Dissolved iron and its speciation in a shallow eutrophic lake and its inflowing rivers

Nagai, Takashi; Imai, Akio; Matsushige, Kazuo; Yokoi, Kunihiko; Fukushima, Takehiko

doi:10.1016/j.watres.2006.10.038

Cited by 57 publications

(41 citation statements)

References 33 publications

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“…The iron (Fe)-HS peak occurs at ,20.6 V, at nearly the same potential as the peak for Fe-DHN. The CSV response for FA (Suwannee River FA) and HA (SRHA) standards in ultraviolet (UV)-digested seawater in the presence of bromate was found to be the same as that for HS in natural waters (fresh, estuarine, and coastal waters), indicating that FA and HA are good model compounds for the natural HS.HS and iron are known to co-precipitate at the lowsalinity end of estuaries (Sholkovitz and Copland 1981), removing more than 99% of the dissolved iron and lowering its concentration from 0.5-10 mmol L 21 , which is typical for freshwaters (Nagai et al 2007), to the 1-20 nmol L 21 range found in end-estuarine and coastal waters (Sanudo-Wilhelmy et al 1996;Buck and Bruland 2007). The estuarine removal reactions indicate that iron complexation with HS might be relatively unimportant in seawater, although it is important in freshwaters.…”

mentioning

confidence: 73%

Evidence for geochemical control of iron by humic substances in seawater

Laglera

Berg

2009

Limnology & Oceanography

264

310

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A new method, based on the direct detection of iron-humic substance (HS) species by cathodic stripping voltammetry (CSV), is used to determine the iron binding capacity and complex stability of fulvic acid (FA), humic acid (HA), and the natural HS in the seawater. The FA binds 16.7 6 2.0 nmol iron (Fe) (mg FA) 21 , whereas the HA and the marine HS bind 32 6 2.2 nmol Fe (mg FA) 21 . The complex stabilities are (log K9 Fe9HS values) 10.6 for FA and 11.1 for HA and coastal HS. Measurements of coastal waters (Irish Sea) show that the HS occur in a widespread fashion, the HS concentration decreasing with increasing salinity and occurring at levels of 400 (at salinity 30) to 70 (at salinity 34) mg L 21 . A sample from the deep Pacific was found to contain 36 mg HS L 21 , amounting to 4% of the dissolved organic matter. Comparative measurement of the total iron complexing capacity by CSV with competitive ligand exchange showed that the natural HS can account for the entire ligand concentration in the shallow coastal and deep ocean waters tested. Measurements of the iron solubility showed that FA added to seawater and the HS in coastal waters maintain iron in solution at a level just below the iron binding capacity. The preliminary data for the open ocean indicate that the same may be true for HS in deep ocean waters. The data are consistent with a mechanism by which iron is transported from land to sea, associated with land-derived HS.Humic substances (HS) are ubiquitous hydrophobic components of the natural organic matter present in soil and aquatic environments that consist predominantly of polyphenols and benzoic/carboxylic acids (Buffle 1990). HS are operationally divided into humic acids (HAs) and fulvic acids ( Previous work has shown that HS in seawater can be determined at good sensitivity by cathodic stripping voltammetry (CSV), which takes advantage of adsorption of the complex on the mercury drop electrode as a concentration step prior to the CSV scan; bromate is added to enhance the sensitivity through a catalytic effect (Laglera et al. 2007). A very similar procedure (Obata and Van Den Berg 2001) is used to determine iron in seawater by means of CSV in the presence of a specific adsorptive ligand (2,3-dihydroxynaphthalene; DHN). The iron (Fe)-HS peak occurs at ,20.6 V, at nearly the same potential as the peak for Fe-DHN. The CSV response for FA (Suwannee River FA) and HA (SRHA) standards in ultraviolet (UV)-digested seawater in the presence of bromate was found to be the same as that for HS in natural waters (fresh, estuarine, and coastal waters), indicating that FA and HA are good model compounds for the natural HS.HS and iron are known to co-precipitate at the lowsalinity end of estuaries (Sholkovitz and Copland 1981), removing more than 99% of the dissolved iron and lowering its concentration from 0.5-10 mmol L 21 , which is typical for freshwaters (Nagai et al. 2007), to the 1-20 nmol L 21 range found in end-estuarine and coastal waters (Sanudo-Wilhelmy et al. 1996;Buck and Bruland 2007). The...

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confidence: 73%

Evidence for geochemical control of iron by humic substances in seawater

Laglera

Berg

2009

Limnology & Oceanography

264

310

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“…Iron limitations on phytoplankton growth may occur even though the DFe-value is abundant (Nagai et al, 2007). The JZB is eutrophic and has had outbreaks of red tides every year since 1997.…”

Section: Iron Speciation and Bioavailabilitymentioning

confidence: 99%

“…It is known that ligand-complexed iron is available and taken up by organisms, for example eukaryotic phytoplankton assimilating porhyrin-complexed iron and prokaryotes uptaking siderophore-complexed iron (Hutchins et al, 1999). On the other hand, Fe-binding organic ligands (L t ) buffer DFe concentrations by preventing the formation of insoluble oxy-hydroxides (Rue and Bruland, 1995;Wu and Luther, 1995;Kuma et al, 1996;Mawji et al, 2008), because Fe-organic complexes have higher stability constants than inorganic ones (Hudson and Morel, 1993;Nagai et al, 2007). Therefore, the character of L t plays an important role in the biogeochemical cycles of iron in global open oceans .…”

Section: Introductionmentioning

confidence: 99%

“…Due to the limited water exchange, semi-closed bays like Jiaozhou Bay (JZB) are vulnerable marine ecosystems, sensitive to any kind of change or pollution, and could be used to evaluate the contribution of natural and anthropogenic sources on DFe and L t concentrations on the system itself (Kremling et al, 1997;Öztürk et al, 2003;Nagai et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

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Distribution and Speciation of Dissolved Iron in Jiaozhou Bay (Yellow Sea, China)

Yang

Pižeta

et al. 2016

Front. Mar. Sci.

