Some Aspects of the Characterization of Humic Substances in Lake Waters

Several different parameters, including elemental and functional group analyses, solid state 13C NMR spectroscopy and E4/E6 ratios, were measured on the dissolved organic matter isolated and fractionated with ultrafiltration and XAD-8 techniques from two highly colored lakes in Finland. The results of the analyses are discussed in relation to the sample isolation (DOM, FA or HA). Multivariate analyses showed some trends in the average molecular masses, in the results of elemental analyses and, especially, in the characteristics of the 13C NMR spectra so far obtained.