Analysis and characterization of natural organic matters in freshwaters

The properties of ‘soluble’ (<0.2 μm) organic matters of freshwaters are compared on the basis of their spectrometric properties (fluorescence and UV absorption), their complexation capabilities for Cu(II), their adsorption ability on kaolinite and their size (ultrafiltration). These parameters were studied for a series of various waters and their annual trends were measured. Correlations between the parameters related to organic matters and the concentrations of inorganic ions (particularly Fe, Al, Si, Ca) or pH were also examined. The results indicate that spectrometric parameters are mainly a measure of fulvic compounds of the water masses, whose origin is mostly the leaching of the surrounding lands. These compounds may be separated from other types of organic matters, from Si(IV) and Ca2+ and from a large portion of Fe by ultrafiltration fractionation. Elimination of fulvic compounds from water masses could occur by means of adsorption on solide silicate or CaCO3, but flocculation does not seem to play an important role. Their complexing ability is large.