Immobilization of metals can be accomplished by decreasing wind-blown dust, minimizing soil erosion, and reducing contaminant solubility or bioavailability to the food chain. The addition of soil amendments, such as organic matter, phosphates, alkalizing agents, and biosolids can decrease solubility of metals in soil and minimize leaching to groundwater. The mobility of contaminants is reduced by the accumulation of contaminants by plant roots, absorption onto roots, or precipitation within the root zone. In some instances, hydraulic control to prevent leachate migration can be achieved because of the large quantity of water transpired by plants. Applicability The use of phytostabilization to keep metals in their current location is particularly attractive when other methods to remediate large-scale areas having low contamination are not feasible.
Remediation is difficult at locales having high metals concentration because of soil toxicity.
Studies also suggest that phytostabilization may reduce metal leaching by converting metals from a soluble oxidation state to an insoluble oxidation state. Performance Results from two phytostabilization projects are summarized in Table 1. The objectives of the field demonstrations were to stabilize the soil and to decrease the vertical migration of leachate to groundwater. Table 1 . SD Data Requirements Depth of contamination, types of heavy metal present, and level of contamination must be determined and monitored.