Preparative gel fractionation of NOM for ecological studies - The fate of mercury in aquatic ecosystems

Forty years ago it was shown that dissolved humic substances (HS) in water could be separated into a number of different size fractions using the gel-matrix Sephadex (1). Since then a number of different techniques and methods have been introduced for the purpose to define and describe the physical properties and chemical composition of HS. During the last few decades the awareness of the ecological importance of this complicated organic matter has increased and it is realized that more knowledge on biological properties and biological functions of HS are needed. We have re-introduced preparative gel-filtration, in order to be able to learn more about the fate of micro pollutants in fresh-water ecosystems. Mercury (Hg) is an element of considerable health concern, mostly due to its global distribution and its bio-magnification potentials in water. The important role of HS both as carrier and as mediator of Hg transport from soil to the surface water is demonstrated by elevated Hg concentrations in humic-rich waters. The purpose of the work to be presented is to fractionate “Hg-spiked” dissolved natural organic matter (NOM), and to investigate the Hg distribution on the NOM in detail. The biological properties of the resulting fractions will later be studied in co-operation with ecologists.