Differentiation of organic matterʹs properties of the Rio Negro basin by cross-flow ultra-filtration and UV-spectrofluorescence

Cross-flow ultra-filtration from the Rio Negro basin (Amazon) samples was undertaken with tangential flow equipment producing concentrated fractions on which UV-fluorescence produced information about the individual characteristics of the organic matter in different size fractions. The major novelty is that conductance (ionic strength) and fluorescence were both linearly (r>0.95) correlated with total organic carbon (TOC) determined at each individual station. The physico-chemical characteristics (fluorescent sensitivity and electro-mobility) of the organic carbon seem to be constant within each size fraction (particulate, colloidal and dissolved). The complexing capacity of copper was found to be elevated, with as consequence that more than 80% of the metal transport occurred in the dissolved phase. By comparing these various results, we have deduced that the functional groups responsible for complexation are not the same as those responsible for fluorescence and conductance.