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EFFECTS OF ALUMINUM-INDUCED AGGREGATION ON THE FLUORESCENCE OF HUMIC SUBSTANCES. (R822251)
Citation:
Sharpless, C. M. AND L. B. McGown. EFFECTS OF ALUMINUM-INDUCED AGGREGATION ON THE FLUORESCENCE OF HUMIC SUBSTANCES. (R822251). ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 33:3264-3270, (1999).
Description:
Aluminum-induced aggregates of terrestrial and aquatic humic acid standards from the International Humic Substances Society are shown to be fluorescent by means of a multiwavelength fluorescence anisotropy experiment in which the data was treated with a model for nonspherical particles. While aggregates of aquatic humic acids appear in the fluorescence signal at both short and long excitation wavelengths, aggregates of terrestrial humic acids are detected only at the long wavelength. Furthermore, the results indicate that emission obtained at longer excitation wavelengths is representative of smaller particles. At pH 4, the aquatic humic acids appear to exist in an extended conformation, whereas the terrestrial humic acids show less extension. The size and shape of the fluorescent particles display a complex dependence on Al concentration. Both enhancement and quenching of fluorescence are observed in the total luminescence spectra upon Al addition. However, quenching is shown to be the result of decreased humic acid concentration due to precipitation by Al rather than photophysical processes.