:00am - 5:00pm
For questions regarding this resource, please contact BCO-DMO via the email address provided.
publisher
Cite this dataset as: John, S. G. (2019) Experimental determination of Fe isotope effect for reduction from Fe(III) to Fe(II). Biological and Chemical Oceanography Data Management Office (BCO-DMO). Version Date 2019-05-09 [if applicable, indicate subset used]. http://lod.bco-dmo.org/id/dataset/767208 [access date]
Experimental determination of Fe isotope effect for reduction from Fe(III) to Fe(II) Dataset Description: <p>All of the experiments described here begin with Fe(III) bound to the organic ligand ethylenediaminetetraacetic acid (EDTA), and proceed as Fe is reduced to Fe(II). The Fe(II)-specific ligand ferrozine (FZ) is added to the experimental solution in order to capture Fe(II) produced during the experiment, similar to methods previously used to capture Fe(II) produced during biological reduction of Fe(III) (Shaked et al., 2004). Fe(II) in the presence of ferrozine forms an Fe(II)FZ3 complex. This complex has a strong purple color, which made it possible to determine reaction extent visually and by absorbance spectrophotometry. The Fe(II)FZ3 complex is also hydrophobic, allowing us to separate it from the solution by passing the solution through a C18 resin (Waters Sep-Pak C18 Plus Light) with a peristaltic pump. The column was then rinsed with 5 mL of seawater and Fe(II)FZ3 was eluted with 5 mL methanol.</p> Methods and Sampling: <p>2.2 Stability of the Fe-ligand complexes<br />
In order to ensure that our experiments are only capturing the isotope effect of Fe(III) reduction to Fe(II) due to our added reductants, we first assessed whether there was any spontaneous reduction of Fe(III)EDTA, spontaneous oxidation of Fe(II)FZ3, or isotope exchange between these complexes. This was tested by separately preparing concentrated solutions of Fe(II)-FZ3 from natural iron, and Fe(III)double-spike-EDTA from an Fe spike consisting of roughly equal portions 57Fe and 58Fe. The stocks were then diluted into surface seawater collected near Bermuda to final concentrations of 2·10-4 M Fe(III) double-spike, 2·10-4 M Fe(II), 10-3 M FZ, and 10-3 M EDTA. Eight such solutions were prepared, to be subsampled over the next 27 h.<br />
At each timepoint, the Fe(II) was first separated from the experimental solution onto the C18 column and eluted with methanol. Then, Fe(III)-EDTA which remained in the experimental solution was reduced to Fe(II)-FZ3 by the addition of 1.5 mL of 1.4 M hydroxylamine hydrochloride, and separated by adsorption as Fe(II)-FZ3 onto C18 resin. Both the Fe(II) and Fe(III) fractions were then purified for isotope analysis as described below.</p>
<p>2.3 Chemical reduction experiments<br />
10 mL experimental solutions were prepared by adding reagents to a 15 mL polypropylene centrifuge tube in the following order: 1) 100 μL Fe(III), 2) 100 μL EDTA, mixed and allowed to equilibrate for &gt; 2 min to allow EDTA to bind the Fe(III), 3) 1 mL buffer, 4) 100 uL ferrozine, 5) 8.6 mL filtered trace-metal clean seawater collected from the surface ocean near Bermuda, 6) 100 μL reductant added in order to initiate the experiment. Experiments at 60°C and 100°C were performed by immersing samples in a heated water bath before adding reductant, while samples performed at 2°C were immersed in an ice bath.<br />
