Plants can be used to clean up pollution in the environment. Certain plants are able to take in and store chemicals out of the air, soil, or water by concentrating them in their leaves or other tissues. Some plants can even break down hazardous chemicals or isolate heavy metals. Plants also partner with fungi and microorganisms that help the plants absorb nutrients. These relationships can also be used to clean up hazards in the soil by allowing the plant to process a greater number of chemicals then it could on it’s own. Using plants to remove pollutants from the environment is called phytoremediation.
If contaminants are moving through an ecosystem, plants can be used to collect the contaminant and lock it into stable plant tissue. When ground water is polluted the plant roots can absorb the contaminant along with the water holding the waste in the plant tissues while releasing the cleaned water back into the atmosphere. Plants also absorb chemicals out of the air that accumulate with dust on their leaves. These particulates can be safely processed by the plant and locked up in the plants tissues. When hazardous chemicals are collected in the leaves or woody tissue of the plant these need to be collected and disposed of properly. Allowing contaminated plant material to return to the site will just reintroduce the hazard to the soil through decomposition.
While phytoremediation is of interest to businesses on a large scale it can also be used by the homeowner. Places in our home garden are vulnerable to pollution. Garden beds along the street can be used to clean up water runoff polluted with gas leaks. Lead and other heavy metals might gather on the leaves of plants near the street and need to be sponged out of the air. Raingardens may also collect contaminated street runoff as well as fertilizers, herbicides, and pesticides applied to neighboring properties. Anywhere stormwater gathers on a property is an excellent place to collect potential hazards out of the soil. Backyard soil could also be contaminated with a wide variety of pollutants from previous occupants and land uses. Knowing the history of a site could guide the choice of certain plants to collect likely contaminants.
There are several common native garden plants that also have special powers to clean up pollution. If a site is contaminated with pesticides or the neighbors use pesticides, plant a grass buffer of big blue stem, switchgrass, Indian grass, and eastern gamagrass. Trees like black willow, river birch, cottonwood, and red mulberry can also lock up pesticides. Along the street use plants that absorb gasoline leaks like big bluestem, little bluestem, switchgrass, Indian grass, blue grama, sideoats grama, bottlebrush grass, Canada wild rye, soft rush, tussock sedge, arrowhead, annual sunflower, and wild senna. Lead is also a common pollutant from cars that can be concentrated in switchgrass, sideoats grama, and fox sedge. If the garden is in the city, air pollution may be a concern. Trees like pine, holly, tulip poplar, tupelo, black cherry, ninebark, rusty blackhaw, and black locust can collect pollutants out of the air with their leaves.
Although not a direct benefit to the gardener, plants can be used for carbon sequestration. Carbon is absorbed out of the atmosphere by all plants but locking it up in the tissues of long lived trees like bald cypress, white ash, tupelo, tulip poplar, pine, and oak is especially useful. Trees are not the only way to store carbon out of the atmosphere, the soil in wetlands and grasslands is an incredible carbon sink. Allowing these ecosystems to be undisturbed with long term protection keeps carbon unavailable and reduces greenhouse gasses. Phytoremediation is just one more way that native plant gardeners are going to save the earth.
For further info look into Phytoremediation with Native Plants by Eric Fuselier.
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