Equilibrium calculations of iron speciation and apparent iron solubility in the Celtic Sea at ambient seawater pH using the NICA-Donnan model

Modelling competition between the siderophore ferrioxamine B and humic like binding sites in seawater v1

10.17504/protocols.io.b27xqhpn ◽

2021 ◽

Author(s):

Kechen Zhu ◽

Martha Gledhill

Keyword(s):

Binding Sites ◽

Major Ions ◽

Side Reaction ◽

Iron Solubility ◽

Desferrioxamine B ◽

Thermodynamic Constants ◽

Reaction Coefficient ◽

Ferrioxamine B ◽

Donnan Model

Here we archive a protocol that can be used to determine competition between a siderophore (ferrioxamine B) and humic like binding sites that are present in marine DOM. We use the NICA-Donnan model to describe binding by humic like binding sites in DOM. Constants for Fe binding to marine DOM are taken from Zhu et al., (2021). Thermodynamic constants describing binding between major ions, iron and ferrioxamine B are taken from Schijf and Burns, (2016). References Schijf, J., Burns, S.M., 2016. Determination of the Side-Reaction Coefficient of Desferrioxamine B in Trace-Metal-Free Seawater. Front. Mar. Sci. 3, 117. https://doi.org/10.3389/fmars.2016.00117 Zhu, K., Birchill, A.J., Milne, A., Ussher, S.J., Humphreys, M.P., Carr, N., Mahaffey, C., Lohan, M.C., Achterberg, E.P., Gledhill, M., 2021a. Equilbrium calculations of iron speciation and apparent iron solubility in the Celtic Sea at ambient pH using the NICA-Donnan model. Mar. Chem

Download Full-text

Characterization of iron speciation in single particles using XANES spectroscopy and micro X-ray fluorescence measurements: insight into factors controlling iron solubility

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-22771-2011 ◽

2011 ◽

Vol 11 (8) ◽

pp. 22771-22799 ◽

Cited By ~ 1

Author(s):

M. Oakes ◽

R. J. Weber ◽

B. Lai ◽

A. Russell ◽

E. D. Ingall

Keyword(s):

Xanes Spectroscopy ◽

Health Concern ◽

Molar Ratio ◽

Iron Speciation ◽

Single Particles ◽

Iron Solubility ◽

X Ray ◽

Soluble Iron ◽

Fe Oxides ◽

Fluorescence Measurements

Abstract. Soluble iron in fine atmospheric particles has been identified as a public health concern by participating in reactions that generate reactive oxygen species (ROS). The mineralogy and oxidation state (speciation) of iron have been shown to influence solubility. In this study, iron speciation was determined in single particles at urban and rural sites in Georgia USA using X-ray Absorption Near-Edge Structure (XANES) spectroscopy and microscopic X-ray fluorescence. Iron solubility of these samples was measured using spectrophotometry. These measurements (XANES and spectrophotometry) were combined to investigate the relationship between iron speciation and solubility in ambient aerosols. XANES measurements indicate that iron in the single particles was present as a mixture of Fe(II) and Fe(III), with Fe(II) content generally between 5 and 35 % (mean: ~25 %). XANES and elemental analyses indicate that a majority (74 %) of Fe particles are best characterized as Al-substituted Fe-oxides, with a Fe/Al molar ratio of 4.9. The next most abundant group of particles (12 %) was Fe-aluminosilicates, with Si/Al molar ratio of 1.4. No correlation was found between fractional iron solubility (soluble iron/total iron) and the abundance of Al-substituted Fe-oxides and Fe-aluminosilicates present in single particles at any of the sites during different seasons, suggesting solubility largely depended on factors other than differences in major iron phases.

