Abstract: A method for the in-situ remediation of contaminants including soluble metals more noble than iron and halogenated hydrocarbons that are present in groundwater, absorbed to soil, and exist in the free product state in a soil volume. An inert pressurized gas in combination with an atomized iron powder-water slurry is used to inject pre-determined quantities of reactive zero valent iron powder relative to the quantity of contaminants present in the soil for obtaining preselected rates of remediation with minimum quantities of iron powder and with reaction products within a preferred acidic pH range. Features, such as particle surface area and carbon content, are identified that enhance the reactivity of the iron powder.