Abstract: Soils are decontaminated in situ by transporting peroxysulfate ions through the soil under the influence of an electric field. The electric field is maintained between one or more anodes and one or more cathodes inserted directly into the contaminated soil and geometrically disposed relative one to the other to take full advantage of a positively biased DC voltage applied between said one or more anodes and one or more cathodes. An aqueous solution of a strong oxidant, either peroxymonosulfate or peroxydisulfate, is added to the contaminated soil. The electric field induces the movement of peroxysulfate ions principally by electromigration and to a lesser extent by electroosmosis. Organic contaminants in the soil are oxidized by the peroxysulfate ions. For very recalcitrant contaminants, electric field-induced heating of the soil produces sulfate radical anions. In most cases the peroxysulfate ions or sulfate radical anions oxidize the contaminants to carbon dioxide and mineral acids.