NONCOVALENT INTERACTIONS BETWEEN ACENAPHTHENONE AND DISSOLVED FULVIC-ACID AS DETERMINED BY C-13 NMR T-1 RELAXATION MEASUREMENTS

Non-covalent interactions between C-13-labeled acenaphthenone (C-13-la beled in the carbonyl position) and Suwannee River fulvic acid in a me thanol/D2O solvent have been examined using C-13 NMR T-1 relaxation me asurements. The influence of solvents upon the non-covalent interactio ns were assessed by examining acenaphthenone in pure solvents of varyi ng solvation capacity (chloroform, methanol, methanol/D2O). Interactio ns with fulvic acid were examined as a function of acenaphthenone and fulvic acid concentrations, fulvic acid counter-cation (H+ or Na+), an d pH. In the presence of fulvic acid in a methanol/D2O solvent, three non-covalent interactions were identified: a weak sorption interaction between acenaphthenone and fulvic acid, an enhanced solubilization of acenaphthenone by fulvic acid, and an interaction between just the so lvent and acenaphthenone. The enhanced solubilization is hypothesized to arise from fulvic acid forming hydrophobic regions that are predomi nantly solvated with methanol and have excluded water. Acenaphthenone in these hydrophobic regions displays similar behavior to when It is d issolved in pure methanol. The ability of fulvic acid to form hydropho bic regions was found to be dependent upon the identity of the fulvic acid counter-cation and upon pH.