Properties of Humic Acids as a Parameter Characteristics for Lake Bottom Sediments

Abstract

The research studied the properties of humic acids formed in lake sediments of varying physicochemical parameters. It was found that humic acids formed in different types of sediments differ predominantly in their elemental composition and spectrometric properties. Humic acids formed in sediments containing carbonates are principally characterised by a significantly lower carbon content in addition to a significantly higher nitrogen and hydrogen content than those derived from carbonate-free sediments. The characteristic feature of humic acids synthesised in lake bottom sediments containing a high number of carbonates is the presence of additional absorption bands (at about 404 and 660 nm) in UV–vis spectra connected with the presence of structures originating from pigments. These bands hinder the interpretation of the results obtained and make their comparison with humic acids of soil origin rather difficult, although they may constitute a specific diagnostic feature in long-term analyses of the progressive acidification of lakes.