Fluorescence spectroscopy of coastal and marine waters

Abstract Fluorescence measurements were performed on a large variety of water samples collected in different estuaries and oceans over the world. Spectra were recorded with a high-sensitivity spectrofluorometer without preconcentration of the samples. Qualitative and quantitative parameters of fluorescence were determined on fully corrected emission, excitation and synchronous fluorescence spectra. Critical conditions required to record the corrected fluorescence spectra of open marine water are emphasized. General results show that with an adequate excitation wavelength (313 nm) the fluorescence signature can be used to differentiate water masses. The variation of the emission wavelength maxima for excitation ranging from 250 to 410 nm give strong evidence that as far as the humic substances themselves are concerned, the fluorescence spectra of the natural water samples we investigated contain at least two distinctive classes of fluorophores. Synchronous spectra as well as all other fluorescence results we have obtained can be accounted for on the basis of a model which includes both the existence of these two classes of fluorophores in different proportions and variations in nature and the distribution of the fluorophores within each class.