Ionic Strength and Species Drive Iron–Carbon Adsorption Dynamics: Implications for Carbon Cycling in Future Coastal Environments

Tomaszewski, Elizabeth J.; Coward, Elizabeth K.; Sparks, Donald L.

doi:10.1021/acs.estlett.1c00432

Cited by 14 publications

(7 citation statements)

References 37 publications

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“…By intensity-normalized formula abundance, the initial DOM contained primarily unsaturated lignin/phenolic (60%) and N– aliphatic (20%) components, with smaller contributions of polyphenols (12%), N+ aliphatic (2%), polycyclic aromatics (5%), and carbohydrate-like (1%) contributions (Supporting Information Table S3 and Figure ). These compounds are typical in DOM. ,,,− …”

Section: Resultsmentioning

confidence: 99%

Secondary Mineral Formation and Carbon Dynamics during FeS Oxidation in the Presence of Dissolved Organic Matter

Wang

Thompson

et al. 2022

Environ. Sci. Technol.

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Iron (Fe) minerals constitute a major control on organic carbon (OC) storage in soils and sediments. While previous research has mainly targeted Fe (oxyhydr)oxides, the impact of Fe sulfides and their subsequent oxidation on OC dynamics remains unresolved in redox-fluctuating environments. Here, we investigated the impact of dissolved organic matter (DOM) on FeS oxidation and how FeS and its oxidation may alter the retention and nature of DOM. After the anoxic reaction of DOM with FeS, FeS preferentially removed high-molecularweight and nitrogen-rich compounds and promoted the formation of aqueous sulfurized organic molecules, according to Fourier transform−ion cyclotron resonance−mass spectrometry (FT-ICR-MS) analysis. When exposed to O 2 , FeS oxidized to nanocrystalline lepidocrocite and additional aqueous sulfurized organic compounds were generated. The presence of DOM decreased the particle size of the resulting nano-lepidocrocite based on Mossbauer spectroscopy. Following FeS oxidation, most solid-phase OC remained associated with the newly formed lepidocrocite via a monodentate chelating mechanism (based on FTIR analysis), and FeS oxidation caused only a slight increase in the solubilization of solid-phase OC. Collectively, this work highlights the under-appreciated role of Fe sulfides and their oxidation in driving OC transformation and preservation.

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Section: Resultsmentioning

confidence: 99%

Secondary Mineral Formation and Carbon Dynamics during FeS Oxidation in the Presence of Dissolved Organic Matter

Wang

Thompson

et al. 2022

Environ. Sci. Technol.

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“…Also relevant to climate change is sea-level rise and over-extraction of groundwater in coastal areas, which can result in seawater intrusion into aquifers, and can have the effect of altering groundwater ionic strength 28 . Changes to ionic strength can affect the ability of DOM to adsorb to mineral surfaces 29 – 31 . Furthermore, seawater intrusion can influence terminal electron acceptor availability and microbial composition of groundwater 32 , 33 which may result in changes to the metabolic pathways used to mineralise DOM and altered mineralisation rates 34 .…”

Section: Introductionmentioning

confidence: 99%

A new conceptual framework for the transformation of groundwater dissolved organic matter

et al. 2022

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Groundwater comprises 95% of the liquid fresh water on Earth and contains a diverse mix of dissolved organic matter (DOM) molecules which play a significant role in the global carbon cycle. Currently, the storage times and degradation pathways of groundwater DOM are unclear, preventing an accurate estimate of groundwater carbon sources and sinks for global carbon budgets. Here we reveal the transformations of DOM in aging groundwater using ultra-high resolution mass spectrometry combined with radiocarbon dating. Long-term anoxia and a lack of photodegradation leads to the removal of oxidised DOM and a build-up of both reduced photodegradable formulae and aerobically biolabile formulae with a strong microbial signal. This contrasts with the degradation pathway of DOM in oxic marine, river, and lake systems. Our findings suggest that processes such as groundwater extraction and subterranean groundwater discharge to oceans could result in up to 13 Tg of highly photolabile and aerobically biolabile groundwater dissolved organic carbon released to surface environments per year, where it can be rapidly degraded. These findings highlight the importance of considering groundwater DOM in global carbon budgets.

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“…The negative correlations between salinity, I Terr , and FDOM indicated that the terrigenous signatures were attenuated mainly through conservative mixing with seawater . In general, the effects of ionic strength on DOM composition (e.g., coagulation and subsequent precipitation) were expected to be negligible due to the narrow salinity range in this study (30.1–34.6). − The average molecular mass, O/C ratios, and I DEG of DOM in bottom water increased from near- to offshore (Table S4), which is typical for the transition from land to ocean. , …”

Section: Discussionmentioning

confidence: 76%

Iron Promotes the Retention of Terrigenous Dissolved Organic Matter in Subtidal Permeable Sediments

Zhou,

Waska,

Henkel

et al. 2024

Environ. Sci. Technol.

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Marine permeable sediments are important sites for organic matter turnover in the coastal ocean. However, little is known about their role in trapping dissolved organic matter (DOM). Here, we examined DOM abundance and molecular compositions (9804 formulas identified) in subtidal permeable sediments along a near- to offshore gradient in the German North Sea. With the salinity increasing from 30.1 to 34.6 PSU, the DOM composition in bottom water shifts from relatively higher abundances of aromatic compounds to more highly unsaturated compounds. In the bulk sediment, DOM leached by ultrapure water (UPW) from the solid phase is 54 ± 20 times more abundant than DOM in porewater, with higher H/C ratios and a more terrigenous signature. With 0.5 M HCl, the amount of leached DOM (enriched in aromatic and oxygen-rich compounds) is doubled compared to UPW, mainly due to the dissolution of poorly crystalline Fe phases (e.g., ferrihydrite and Fe monosulfides). This suggests that poorly crystalline Fe phases promote DOM retention in permeable sediments, preferentially terrigenous, and aromatic fractions. Given the intense filtration of seawater through the permeable sediments, we posit that Fe can serve as an important intermediate storage for terrigenous organic matter and potentially accelerate organic matter burial in the coastal ocean.

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Ionic Strength and Species Drive Iron–Carbon Adsorption Dynamics: Implications for Carbon Cycling in Future Coastal Environments

Cited by 14 publications

References 37 publications

Secondary Mineral Formation and Carbon Dynamics during FeS Oxidation in the Presence of Dissolved Organic Matter

Secondary Mineral Formation and Carbon Dynamics during FeS Oxidation in the Presence of Dissolved Organic Matter

A new conceptual framework for the transformation of groundwater dissolved organic matter

Iron Promotes the Retention of Terrigenous Dissolved Organic Matter in Subtidal Permeable Sediments

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