Phytoextraction

? The cost of phytoextraction is fairly Inexpensive;

? The contaminant is permanently removed from the soil ;

? The amount of waste material that must be disposed of is substantially decreased ( up to 95%);

? The contaminant can be recycled from the contaminated plant biomass.

? Metal hyperaccumulators are generally slow-growing with a small biomass and shallow root systems;

? Plant biomass must be harvested and removed, followed by metal reclamation or proper disposal of the biomass;

? Metals may have a phytotoxic effect.

Phytostabilization

? The disposal of hazardous material or biomass is not required ;

? Very effective when rapid immobilization is needed to preserve ground and surface waters ;

? The presence of plants also reduces soil erosion and decreases the amount of water available in the system;

? Soil removal is unnecessary;

? It has a lower cost and is less disruptive than other more-vigorous soil remedial technologies;

? Revegetation enhances ecosystem restoration;

? Method with good results in prevention of acid mine discharges and metal stabilization.

? The contaminants remain in place;

? The vegetation and soil may require long-term maintenance to prevent rerelease of the contaminants and future leaching;

? Vegetation may require extensive fertilization or soil modification using amendments;

? Plant uptake of metals and translocation to the aboveground portion must be avoided;

? The root zone, root exudates, contaminants, and soil amendments must be monitored to prevent an increase in metal solubility and leaching;

? Phytostabilization might be considered to only be an interim measure;

? Contaminant stabilization might be due primarily to the effects of soil amendments, with plants only contributing to stabilization by decreasing the amount of water moving through the soil and by physically stabilizing the soil against erosion.

Phytovolatilization

? The contaminant, mercuric ion, may be transformed into a less toxic substance;

? Contaminants could be transformed to less-toxic substances;

? Contaminants or metabolites released to the atmosphere might be subject to more effective or rapid natural degradation processes such as photodegradation.

? The contaminant or a hazardous metabolite might be released into the atmosphere;

? The contaminant or a hazardous metabolite might accumulate in vegetation and be passed on in later products such as fruit or lumber;

? Low levels of metabolites have been found in plant tissue.

Rhizofiltration

? The ability to use both terrestrial and aquatic plants for either in situ or ex situ applications;

? Species other than hyperaccumulators may be used;

? An ex situ system can be placed anywhere because the treatment does not have to be at the original location of contamination.

? The constant need to adjust pH to obtain optimum metals uptake;

? Plants may first need to be grown in a greenhouse or nursery;

? Periodic harvesting and plant disposal are required;

? Tank design must be well engineered;

? A good understanding of the chemical speciation/interactions is needed;

? The chemical speciation and interaction of all species in the influent have to be understood and accounted for;

? Metal immobilization and uptake results from laboratory and greenhouse studies might not be achievable in the field.