Binding characteristics and dissociation kinetics for iron(II) complexes with seawater extractable organic matter and humic substances in a compost

A steel-slag/compost fertilizer can be useful in supplying complex Fe(II) species to barren coastal regions. Seawater extractable organic matter (SWEOM) was examined for use as a novel chelator of Fe(II) in the compost. The dissociation kinetics for Fe(II)-SWEOM were evaluated, based on the rate of ligand-exchange with ortho-phenanthroline. The ΔH for the Fe(II)-SWEOM (19 kJ mol^-1) was significantly smaller than the corresponding values for Fe(II) complexes with humic substances (27 kJ mol^-1), suggesting that the Fe(II)-SWEOM is kinetically less stable.