All posts by Sarick Matzen

Worcester Roots dig deep on lead cleanup

“For the record, there is no valid phytoremediation method for [lead].”(1) That’s how Rufus Chaney began a recent email regarding a contaminated community garden. Chaney would know — he was one of the original researchers in the promising field of phytoremediation, or the use of green plants to remove contaminants from soil. He believes that current phytoremediation strategies offer few solutions to people concerned about lead levels in yards and gardens. Questions lingered in my mind as well, after I documented activists uses of phytoremediation for Slingshot Issue 99. How long does it take to clean up lead with plants? Is this a practical strategy? Plants and mushrooms can remove or break down other contaminants, like arsenic and petroleum products, relatively easily. Getting plants to take up meaningful quantities of lead is tricky.

Successful lead remediation involves a multi-faceted approach, suggests Anita Malpani, the Research Coordinator at Worcester Roots Project, a community group in eastern Massachusetts with a great track record in neighborhood lead remediation. What makes the Worcester Roots Project stand out is their ability to combine activism and science to tangibly improve community soil health. With guidance from experts in the field of lead remediation, like Rufus Chaney and Sally Brown (Univ. of Washington), Worcester Roots conducts their own field experiments. They have strong connections with the UMASS soil testing laboratory. Youth comprise a large part of their organization and are the primary purveyors of the free soil test kits. In fact, neighborhood soil testing is specifically written into their budget and is a cornerstone of their mission “[t]o struggle for a world where everybody is able to access the necessary resources to live a healthy, dignified life, without prejudice, exploitation or toxic environments.”

Malpani took time out from moving offices — their old office in Worcester’s Stone Soup community center recently caught fire — to answer my questions and explain her organization’s new angle on lead remediation. After years of experimenting with lead phytoremediation using Pelargoniums (scented geraniums), the Roots Project is now looking into chemically immobilizing the lead right where it is.

Although Malpani says they’re still hoping to find practical phytoremediation techniques, and are running new experiments with Indian Mustard, she says their new strategy focuses on phytostabilization. They are experimenting with adding phosphate rock, ferrous materials, and compost to the soil, assessing each soil amendment’s ability to bind up and stabilize lead. After adding the amendments, they plant Pelargoniums, which act as a ground cover and keep down dust, in addition to possibly sucking up some lead.

Phosphorus is key to the problems associated with lead phytoremediation, and also to the potential success of their new tactic. A necessary plant nutrient, phosphorus (P) also binds with lead (Pb) in the soil to form the non-toxic mineral pyromorphite. EPA scientists and other researchers like Chaney find that lead joins with phosphorus to make pyromorphite rapidly, and that “pyromorphite will rarely be absorbed if ingested.”(2) The Worcester Roots strategy now depends not on taking the lead away, but on reducing it’s bioavailability. Bioavailable lead is the lead that can damage our bodies when we absorb it. Scientists estimate that only 30% of the total amout of lead in soil is bioavailable.(2) The rest is already sitting tight in complexes with phosphates, sulphates, and organic matter naturally in the soil. Instead of trying to divorce the lead that’s already bound up, why not try to immobilize the rest of it?

“No plant naturally accumulates really high levels of lead from soils,” Chaney points out. Plants physically can’t absorb lead when phosphates are around. He suggests scientists get good results — i.e. experiments showing that plants do absorb a lot of lead — by growing plants in a laboratory and feeding them nutrient solutions that don’t contain phosphates and sulfates. This loophole guarantees that the lead stays soluble instead of forming pyromorphite or other mineral complexes. But a plant growing in a phosphorus-deficient environment is unheathy and won’t give a good yield. Successful phytoremediation depends on a plant’s ability to remove a lot of lead, which is directly related to how large the plant grows. To negotiate this catch-22, Worcester Roots is experimenting with spraying the Pelargoniums with a foliar application of phosphorus. This helps insure the Pelargoniums grow densely and are an effective groundcover, regardless of the amount of lead they might be extracting from the soil.

