Differential thermal analysis of sedimentary humic acids in the light of their origin

Results of studies on thermal decomposition using differential thermal analysis (DTA) of humic acids (HAs) extracted from the Szczecin Lagoon bottom sediments as dependent on their origin are presented in this paper. The results show that elemental composition and parameters of thermal decomposition can be promising parameters for classification of sedimentary HAs. Three types of sediments were distinguished according to their origin: allochthonous (mainly anthropogenous), terrestrial, and aquatic. Significant correlations were found between the HA elemental composition and the parameters of their thermal decomposition. The results show that nitrogen content in HAs is inversely proportional to aromaticity of HA molecules and to their heat of combustion.