Phytoremediation: Putting Plants to Work

By Heather Prince

Howlovely are the delicate pink blossoms of redbud clasping elegant twigs on a warm spring day! This beloved native understory tree is a favorite with homeowners and commercial clients for its charming sprays of flowers, heart-shaped leaves, and golden fall color. What you may not realize is despite its delicate appearance, this tough ornamental tree also absorbs a range of industrial chemicals and is particularly petroleum tolerant. Eric Fuselier, PWS, spoke at the recent Impact Conference on the intriguing world of phytoremediation; the use of plants to clean up low to moderate levels of contaminants on landscapes. An environmental project scientist for Olsson, a nationally recognized engineering and design firm, and active member of Wild Ones, Fuselier has made phytoremediation his field of study. We sat down with him to learn how native plants can be surprisingly impactful. They’re not just a pretty flower or graceful grass. As landscapers, we are particularly poised to make a significant impact on client sites with savvy plant choices. The naturalistic movement has inspired clients to request plantings that reflect our Midwestern heritage and some specifically request native species. Why not create beautiful designs that also offer surprising benefits?

Combating Contaminants

Across the Midwest we have a proud industrial and commercial heritage. Our biggest urban hub, the city of Chicago, is deeply rooted in the past, present, and future of manufacturing. However, industrial activities are not limited to Chicago city limits. You’ll find facto- ries, railroads, highways, shipping ports, warehouses, industrial plants, manufacturing concerns, mines, military bases, and even your neighborhood dry cleaner contributing to the chemical contaminant ecological footprint. Once you start looking, you’ll find we live, work, and play in landscapes with a chemical history. “For example, chlorinated solvents can migrate from areas like rail yards, dry cleaners, or anywhere where they’re using solvents to clean things,” commented Fuselier. “Think about degreasers at a mechanics shop or on military bases. It’s not uncommon for the soil and groundwater at these sites to be contaminated with these types of chemicals. Your project might be next door or downstream from this type of land use. Chlorinated solvents are heavy and can easily move to area landscapes and contaminate the soil and groundwater. What’s terrific is how native species like the eastern redbud, are able to absorb these chlorinated solvents.”

When managing commercial sites, you’ll often find legacy chemicals that are no longer used lingering in soils. One example is polychlorinated biphenyl or PCBs. They were banned by the Toxic Substances Control Act, but due to their prolific use, they’ll often turn up in soil analyses. “It was a lubricant for electrical equipment among other things,” said Fuselier. “It was used in all kinds of applications before they realized how bad it was for the environment. Unfortunately, it’s also very persistent. Yet, there are a number of native species that are able to break it down into harmless chemicals, including the native river birch.” Big bluestem, red mulberry, and prairie cordgrass (see sidebar 44) are also good candidates for PCB amelioration.

The possible presence of legacy chemicals and ongoing pollutants makes a detailed site assessment crucial at the beginning of a project. When thinking about possible contaminants, some questions to investigate include:

• What is the land use history for the parcel? Was it a farm field, suburban lot, or urban site?

• What is the land use history of the surrounding parcels? What was upwind, downwind, or upstream from the site?

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