Despite Chaney’s grim prognosis on the future of lead phytoremediation, other researchers are still trying to find the right plant–soil chemistry combination for significant lead removal. If scientists aren’t using the “no phosphorus in nutrient solution” trick, they’re probably using the chemical EDTA. EDTA is a chelating agent, meaning it surrounds the lead molecules and prevents them from absorbing onto the soil particles, or even prys the lead-mineral complexes apart. Malpani let me in on an interesting conundrum: it’s illegal in all 50 states to use EDTA in phytoremediation projects, because it’s essentially a recipe for groundwater contamination. Once the EDTA frees the lead, the lead can travel easily through the soil and into the groundwater. So why do scientists and remediation companies pursue research with EDTA and other, biodegradable additives like citric acid anyway? Because phytoremediation is potentially so much cheaper than traditional clean up methods, like excavating tons of contaminated top soil and dumping it elsewhere.

The threat of groundwater contamination is real. Minnesota sued a Superfund lead cleanup project at a Twin Cities ammunition plant when the state discovered lead migrating into the groundwater. The EDTA applied to the experimental phytoremediation plot of corn and mustard plants, to increase the plants’ ability to access and remove the soil lead, was instead helping the lead move deeper into the soil and reach the groundwater. The remediation contractors had failed to obtain a permit for using EDTA in the first place.(3)

Back east amidst a sea of old clapboard houses covered in layers of lead paint, the Worcester Roots Project began their foray into lead clean-up with a series of experiments in 2003 and 2004. They set up 8 test plots, tested for lead content, and planted mostly Pelargoniums, with some corn and pumpkins thrown in for variety. They also looked at how the simple addition of compost to the contaminated soil affected the lead content. Malpani told me the experiments were basic, mimicking the lack of control experienced in peoples’ yards. But the concept was proven: lead content was reduced by about 30% in three of the Pelargoniums test plots, which started out with between about 1,000-6,000 parts per million lead. Adding compost also seemed effective. In 17 community gardens and 1 residence with relatively low lead levels (ranging from 48-323 parts per million), no lead was present after annual additions of compost. And in the one compost-only test plot, lead was reduced 41%, down to about 3,500 ppm, after Roots Project volunteers removed the sod and added 1 inch of compost.

These results are great — they make home-scale lead remediation look easy! I wondered, though, if you could really pull out all the lead after planting Pelargoniums for 3 years, or if less and less lead would be taken up each year. Perhaps that 30% was the fraction of the soil lead that was unabsorbed and easy for roots to access.

I found cautious optimism in the scientific literature regarding phytoremediation with Pelargoniums. I also found the time estimate for lead phytoremediation that I had been longing for: a whopping 150 years to remove all the lead from a contaminated field in northern France!(4) With 1830 mg/kg lead, the field was not that different than some of the backyards tested by Worcester Roots. Even if you were only trying to reduce the lead to below 400 mg/kg, the EPA limit for yards (not playgrounds or vegetable gardens), it would still take upwards of 110 years. That’s a long time to harvest yearly crops contaminated with lead. To make Worcester soils safe for vegetable cultivation and children’s games, Roots Project activists would have to plant, harvest, and dispose of Pelargoniums for more than a century!

Hence the fundamental change in the Roots Project approach. However, a quick search of the scientific literature revealed that there are, of course, still questions about remediating lead with phosphorus and other soil amendments. For instance, what happens when you add phosphorus to the lead-rich soil of a firing range? After 32 months – almost 3 years – only 45% of that soil lead was bound into pyromorphite.(5) Immobilizing more lead would probably require understanding and changing the soil pH. Plus, it’s important to use a less soluble source of phosphate, like bone meal or rock phosphate, to avoid turning any ponds or streams in the area into bright green algae blooms as inorganic phosphate fertilizers leach into the water.

While they’re researching new methods of lead cleanup, what does the Roots Project recommend in the mean time? “If the lead levels are really high (more than 2,000 parts per million), you have bare soil and you have children who play in the yard, we advise you to use barrier methods like building patios, landscaping fabric with mulch, raised beds, and maybe other lead-safe landscaping methods we use,” suggested Malpani. “If it is between 400 to 1200 ppm you could add layers of compost and phosphorus to bind lead and grow Pelargoniums and dispose of them safely.”

