Some Grasses Can Stop Lead From Spreading In Soil

5:05 minutes

state of science icon

This article is part of The State of Science, a series featuring science stories from public radio stations across the United States. This story, by NPR Midwest Newsroom and The Missouri Independent reporter Niara Savage, was originally published by KCUR.

An illustration of cabbage growing out of soil that's been tainted by a poison bottle. Pollutants (construction vehicles, smoke, rain) threaten to enter the soil.
Historic lead mining and smelting in the Midwest left behind toxic levels of lead in soil that pose a health threat to locals when rain causes the toxin to spread. Credit: Crysta Henthorne, KCUR

Lead left behind in soil from mining and smelting poses a major health risk to people who live nearby. Researchers in Nebraska and Kansas believe plant life and organic material can limit lead’s spread.

In parts of the Midwest where lead mining and smelting lasted for over a century, communities are still dealing with toxic waste left behind by the industry.

Lead, a dangerous neurotoxin, persists in the environment, including in water and soil, where it can pose a threat to the health of people living nearby. The risk is especially acute for children, who can unintentionally ingest lead by putting their hands in their mouths and whose brains and bodies are still developing.

It can be spread to other areas, like yards and schools, by rainfall, and can also taint aquifers or vegetables in gardens, making them harmful to consume.

Now researchers are working to limit the impact of lead in the environment on people, and they believe they’ve found a promising solution: Plant life.

Phytostabilization involves moving lead from soil into the roots, stems and leaves of plants to prevent it from spreading and to limit people’s contact with it.

“One of the goals of phytostabilization is to take the site with lead and put it in a stable state, so that the risk is reduced, and the issues related to lead in the soil can be managed,” said Larry Erickson, a professor emeritus at Kansas State University and former director of the university’s Center for Hazardous Substance Research.

His research is focused on using miscanthus grass to stabilize lead in soil.

“One of the benefits of having vegetation in the soil, where the lead is, is that we can have an opportunity for the water to be taken up by the plant that keeps the water from moving in other directions and transporting the lead,” Erickson said.

Stabilizing lead in soil to prevent it from spreading can help avert and alleviate potentially dangerous consequences.

“In the operation of (lead smelters), lead has gone up and out of the smokestack and fallen on soil and there may be lead associated with the soil in terms of a five-mile radius of the shelter,” Erickson said.

Leftover mining waste can cause metal contaminants to spread up to 100 miles along rivers and streams when the lead is washed away by rainfall, Erickson said.

Erickson published the results of his experiments with phytostabilization in 2021. The focus was on Fort Riley, Kansas. Erickson found the root systems of miscanthus grass are complex enough to significantly limit the movement of lead on a contaminated site from rainfall in about two years.

That means lead in soil at a contaminated site can’t spread and flow to other areas and put people at risk of exposure. In an ideal situation, planting miscanthus grass would be paired with remediating the top several inches of contaminated soil to limit the spread of lead.

Researchers have known for decades that exposure to lead can cause irreversible brain damage in children, even at low levels. Children are most at risk because their bodies are still developing.

The Food and Drug Administration recommends children consume no more than 2.2 µg per day of lead from food.

“Unfortunately, a lot of those areas also have higher contamination of soils just by location, near highly trafficked areas, or railroads.”

Another plant-based solution for lead exposure being studied by researchers is biochar, a carbonized substance produced from plant materials with absorption abilities that could have applications for urban farming by reducing the amount of lead taken up by the lettuce planted in it, according to a 2020 experiment led by a student at the University of Nebraska-Lincoln.

The results of the small study showed that adding biochar to soil reduced the amount of lead taken up by the lettuce planted in it.

Biochar-treated garden soil produced lettuce with just 0.41 µg of lead per serving. Untreated soil produced lettuce with a lead level of 1.22 µg of lead per 85 grams.

Ryley Thomas, the student who led the experiment under the supervision of Michael Kaiser and Jennifer Cooper, professors with the university’s Department of Agronomy and Horticulture, said she designed it to help people who live in food deserts.

“Community Crops Lincoln is a community garden nonprofit organization, and they go into areas that have food deserts, and they tried to create community gardens where people can go and have fresh produce,” Thomas said.

“Unfortunately, a lot of those areas also have higher contamination of soils just by location, near highly trafficked areas, or railroads.”

Kaiser said food deserts are a major problem in Lincoln, Nebraska.

“This means a large distance between people and grocery stores,” he said. “A potential solution would be community crops or urban agriculture.”

Thomas and Kaiser sampled soil near railroads in the state where lead levels are often high. Adding biochar to soil could be a long-term solution for entrapment of lead because it remains in soil for hundreds of years. But they emphasized that the study was small and needs to be repeated before significant implications can be drawn from the results.

In June, Bloomberg Philanthropies awarded Lincoln $400,000 in funding to support a project to turn wood waste into biochar. The city will establish the Lincoln Biochar Initiative by working closely with the Nebraska Forest Service and the University of Nebraska.

