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Main Title Investigation of the Electrostatic Properties of Humic Substances by Fluorescence Quenching.
Author Green, S. A. ; Morel, F. M. M. ; Blough., N. V. ;
CORP Author Woods Hole Oceanographic Institution, MA. Dept. of Chemistry. ;Massachusetts Inst. of Tech., Cambridge. Dept. of Civil Engineering.;Environmental Research Lab., Athens, GA. Office of Research and Development.
Publisher 1992
Year Published 1992
Report Number EPA-R-815293; EPA/600/J-93/521;
Stock Number PB94-158821
Additional Subjects Electrostatics ; Humic acid ; Fulvic acid ; Environmental effects ; Humus ; Reprint ; Decomposing organic matter ; Cations ; Photochemical reactions ; Surface chemistry ; Reaction kinetics ; Environmental transport ; Land pollution ; Water pollution ; Molecular weight ; pH ; Fluorescence quenching
Library Call Number Additional Info Location Last
NTIS  PB94-158821 Some EPA libraries have a fiche copy filed under the call number shown. 07/26/2022
Collation 10p
A fluorescence quenching technique was employed to explore the electrostatic properties of fulvic acid (FA) and humic acid (HA). Cationic nitroxides were found to be up to 16 times more effective than neutral analogues in quenching the fluorescence of humic materials. The result is attributed to the enhanced Coulombic attraction of cations to the anionic FA or HA surface and is interpreted as an estimate of surface potential. Reduction of molecular charge at low pH and shielding of charge at high ionic strength produced diminished enhancements, consistent with this interpretation. High molecular weight fractions of HA have a higher apparent surface potential than lower molecular weight fractions, indicating that larger humic molecules may have an enhanced ability to bind metal ions. (Copyright (c) 1992 American Chemical Society.)