This method utilizes the high reductive potential of the elementary (zero valent) iron nanoparticles that oxidize immediately upon contact with the groundwater. Consequently, a large amount of electrons is released, causing a rapid drop in the environment's oxidation-reduction potential. This technology is most frequently used for difficult-to-treat pollutants such as chlorinated hydrocarbons (PCE, TCE, DCE, VC) or for polychlorinated biphenyls (PCBs).