Photochemical Properties of Humic Substances: Toward a Better Characterization of the Photosensitizing Chromophores (Localisation, Fluorescence Characteristics)

The ability of humic substances (HS) to generate reactive species under excitation by solar light is an environmentally important property leading to the possible elimination of organic pollutants in all the terrestrial compartments. The capacity of dissolved HS to interact with solar light also opens the way to characterization studies based on photochemistry. The objective of our work is to characterize the chromophoric constituents of HS and of coloured natural organic matter that generate singlet oxygen and oxidize organic compounds under excitation [1]. We tried to answer two questions: 1) are they randomly distributed within the humic or concentrated in some specific moieties and 2) do they have some spectral characteristics that may be of help for further identification?