For more information, contact Worcester Roots Project at or visit


1. Email from Rufus Chaney, USDA-Agricultural Research Service, to Barbara Emeneau, regarding lead remediation in a community garden in Ottawa, Ontario, Canada pipermail/compost/2009-May/015737.html


3. EPA (2001). Providing Solutions for a Better Tomorrow : Reducing the Risks Associated with Lead in Soil. EPA/600/F-01/014


5. MPCA Settles Alleged Violations at Twin Cities Army Ammunition Plant, 06/09/2004.


7. Arshad, M. et al. (2008) A field study of lead phytoextraction by various scented Pelargonium cultivars. Chemosphere, Vol 71, Issue 11, pp. 2187-2192.


9. Chrysochoou, M. et al. (2007) Phosphate application to firing range soils for Pb immobilization: The unclear role of phosphate. Jour. Haz. Matls. Vol 144 Issue ½, p. 1-14.


Get the Lead Out – Sunflowers love Heavy Metal

Dumbfounded, I watched the toxic sunflowers sail over the fence — seeds, heads, stalks, and all. It was one more comic moment in the struggle to bring phytoremediation, the use of green plants to clean up toxic soil, out of the laboratory and into the hands of backyard and community gardeners. I hopped the fence, collected the plants from the empty lot, and routed them towards their proper new home, Milwaukee’s lined landfill.

Using sunflowers to clean lead out of soil has become popular in activist gardener circles, thanks in part to widely-publicized efforts by Common Ground volunteers in post-Katrina New Orleans. This past fall I visited two current phytoremediation (“fido-ree-mee-diation”) projects, and spoke with one of the founders of the 2006 Common Ground sunflower campaign. These activists are tackling soil toxicity head-on by growing sunflowers in lead-contaminated soil, harvesting them after the plants have sucked up some of the heavy metal, and disposing of them like hazardous waste. With every crop the soil gets cleaner.

Low-tech, low-cost tools for Do-It-Yourself soil remediation are desperately needed, and bioremediation might be the key: many plants, mushrooms, and bacteria can be used to take up toxic metals like arsenic and mercury, and break down organic chemicals like pesticides and diesel fuel. Traditional cleanup methods include removing toxic soil and putting it in a landfill or chemically washing it, techniques that are expensive, wasteful, and rarely benefit poor people. Lead in particular is a problem in urban areas where as much as twenty percent of children might face lower IQ’s, attention deficit disorders, and behavioral problems from high exposure. Furthermore, communities organizing to build food security need to restore soils full of leaded house paint, gasoline, and battery remains.

Phytoremediation is not new, but transferring the available research into good guidelines for smaller, DIY projects is tricky. For more than 20 years, capitalist heavyweights like the United States Military, Dow Chemical, Chevron, and Ford have been investing in the field. Most research has been done in controlled laboratory conditions, not in field experiments that reflect nature’s great variety. The published case studies that do exist are mostly industrial scale and report mixed results. Lead cleanup with sunflowers is chemistry, not magic; the process is affected by numerous variables, including soil pH, the form of lead in the soil, and the variety of sunflower used. Since phytoremediation is still experimental, soil testing is an important part of knowing whether it’s working. Although soil lead tests are cheaper than others, the expense of repeated testing is a common hurdle for low-income projects.

Despite the difficulties, sunflowers are a promising tool enabling people to take soil clean up into their own hands. Several positive, field-based test studies have been published recently in scientific journals, and one of the groups I interviewed for this article is doing their own New Orleans-specific experiment. Using phytoremediation safely doesn’t hurt the soil and probably helps, as Scott Kellogg and Stacy Pettigrew point out in their recently-published book, Toolbox for Sustainable City Living, which includes excellent guidelines for soil cleanup.

Milwaukee mix-up

I heard through the grapevine that an old friend of mine was working at a community health clinic in Milwaukee, WI, and was a part of a project using sunflowers to remediate the soil in the clinic’s garden for chronic care patients. I stopped by for a visit, excited to learn something from their project.

When I arrived, my friend told me that we could certainly visit the clinic garden, but there wasn’t much to see because the sunflowers were already harvested and in the compost pile. “What?” I replied, “You can’t put those sunflowers in the compost pile- they might be full of heavy metals!” A little knowledge can be dangerous, I realized. We got in touch with the head gardener and arranged to pull the contaminated plants out of the hopefully not-yet-frozen compost pile and put them in the dumpster.

