Artificial permeable redox barriers for purification of soil and ground water: A review of publications.

Artificial permeable barriers are used for purification of soil- and groundwater from organic (Cl-containing hydrocarbons and Cl-pesticides) and inorganic (heavy metals and nitrates) pollutants. Most of the created redox barriers are based on introducing electron donors-both inorganic (most often, Fe and Fe(II)) and organic. By their construction type, they are subdivided into one-time filled barriers arranged in trenches and multiple-time filled barriers that use boreholes for reagent injection. Fe barriers operate not only as reducers but also as sources of newly formed Fe(III) colloids adsorbing elements with permanent and variable valence. Iron sulfides are also used as a reagent, while Fe(II) and S(-I, -II) serve as reducers. Biochemical redox barriers are also applied, in which the activity of natural anaerobic metal-reducing bacteria is stimulated by adding an available organic substance. [ABSTRACT FROM AUTHOR]