Adsorption of dissolved organic matter (DOM) to mineral surfaces is an important process determining DOM bioavailability and carbon sequestration in soils. However, little is known about preferential adsorption of DOM at the molecular level. In this study, structural changes in DOM due to adsorption to soil, containing iron mineral components were studied using two complementary approaches: (i) macroscale analysis including resin separation; and (ii) molecular characterization using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Both approaches demonstrated consistency regarding the DOM adsorptive fractionation. Resin separation showed preferential adsorption of the hydrophobic acid (HoA) fraction by soil surfaces, with up to 70% of total adsorbed carbon; this fraction was apparently responsible for low DOM desorption. FT-ICR MS data demonstrated preferential adsorption of polyphenols, which are components of the HoA fraction.<i> </i>Adsorption of highly oxidized, saturated “carbohydrate-like” molecules was also observed, which might be a result of adsorption of the hydrophilic neutral (HiN) fraction. Soil iron -containing minerals are responsible for preferable adsorption of DOM components. DOM adsorption exhibited concentration-dependent fractionation: enhanced adsorption of highly oxidized compounds at low DOM concentrations due to close contact with iron-enriched mineral surfaces, and selective adsorption of less oxidized components at higher DOM concentrations, suggesting that adsorptive fractionation of DOM depended on the extent of its loading.<br/>Our findings demonstrate the importance of iron-containing mineral surfaces for DOM environmental behavior, and  for stabilization of DOM-originated organic carbon

Adsorptive fractionation of dissolved organic matter by iron-containing mineral soil: Macroscale approach and molecular insight

254th National Meeting (2017)

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