hide
Free keywords:
-
Abstract:
Adsorption of the DOM on XAD-2, PVP and Polyamide-6 at different pH was studied.
Adsorption was significant pH depending. Polyphenols in the adsorbed fractions were
determined by GLC. OH and CO2H groups preferentially in ortho- and meta-position were
predominate and developed hydrogen bridge bonding to proteins. By this mechanism
polyphenol humic matter and labile substrates (proteins and carbohydrates) coexist in a same
molecular matrix. Fractionation experiments with Sephadex, PAGE and IEF revealed a
complex structure in the DOM with varying molecular weight pattern. Three major fractions
were found with different subunits. Molecular weights ranged between 1,500 to 90,000
Dalton. The high molecular weight substrates are stratified and corresponded with the
autotrophic and heterotrophic activity in their dynamics and distribution. Humic substrates
contained acidic groups with IEPs between pH 2-3. Polyphenols, proteins and acidic
glycoproteins were associated in these fractions. These humic substrates showed high free
electrophoretic mobility in the PAGE experiments. Flexible structure units were confirmed.
Free dissolved monomeric carbohydrates existed in only low steady state concentrations.
Bound polymeric carbohydrates showed 10 to 100 times higher concentrations and significant
gradients that corresponded with autotrophic and heterotrophic activities.
