Mobility of Iron-Cyanide Complexes in a Humic Topsoil under Varying Redox Conditions

Abstract

The potentially toxic Fe-CN complexes ferricyanide, [Fe III (CN) ) to which we added ferricyanide (20 mg l −1 ). We varied the redox potential (E H ) from −280 to 580 mV by using O 2 , N 2 and glucose. The decrease of E H led to decreasing concentrations of Fe-CN complexes and partial reductive dissolution of (hydrous) Fe and Mn oxides. The dynamics of aqueous Fe-CN concentrations was characterized by decreasing concentrations when the pH rose and the E H dropped. We attribute these dependencies to adsorption on organic surfaces, for which such a pH/E H behavior has been shown previously. Adsorption was reversible, because when the pH and E H changed into the opposite direction, desorption occurred. This study demonstrates the possible impact of soil organic matter on the fate of Fe-CN complexes in soil.