Scientists Ask: Can Activated Carbon Clean the Environment?

Faculty researcher Amanda Harwood and her students are testing the feasibility of using activated carbon to reduce the bioavailability of DDT in contaminated soil.

Researchers Amanda Harwood, Nichole PelletierResearchers Amanda Harwood, Nichole Pelletier

A full range of activated carbon consumer products have proven effective in purifying water, air, foods and pharmaceuticals. Environmental scientists believe activated carbon also can be used to address ecological risks.

Alma College faculty researcher Amanda Harwood and her students are testing the feasibility of using activated carbon to reduce the bioavailability of DDT — an environmentally toxic compound originally developed as an insecticide — in contaminated floodplain soil near St. Louis, Mich.

The research is part of a pilot study funded by the Environmental Protection Agency and is part of Harwood’s ongoing environmental research with the EPA.

“When soil is contaminated by chemicals that are harmful to the environment, the first question that emerges is how do we get rid of it,” says Harwood, who teaches classes in biology and environmental studies. “One way is to dredge or remove the soil, along with the trees and vegetation. But there are problems with that method, and it’s costly.”

Pins and Magnets

Instead of removing the soil, Harwood is testing a remediation method that potentially decreases a chemical’s bioavailability — a term that refers to the degree and rate at which a substance is absorbed into a living organism.

“Just because a chemical is present in the soil does not mean it’s available to be absorbed by animals or other living organisms,” she says. “Instead of removing soil, can we reduce the bioavailability of a toxic pollutant so that animals can’t absorb it, or absorb less of it?”

Harwood explains the concept using the example of pins and magnets. If you drop pins on the floor, you can step on them and hurt yourself. But if you add magnets, the pins attach to the magnets. The pins weren’t removed, but they are no longer available to hurt you.

The same principle applies to Harwood’s research.

According to Harwood, chemicals that are bound tightly to soil particles are less available to living organisms, such as earthworms. But some chemicals are loosely-bound, which means animals can absorb the chemicals and be exposed to the pollutant’s toxic effects. One way to determine if a chemical is bioavailable is to measure the concentration of that chemical in the tissue of animals or plants that have been exposed to contaminated soil.

Soil packet with SPME fiber.Soil packet with SPME fiber.Fiber and Carbon

For their study, Harwood plans to use a passive sampling technique called Solid Phase Microextraction (SPME) using fibers to measure the concentration of pollutants that are available to animals.

“Why use SPME fiber? It doesn’t require the use of animals and is less labor intensive,” says Harwood. “We put the fiber in packets, deposit the packets in the soil, then collect them later to measure the DDT concentrations in the fiber.”

Soil samples from the contaminated site will be taken and analyzed to determine the bioavailability of the DDT in the soil. Then activated carbon will be added to the soil, and bioavailability will be remeasured using earthworms and SPME at six and 12 months.

“We add activated carbon because DDT binds tightly to activated carbon,” says Harwood. “Instead of removing DDT from the soil, we are using the carbon to reduce DDT bioavailability and make the pollutant less available for animals to absorb.”

The study will determine the effectiveness of activated carbon for reducing DDT bioavailability, and if using SPMEs is effective for long-term monitoring.

“We hope to provide remediation without excavating the soil, digging up trees or putting animals at risk,” says Harwood. “If our research proves successful, we will be one of the few colleges or universities in the country training undergraduate students in this method.”

Promoting Planet Health

Nichole Pelletier, an environmental studies senior from St. Charles, will assist in the study as part of her senior capstone project.

“Pollution and contamination are global issues that impact all species inhabiting this planet,” says Pelletier. “Understanding bioaccumulation in organisms when assessing certain contaminates can provide insight as to how an ecosystem may be impacted by pollution.

“My passion for this field lies within promoting the health of our planet, whether through research or through pushing to modify legislation,” she says. “This research is critical to my education and career goals after Alma College.”

Story published on July 31, 2019