Larger Metal Affinity of Freshwater Dissolved Organic Matter in Wastewater Affected Rivers

In freshwater, complexation of trace metals by dissolved organic matter (DOM) alleviates metal toxicity. The toxic effect of metals is modelled by the biotic ligand model (BLM). Usually it is assumed that different aquatic DOM samples have equal metal affinity. However, our results showed a 4-fold (Cu) to 10-fold (Cd, Ni, Zn) variability in metal affinity. Metal affinity of DOM from water bodies that receive important wastewater inputs is higher than that of natural DOM. WHAM6 underestimates metal complexation in these waters by an average factor of 3. The BLM assumption of equal DOM quality may be violated in such water bodies, and the BLM is likely to set over-protective water quality criteria.status: publishe