Relevance of peat-draining rivers for the riverine input of dissolved iron into the ocean

Krachler, Regina; Krachler, Rudolf F.; Kammer, Frank von der; Süphandag, Altan; Jirsa, Franz; Ayromlou, S.; Hofmann, Thilo; Keppler, Bernhard K.

doi:10.1016/j.scitotenv.2010.02.018

Cited by 94 publications

(94 citation statements)

References 41 publications

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“…Furthermore, sulfidic soils are found in every coastal wetland of this region in Australia (Fitzpatrick et al, 2008), and shallow groundwater samples had a distinct sulfidic smell during both sampling campaigns of this work. In organic-rich wetlands, dissolved Fe concentrations often are relatively high and may even reach several mM in coastal acidic sulfate soil wetlands ( (Krachler et al, 2010(Krachler et al, , 2012, which is close to our values ranging between 5.63 and 8.02 μM.…”

Section: Geochemistry Of Surface Waterssupporting

confidence: 89%

“…The combined global length of tidal estuaries is almost 100,000 km (Dürr et al, 2011), which is almost twice as long as the world's ten longest rivers combined. The geochemical processes associated with Fe dynamics along large rivers may differ greatly to short wetland creeks, as indicated by high Fe yields (i.e., export normalized to catchment area) from wetland creeks with short residence times (Krachler et al, 2010(Krachler et al, , 2012.…”

Section: Introductionmentioning

confidence: 99%

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Dissolved iron exports from an estuary surrounded by coastal wetlands: Can small estuaries be a significant source of Fe to the ocean?

et al. 2015

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Section: Geochemistry Of Surface Waterssupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Dissolved iron exports from an estuary surrounded by coastal wetlands: Can small estuaries be a significant source of Fe to the ocean?

et al. 2015

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“…Rivers are a major source of Fe to the ocean, and Fe is an essential nutrient for marine primary production (Martin and Fitzwater, 1988;Morel et al, 1991;Boyd et al, 2000;Poulton and Raiswell 2002;Smetacek et al, 2012). Recent evidence suggests that peatlands play a pivotal role in the delivery of Fe to coastal waters, and the organic acids that originate in peat likely serve as the principal metal chelator for Fe transport in rivers (Krachler et al, 2005(Krachler et al, , 2010. The transport of Fe in these colloidal (<10 kD) metal-organic complexes is considered a major way for peat-derived riverine Fe to escape Fe oxyhydroxide precipitation and flocculation, and hence escape estuarine removal (Boyle and Edmond, 1977;Krachler et al, 2005Krachler et al, , 2010.…”

Section: Introductionmentioning

confidence: 99%

Iron and silicon isotope behaviour accompanying weathering in Icelandic soils, and the implications for iron export from peatlands

Opfergelt

Williams

Cornélis

et al. 2017

Geochimica et Cosmochimica Acta

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Incipient warming of peatlands at high latitudes is expected to modify soil drainage and hence the redox conditions, which has implications for Fe export from soils. This study uses Fe isotopes to assess the processes controlling Fe export in a range of Icelandic soils including peat soils derived from the same parent basalt, where Fe isotope variations principally reflect differences in weathering and drainage. In poorly weathered, well-drained soils (non-peat soils), the limited Fe isotope fractionation in soil solutions relative to the bulk soil (D 57 Fe solution-soil = À0.11 ± 0.12‰) is attributed to proton-promoted mineral dissolution. In the more weathered poorly drained soils (peat soils), the soil solutions are usually lighter than the bulk soil (D 57 Fe solution-soil = À0.41 ± 0.32‰), which indicates that Fe has been mobilised by reductive mineral dissolution and/or ligand-controlled dissolution. The results highlight the presence of Fe-organic complexes in solution in anoxic conditions. An additional constraint on soil weathering is provided by Si isotopes. The Si isotope composition of the soil solutions relative to the soil (D 30 Si solution-soil = 0.92 ± 0.26‰) generally reflects the incorporation of light Si isotopes in secondary aluminosilicates. Under anoxic conditions in peat soils, the largest Si isotope fractionation in soil solutions relative to the bulk soil is observed (D 30 Si solution-soil = 1.63 ± 0.40‰) and attributed to the cumulative contribution of secondary clay minerals and amorphous silica precipitation. Si supersaturation in solution with respect to amorphous silica is reached upon freezing when Al availability to form aluminosilicates is limited by the affinity of Al for metal-organic complexes. Therefore, the precipitation of amorphous silica in peat soils indirectly supports the formation of metal-organic complexes in poorly drained soils. These observations highlight that in a scenario of decreasing soil drainage with warming high latitude peatlands, Fe export from soils as Fe-organic complexes will increase, which in turn has implications for Fe transport in rivers, and ultimately the delivery of Fe to the oceans.

