Molecular fractionation of dissolved organic matter on ferrihydrite: effects of dissolved cations

2019 ◽  
Vol 16 (2) ◽  
pp. 137 ◽  
Author(s):  
Minqin Liu ◽  
Yang Ding ◽  
Shimeng Peng ◽  
Yang Lu ◽  
Zhi Dang ◽  
...  

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.

2021 ◽  
pp. 108191
Author(s):  
Morgan Luce McLeod ◽  
Lorinda Bullington ◽  
Cory C. Cleveland ◽  
Johannes Rousk ◽  
Ylva Lekberg

2016 ◽  
Vol 92 (5) ◽  
pp. fiw048 ◽  
Author(s):  
Christian Lønborg ◽  
Mar Nieto-Cid ◽  
Victor Hernando-Morales ◽  
Marta Hernández-Ruiz ◽  
Eva Teira ◽  
...  

2019 ◽  
Vol 53 (8) ◽  
pp. 4295-4304 ◽  
Author(s):  
Tyler D. Sowers ◽  
Kathryn L. Holden ◽  
Elizabeth K. Coward ◽  
Donald L. Sparks

2018 ◽  
Vol 59 (77) ◽  
pp. 31-40 ◽  
Author(s):  
Lin Feng ◽  
Yanqing An ◽  
Jianzhong Xu ◽  
Shichang Kang

AbstractDissolved organic matter (DOM) in mountain glaciers is an important source of carbon for downstream aquatic systems, and its impact is expected to increase due to the increased melting rate of glaciers. We present a comprehensive study of Laohugou glacier no. 12 (LHG) at the northern edge of the Tibetan Plateau to characterize the DOM composition and sources by analyzing surface fresh snow, granular ice samples, and snow pit samples which covered a whole year cycle of 2014/15. Excitation–emission matrix fluorescence spectroscopy analysis of the DOM with parallel factor analysis (EEM-PARAFAC) identified four components, including a microbially humic-like component (C1), two protein-like components (C2 and C3) and a terrestrial humic-like component (C4). The use of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) showed that DOM from all these samples was dominated by CHO and CHON molecular formulas, mainly corresponding to lipids and aliphatic/proteins compounds, reflecting the presence of significant amounts of microbially derived and/or deposited biogenic DOM. The molecular compositions of DOM showed more CHON compounds in granular ice than in fresh snow, likely suggesting newly formed DOM from microbes during snowmelting.


2020 ◽  
Vol 392 ◽  
pp. 122260 ◽  
Author(s):  
Peng Zhang ◽  
Aiju Liu ◽  
Peng Huang ◽  
Lujuan Min ◽  
Hongwen Sun

2019 ◽  
Vol 6 (7) ◽  
pp. 2037-2048 ◽  
Author(s):  
Yang Ding ◽  
Yang Lu ◽  
Peng Liao ◽  
Shimeng Peng ◽  
Yuzhen Liang ◽  
...  

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


Water ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 331 ◽  
Author(s):  
Christin Wilske ◽  
Peter Herzsprung ◽  
Oliver J. Lechtenfeld ◽  
Norbert Kamjunke ◽  
Wolf von Tümpling

Photochemical processing is an important way to transform terrestrial dissolved organic matter (DOM) but was rarely investigated by ultra-high resolution mass spectrometry. We performed an irradiation experiment with water from a shaded forest stream flowing into a lit reservoir. Bacterial activity explained only 1% of dissolved organic carbon (DOC) decline in a combined bacterial and photodegradation approach. Photodegradation decreased the DOC concentration by 30%, the specific ultraviolet (UV) absorption by 40%–50%, and fluorescence intensity by 80% during six days. The humification index (HIX) decreased whereas the fluorescence index (FI) did not change. Two humic-like components identified by parallel factor analysis (PARAFAC) of excitation–emission matrices followed the decrease of fluorescent DOM. Changes of relative peak intensities of Fourier transform-ion cyclotron resonance mass spectroscopy (FT-ICR MS) elemental formula components as a function of cumulated radiation were evaluated both by Spearman’s rank correlation and linear regression. The FT-ICR MS intensity changes indicate that high aromatic material was photochemically converted into smaller non-fluorescent molecules or degraded by the release of CO2. This study shows the molecular change of terrestrial DOM before the preparation of drinking water from reservoirs.


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