Comparison of the effects of sonolysis and gamma-radiolysis on dissolved organic matter.

The effects of 640 kHz sonolysis and 60Co gamma-radiolysis on dissolved organic matter (DOM) were compared through UV/ vis absorption spectrometric, dissolved organic carbon concentration ([DOC]), and potentiometric titration analyses. A reverse-phase chromatographic technique was used to compare changes in the DOM hydrophobicity distribution, and a size exclusion chromatographic technique with inline UV-A absorbance, fluorescence, and [DOC] detectors was used to compare changes in the DOM molecular weight distribution. Whereas upon radiolysis major decreases in absorbance and [DOC] were induced and near-total DOC removal was achieved, upon sonolysis there were major decreases in UV/vis absorbance but only minor decreases in [DOC], and a substantial quantity of hydrophilic nonchromophoric material remained in solution. In radiolysis, hydrophilic and hydrophobic DOM solution components were exposed to equal hydroxyl radical (*OH) concentrations. However, in sonolysis, hydrophobic DOM components were exposed to more elevated *OH concentrations than the hydrophilic components and consequently had enhanced rates of degradation. Sonolysis may be of interest in the design of advanced oxidation processes in which the selective elimination of hydrophobic solution components, such as hydrophobic organic contaminants and hydrophobic DOM domains into which they partition, is desired.