Greetings readers, I have been slacking on making regular blog posts, but we all know life gets hectic before it calms down.
Today, I will be writing about some common plants used in restoration projects of contaminated sites, in a location such as Southern Ontario.
I use Southern Ontario as my location because that is the area in which I am most familiar with in terms of species, though some species are transferable to other locations of similar climate.
When working to restore a contaminated site, one will seek plants that can thrive in environments with heavy metals, they can absorb and break down the contaminants, and they will grow and thrive with the surrounding ecosystem and/or may be found at a similar site.
Native prairie species are excellent because they are accustomed to open spaces, the wind will not blow them away, they have very deep roots, they grow quickly, provide a soil base which builds the soil community and nutrient profile for larger species such as trees to begin to establish, require very little maintenance once planted, and they provide a habitat to reintroduce organisms such as small animals, insects, and birds.
These plants can be used for more than decontaminating a site, but for restoring a section of an individual's property if it has in the past been gravel, contaminated, or used for commercial/industrial purposes.
The term “ecosystem services” refers to how the plant and the environment interact with one another. A plant could perform an ecosystem service by attracting pollinators to the area and/or replacing nutrients in the soil through decomposition for example. Some plants carry out the ecosystem services of contaminant removal, this process is called phyto-remediation.
Phyto-remediation is a really cool process and it occurs because the contaminants in the soil mimic what the plant would already be needing. For example cesium mimics potassium which is a key nutrient for plant growth and health. This causes the plant to uptake the contaminants and metabolize them as if it were the nutrient their receptors thought it was.
The following species have been mentioned in scholarly papers for their significance in ecosystem restoration. There would be no point for me to rank them best to worst because every individual site has unique conditions and each plant uptakes different contaminants.
Another point worth mentioning is being aware that nature is not sedentary, rather, it is very fluid and dynamic in the way it never remains the same through time.
Plants for restoring a contaminated site
Sunflowers
Sunflowers (Helianthus sp.), particularly Rough Woodland Sunflowers and tall sunflowers native to Ontario, have the ability to hyper accumulate radioactive materials such as uranium and strontium compounds. Sunflowers are also well known for their ability to take up Cesium and Bromine compounds.
Sunflowers have been used at the Fukushima radioactive site in Japan to clean up the radioactive soil. This has also been tested at the Chernobyl power plant melt down, and has proven effective, at least in the water due to the complex structure of cesium in dryer soil. For more information or a place to start in your own research, check out this case study here
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Mushrooms
Mushrooms provide a very unique form of ecosystem remediation. One case study found talks about myco-filtration. The mushrooms has filtered out the harmful coliform bacteria which was growing in the water adjacent to a clam farm. Using myco-filtration or a fungal mat to clear bacteria from water is an effective method. To see the case study, go here.
Using mushrooms, mycorrhizae, or fungus to remediate a site is called Myco-remediation. Mushrooms have been proven effective at comparing bacteria in water bodies like a sponge. Mycorrhizae deep in the soil works to transfer nutrients and helps balance the contamination. Mycelium is effective at removing petroleum products, pesticides, and PCBs from the environment.
The benefit to using mushrooms includes the relative cost effectiveness, the ability to uptake a wide range of usually persistent chemicals, and they are easy to grow in a more hands off way.
Duckweed
Duckweed (Lemnoideae sp.) is an aquatic plant which grows in slow-moving or stagnant water. All genera have reportedly been successful in phytoremediation projects. It has the ability to remove heavy metals such as lead from industrial or municipal waste waters. Duckweed is a really great plant to use for remediating metal contaminated water since it grows in water naturally, it is native, easy to grow, it can be used as biofuel or can be fed to animals such as pigs when the project is complete.
Having a purpose post remediation makes Duckweed even more effective and sustainable than some other plants. Some plants cannot be used once they have been planted in the contaminated site, or they may not uptake the contaminants as quickly as Duckweed does. Duckweed is very easy to grow, cost effective, low maintenance, and it grows very quickly. For more information on Duckweed, go here.
