Fulvic acid characterization in an alluvial sediment sequence: differences between clay and sand environments

Abstract

Fulvic acids (FAs) from the whole Quaternary sequence (to a depth of 26 m) of the alluvial sediment of the Sava river (taken from a site in Novi Beograd, Belgrade, Yugoslavia) were investigated with the aim of examining the effect of the environment (clay or sand) on their characteristics. Characterization of the FAs was carried out by correlating the results obtained by various instrumental techniques (u.v.-vis. and i.r. spectroscopy, fluorimetry). Differences were noticed between the FAs, depending on whether they originated from sand or clay, which indicates that the hydrogeological environment represents an important factor in determining their characteristics, though the role of the precursor material may be significant. FAs found in clay layers are less aliphatic, have a greater non-aliphatic hydroxyl group content and exhibit more similar fluorescence ntensities compared to FAs originating from sand. The greater mutual similarities of the clay FAs in comparison to those from sands is a result of diagenesis occurring in a more "closed" system.