CHANGES IN THE HUMIC ACID-METAL COMPLEX-FORMING CHARACTERISTICS DEPENDING ON THE HUMIFlCATION DEGREE

摘要

The aim of this study was to determine the Cu(II) complexing capacity and stability constants of Cu(II) complexes of humic acids isolated from two well-characterized raised bog peat profiles in respect to the basic properties and humification characteristics of the studied peats and their humic acids. Found complex stability constants (logK=4.06-5.73) significantly change within the studied bog profiles and are well correlated with the age and decomposition degree of the peat layer from which the humic acids have been isolated. None of the basic characteristics of humic acids (such as concentration of carbox-ylic groups and total acidity, hydrophobicity, and others) alone can fully explain the complex-forming capacity of humic acids thus indicating complexity of the metal -natural organic matter interaction. Among factors that influence this complex forming process, molecular mass and ability to form micellar structures (supramolecules) of humic substances are of key importance.