The reverse osmosis/electrodialysis (RO/ED) method has been used to isolate natural organic matter (NOM) from two coastal riverine/estuarine systems in Georgia. In the RO/ED method, water is removed from samples by reverse osmosis while inorganic salts are removed using electrodialysis. Two problematic solutes - boric acid and silicic acid - are uncharged and cannot be removed efficiently from raw source waters. Both solutes were removed sucessfully by treating partially processed samples with stoichiometric quantities of HF, which converts these acids into their perfluorinated anions (BF4- and SiF62-), both of which can then be removed using electrodialysis. The major goal of the work was to develop a unified method of isolation of NOM from both fresh and saline waters. Two sampling trips were made to the Satilla River and one trip was made to the Altamaha River. Nine samples were collected from each river on each trip over a salinity range of 0-30. Average yields of NOM (as carbon) ranged from 80% to 84%. Given the relatively high and consistent yields of NOM at all salinities, it is believed that compositional trends with increasing salinity are likely to result from biogeochemical processes and not from isolation artifacts that are variable along a salinity gradient. This presentation will describe trends that can be observed using Fourier transform ion cyclotron resonance mass spectrometry.

Using the reverse osmosis/electrodialysis method to isolate natural organic matter from rivers and estuaries in coastal Georgia

253rd National Meeting (2017)

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