Download Full-text

Characterization of iron speciation in urban and rural single particles using XANES spectroscopy and micro X-ray fluorescence measurements: investigating the relationship between speciation and fractional iron solubility

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-745-2012 ◽

2012 ◽

Vol 12 (2) ◽

pp. 745-756 ◽

Cited By ~ 66

Author(s):

M. Oakes ◽

R. J. Weber ◽

B. Lai ◽

A. Russell ◽

E. D. Ingall

Keyword(s):

Total Iron ◽

Molar Ratio ◽

Iron Speciation ◽

Single Particles ◽

Iron Solubility ◽

X Ray ◽

Soluble Iron ◽

Fe Oxides ◽

Fluorescence Measurements ◽

The Relationship

Abstract. Soluble iron in fine atmospheric particles has been identified as a public health concern by participating in reactions that generate reactive oxygen species (ROS). The mineralogy and oxidation state (speciation) of iron have been shown to influence fractional iron solubility (soluble iron/total iron). In this study, iron speciation was determined in single particles at urban and rural sites in Georgia USA using synchrotron-based techniques, such as X-ray Absorption Near-Edge Structure (XANES) spectroscopy and microscopic X-ray fluorescence measurements. Soluble and total iron content (soluble + insoluble iron) of these samples was measured using spectrophotometry and synchrotron-based techniques, respectively. These bulk measurements were combined with synchrotron-based measurements to investigate the relationship between iron speciation and fractional iron solubility in ambient aerosols. XANES measurements indicate that iron in the single particles was present as a mixture of Fe(II) and Fe(III), with Fe(II) content generally between 5 and 35% (mean: ~25%). XANES and elemental analyses (e.g. elemental molar ratios of single particles based on microscopic X-ray fluorescence measurements) indicate that a majority (74%) of iron-containing particles are best characterized as Al-substituted Fe-oxides, with a Fe/Al molar ratio of 4.9. The next most abundant group of particles (12%) was Fe-aluminosilicates, with Si/Al molar ratio of 1.4. No correlation was found between fractional iron solubility (soluble iron/total iron) and the abundance of Al-substituted Fe-oxides and Fe-aluminosilicates present in single particles at any of the sites during different seasons, suggesting solubility largely depended on factors other than differences in major iron phases.

Download Full-text

Trace elements in shells of common gastropods in the near vicinity of a natural CO<sub>2</sub> vent: no evidence of pH-dependent contamination

Biogeosciences Discussions ◽

10.5194/bgd-11-5215-2014 ◽

2014 ◽

Vol 11 (4) ◽

pp. 5215-5237 ◽

Cited By ~ 4

Author(s):

J. B. McClintock ◽

C. D. Amsler ◽

M. O. Amsler ◽

A. Duquette ◽

R. A. Angus ◽

...

Keyword(s):

Trace Elements ◽

Sampling Site ◽

Low Ph ◽

Ambient Seawater ◽

Vulcano Island ◽

Potentially Harmful Elements ◽

Seawater Ph ◽

Hexaplex Trunculus ◽

Spatial Differences ◽

Patella Caerulea

Abstract. There is concern that the use of natural volcanic CO2 vents as analogs for studies of the impacts of ocean acidification on marine organisms are biased due to physiochemical influences other than seawater pH alone. One issue that has been raised is whether potentially harmful trace elements in sediments that are rendered more soluble and labile in low pH environments are made more bioavailable, and sequestered in the local flora and fauna at harmful levels. In order to evaluate this hypothesis, we analyzed the concentrations of trace elements in shells (an established proxy for tissues) of four species of gastropods (two limpets, a topshell and a whelk) collected from three sites in Levante Bay, Vulcano Island. Each sampling site increased in distance from the primary CO2 vent and thus represented low, moderate, and ambient seawater pH conditions. Concentrations of As, Cd, Co, Cr, Hg, Mo, Ni, Pb, and V measured in shells using ICP-OES were below detection thresholds for all four gastropod species at all three sites. However, there were measurable concentrations of Sr, Mn, and U in the shells of the limpets Patella caerulea, P. rustica, and the snail Osilinus turbinatus, and similarly, Sr, Mn, U, and also Zn in the shells of the whelk Hexaplex trunculus. Levels of these elements were within the ranges measured in gastropod shells in non-polluted environments, and with the exception of U in the shells of P. caerulea, where the concentration was significantly lower at the collecting site closest to the vent (low pH site), there were no site-specific spatial differences in concentrations for any of the trace elements in shells. Thus trace element enhancement in sediments in low-pH environments was not reflected in greater bioaccumulations of potentially harmful elements in the shells of common gastropods.

Download Full-text