“We are looking to build our own biochar plant and then produce about 700 tons of biochar per year,” Kaiser said.

Aside from its absorption properties with implications for lead-tainted soil, biochar also promotes plant growth, carbon sequestration and fertilizer reduction. The facility is set to be fully operational by summer 2023.

The Missouri Independent and the Midwest Newsroom are jointly exploring the issue of high levels of lead in the children in Iowa, Kansas, Missouri and Nebraska.

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Segment Guests

Niara Savage

Niara Savage is a reporting fellow at the NPR Midwest Newsroom and Missouri Independent, based in St. Louis, Missouri. 

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow. Now, it’s time to check in on The State of Science–



RADIO ANNOUNCER: St. Louis Public Radio.

RADIO ANNOUNCER: Iowa Public Radio News.

IRA FLATOW: –local science stories of national significance.

Lead mining and smelting, a process to extract metal, lasted for more than a century in some parts of the Midwest. And where you have mining, you have waste. Lead is still being detected in the water and soil, posing a serious health threat. But now researchers are turning to plants for help.

Here to tell us more about it is Niara Savage, a Fellow with the NPR Midwest Newsroom and The Missouri Independent, based in St. Louis. Welcome to Science Friday.

NIARA SAVAGE: Glad to be here.

IRA FLATOW: Nice to have you. OK, first of all, how did the lead from these mines spread out?

NIARA SAVAGE: So after the mining industry left states like Kansas and Missouri, the mine tailings were left behind, for many years unstabilized. And so, in places like Missouri, there’s mine piles that span more than 1,000 acres.


NIARA SAVAGE: And so there’s a couple of ways that it was spread. And one of those is actually people mechanically transporting those materials and taking them to use for their own yards, as gravel and things like that for home projects. And another way is that, when it rains, well, of course the soil is wet, and that can create runoff that can cause that contaminated soil to spread.

IRA FLATOW: So it’s a very urgent problem, obviously, to solve. Tell me the idea of using plants to help solve that problem.

NIARA SAVAGE: Larry Erickson is the former director for the Center for Hazardous Substance Research at Kansas State University. And so he published some research last year that shows that plants can actually form root systems that are complex enough to contain the lead in soil. And so if you plant– a specific plant they refer to in the study is miscanthus grass. And so this is a really great candidate because it produces a lot of biomass. It only needs tillage in the first year.

Planting that into contaminated soil sites in Fort Riley, Kansas yielded root systems complex enough to actually maintain and contain the water that fell onto that land in just a two-year period. And so that keeps the contaminated soil and water from running off into different locations.

IRA FLATOW: Wow. And how is that affecting what people can eat and drink?

NIARA SAVAGE: Lead could contaminate the drinking water. And so that’s especially true for communities that depend on well water. And another factor is also that plants or crops that are planted in contaminated soil can actually absorb and take up that lead into their roots and leaves, and that can become another threat– a lead hazard for people who are consuming crops that may have been planted in contaminated soil.

IRA FLATOW: Are some people living in higher-risk areas than other people?

NIARA SAVAGE: There’s definitely people who are living in higher-risk areas. So regions that are near places where the lead mining industry was taking place– so that could be lead smelting or mining– the soil in those areas is definitely associated with higher levels of lead. And then, as a result, the people in those communities typically have elevated blood lead levels as well.

Ryley Thomas was inspired to do research on how to prevent crops from taking up that lead. She noticed that, in Lincoln, there’s an organization called Community Crops that is purposed with trying to serve people who might live in food deserts by planting vegetables. But she noticed that a lot of the locations where that organization was planting vegetables were tainted with lead.

RYLEY THOMAS: We tried to create community gardens where people can go and have fresh produce. So unfortunately, a lot of those areas also have higher contamination of soils just by location near highly trafficked areas or railroads. As the case in the soil that we sampled, it was near a railroad, so that’s why I have the high lead.

IRA FLATOW: Could any of these projects be scaled up?

NIARA SAVAGE: So there are definitely efforts to scale up the projects. Specifically, the research in Nebraska focused on biochar. Michel Kaiser is a professor of agronomy and horticulture at the University of Nebraska-Lincoln. And he explains what biochar is.

MICHAEL KAISER: It’s basically charcoal, right? So it’s transforming organic feedstock by pyrolysis means– combustion under low oxygen– into charcoal-like material, which you actually put on your– if you do a barbecue, right– we just put it in soil.

NIARA SAVAGE: The University of Nebraska-Lincoln is working with the city– and money from Bloomberg Philanthropies that they received earlier this year– to establish a biochar plant to produce more than 700 tons of biochar a year. One of the applications of biochar is to prevent the crops that are planted in perhaps lead-tainted soil from actually taking up that lead and absorbing it into the plant and becoming a hazard for the people who might eat them.

IRA FLATOW: Niara, thank you for sharing your reporting with us.

NIARA SAVAGE: Thanks for having me.

IRA FLATOW: Niara Savage is a Fellow with the NPR Midwest Newsroom and The Missouri Independent, based in St. Louis, Missouri.

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