Phytoremediation is the use of plants to partially or completely remediate contaniments from soil, sludge, sediments, wastewater and ground water.
An anomaly of a certain species of plants, hyperaccumulators, have the ability to grow in noxious soils and accumulate relatively high amounts of heavy metals and organic pollutants in the aerial organs (plant tissues above ground vs. roots that are underground) with little to no toxic effect on the plant itself. There are three main differences between hyperaccumulators and flowering plants:
Enhanced rate of heavy metal uptake without phytotoxic (plant-toxic) damage.
Faster root to shoot translocation, meaning small ions, or rather toxic ions, move quickly from soil to root to shoot, the harvestable aerial plant tissue.
A greater ability to detoxify and sequester heavy metals in aerial organs.
Phytoremediation: using plants to remove toxic elements is accomplished by six different techniques.
Phytofiltration: uses plants to clean water systems.
Phytostabilization: plants that stabilize toxic materials within the soils.
Phytovolatilization: occurs when plants extract metals and release them into the air.
Phytoextraction: where metals are translocated (moved) and accumulated in harvestable shoots (aerial plant tissue) and incinerated.
Phytodegradation: plants use their metabolism to break down pollutants to non-pollutant compounds.
Rhizosphere degradation: breakdown of metals by rhizospheric microorganisms (organism related to the soils around plants roots)
One well known disaster, Chernobyl, has had multiple instances of using hyperaccumulators for bioremediation. In Germany, France, Sweden and Russia, months after the meltdown, fresh mushrooms contained 4 times (dried contained 20 times!) the acceptable rates of Cesium, traceable to Chernobyl! Twenty-two species of mushrooms were found to have Strontium-90 and Cesium-137 just a few months after the disaster.
Sunflowers are being used at the Fukushima nuclear disaster site after experimentation at Chernobyl proved hyperaccumulators amazing natural ability.
On many levels, the plant’s biomass or aerial plant organs are easier to incinerate than storing large quantities of a non-renewable, precious, life giving source that is SOIL! And to see a field of plants out there growing and you’d be able to harness nature, to correct our mistakes, it’s one of those things you feel really good about. (Baylock 1997)
Hyperaccumulators are a viable option for remediation of man to become more symbiotic with the natural world. Maybe you could try this at home with the old heating oil spills especially on above ground tanks!
FUN FACT! mushrooms, in the kingdom fungi, acquire food by dissolving molecules including heavy metals.
List of Hyperaccumulators
All you need Is Biology
Metal Hyperaccumulation in plants: A Review focusing on Phytoremediation Technology
Bioremediation: Microorganisms Cleaning the Environment
This is a great little site produced by 10th graders!
Mushroom photo from http://ibhomeremedies.com/belarusian-mushrooms-found-to-be-contaminated-with-radioactive-cesium/
Image of sunflowers at Fukushima