Fluorescence Characterization of IHSS Humic Substances: Total Luminescence Spectra with Absorbance Correction

Total luminescence spectroscopy was applied to the fluorescence characterization of humic substances obtained from the International Humic Substances Society (IHSS). Results show that total luminescence spectra, represented as excitation−emission matrices (EEMs), may be used to discriminate between soil-derived and aquatic-derived IHSS humic substances and between humic and fulvic acids derived from the same source (soil or aquatic). Ionic strength in the range of 0−1 M KCl and humic substance concentration in the range of 5−100 mg/L had little effect on the fluorescence spectral characteristics of the humic substances, while pH had significant effects as expected. Absorbance correction was shown to be essential for accurate representation and comparison of the EEMs of the humic substances at high concentrations.