Characterization by fluorescence of the dissolved organic matter in natural water. application to fractions obtained by tangential ultrafiltration and XAD resin isolation

Abstract

A tangential ultrafiltration procedure has been applied to separate the dissolved organic matter in the order of decreasing molecular weights of two water samples from a dam reservoir. Four fractions have been isolated and their fluorescence emission spectra, fluorescence excitation spectra and their fluorescence quantum efficiencies were compared with those of macroporous XAD8 and XAD4 extracts isolated from the same water samples. A clear one to one correspondence between the ultrafiltrated fractions and the resin extracts was observed which indicates that the two methods lead to isolate very similar type of organic material. The “apparent”; mean molecular weights deduced for humic, fulvic and hydrophilic acids appear consistent with previous values drawn from waters of various origins. Moreover, by using the fluorescence spectra characterizing each of these acids we have been able to estimate the contribution of their respective fluorescence to the total fluorescence spectra of the two studied crude water samples.