Characterization of the chemical composition of soil humic acids using Fourier transform ion cyclotron resonance mass spectrometry

Ikeya, Kosuke; Sleighter, Rachel L.; Hatcher, Patrick G.; Watanabe, Akira

doi:10.1016/j.gca.2015.01.002

Cited by 76 publications

(55 citation statements)

References 55 publications

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“…These processes are known to produce condensed molecules with sufficient oxygenated functional groups such as hydroxyl and carboxyl to exhibit polarity and solubility, and several structures have been proposed. 44,48,49 Fewer studies have identified structures for N-containing condensed aromatic compounds in soils. 52,53 Pyrrole-type forms of condensed aromatics have been proposed in fire-affected soils, 52 and these structures, such as porphyrins, also form quite stable complexes with iron.…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

Substructural Components of Organic Colloids from a Pu-Polluted Soil with Implications for Pu Mobilization

DiDonato

Santschi

et al. 2017

Environ. Sci. Technol.

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Contaminated soil organic matter from the Rocky Flats Environmental Technology Site (RFETS) has been previously shown to accumulate plutonium (Pu) in a colloidal subfraction and is hypothesized to contain cutin-like chemical structures cross-linked with hydroxamate functionality. The present study further characterizes this high Pu affinity subfraction using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICRMS) and discovers additional substructural components. The Pu-enriched fraction was extracted and purified through a series of ultrafiltration and isoelectric focusing (IEF) electrophoresis steps. Predominantly low H/C and high double-bond equivalence (DBE) aromatic and condensed aromatic molecular formulas were detected, 66% of which are included in a COO Kendrick mass defect (KMD) homologous series. This suggests the existence of polycarboxylated aromatic and condensed aromatic formulas, with CHON-type COO KMD formulas relatively more abundant in the purified subfraction where Pu had been observed than in the crude soil fractions which had successively lower Pu concentrations. Nitrogen contents increased with the progression of purification (bulk soil → crude colloid → IEF colloid) and coincided with the trend of Pu concentration; thus, we propose that these nitrogen and carboxyl functionalities of aromatic compounds may also impart significant Pu chelation character to the colloid.

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Section: ■ Materials and Methodsmentioning

confidence: 99%

Substructural Components of Organic Colloids from a Pu-Polluted Soil with Implications for Pu Mobilization

DiDonato

Santschi

et al. 2017

Environ. Sci. Technol.

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“…Humic acids are composed of molecules rich in both acidic functional groups, mainly carboxyl and phenolic groups, and hydrophobic moieties such as alkyl chains and aromatic cores. Humic acids are complex mixtures of many different acids containing carboxyl and phenolate groups with elemental compositions of C (52-62%), H (3-5.5%), O (30-33%) and N (3.5-5%) (Kumada, 1955, Ikeya et al, 2015. However, other authors reported lower C percentages, close to 32% (Wang et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Use of Fenton reagent combined with humic acids for the removal of PFOA from contaminated water

Santos

Rodríguez

Pardo

et al. 2016

Science of The Total Environment

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“…Direct comparisons of FT ion cyclotron resonance mass spectrometry and fluorescence analyses have indicated that humic‐like fluorescence component generally covaried with aromatic moieties such as quinones and hydroquinones (Boyle, Guerriero, Thiallet, Del Vecchio, & Blough, ; Del Vecchio & Blough, ; Herzsprung et al, ). A low value of E 4 :E 6 is mainly due to absorption by the moieties with carbon double bond of benzene ring (Ikeya, Sleighter, Hatcher, & Watanabe, ; Kleber & Johnson, ; Li & Hur, ). The above information indicates that the C:H, HIX, humic‐like component, and E 4 :E 6 of HS can be utilised as indicators for quinonoid structures.…”

Section: Discussionmentioning

confidence: 99%

“…Direct comparisons of FT ion cyclotron resonance mass spectrometry and fluorescence analyses have indicated that humic-like fluorescence component generally covaried with aromatic moieties such as quinones and hydroquinones (Boyle, Guerriero, Thiallet, Del Vecchio, & Blough, 2009;Del Vecchio & Blough, 2004;Herzsprung et al, 2012). A low value of E 4 :E 6 is mainly due to absorption by the moieties with carbon double bond of benzene ring (Ikeya, Sleighter, Hatcher, & Watanabe, 2015;Kleber & Johnson, 2010;Li & Hur, 2017 (Aeschbacher et al, 2010;Lovley et al, 1996;Scott et al, 1998;Tan et al, 2017). Although HAs and FAs show remarkable differences in degree polymerisation, MW, and solubility at a strong acidic pH (Stevenson, 1994), our results showed that the significant relationships between microbial RCs and chemical properties were present both in individual data sets of HAs and FAs and in the integrated data set including HAs and FAs ( Figure S5), thus indicating that the responsibility of aromatic systems for the microbial RCs of HSs was independent of HS fraction.…”

Section: Relationships Between the Microbial Rcs Of Hss And Their Imentioning

confidence: 99%

Molecular‐weight‐dependent redox cycling of humic substances of paddy soils over successive anoxic and oxic alternations

et al. 2019

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Humic substances (HSs) are critical to regulating methane cycling in temporary anoxic systems because their redox‐active functional groups can sustainably shuttle electrons from microorganisms to oxygen (O2) over successive anoxic and oxic alternations. Whether the relative amount of these redox‐active functional groups involved in redox cycles is associated with the overall chemical structures of HS still remains poorly understood. In this study, variations in the reducing capacities (RCs) of HSs extracted from paddy soils were monitored over consecutive cycles of reduction by iron‐reducing microorganisms and oxidation by O2. Our results show that about 10–40% of the microbially reduced redox‐active moieties within HS, which were reoxidised by O2, cannot restore the same redox state as those before microbial reduction. The restoration extents of RCs of HSs after microbial reduction and O2 reoxidation were greatly negatively correlated with average molecular weight (AMW). The microbially reduced HSs having large AMWs (>1,000 Da) were more kinetically difficult to restore by O2 from a reduced state to an oxidised state than were those having small AMWs (<1,000 Da) possibly because the former, which underwent process of microbial reduction and O2 reoxidation, were more easily sheltered by other parts of HS structures than were the latter. Nevertheless, the unsheltered redox‐active groups that accounted for about 50–85% in HSs can be fully reversible and sustainable to switch between a reduced state and an oxidised state over successive redox cycles. Our results can help to understand the redox dynamics of HSs in biogeochemical cycles in environments.

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Characterization of the chemical composition of soil humic acids using Fourier transform ion cyclotron resonance mass spectrometry

Cited by 76 publications

References 55 publications

Substructural Components of Organic Colloids from a Pu-Polluted Soil with Implications for Pu Mobilization

Substructural Components of Organic Colloids from a Pu-Polluted Soil with Implications for Pu Mobilization

Use of Fenton reagent combined with humic acids for the removal of PFOA from contaminated water

Molecular‐weight‐dependent redox cycling of humic substances of paddy soils over successive anoxic and oxic alternations

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