Effect of mineral surface properties (alumina, kaolinite) on the sorptive fractionation mechanisms of soil fulvic acids: Molecular-scale ESI-MS studies

Selective Adsorption of Terrestrial Dissolved Organic Matter to Inorganic Surfaces Along a Boreal Inland Water Continuum

“…This is also where WRT and the adsorption treatment diverge in their effect on DOM composition: Whereas unsaturated compounds are generally lost from solution in both processes, even fairly saturated compounds can be adsorbed as long as they have a high O/C (Figures 3c and S3). The observed adsorption of oxygen-rich compounds is in agreement with various other studies, where both highly oxidized aromatics (Coward et al, 2018;Fleury et al, 2017;Galindo & Del Nero, 2014;Lv et al, 2016), and in some cases also oxidized saturated, aliphatic compounds (Galindo & Del Nero, 2014;Avneri-Katz et al, 2017) were preferentially adsorbed. The preferential adsorption of oxygen-rich compounds indicates that the presence of carboxyl and hydroxyl functional groups may be important for adsorptive processes, as these groups allow for ligand exchange with oxide and hydroxide groups at the sorbent's surface (Chassé et al, 2015;Gu et al, 1995;Kaiser, 2003;Kaiser et al, 1997;Kothawala et al, 2012;Lv et al, 2016;Meier et al, 1999;Tipping, 1981b).…”

“…The pH dependence of DOM adsorption onto clay surfaces has been observed in other studies (Davis, ; Fleury et al, ; Gu et al, ; Kaiser et al, ; Shen, ; Tipping, , ). Both DOM and clay surfaces are generally negatively charged: DOM through the abundance of carboxylic and hydroxylic groups and clay through the presence of (e.g., Al and Fe) oxides and hydroxides in the mineral lattice.…”

“…Unsaturated compounds (low H/C) are preferentially adsorbed while saturated compounds (high H/C) remain in solution. The same trend has been reported by studies using mass spectrometry to investigate the adsorption of Suwannee River fulvic acid from the International Humic Substances Society on alumina colloids (Galindo & Del Nero, 2014) and soil DOM, International Humic Substances Society Pahokee peat (Chassé et al, 2015) and peat DOM on iron oxyhydroxides (Lv et al, 2016), and soil fulvic acid on alumina colloids (Fleury et al, 2017). Accordingly, studies using other methods than mass spectrometry also found that compounds with low H/C such as polyphenols and aromatics are preferentially adsorbed (Kaiser, 2003;Kaiser et al, 1997;Kalbitz et al, 2005; Kothawala et al, Figure 6.…”

“…The clay we used is a commercially available reference material, which we chose for its expected high affinity for DOM due to the presence of aluminum and iron oxides (see SI Text S2). The added clay is not a direct representation of mineral surfaces naturally occurring in the sampled watersheds, and it is important to note that the nature of the sorbate, the solution, and the sorbent may affect the selective partitioning of DOM to particle surfaces (e.g., Fleury et al, ; Kaiser et al, ; Meier et al, ). As such, the results observed here apply to this specific combination of mineral particles and water samples (including both the DOM and the solution characteristics).…”

Natural organic matter contained in clay rock pore water: Direct quantification at the molecular level using electrospray ionization mass spectrometry

“…For instance, it has been shown recently by means of electrospray ionization Fourier transform mass spectrometry analysis that the sorption‐driven fractionation of a soil fulvic acid depended upon the mineral surface properties, i.e. kaolinite versus aluminium oxide . Thus, the accurate quantification of DOM in pore water from the COx rock is of utmost importance for determining the interactions between the geological medium and the materials that would be introduced during the disposal phase.…”