The effect of humic acids on the water solubility and water-organic carbon partitioning of fluorene and its NSO-heteroanalogues: carbazole, dibenzofuran, and dibenzothiophene.

The solubilizing effect of humic acids on fluorene and its NSO analogues carbazole, dibenzofuran and dibenzothiophene has been studied. The interaction between these substances and humic acids was found to depend significantly on the actual humic acid concentration. A pronounced decrease in the interaction constant, as well as in the water-organic matter partitioning coefficient was observed with increasing humic acid concentration. The effects are discussed in terms of concentration dependent macromolecular structural changes in the humic acids. A linear free energy relation for the interaction is suggested.