The progress of reaction was monitored by visually examining tubes for the appearance of purple-colored Fe(II)FZ3. For comparison, a standard was made containing 10 μM Fe(II)-FZ3, equivalent to reducing 5% of the initial Fe(III)-EDTA, so that when the color in the experimental tube matched that of the standard, experiments could be terminated at a reaction extent of about 3-7% completion. The exact extent of reaction was then determined by comparing sample adsorption at 562 nm to iron standards prepared using the ferrozine method (Viollier et al., 2000).<br />
<br />
2.4 Photochemical reduction experiments<br />
Photochemical reduction experiments were performed as above, except that no chemical reductant was added. Instead samples were either amended either with glucaric acid or not, and the experiment was initiated by bringing samples outside and exposing them to natural sunlight on a nearly-cloudless summer mid-day in South Carolina.</p>
<p>2.5 Isotope analysis<br />
Methanol samples containing Fe(II)FZ3 were evaporated, then reacted overnight on a hot-plate with 500 μL 0.1N HNO3 and 500 μL concentrated H2O2 to destroy the FZ. Samples were then evaporated again and observed to make sure that no purple color (Fe(II)FZ3) remained. If necessary, samples were reacted again with HNO3 and H2O2 until no purple color remained. Samples were analyzed for Fe stable isotope ratios (δ56Fe) at the University of South Carolina according to published methods (Conway et al., 2013) as modified for analysis of marine particles (Revels et al., 2015). Briefly, samples were amended with a ~1:1 57Fe:58Fe double spike, purified by anion exchange chromatography, and analyzed on a Neptune multi-collector ICP-MS. Sample δ56Fe was analyzed compared to IRMM-014 and the δ56Fe of the FeCl3 used to prepare stock solutions was also analyzed, so that all data are reported here as Δ56Fe, calculated as δ56FeFe(II)-δ56FeFe(III).</p>
Funding provided by NSF Division of Ocean Sciences (NSF OCE) Award Number: OCE-1446327 Award URL: https://www.nsf.gov/awardsearch/show-award?AWD_ID=1446327
Funding provided by NSF Division of Ocean Sciences (NSF OCE) Award Number: OCE-1649435 Award URL: https://www.nsf.gov/awardsearch/show-award?AWD_ID=1649435
Funding provided by NSF Division of Ocean Sciences (NSF OCE) Award Number: OCE-1334029 Award URL: https://www.nsf.gov/awardsearch/show-award?AWD_ID=1334029
Funding provided by NSF Division of Ocean Sciences (NSF OCE) Award Number: OCE-1333566 Award URL: https://www.nsf.gov/awardsearch/show-award?AWD_ID=1333566
onGoing
Seth G. John
University of South Carolina
213-740-0696
USC ZHS 117 2651 Trousdale Pkwy.
Los Angeles
CA
90089
USA
sethjohn@usc.edu
pointOfContact
asNeeded
Unknown
Sample_ID
Buffer
pH
Reductant
Reductant_conc
Temp
Replicate
d56Fe
err
Dd56Fe
theme
None, User defined
sample identification
No BCO-DMO term
pH
temperature of sample or a generic measurement (not in-situ water temp)
replicate
Iron
Fe_err
featureType
BCO-DMO Standard Parameters
otherRestrictions
otherRestrictions
Access Constraints: none. Use Constraints: Please follow guidelines at: http://www.bco-dmo.org/terms-use Distribution liability: Under no circumstances shall BCO-DMO be liable for any direct, incidental, special, consequential, indirect, or punitive damages that result from the use of, or the inability to use, the materials in this data submission. If you are dissatisfied with any materials in this data submission your sole and exclusive remedy is to discontinue use.
