STUDY OF INTERACTION OF DOC WITH ALUMINUM AND HYDROGEN-ION IN SOIL AND SURFACE-WATER USING A SIMPLE EQUILIBRIUM-MODEL

A simple equilibrium model involving the interaction of dissolved orga nic carbon (DOC) with Al and H+ is applied to soil solution and surfac e water data from the experimental HUMEX catchment in western Norway a nd the acidified Birkenes catchment in southern Norway. The model cove rs the major covariation in the components. Model testing and calculat ions of uncertainties in the results were undertaken by use of synthet ic data, i.e. data produced with the model taking estimated measuremen t errors into account. The DOC behaved only slightly different in vari ous soil solutions and surface water within one catchment, but differr ed substantially from the Birkenes to the HUMEX catchment. The binding of Al and H+ involved more sites per mg C of DOC in Birkenes, but the average binding strength was much weaker than in HUMEX. This differen ce may be induced by acidification and may increase the level of toxic inorganic Al in acidified areas. No significant difference has evolve d at this stage between the experimentally acidified and the control s ide of the HUMEX catchment.