Why the free ion activity model does predict Cd uptake by green algae in the presence of humic acid, but fails for Pb

摘要

The role of humic acid on Cd and Pb biouptake by green algae Chlorella kesslerii was studied in detail. Experimental data revealed that in the presence of 10mg·L humic acid, cellular Cd corresponded to that expected from free Cd measurements, while cellular Pb exceeded that predicted by the free ion activity model (FIAM). The obtained results suggest that simplified equilibrium models such as free ion activity model and biotic ligand model can be applied successfully to predict Cd bioavailability, while they underestimate biouptake of lead. The extension of the FIAM by taking into account formation of a ternary complex at the algal surface, allowed for overcoming the observed discrepancy for lead.