Experimental constraints on marine Fe isotope effects - Biology, ligands, and particles
https://osprey.bco-dmo.org/project/664673
Experimental constraints on marine Fe isotope effects - Biology, ligands, and particles
<p><em>Extracted from the NSF award abstract:</em></p>
<p>Iron is an essential micronutrient for marine phytoplankton, which plays a key role in the global carbon cycle and marine ecosystems, and there is a need to better understand the sources and sinks of this essential micronutrient in the oceans. Iron isotopes are a recently developed tracer of iron biogeochemical cycling, and new iron isotope results indicate that iron-binding ligands may play a critical role in the isotopic fractionation of dissolved iron. At present, however, the quantitative importance of iron dissolution or biological iron uptake in the isotopic fractionation of dissolved iron in the oceans is not well-known. In this study, researchers from the University of South Carolina and the Bermuda Institute of Ocean Sciences will collect and analyze samples from the Bermuda Atlantic Time-series Station (BATS) in order to; 1) measure the rate and isotope fractionation of iron dissolution from natural aerosols and oxic sediments in the presence of natural iron-binding ligands, and; 2) examine how phytoplankton fractionate iron isotopes during biological uptake. Results from this study will advance the development of iron isotopes as a tool for tracing iron biogeochemical cycling in the oceans.</p>
Fe isotope effects
largerWorkCitation
project
eng; USA
oceans
2019-05-09
Eastern Tropical Pacific
0
BCO-DMO catalogue of parameters from Experimental determination of Fe isotope effect for reduction from Fe(III) to Fe(II)
Biological and Chemical Oceanography Data Management Office (BCO-DMO)
Unavailable
508-289-2009
WHOI MS#36
Woods Hole
MA
02543
USA
info@bco-dmo.org
http://www.bco-dmo.org
Monday - Friday 8:00am - 5:00pm
For questions regarding this resource, please contact BCO-DMO via the email address provided.
pointOfContact
http://lod.bco-dmo.org/id/dataset-parameter/767217.rdf
Name: Sample_ID
Units: unitless
Description: <p>The internal sample identification number</p>
http://lod.bco-dmo.org/id/dataset-parameter/767218.rdf
Name: Buffer
Units: unitless
Description: <p>The name of the buffer used</p>
http://lod.bco-dmo.org/id/dataset-parameter/767219.rdf
Name: pH
Units: unitless
Description: <p>The pH of the reaction solution</p>
http://lod.bco-dmo.org/id/dataset-parameter/767220.rdf
Name: Reductant
Units: unitless
Description: <p>The name of the reductant used</p>
http://lod.bco-dmo.org/id/dataset-parameter/767221.rdf
Name: Reductant_conc
Units: millimolar
Description: <p>The concentration of the reductant</p>
http://lod.bco-dmo.org/id/dataset-parameter/767222.rdf
Name: Temp
Units: degrees Celsius
Description: <p>Reaction temperature</p>
http://lod.bco-dmo.org/id/dataset-parameter/767223.rdf
Name: Replicate
Units: unitless
Description: <p>Number of replicate (1; 2; or 3)</p>
http://lod.bco-dmo.org/id/dataset-parameter/767224.rdf
Name: d56Fe
Units: permil
Description: <p>Fe isotope ratio compared to IRMM-014</p>
http://lod.bco-dmo.org/id/dataset-parameter/767225.rdf
Name: err
Units: permil
Description: <p>Analytical error in d56Fe</p>
http://lod.bco-dmo.org/id/dataset-parameter/767226.rdf
Name: Dd56Fe
Units: permil
Description: <p>Fe isotope ratio compared to the Fe starting material</p>
GB/NERC/BODC > British Oceanographic Data Centre, Natural Environment Research Council, United Kingdom
Biological and Chemical Oceanography Data Management Office (BCO-DMO)
Unavailable
508-289-2009
WHOI MS#36
Woods Hole
MA
02543
USA
info@bco-dmo.org
http://www.bco-dmo.org
Monday - Friday 8:00am - 5:00pm
For questions regarding this resource, please contact BCO-DMO via the email address provided.
