In various areas of the world we are seeing more and more sites being polluted from industrial chemicals from factories to petrochemicals from oil refineries it is near inevitable that some of it will leach into surrounding soils and waterways. Even if we halted the processes that cause these problems there is still the question of how to deal with the damage that has already been done.
Phytoremediation is a process that uses plants to clean contaminants from soils. This process can be used to clean up soils polluted with heavy metals like aluminum and zinc, petroleum hydrocarbons for example from oil refinery sites and other chemical substances. The process works by choosing plants suited for the region and soil conditions that preferably grow quickly and placing them in the contaminated sites. These plants them do two things:
- They help slow down or stop the leaching of chemicals further outwards. The roots of the plants basically acts as a suction system as it takes up water and minerals from the soil.
- They absorb some of the pollutants in the soil as they uptake water and minerals. These contaminants are then incorporated into the plants biomass and can no longer spread or affect the health of the soil or they are transformed into less harmful substances.
In some cases when the plants store the chemicals in their biomass then a process called phytomining can be used, this is where the plant is harvested and incinerated then the heavy metals can be extracted from the ashes.
Willow is a good choice for phytoremediation and is a fast growing tree and can generate a lot of biomass quickly thus being able to absorb more contaminants at a faster rate. It can also absorb a wide variety of different types of pollutants where as most plants are only able to to absorb one or two specific specific chemicals. Because willow is a tree it is also a good choice as it has a deeper root system and can access further down into the soil than other plants like grasses with shallow root systems. However grasses and smaller perennial plants can be good choices if the only the top surface of the soil is affected.
The only down side of phytoremediation is that it takes time and patience even with the fastest growing of plants. It can sometimes take several years for a site to be restored using this process. However, it a low cost and environmentally friendly approach to dealing with polluted sites.