We take a closer look at 5 of best plants for phytoremediation. One of our most basic natural resource, soil, is threatened. The soil has been neglected and contaminated for decades now. Although, the global map of contamination is difficult to define, the European Environment Agency has identified heavy metals and mineral oil as the main soil pollutants. Knowing that just in Europe the number of polluted sites is expected to increase by 50% in the next 10 years, it seems clear that one of our biggest environmental challenges is under our feet. As landscape architects, should we not be aware of all our potential to play a role on the solutions side?
What is Phytoremediation?
Clean techniques to remediation are getting more popular, and most likely, you are already familiar to phytoremediation. Through this article, you will find a useful guidance on plants with proven qualities to naturally reduce, degrade or remove contaminants from soil and water. Advantages are outstanding: they do not involve visual impact, expensive engines and toxic chemicals. Do you remember Top 10 Reused Industrial Landscapes by Lisa Tierney? Landschaftspark, number five on the list, is a great model of phytoremediation in recreational projects. WATCH: Landschaftspark Duisburg-Nord | Industrienatur + Industriekultur
Best Plants For Phytoremediation
1. Indian mustard (Brassica juncea L.) Info: Brassica juncea (L.) Czern. – Indian Mustard
As International Journal of Molecular Sciences has published, heavy metals affect not only industrial sites but also cultivated land, spreading risks for human health. Brassicaceae species are really useful to accumulate certain metals while producing high quantities of biomass in the process, and Indian mustard is the star of this group.It can remove three times more Cd than others, reduce 28% of Pb, up to 48% of Se, and it is effective against Zn, Hg and Cu as well. However, what is unknown is that Indian mustard removed radioactive Cs137 from Chernobyl (Phytoremediation of Radiocesium-Contaminated Soil in the Vicinity of Chernobyl, Ukraine) in the 80´s as well.
2. Willow (Salix species). (White Willow)
The water loving plants beautify landscapes, however, it’s worth is not confined to its appearance only. They have a more interesting use for phytoremediation as well: their roots have demonstrated (Response of Salix alba L. to heavy metals and diesel) viability, accumulating lower levels of heavy metals than Brassicaceae, and they deal with Cd, Ni and Pb, and work even in mixed heavy metals like diesel fuel polluted sites.Maybe you remember Westergasfabriek Park in Amsterdam, which LAN talked about in the article Westergasfabriek Park Goes from a Polluted Gas Factory to an Award Winning Design by Gerard De Silva. It shows recreational and remediation features of willows through ponds and aquatic gardens. Large-scale systems for urban waste water are also effective, as the Swedish projects mentioned in Willows for energy and phytoremediation in Sweden do.
3. Poplar tree (Populus deltoides). (Populus deltoides W. Bartram ex Marshall eastern cottonwood)
The advantageous effect of poplar trees on soil and underwater has also been widely studied. Their secret lies in the naturally well-designed root system which take up large quantities of water.Chlorinated solvents such as trichloroethylene, or the well-known carcinogenic carbon tetrachloride (95% of substance removed) are the organic pollutants that hybrid poplars face better, according to research from National Institute of Environmental Health Sciences. What is more, PhytoPet(Bioremediation of Aquatic and Terrestrial Ecosystems), the Canadian database for bioremediation methods, remarks that poplar trees can degrade petroleum hydrocarbons like benzene, toulene and o-xylene. Although they are not very common in public gardens, you have one sample of poplar tree integration in this interesting LAN article, The Sensational Hive Project by World Renowned Grant Associates written by Erin Tharp.
4. Indian grass (Sorghastrum nutans) (Sorghastrum nutans (L.) Nash)
Research looked at how this Midwestern U.S. native plant benefits soil and ground water around them. Many people can find Indian grass growing along the roadsides without noticing its power to detoxify common agro-chemical residues such as well-known pesticides and herbicides related to atrazine and metalochlor.Indian grass is one of the nine members of the graminae family identified by PhytoPet(Bioremediation of Aquatic and Terrestrial Ecosystems), as capable to remediate petroleum hydrocarbons. The list includes other grasses like Common buffalo grass or Western wheatgrass, leading the ranking.
5. Sunflower (Helianthus Annuus L.) (Helianthus annuus L. common sunflower)
Experiments like Influence of the sunflower rhizosphere on the biodegradation of PAHs in soil reveals that sunflowers reduce different PAH level from soil, in an effective way, but what is really surprising is how varied range of contaminants they can accumulate. Heavy metals such as Pb, Zn (Heavy Metals Extraction Potential of Sunflower (Helianthus annuus) and Canola (Brassica napus)), N, P, K, Cd, Cu or Mn (Capability Of Heavy Metals Absorption By Corn, Alfalfa And Sunflower Intercropping Date Palm), seem to be its food, which is great news because sunflowers have a quick growth to start working soon.In fact, one month old plants reached the incredible goal of removing more than 95% of uranium in 24 hours, (SUNFLOWER (Helinathus annuus L.) – A POTENTIAL CROP FOR ENVIRONMENTAL INDUSTRY ) which shows their power to remove radioactive metals, including Cs and Sr from superficial underground water. When reinforcing the effect of sunflowers with other species, it seems highly successful for many sites, for example waste mining sites. – New plants are discovered every year, and the already known ones are included in experiments to determine the effects of pollutants exposure. There is no fixed recipe, but as you have checked, the results are more than promising and economically viable. What plants would you choose for Phytoremediation? Let us know in the comments below! Go to comments
Recommended Reading on Phytoremediation:
- Phytoremediation: Transformation and Control of Contaminants by Steven C. McCutcheon
- Phytoremediation: Role of Aquatic Plants in Environmental Clean-Up by Bhupinder Dhir
Article by Elisa García Nieto Return to Homepage