On the next garden workday we biked the 8 miles under grey November skies down to the clinic. The clinic was sited on an old industrial site and the factory rubble had been topped with a thin layer of topsoil and sod. The garden beds were all raised, but sunflowers had been planted around them to clean up the soil around the beds. The paths were covered in woodchip in an effort to add organic matter and keep the potentially contaminated dust off the vegetables and away from children’s hands. I also learned that while they had researched the history of the site to understand the past soil contamination, they had not done any soil testing to see what was actually in the layer of topsoil, rendering their sunflower-based cleanup essentially a good-faith effort. Quite possibly the topsoil was clean since it had been brought in to cap the site.

Let’s be clear: lead is a heavy metal, an element, by definition something that cannot be broken down by plants. As we worked, we discussed the basics of phytoremediation. Some plants accumulate toxic elements like lead, cadmium, mercury, and arsenic, requiring that the plant be harvested and disposed of in some appropriate manner. Other contaminants, like diesel fuel, pesticides, and fertilizers — which are organic compounds made of chains of carbon, hydrogen, oxygen, and possibly other atoms like chlorine — can be broken down into harmless carbon-based compounds by secreted root enzymes and microbial activity hosted by some roots, as well as by some mushrooms. When the clinic gardeners put the sunflowers in the compost pile, they were essentially adding heavy metals to the compost that would later be mixed into the raised beds.

There is quite a bit of debate about what to do with harvested toxic plants, especially in the DIY community. Industrially, plants may be incinerated, composted, or chemically treated to leach out the heavy metals. If you don’t live near an old mine shaft, appropriate disposal means at the very least making sure the bagged plant material goes to a lined landfill, or possibly taking it to household hazardous waste sites. It could also be carefully composted before disposal, but only in a separate, enclosed area, to prevent the lead from leaching out as the plants break down.

At the clinic, the sunflowers heads were still fully seeded even though it was late fall. We wondered if the plants transmitted any heavy metal load into the seeds, and if animals had shied away from the seeds due to a potential bad taste. I later read that there is some evidence suggesting that seeds of sunflower plants used for remediation have an almost negligible amount of heavy metals, which would still make it a bad idea to eat them, but would allow the oil to be used for industrial purposes (Madejon et al). I also read that animals do seem to avoid plants naturally high in heavy metals due to their bad taste (Henry). When I saw my friend’s co-worker throwing the plants over the fence in that misguided attempt to seed sunflowers in the empty lot, I realized again how complicated the issue is. Safe phytoremediation means posting signs advising against eating the plants, and emphasizing that the plants are toxic once they’ve done their job.

Old toxins, new energy

Hurricane Katrina didn’t necessarily bring more lead to New Orleans’ already toxic soil. It did, however, bring a flood of volunteer energy geared towards finding creative, accessible techniques for cleaning up the city at the mouth of the entire Mississippi basin. One of the projects started by Common Ground Relief volunteers was the Meg Perry Healthy Soil Project, which ran a sunflower-planting campaign in 2006. After I witnessed the confusion around bioremediation in Milwaukee, I wanted to find out more about one of the first well-publicized activist uses of sunflowers for lead cleanup. I tracked down Emily Posner, one of the founders of the project along with veteran gardeners Starhawk, Lisa Fithian, and Scott Kellogg of the Austin-based Rhizome Collective.

One of the first things Healthy Soil Project volunteers did was independently verify the post-Katrina soil analysis done by the EPA and the Natural Resources Defense Council. Already-high lead concentrations had been spread around by the floodwaters. In 2006, forty percent of New Orleans properties were in areas with soil lead content over the EPA residential limit of 400 mg Pb/kg soil. Common Ground recommends following lower limits: the Canadian standard for children’s play areas is 140 mg/kg soil lead, while the agricultural soil lead limit is 11 mg/kg!

The sunflower project really got off the ground during Spring Break when volunteers planted sunflowers in people’s yards and adjacent empty lots. There are a number of plants that accumulate lead, including Indian and Japanese mustard, scented geraniums, corn, penny cress, and sunflowers. Emily said they chose sunflowers for the summer project because “sunflowers can grow much better than Indian mustard down here in the summer time. You can’t really use Indian mustard because it’s too hot; they’re a brassica.” Eventually they used Indian mustard during the cooler winter months, in a two-pronged approach.

