Total luminescence spectroscopy of NOM-typing samples and their aluminium complexes

Abstract

Samples from the Scandinavian NOM-typing set were studied by total luminescence spectroscopy (TLS). All samples showed fluorescence spectra typical for NOM of aquatic origin, or fulvic acids from both aquatic and terrestrial sources, but were lacking additional features typical for humic acid and leaf litter extract spectra. A comparison of the NOM spectra from the same source, but isolated by different methods, suggests that the reversed osmosis isolation procedure removes a small percentage of all fluorescing compounds when compared to the evaporation procedure. Spectral differences between NOM samples of different age suggest reduction of the more highly conjugated aromatics with increasing residence time in the water either by precipitation or by biodegradation to simple phenolics. NOM samples were spiked with aluminium, which led to pronounced qualitative changes in the NOM TLS. The most prominent change was the appearance of a shoulder at λ ex λ em = 350 375 . The fluorescence intensity at this wavelength pair was found to be positively correlated with inert and “bound” Al, as determined by fast reaction with 8-hydroxy-quinoline and capillary electrophoresis, respectively.