The effect of purification using ionic and non-ionic resin chromatography on the charge density and fluorescence properties of dissolved organic matter (DOM) was evaluated. Aqueous extracts of a forest soil O horizon and field corn residue were used to represent DOM from a well humified DOM source and the initial reactants for DOM formation in agricultural soils. Treatments included purification with a H+-saturated cation exchange resin (CAT), H++ OH#x2212;-saturated mixed bed resin (MBR), and serial columns of XAD-8 and XAD-4 resins (XAD). In general, the alteration of DOM characteristics by purification was less for the O horizon DOM than for the corn residue DOM. The commonly used CAT purification did not alter the chemical properties measured in this study for the O horizon DOM. The CAT purification did result in a 15 loss of carbon content for corn residue DOM, but caused no difference in charge density. The benefits of MBR purification in removing both inorganic cations and anions are offset by decreased DOM recovery and charge density, especially for the corn residue extract. The use of XAD purification significantly favors a DOM fraction with a higher charge density than in the control (CTL) extract. The pragmatic need to concentrate DOM in natural solutions with low dissolved organic carbon concentration may favor the use of a XAD treatment. Careful evaluation of how purification affects the chemical characteristics of the DOM is required, especially with plant-derived materials, to ensure that the DOM used in investigation is representative of DOM in the ecosystem.
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