THE PERSULFATE OXIDATION OF A SOIL HUMIC ACID

We extracted humic acid (HA) from an Encinillas soil, Xeroumbrepts, Inceptisols, and oxidized it with potassium persulfate for 2 hours at 140°C. The oxidation products, after methylation, were analyzed by direct injection into a gas chromatographic-mass spectrometric computer system. The most abundant compounds isolated from the HA oxidation products were n-C16 and n-C18 fatty acids, followed by several benzenecarboxylic and phenolic acids. Dicarboxylic acids and dialkyl phthalates constituted only a relatively small proportion of the isolated compounds. No n-alkanes were detected. Persulfate degrades only 40 percent of total weight HA, leaving a residue that can easily be recovered for further structural investigations. Persulfate, therefore, may be used as first oxidant in a sequential HA degradation.