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Phytoremediation: Can It Solve the Brownfield Problem?

When sparsely used industrial and commercial facilities are retired or abandoned, one of the biggest issues that arises is what to do with the remaining land.  This land, referred to as a “brownfield site,” or simply “brownfield,” is often contaminated with waste and pollutants left behind by the defunct industrial facilities and factories that stand on the land. Some of the remnants left behind by the industrial facilities include oil spillages, toxic heavy metals such as lead, as well as paints, asbestos, and various pesticides.  Brownfields are notable because, unlike Superfund sites, which contain very high levels of hazardous wastes and need extensive and expensive decontamination, the level of contamination in a brownfield is comparatively low, making re-use and redevelopment a viable option.

Brownfield site in Industrial Area outside San Francisco. Source: ca.gov

Often, however, due to economic reasons, the brownfields sit idle for decades at a time without any redevelopment, rendering the brownfield ground useless. This “dead” area becomes unavailable for use by humans, animals, and plants alike.  Not only that, but the contaminants can seep into the areas surrounding the brownfield, including the underlying groundwater, and any rainwater that falls on the brownfield is immediately contaminated and must undergo extensive purification before it can become drinkable.

So the question becomes: How do we go about cleaning up the brownfields and the underlying water supply?

Most of the current cleaning techniques employed involve bioremediation methods such as in-situ oxidation and soil vapor extraction. Both of these methods involve injecting anti-contaminant material directly into the soil, and then extracting the contaminants into containers above the soil.  This makes the cleanup process invasive, expensive, and quite energy dependent. Additionally, using current cleanup techniques, post-redevelopment sites are universally restricted in both their immediate and future use in order to ensure that the fragile brownfield does not receive further exposure to contaminants.

Contaminated water at a defunct gasworks site. Source: Wikimedia

Perhaps a better and more innovative solution to the problem that may address some of the current redevelopment issues is a form of bioremediation called phytoremediation.

Phytoremediation uses deep-rooted plants that are immune to the hazardous wastes in the soil to harvest some of the heavy metals and toxins that are normally difficult to extract using standard bioremediation techniques. After the plants are planted, they harvest the contaminants in the soil as they mature, and then can be disposed as chemical waste once they reach adulthood. By using the plants to clean the soil, contaminants in the underlying groundwater begin to dissipate, and rainwater no longer adds to the contamination by carrying pollutants from the soil into the groundwater.

Phytoremediation in action at an Aircraft Repair Center in Elizabeth City, NC. Source: Ideonexus

All in all, phytoremediation is a less invasive and cheaper method than standard techniques, as well as more environment-friendly. The biggest disadvantage to phytoremediation is that it takes longer than standard bioremediation as the plants need time to grow and absorb the hazardous materials from the brownfield.

Despite the advent of phytoremediation, there remains much work to be done on brownfields, including not only their redevelopment, but also the prevention of future brownfields emerging in dying industrial sectors. Regardless, with the demand for clean, accessible water and green land increasing, brownfields remain a growing problem; one that needs to be addressed sooner rather than later.

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