pointOfContact
https://osprey.bco-dmo.org/dataset/767208/data/download
download
onLine
dataset
<p>2.2 Stability of the Fe-ligand complexes<br />
In order to ensure that our experiments are only capturing the isotope effect of Fe(III) reduction to Fe(II) due to our added reductants, we first assessed whether there was any spontaneous reduction of Fe(III)EDTA, spontaneous oxidation of Fe(II)FZ3, or isotope exchange between these complexes. This was tested by separately preparing concentrated solutions of Fe(II)-FZ3 from natural iron, and Fe(III)double-spike-EDTA from an Fe spike consisting of roughly equal portions 57Fe and 58Fe. The stocks were then diluted into surface seawater collected near Bermuda to final concentrations of 2·10-4 M Fe(III) double-spike, 2·10-4 M Fe(II), 10-3 M FZ, and 10-3 M EDTA. Eight such solutions were prepared, to be subsampled over the next 27 h.<br />
At each timepoint, the Fe(II) was first separated from the experimental solution onto the C18 column and eluted with methanol. Then, Fe(III)-EDTA which remained in the experimental solution was reduced to Fe(II)-FZ3 by the addition of 1.5 mL of 1.4 M hydroxylamine hydrochloride, and separated by adsorption as Fe(II)-FZ3 onto C18 resin. Both the Fe(II) and Fe(III) fractions were then purified for isotope analysis as described below.</p>
<p>2.3 Chemical reduction experiments<br />
10 mL experimental solutions were prepared by adding reagents to a 15 mL polypropylene centrifuge tube in the following order: 1) 100 μL Fe(III), 2) 100 μL EDTA, mixed and allowed to equilibrate for &gt; 2 min to allow EDTA to bind the Fe(III), 3) 1 mL buffer, 4) 100 uL ferrozine, 5) 8.6 mL filtered trace-metal clean seawater collected from the surface ocean near Bermuda, 6) 100 μL reductant added in order to initiate the experiment. Experiments at 60°C and 100°C were performed by immersing samples in a heated water bath before adding reductant, while samples performed at 2°C were immersed in an ice bath.<br />
The progress of reaction was monitored by visually examining tubes for the appearance of purple-colored Fe(II)FZ3. For comparison, a standard was made containing 10 μM Fe(II)-FZ3, equivalent to reducing 5% of the initial Fe(III)-EDTA, so that when the color in the experimental tube matched that of the standard, experiments could be terminated at a reaction extent of about 3-7% completion. The exact extent of reaction was then determined by comparing sample adsorption at 562 nm to iron standards prepared using the ferrozine method (Viollier et al., 2000).<br />
<br />
2.4 Photochemical reduction experiments<br />
Photochemical reduction experiments were performed as above, except that no chemical reductant was added. Instead samples were either amended either with glucaric acid or not, and the experiment was initiated by bringing samples outside and exposing them to natural sunlight on a nearly-cloudless summer mid-day in South Carolina.</p>
<p>2.5 Isotope analysis<br />
Methanol samples containing Fe(II)FZ3 were evaporated, then reacted overnight on a hot-plate with 500 μL 0.1N HNO3 and 500 μL concentrated H2O2 to destroy the FZ. Samples were then evaporated again and observed to make sure that no purple color (Fe(II)FZ3) remained. If necessary, samples were reacted again with HNO3 and H2O2 until no purple color remained. Samples were analyzed for Fe stable isotope ratios (δ56Fe) at the University of South Carolina according to published methods (Conway et al., 2013) as modified for analysis of marine particles (Revels et al., 2015). Briefly, samples were amended with a ~1:1 57Fe:58Fe double spike, purified by anion exchange chromatography, and analyzed on a Neptune multi-collector ICP-MS. Sample δ56Fe was analyzed compared to IRMM-014 and the δ56Fe of the FeCl3 used to prepare stock solutions was also analyzed, so that all data are reported here as Δ56Fe, calculated as δ56FeFe(II)-δ56FeFe(III).</p>
Specified by the Principal Investigator(s)
<p>BCO-DMO Processing Notes:<br />
-&nbsp;added conventional header with dataset name, PI name, version date<br />
- modified parameter names to conform with BCO-DMO naming conventions</p>
<p>&nbsp;</p>
Specified by the Principal Investigator(s)
asNeeded
7.x-1.1
Biological and Chemical Oceanography Data Management Office (BCO-DMO)
Unavailable
508-289-2009
WHOI MS#36
Woods Hole
MA
02543
USA
info@bco-dmo.org
http://www.bco-dmo.org
Monday - Friday 8:00am - 5:00pm
For questions regarding this resource, please contact BCO-DMO via the email address provided.
pointOfContact