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“…Overall, the flux of dissolved iron (, 0.45 mm) from riverine sources has been estimated at 1.5-26 3 10 9 mol Fe yr 21 based on the average concentration of dissolved iron (40 nmol Fe L 21 ) in the major world rivers (Martin and Meybeck 1979;Poulton and Raiswell 2002). Conversely, rivers draining organicrich peatlands provide an estimated 12 3 10 9 mol Fe yr 21 as dissolved organic-Fe(III) complexes to ocean margins (Krachler et al 2010). These findings suggest that small rivers containing high levels of DOM are capable of delivering considerable organic-Fe(III) complexes to the surface ocean and may be underrepresented in world riverine flux calculations.…”

mentioning

confidence: 99%

The flux of soluble organic‐iron(III) complexes from sediments represents a source of stable iron(III) to estuarine waters and to the continental shelf

Jones

Beckler

Taillefert

2011

Limnology & Oceanography

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Iron speciation in the Satilla River Estuary was investigated using competitive ligand equilibration-adsorptive cathodic stripping voltammetry (CLE-ACSV) with the ligand 1-nitroso-2-naphthol (1N2N). The blackwater Satilla River contains high concentrations of dissolved organic matter and iron, suggesting that it could provide a source of dissolved iron to the continental shelf. Total dissolved iron in the water column decreases along the estuary, likely due to flocculation and precipitation processes associated with the increase in salinity. Simultaneously, the percentage of dissolved organic-Fe(III) complexes measured by CLE-ACSV in overlying waters of sediment cores increases with salinity. The speciation of dissolved iron in the pore waters indicates that these complexes originate in the underlying sediments. Diffusive fluxes calculated from depth profiles in the sediments indicate that only 8% of the sedimentary flux of Fe(III) is delivered to the continental shelf during low riverine discharge. During normal flow conditions, however, the sediment flux of Fe(III) represents 63% of the total riverine flux of Fe(III). These findings suggest that the flux of dissolved iron to the continental shelf is controlled by the sedimentation of iron in the estuary and the remobilization of soluble organic-Fe(III) complexes produced either during iron reduction deep in the sediment or oxidation of Fe(II) close to the sediment-water interface. The Satilla River Estuary generates five to eight times higher concentrations of dissolved Fe(III) than the average major world rivers, suggesting that it is, along with other small blackwater rivers, currently underrepresented in world average river flux calculations.

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Relevance of peat-draining rivers for the riverine input of dissolved iron into the ocean

Cited by 94 publications

References 41 publications

Dissolved iron exports from an estuary surrounded by coastal wetlands: Can small estuaries be a significant source of Fe to the ocean?

Dissolved iron exports from an estuary surrounded by coastal wetlands: Can small estuaries be a significant source of Fe to the ocean?

Iron and silicon isotope behaviour accompanying weathering in Icelandic soils, and the implications for iron export from peatlands

The flux of soluble organic‐iron(III) complexes from sediments represents a source of stable iron(III) to estuarine waters and to the continental shelf

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