The fate and persistence of the chemical agent Soman (GD; methylphosphonofluoridic acid 1,2,2-trimethylpropyl ester; a phosphonate nerve agent) delivered onto different soil constituents was investigated. Soil System Units (SSU) were designed and fabricated; atmospheric concentrations of GD above the soil surface were measured, and extractable GD determined. Results showed that in soil environments surface-controlled reactions can predominate over bulk solution hydrolysis, persistence of GD in soil may be expected for at least the days-to-months, that potentially life-threatening atmospheric levels of GD may be expected to be successively displaced into the overlying atmosphere in response to small (0.3mm) additions of moisture onto the soil. Successive GD displacements from soil, causing subsequent reoccurrences of GD in overlying atmosphere, had not been previously documented. GD displaced from soil into overlying atmosphere was not stoichiometric with respect to moisture levels applied to soil. GD-contaminated soil may present a potential hazard to unprotected individuals even when classic “All Clear” conditions exist. Investigation of GD extractability showed that longer contact times with soil constituents resulted in less GD being extracted: 24-hr extractions of GD using isopropanol yielded recoveries from: sand of 90-100% when GD was in contact ≤24hrs, 45% with 48hrs contact, and 16% with 72hrs contact; recoveries from Montmorillonite were approximately 40% when GD was in contact ≤48hrs, deceasing to approximately 30% with 72hrs contact. Investigation of soil factors affecting persistence showed: Coarse sand yielded highest levels of GD displacement from additions of soil moisture, measured as GD in the atmosphere above the soil surface; successive displacement of GD from the coarse and medium sands, and sandy loam soil, persisted over the days-to-weeks timeframe. Montmorillonite yielded lower individual-levels of GD displacement from moisture additions, but yielded continuing appreciable levels of atmospheric GD over the weeks-to-months timeframe. Potential toxicity of unextractable residual-GD in soil is unknown.