Aquatic colloids composed of humic substances

Natural aquatic colloids from different Gorleben aquifer systems have been investigated. In selected groundwaters, colloids are separated by ultrafiltration to different size fractions from 1 to 1000 nm. The chemical composition of colloids and filtrate fractions are analysed for major and minor constituents. The colloids in these groundwaters are found to be a composite of organic compounds and polyvalent metal ions with the size range below 100 nm. The separation and characterization of these compounds show that they consist mainly of humic and fulvic acids. More than 94% of polyvalent metal ions are found as bound on the groundwater colloids. The concentration of metal ions sorbed on the ''humic'' colloids is below the proton exchange capacity of the corresponding humic and fulvic acids, indicating an ordered complexation of metal ions with functional groups. (authors). 20 refs., 4 figs., 4 tabs