Molecular-Scale Investigation with ESI-FT-ICR-MS on Fractionation of Dissolved Organic Matter Induced by Adsorption on Iron Oxyhydroxides

Abstract

Adsorption by minerals is a common geochemical process of dissolved organic matter (DOM) which may induce fractionation of DOM at the mineral-water interface. Here, we examine the molecular fractionation of DOM induced by adsorption onto three common iron oxyhydroxides using electrospray ionization coupled with Fouriertransform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS). Ferrihydrite exhibited higher affinity to DOM and induced more pronounced molecular fractionation of DOM than did goethite or lepidocrocite. High molecular weight (>500 Da) compounds and compounds high in unsaturation or rich in oxygen including polycyclic aromatics, polyphenols and carboxylic compounds had higher affinity to iron oxyhydroxides and especially to ferrihydrite. Low molecular weight compounds and compounds low in unsaturation or containing few oxygenated groups (mainly alcohols and ethers) were preferentially maintained in solution. This study confirms that the double bond equivalence and the number of oxygen atoms are valuable parameters indicating the selective fractionation of DOM at mineral and water interfaces. The results of this study provide important information for further understanding the behavior of DOM in the natural environment.

Preservation of organic matter in marine sediments by inner-sphere interactions with reactive iron

“…Another peak of interest at 289.5 eV suggests the presence of alcohols (C-OH 32 ) co-occurring in most cases alongside aromatic and carbonyl functional groups. Overall, the absorption bands observed for these sediments are similar to those observed for complex soils and synthetic co-precipitates, with the notable absence of peaks at 286.6 eV commonly attributed to ketone 32–34 . Note that absorption bands in the post-edge region found at ~297 and 300 eV correspond to the potassium L-edge X-ray absorption bands 35 , but are not discussed further in this text.

Figure 5Chemical composition of co-localized iron (panels a and b–d) and organic matter (panels a and e–h).

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Global change‐driven effects on dissolved organic matter composition: Implications for food webs of northern lakes

“…Certain organisms may benefit from the harmful effects of UV exposure or reactive oxygen species if their predators, parasites, or competitors have a higher vulnerability to these stressors (Häder et al., ; Imlay, ). For example, in the surface waters of DOM‐rich lakes, the conversion of light energy into heat in oxygenated waters results in the formation of harmful reactive oxygen species that are known disinfecting agents (Lv et al., ). Cyanobacteria that aggregate and accumulate in assemblages or mats near the surface may have an advantage over other autotrophs in their ability to neutralize reactive oxygen species through superoxide dismutase and other enzymes (Latifi, Ruiz, & Zhang, ; Ross, Santiago‐Vázquez, & Paul, ).…”

Solid-phase extraction-stepwise elution (SPE-SE) procedure for isolation of dissolved organic matter prior to ESI-FT-ICR-MS analysis

“…DOM entrapped by the cartridges was then collected by one-step elution and stepwise elution, respectively. One-step elution, equivalent to the method conventionally used [18,27] …”

“…Ultrahigh resolution mass spectra were acquired using a Bruker SolariX FT-ICR-MS equipped with a 15.0 T superconducting magnet and an ESI ion source as described in our previous study [27]. Samples for FT-ICR-MS analysis were continuously fed into the ESI unit by syringe infusion at a flow rate of 120 mL h…”