Dissolved humic substances DHS

Special precautions are unnecessary in DHS determinations, although extensive exposure to light should be avoided as UV radiation leads to the partial destruction of humic com- 

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The amphiphilic nature of dissolved humic substances (DHS) lends them the ability to associate with both hydrophobic organics and polar or ionic species [62-64]. Inorganic ions or mineral colloids in solution will interact with the electrically active surface of humic material in solution or in the solid phase according to the same bonding forces which lead to the association between SP0M and the solid mineral matrix. Humic matter in water is associated with... 

Dissolved humic substances (DHS) are the main constituents of the dissolved organic carbon (DOC) pool in surface waters (freshwaters and marine waters), groundwaters, and soil porewaters and commonly impart a yellowish-brown color to the water system. Despite the different origins responsible for the main structural characteristics of DHS, they all constitute refractory products of chemical and biological degradation and condensation reactions from plant or animal residues and play a crucial role in many biogeochemical processes. 

CMC Critical micelle concentration COMs Complex organic mixtures DHS Dissolved humic substances... 

It is commonly reported that dissolved humic substances (i. e., DHS) tend to coat mineral particles and thereby affect the surface chemistry of those materials. DHS coat the surfaces of solid particles even when they are present at very low concentrations. They furthermore impart a negative charge to the surfaces which they coat. The organic coating is expected to have a great significance on subsequent adsorption of various pollutants [88,91-93,287,288]. 

Various workers have attempted to relate DHS measurements to dissolved organic carbon concentrations (e.g., Wheeler, 1977 Laane and Koole, 1982 Liebezeit, 1988 Ferrari et al., 1996). ITie results, however, were far from conclusive. After its introduction by Kalle (1949, 1963), fluorescence spectrometry has become the most widely used technique to determine DHS. Owing to their largely conservative nature (e.g., Laane, 1981), the fluorescence properties of DHS can be exploited for estuarine mixing studies (Zimmerman and Rommets, 1974) or in remote sensing applications (e.g., Karabashev et al., 1993 Reuter et al., 1993). Standardization of the measurements, however, still presents a major problem as the only seawater standard available is that from the International Humic Substances Society. 

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