Natural organic molecules are common in aquatic systems, and adsorb on mineral surfaces and alter their surface reactivity. However, sorption of humic substances by minerals varies as a function of mineral surface chemistry, and composition of humics and other chemical species in the aqueous phase. We examined the reactions of freshly obtained dissolved humic substances (filtered stream water from Pine Barrens, NJ; Great Dismal Swamp, VA) with Fe-oxides (ferrihydrite), Al-oxides (boehmite), calcite, and clay minerals (kaolinite, smectite) as a function of pH. The samples are examined using in-situ FTIR spectroscopy, and high-resolution FTICR ESI-mass spectrometry. Our results suggest that the composition of dissolved humics change substantially with the oxidation of associated metals, such as Fe, and results in the production of colloidal organic carbon. In association with these changes in aqueous phase, the sorption of humic substances on mineral surfaces also changed drastically. The sorption of humics by minerals is highly selective, and shows significant variations for the interactions of carboxyls, and amides (e.g. proteinaceous carbon) as a function of mineral composition and pH. The results of these studies, and their implications for metal sorption on mineral surfaces will be discussed.

Selective sorption of humic substances on mineral surfaces

251st National Meeting (2016)

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