The Healthy Soil project chose Giant sunflowers because of their prolific roots systems. Wide-spread root systems are important for two reasons. First, experiments are still being done to determine where exactly the lead ends up in a sunflower plant. While it’s more desirable for the lead to be transported up into the stalk and leaves, making it easier to harvest the sunflowers without worrying about pulling up the roots, I found several studies indicating that a generous portion of lead remains in sunflower roots (Nehnevajova et al 2007; Rock 2003). Sunflowers have a strong tap root that can penetrate down 6.5 ft, and an extensive lateral spread of root near the surface. Phytoremediation is only effective in the root zone, which typically includes 8-10 inches of soil below the surface, where most soil contamination usually is. Perhaps sunflowers are effective at removing lead from deeper soil horizons with their branched taproot. Pulling up a long taproot is not realistic, but it is important to include as many roots as possible when the plants are harvested.

Extensive root systems also help combat potential groundwater contamination during cleanup efforts. One challenge with lead is that it is “molecularly sticky”: lead wants to be attached to something, whether it’s joining with soil organic matter, clay particles, or forming complexes with carbonates, phosphates, and other soil molecules. There are very few free lead cations (Pb2+) available in the soil for plants to uptake. What lead the plant does absorb tends to complex with plant nutrients in the roots, instead of traveling up into the plant shoots. In other words, lead is not very bioavailable.

Fortunately, soil amendments can be added to make the soil more acidic, ideally with a pH around 5.0, which makes the lead more soluble while still allowing plant growth. Backyard gardeners can add sulfur, coffee grounds, or pine needles. Many published case studies and industrial operations use synthetic chelating agents like EDTA (ethylene-diamine tetraacetic acid), which are organic compounds that surround metals to inactivate them, preventing metal atoms from precipitating with soil molecules, for example. One of the great quandaries of metal phytoremediation is that soluble lead that is bioavailable to plants is also bioavailable to humans, and available to contaminate groundwater. It is particularly easy to add too much EDTA and essentially just leach all the lead into the groundwater, instead of making it gradually available to plants at the rate they can absorb it.

“Everyone recommends adjusting the pH. We tried to do that with sulfur,” Emily said. “One strategy we used to try to confront [groundwater contamination] was that we did a massive, almost scatterseed project so the root systems of the sunflowers really dominated the plots of land.”

In late summer 2006 they harvested the sunflowers with machetes, making sure to get the whole plant including the roots, and chose to contain the potentially contaminated plants in plastic bags and dispose of the bags in a lined landfill. “That’s a huge debate, what to do with the plants now that they’ve accumulated lead,” Emily noted. “Our solution isn’t the best solution but we had no other choice really. Some folks would say you should do some composting [of the contaminated plants in an isolated pile] and then contain the lead in that spot. But resource and space-wise we thought it would be best for us to have it contained with all the other toxic shit that’s in landfills.”

A major part of any clean-up project is follow-up soil testing, but it was hard for the Healthy Soil project to accomplish this due to issues with funding and personnel. “One of the mistakes I learned was that . . . gardens are long term. . . . You put a seed in the ground and you have to wait 40 to 120 days for it to produce, and you have to take care of it the whole time. It’s a constant project; it’s hard to have that kind of sustained interest. But the financial thing was also a huge barrier. It was hard to keep going when we were having trouble doing follow-up testing. We couldn’t necessarily produce our results. . . . Our biggest impediment is . . . develop[ing] a more scientific understanding of what’s going on. Some people say that it works and some say that it doesn’t, and I can’t necessarily answer that question based off of our experience, …because soil testing is so expensive.” With a soil heavy metal test running $30 at the well-respected UMASS Amherst soil testing laboratory, for example, it is easy to see how the repeated testing needed to build a good foundation of data could have been cost-prohibitive.

Critics of the Common Ground project with whom I spoke in New Orleans felt Common Ground’s efforts channeling outside volunteers into solidarity relief efforts made the project less interesting and accessible to city residents, who might have had the long-term commitment necessary to help the project reach a fuller potential. Although the sunflower project is long over, local involvement is something the Healthy Soil Project is addressing with their new focus on community gardens. An active member of the Lower Ninth Ward Urban Farming Coalition, they still provide soil testing to residents looking to start gardens.

