Characterization of humic substances extracted from Canadian lake sediments

Abstract

Humic substances (HS) were extracted from the sediments of four Sudbury area lakes, namely, Tilton, Clearwater, Silver, and Ramsey Lakes, with the aid of 0.1 M Na4P2O7 and 0.5 M NaOH solutions. The HS (humic and fulvic acids) were purified and characterized using the methods of elemental analysis, visible spectroscopy (E4/E6 ratio), FTIR, and solid-state 13C CPMAS NMR. A substantial amount of information with regard to the composition and chemical nature of lake sediment HS was obtained. The results obtained for the Sudbury area lake sediments were compared with one another and with HS from other sources, such as soils. The elemental composition, atomic ratios, E4/E6 ratios, and FTIR and NMR features of the samples from the above lakes were found to be nearly identical, suggesting that HS formed in the Sudbury area have similar chemical properties. Compared with soil HS, the Sudbury lake sediments HS have undergone a low degree of aromatic condensation and are considerably more aliphatic in nature. Keywords: humic substances, characterization, lake sediments, extraction, 13C NMR.