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The distribution of total dissolved iron (DFe) and its chemical speciation were studied in vertical profiles of the shallow and semi-closed Jiaozhou Bay (JZB, China) during two contrasting periods: summer (July 19 th , 2011) and spring (May 10 th , 2012). Samples collected from the surface, middle and bottom layers were analyzed by competitive ligand exchange-adsorptive cathodic stripping voltammetry (CLE-aCSV). The mean DFe concentration during the summer period (median 18.8 nM; average 20.7 nM) was higher than in the spring period (median 12.4 nM; average 16.9 nM), whereas the spatio-temporal variation in spring was larger than in summer. The DFe-values showed distinct regional and seasonal differences, ranging from 5.6 to 107 nM in spring period and 13.4 to 43.4 nM in summer period. In spring, the highest DFe-values were observed in the eastern coastal region, especially near an industrial area (up to 107 nM), whereas the DFe distribution in summer was relatively even. Due to a tide influence, the vertical variations in the DFe and L t in both seasons were not significant. On average, the L t concentration (one class of ligand was estimated in all samples), was higher in spring (35.2 ± 23.4 nM) than in summer (31.1 ± 10.3 nM). A statistically significant correlation was found between L t and DFe concentrations, it was higher for the summer period than for the spring period. The conditional stability constants (logK ′ ) of organic complexes with iron were weaker in spring (11.7 ± 0.3) than in summer (12.3 ± 0.3). The concentrations of L t were higher in comparison to DFe in all samples: the average [L t ]/[DFe] ratio in the spring and summer samples was 2.4 and 1.5, respectively. Speciation calculations showed that the DFe in the JZB existed predominantly (over 99.99%) in the form of strong organic complexes in both seasons.

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“…Considering a 5-10 fold lower Fe demand for non-N-fixing phytoplankton than for N 2 fixing cyanobacteria (Kustka et al, 2003a), and an approximate C fixation rate of 30 µg C L −1 day −1 (Johansson et al, 2004) a rough estimation of the iron uptake during the same growth period ranges from 1.4-2.9 nmol L −1 (0.025-0.05 nmol L −1 day −1 ). Half saturation constants with respect to inorganic iron reported for growth of the cyanobacteria Microcystis aeruginosa and Planktothrix agardhii were 0.14 and 0.31 nmol L −1 , respectively (Nagai et al, 2007). Diatom species of the genus Thalassiosira have Fe' half saturation constants to sustain their growth of 0.004-0.068 nmol L −1 (Sunda and Huntsman, 1995).…”

Section: Significance Of Fe(ii) For Cyanobacterial Growthmentioning

confidence: 99%

Dissolved iron (II) in the Baltic Sea surface water and implications for cyanobacterial bloom development

Breitbarth

Gelting²,

Walve

et al. 2009

Biogeosciences

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Abstract. Iron chemistry measurements were conducted during summer 2007 at two distinct locations in the Baltic Sea (Gotland Deep and Landsort Deep) to evaluate the role of iron for cyanobacterial bloom development in these estuarine waters. Depth profiles of Fe(II) were measured by chemiluminescent flow injection analysis (CL-FIA). Up to 0.9 nmol Fe(II) L −1 were detected in light penetrated surface waters, which constitutes up to 20% to the dissolved Fe pool. This bioavailable iron source is a major contributor to the Fe requirements of Baltic Sea phytoplankton and apparently plays a major role for cyanobacterial bloom development during our study. Measured Fe(II) half life times in oxygenated water exceed predicted values and indicate organic Fe(II) complexation. Potential sources for Fe(II) ligands, including rainwater, are discussed. Fe(II) concentrations of up to 1.44 nmol L −1 were detected at water depths below the euphotic zone, but above the oxic anoxic interface. Mixed layer depths after strong wind events are not deep enough in summer time to penetrate the oxic-anoxic boundary layer. However, Fe(II) from anoxic bottom water may enter the sub-oxic zone via diapycnal mixing and diffusion.Correspondence to: E. Breitbarth (ebreitbarth@chemistry.otago.ac.nz)

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Dissolved iron and its speciation in a shallow eutrophic lake and its inflowing rivers

Cited by 57 publications

References 33 publications

Evidence for geochemical control of iron by humic substances in seawater

Evidence for geochemical control of iron by humic substances in seawater

Distribution and Speciation of Dissolved Iron in Jiaozhou Bay (Yellow Sea, China)

Dissolved iron (II) in the Baltic Sea surface water and implications for cyanobacterial bloom development

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