Lesley Stout
The effects of ammonia concentration on the bioremediation of heavy metal ions in subsurface environments.
BSES Senior Research 2003

The adsorption of zinc(II) onto goethite facilitated by shewanella putrefaciens was studied as a function of ammonia concentration. Ammonia has been found to complex with zinc in aqueous samples and inhibit adsorption and coprecipitation of zinc on iron-oxide surfaces.

The model organism, shewanella putrefaciens, has been shown to use iron-oxide minerals as electron acceptors for anaerobic growth. At pH 8.5, ammonia showed a statistically significant, but minor, effect on immobilization of zinc. There was a decrease in percent zinc strongly bound into the goethite structure, and a corresponding increase in both aqueous zinc concentrations and bound zinc concentrations, as ammonia concentrations increased from 0mM to 300mM. It is suggested that at higher pH, this effect would become more dramatic and influencial for bioremediation of zinc and other heavy metals.