Investigations of the Molecular Weight,Free Radical and Metal Interactions of Isolated Aquatic and Soil Fulvic Acid.

摘要

Soil and aquatic fulvic acid were isolated from a 3horizon and a Podzol soil and the Oyster River in Lee, N.H.,respectively. The isolated materials were characterized initially by total acidity,functional group (carboxyl,carbonyl),elemental (C,H,N) and UV-visible spectrophotometric analyses. The molecular weights of soil and aquatic fulvic acids were determined using a cryoscopic method of analysis. Data were corrected for the dissociation of carboxyl groups. Dissociation corrected number average molecular weights of 644and 626were obtained for soil and aquatic fulvic acid,respectively. Additional studies were performed on the free radical specie associated with fulvic and humic acids. Electron paramagnetic resonance (epr) spectra for soil fulvic and humic acids reveal an unsymmetric first derivative signal with g-values of 2.0037 + 0.0002and line widths of 3.3to 5.6Gauss. Analysis of the relative spin concentration revealed a free radical concentration pattern;soil humic acid,aquatic humic acid,soil fulvic acid,aquatic fulvic acid. Deoxygenated aqueous solutions of soil and aquatic fulvic acid were titrated with base to determine any change in the free radical concentration as a function of pH. The free radical signal showed a dramatic increase in intensity at pH values greater than 8. A Henderson-Hasselbalch equation was used to explain increases in the free radical concentration with pH. It was proposed that quinone and hydroquinone molecules interact to produce semiquinone molecules at high pH. (Portions of this document are not fully legible)