Canola
Canola and Rapeseed do not have a specified Latin name, but rather are referred to as Brassicaceae sp. napus which refers to a large group of plants. Canola is excellent at soaking up heavy metals such as mercury. Mercury is a very dangerous metal and can be a byproduct of gold mining. When mercury leaks into the surrounding soil and water, it is absorbed by grasses, which may potentially be eaten by a herbivorous animal such as a cow, then following the food chain up, it may be ending up on your plate (unless you are vegan).
One great case study that showcases how canola can remove mercury from the soil is from Brazil. Farmers who planted canola in their field, which was contaminated from the gold mine adjacent to the cow enclosure, saw a significant decrease in the amount of mercury.
As well as, cleaning the soil, avoiding global mercury poisoning, planting oxygen producing canola, and saving the cows, the farmers have the potential to get a kilogram of gold per hectare from the gold still attached to the mercury. This could aid in paying for the clean up! For more information on canola and this case study go here.
Blue-Sheep Fescue
Similar to Duckweed species, Sheep Fescue offers lead removal services to its environment. The main reason this plant uptakes lead more effectively than most other plants is due to its intricate deep root system. The deep roots allow it to reach for the lead which is slow moving in the environment. Dense roots mean that the plant has access to a wider range of nutrients in the soil that are immobile.
Blue-Sheep Fescue and other Fescue species are a prairie/grass species which means they grow fast. This species is found on many lawns in North America, seed is widely available and affordable, and it requires next to no maintenance.
For more information on Blue Fescue/Sheep Fescue, go here. This plant would be excellent for remediating your own property if you find it to have high concentrations of heavy metals.
Water Hyacinth
Water Hyacinth (Eichhornia crassipes) is a common plant found in North American plant nurseries. They may produce a sweet smell and a beautiful flower, but these plants are not native. In fact, they are originally from the Amazon basin and have since been named an invasive species in North America.
This is not a native species, though I decided to include it in this list of restoration plants because of its effectiveness against many different contaminants ranging from heavy metal to nuclear to pesticide. Water Hyacinths, as the name suggests, is an aquatic plant, and thus, removes toxins from the water.
Case studies have proven Hyacinth to be effective at cleaning municipal wastewater removing the organic contaminants, inorganic contaminants, and heavy metals before the water is released back into the environment. Though it is invasive, it can be used after for biofuel, feeding livestock in a very cost effective manner, and/or can be used for fibre/composting board material. To learn more about the many potential uses for Water Hyacinth, go here.
Willow trees
Willow species (Salix sp.) are the final restoration species I will present, it offers a unique profile of ecosystem services by hyper accumulating copper, zinc, cadmium, selenium, silver, chromium, uranium, petrochemicals and many other metals and contaminants.
One of my favourite facts about Willow trees is that when one dies or is disturbed by humans, the surrounding willow trees, through an underground mycelium (fungal) network, will share the needed nutrient to ensure the other Willow tree continues to grow and survive. Have you ever seen a Willow tree stump growing bright yellow new growth out the top? That is what is happening, all underground!
The only obvious downside to using Willow alone is that trees take much longer to grow and establish than a prairie species such as Blue-Sheep Fescue, and can be harder to establish in an open area until the trunk has become thick and woody, even then, trees grow better in numbers. The best way to use Willow trees is to pre-establish them in a controlled environment such as a greenhouse for a few years, then introduce the site soil with the greenhouse soil, slowly transitioning the tree until it is ready to be planted in the desired area.
Willow trees are very effective if you have time to wait for them to grow, they will provide effective phytoremediation services, shade, habitat, wind break, and potentially nutrients to surrounding Willow trees. Willow trees can also be used as medicine, such as a natural painkiller, when the bark is prepared properly. For more information about using Willow sp. for remediation, go here.
Final Remarks
Thank you so much for reading about all of these beautiful, useful, and effective plants for restoration. I hope that if you have an area on your property or a friend’s that you are able to use some of the shared knowledge. This may have even inspired you to help restore a local area such as an old industrial brown site, which could be turned into a park, housing, or greenspace for the community to enjoy rather than be an eye-sore.
For more environmental type information similar to this as well as naturalizing a property, check out some more of my posts on my blog here.