Direct Evidence for Temporal Molecular Fractionation of Dissolved Organic Matter at the Iron Oxyhydroxide Interface

Environmental contextCarbon sequestration and dynamics are influenced by adsorptive fractionation of dissolved organic matter (DOM) on minerals. We found that the molecular fractionation of DOM on ferrihydrite was highly dependent on the presence of Na, Ca and Cu ions in water. These results advance our mechanistic understanding of the dynamic behaviour of DOM, and contribute to predicting carbon cycling and contaminant behaviour in the natural environment. AbstractThe adsorptive fractionation of dissolved organic matter (DOM) at the ferrihydrite and water interface is a key geochemical process controlling DOM compositions and reactivity, thus affecting carbon cycling and contaminant behaviour in the environment. However, the effects of cations on DOM fractionation and the underlying mechanisms are poorly understood. In this study, Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) combined with spectroscopic methods were employed to investigate molecular fractionation of DOM on ferrihydrite under different cations in the background electrolytes, including Na, Ca, and Cu ions. The results indicated that DOM fractionation was influenced by the combined effects of cation type, intrinsic molecular property, and extent of DOM adsorption. DOM adsorption on ferrihydrite exhibited the strongest and the weakest fractionation under Na and Ca background electrolytes, respectively. Both Ca and Cu background electrolytes reduced the adsorption of highly unsaturated and phenolic/polyphenolic molecules with high molecular weight and number of O atoms. In addition to the molecular acidity, the complexation of Ca and Cu ions to DOM binding sites and the coagulation effect of divalent cations may affect molecular fractionation. Additionally, DOM fractionation was enhanced with increasing DOM adsorption. Our results contribute to predicting carbon cycling and contaminant behaviour in the natural environment.

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Molecular fractionation and sub-nanoscale distribution of dissolved organic matter on allophane

Environmental Science Nano ◽

10.1039/c9en00335e ◽

2019 ◽

Vol 6 (7) ◽

pp. 2037-2048 ◽

Cited By ~ 6

Author(s):

Yang Ding ◽

Yang Lu ◽

Peng Liao ◽

Shimeng Peng ◽

Yuzhen Liang ◽

...

Keyword(s):

Organic Matter ◽

Spatial Distribution ◽

Dissolved Organic Matter ◽

Molecular Fractionation

We elucidated the spatial distribution of DOM on allophane and the mechanisms controlling the adsorptive fractionation of DOM molecules.

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Molecular Fractionation of Dissolved Organic Matter with Metal Salts

Environmental Science & Technology ◽

10.1021/es203901u ◽

2012 ◽

Vol 46 (8) ◽

pp. 4419-4426 ◽

Cited By ~ 107

Author(s):

Thomas Riedel ◽

Harald Biester ◽

Thorsten Dittmar

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Metal Salts ◽

Molecular Fractionation

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Effects of land use and nutrients on the characteristics of dissolved organic matter in the Nanchong Section of Jialing River, China in December 2019

Water Science & Technology Water Supply ◽

10.2166/ws.2021.307 ◽

2021 ◽

Author(s):

Liuqing Zhang ◽

Xiaohua Zhu ◽

Xing Huang ◽

Chaorong Liu ◽

Yan Yang

Keyword(s):

Land Use ◽

Organic Matter ◽

Dissolved Organic Matter ◽

Absorption Coefficient ◽

Aquatic Ecosystems ◽

Direct Evidence ◽

Chromophoric Dissolved Organic Matter ◽

Jialing River ◽

Parallel Factor ◽

Effects Of Land Use

Abstract Chromophoric dissolved organic matter (CDOM) in aquatic ecosystems can reflect the impacts of human activities on the carbon-cycling process. However, direct evidence of the combined effect of land use and anthropogenic nutrients on CDOM characteristics in river ecosystems is limited. Herein, we collected water samples from 18 sites in the Nanchong section of Jialing River in December 2019 to elucidate how the land use and nutrients affect the source and composition of CDOM through parallel factor (PARAFAC) analysis of excitation–emission matrices (EEMs). First, the absorption coefficient a254 (r2=0.29, p<0.01) and three fluorescence components (humic-like C1 and C2 and protein-like C3) (r2=0.31–0.37, p<0.01) significantly increased with increased urban area, and the four parameters were higher in the urban than in the suburb (p<0.05). The correlation between small CDOM molecule and cropland land was positive (p<0.01). Second, the increase in nutrient levels increased the a254 (r2=0.84 and 0.33, p<0.01) and three fluorescence components (r2=0.30–0.84, p<0.01 or p<0.05). Third, allochthonous CDOM were prevalent in the Nanchong Section of Jialing River, and the proportions of C1 and C2 were 42 and 41%, respectively. Our findings indicated that the variability of source and composition of CDOM significantly depended on urbanization and increased nutrients in the Nanchong Section of Jialing River.

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