Certain exemplary compositions, methods, and systems are disclosed that can be useful for reducing a concentration of a contaminant associated with a medium, which can be any substance or material, such as soil, water, air, and/or fluid. In one exemplary method, the medium is treated with Fe-MGDA and an oxidizing agent in amounts effective to oxidize at least a portion of the contaminant. It is emphasized that this abstract is provided to comply with the rules requiring an abstract that will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure.