Enhanced terrestrial carbon preservation promoted by reactive iron in deltaic sediments

Shields, Michael R.; Bianchi, Thomas S.; Gélinas, Yves; Allison, Mead A.; Twilley, Robert R.

doi:10.1002/2015gl067388

Cited by 106 publications

(103 citation statements)

References 57 publications

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“…After 27 months of WTD treatment, extracellular enzyme activity, SOC and lignin phenols are examined together with different Fe species in the air-exposed (0–20 cm) relative to the submerged (30–40 cm) soil layers. In particular, similar to Shields et al 34,. we use dithionite to remove crystalline and amorphous Fe oxides25 that may associate with SOC and quantify Fe-bound lignin phenols that are subsequently exposed and amenable to CuO oxidation.…”

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confidence: 76%

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Iron-mediated soil carbon response to water-table decline in an alpine wetland

et al. 2017

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The tremendous reservoir of soil organic carbon (SOC) in wetlands is being threatened by water-table decline (WTD) globally. However, the SOC response to WTD remains highly uncertain. Here we examine the under-investigated role of iron (Fe) in mediating soil enzyme activity and lignin stabilization in a mesocosm WTD experiment in an alpine wetland. In contrast to the classic ‘enzyme latch’ theory, phenol oxidative activity is mainly controlled by ferrous iron [Fe(II)] and declines with WTD, leading to an accumulation of dissolvable aromatics and a reduced activity of hydrolytic enzyme. Furthermore, using dithionite to remove Fe oxides, we observe a significant increase of Fe-protected lignin phenols in the air-exposed soils. Fe oxidation hence acts as an ‘iron gate’ against the ‘enzyme latch’ in regulating wetland SOC dynamics under oxygen exposure. This newly recognized mechanism may be key to predicting wetland soil carbon storage with intensified WTD in a changing climate.

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confidence: 76%

“…Therefore, an improved method is needed to quantify Fe-bound lignin phenols in the soil matrix. Recently, Shields et al 34. observed altered yields of lignin phenols upon CuO oxidation after removing reactive Fe with dithionite from Mississippi delta sediments due to the release of Fe-bound lignin.…”

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confidence: 99%

Iron-mediated soil carbon response to water-table decline in an alpine wetland

et al. 2017

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“…The higher sedimentary sand fractions (~85%) at sites such as L1 and L2 in the river channel have reduced the amount of clay particles (average CF ~3%) and associated negative charges, which could hindered the formation of aggregates and enabled the decomposition of terrestrial C org (enriched in δ 13 C values). Moreover, recent work has shown that approximately 15.0%–(21.5 ± 8.6)% of the C org in marine sediments is directly bound to reactive terrestrial‐derived Fe through the chelation or coprecipitation (Lalonde et al, ; Shields et al, ). Coarse particles in the river channel sediments tend to have low fractions of highly reactive iron (indicated by low contents of Fe; Figure ), suggesting that these sites likely contain the low proportions of reactive Fe‐associated C org compared to the estuarine sites.…”

Section: Discussionmentioning

confidence: 99%

Fate of Organic Carbon Burial in Modern Sediment Within Yangtze River Estuary

et al. 2020

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Large river‐dominated margins play a potential key role in regulating global carbon cycle and budget due to high terrestrial organic carbon (Corg) inputs and sediment accumulation rates. Here bulk elements (Corg and TN), isotopic compositions (δ13Corg and δ15N), radioisotope 210Pb, sedimentary grain size, pH, Eh, and physicochemical properties were analyzed on samples from the Yangtze River Estuary to determine the mechanism involved in transporting sedimentary Corg offshore. In addition, nine box‐cores were analyzed to further reveal the potential effects of the declining sediment load on the modern depositional pattern of Corg. The statistical analyses indicate that the hydrodynamically driven sediment composition exerts a significant control on the transport, mobilization, and accumulation of sedimentary Corg from the river to the estuary, with respect to the redistribution of fine‐grained sediments. Furthermore, X‐radiographs and 210Pb indicate that reworked environment dominates carbon burial in the Yangtze proximal deposit, while a stable sedimentary environment of Corg (3.50–5.58 g cm−2 year−1) is observed in the Yangtze distal mud. Notably, the enhanced erosional inputs that contain terrestrial plant debris (mainly the coarse fractions) have tended to become important sources for Corg. Although reworked sediments in the Yangtze River Estuary are frequently exposed to oxygen during physical and biological processes, there appears to be a high potential for long‐term sedimentary Corg storage, due to its association with sediment particles (mainly the clay fractions) that provide physical protection against its degradation.

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“…Reactive Fe minerals, such as oxides, sulfides, phosphates and carbonates, are involved in diagenetic reactions in sediments and consequently influence the cycling of carbon and nutrients (e.g., Berner, 1970;Slomp et al, 1996a,b;Lovley et al, 2004;Jilbert and Slomp, 2013;Kraal et al, 2015;Robertson et al, 2016). Iron has also recently been shown to stabilize organic carbon in sediments, promoting carbon 5 burial (Lalonde et al, 2012;Shields et al, 2016). Hence, the lateral and vertical distribution of Fe in sediments is important for broader biogeochemical cycles.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, Fe has recently been suggested to play an important role in carbon burial (Lalonde et al, 2012;Shields et al, 2016) and nitrogen cycling (Robertson et al, 2016) in marine sediments. 15…”

Section: Introductionmentioning

confidence: 99%

Flocculation of dissolved organic matter controls the distribution of iron in boreal estuarine sediments

Jilbert¹,

Asmala²,

Schröder³

et al. 2017

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Abstract. Iron (Fe) plays a key role in sedimentary diagenetic processes in coastal systems, participating in various redox reactions and influencing the burial of organic carbon. Large amounts of Fe enter the marine environment from boreal river catchments associated with dissolved organic matter (DOM). However, the fate of this Fe pool in estuarine sediments has not been extensively studied. Here we show that flocculation of DOM along salinity gradients in an estuary of the northern Baltic Sea efficiently transfers Fe from the dissolved phase into particulate material that accumulates in the sediments. Consequently, 5we observe a decline with distance offshore in both the Fe content of the sediments and proportion of terrestrial material in the sedimentary organic matter pool. Mössbauer spectroscopy and sequential extractions suggest that large amounts of Fe in sediments of the upper estuarine zone are associated with organic matter as unsulfidized Fe (II) complexes, or present in the form of ferrihydrite, implying a direct transfer of flocculated material to the sediments. Accordingly, the contribution of these components to the total sedimentary Fe declines with distance offshore while other Fe phases become proportionally more 10 important. Sediment core records show that the observed lateral distribution of Fe minerals has remained similar over recent decades, despite variable Fe inputs from anthropogenic sources and eutrophication of the coastal zone. Pore water data suggest that the vertical zonation of diagenetic processes in the sediments is influenced by both the availability of Fe and by bottom water salinity, which controls the availability of sulfate (SO4 2-).

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Enhanced terrestrial carbon preservation promoted by reactive iron in deltaic sediments

Cited by 106 publications

References 57 publications

Iron-mediated soil carbon response to water-table decline in an alpine wetland

Iron-mediated soil carbon response to water-table decline in an alpine wetland

Fate of Organic Carbon Burial in Modern Sediment Within Yangtze River Estuary

Flocculation of dissolved organic matter controls the distribution of iron in boreal estuarine sediments

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