Despite the fact that the amount of lead removed from the soil remains unknown, Emily counts the project a success. “Whether it removed a ton of lead or it didn’t, it certainly added to the regeneration of soil by adding to the microbial life through the compost tea that we added, and by turning the soil and getting it uncompacted. Based off of scientific evidence I know we were adding some more life to the soil, as well as adding more life to the community. We were planting some of these lots in places that were so destroyed and devastated; for people to come across lots in places that were filled with sunflowers in bloom I think was a really powerful experience. . . . This type of activity adds life and proves that life can come in some of the most unusual places. I think that was a good stepping-stone for us to establish ourselves, our roots metaphorically and the fact that we do care about healthy soil and we care about having food access. Now we have an opening to be able to work under the guidance of local people who are taking care of some of this land. It’s been a really good experience in that way.”

Filling in research gaps

Across town from the Lower Ninth Ward where Common Ground Relief is based, a community coalition is attempting to answer some of the questions surrounding the efficacy of using sunflowers for lead cleanup. On a sunny afternoon in early December I met Brice White, one of the coalition members, at a test plot on a street corner a mile west of Downtown. Brice is the Operations Manager for the People’s Environmental Center (PEC), an organization started after the storm with the goal of making soil testing accessible to the people of New Orleans. Like many groups started in the post-hurricane ferment of 2005-6, PEC has gone through many changes; now their main focus is supporting this sunflower experiment along with students from Dillard University, where the Director of PEC, Dr. Lovell Agwarmgbo, teaches chemistry; students from Delgado Community College; and the New Orleans Food and Farm Network.

Thanks to New Orleans’ long growing season, all the sunflowers had been harvested mere weeks before I visited, and were in the lab awaiting analysis. The project, started this past spring, is the next logical step in Katrina clean-up: “Everybody was talking about remediation after the storm, what the contaminants were, and doing a lot of testing. . . . We decided to find a place were we could test out sunflowers to see if they actually worked. Sunflowers became the thing for everybody to use, to talk about and plant,” Brice explained. “I was discouraged . . . with people coming from the radical hippie punk thing, where they’re like, ‘If you plant the plants it gets rid of the lead!’ But when you look at lead, which is a metal, it doesn’t go anywhere. People don’t even think that far, they just think ‘sunflowers get rid of lead.’”

Brice eventually developed a positive working relationship with Healthy Soil Project phytoremediators, although initially he shared Emily’s concerns about Common Ground’s approach to the sunflower campaign. “I had a lot of backlash against Common Ground . . . for several reasons, about this sort of North-South divide, liberal people coming down to say they know what to do — it’s kind of a classic, too. Some of those people didn’t mean that, but they didn’t stay here long enough to really see projects through. A lot of it’s an organizational problem. But for whatever reason, a lot of sunflowers got planted in New Orleans after Katrina…” This was fine, he pointed out, but any phytoremediation project needs a caveat: “If you’re actually trying to remediate, there’s just not much data. …You can’t plant sunflowers and then say that somehow there’s less lead . . . if you haven’t done testing to at least get a sense of what it does.”

PEC and other coalition members saw an opportunity to fill in some of the research gaps when a donation of sunflower Seedballz arrived. The gift was a trademarked version of a standard seedball with sunflower seeds rolled into a ball of clay to make them easy to grow. Through their connections with Dillard University, the coalition has the testing facilities that the Healthy Soil Project struggled to access.

The test plot is a corner lot on Oretha Castle Haley Boulevard that was donated to Café Reconcile, a job-training organization for young people. In exchange for upkeep, they were happy to have the lot used as a test site. With a history of several houses now torn down, illegally parked vehicles, and illegal dumping of house foundation material, the lot is typical of New Orleans. Because the study hasn’t yet been published, Brice couldn’t tell me any specific lead content numbers, but presumably they reflect the fairly high background levels of lead in the city.

One early lesson learned was that community-oriented science isn’t easy. Brice and his fellow coalition members encountered numerous difficulties in the process of turning the rubble-filled lot into a functioning field experiment. After trying to till it themselves, they were forced to hire a bulldozer to level the lot. Despite the addition of weed fabric, it was hard to control weeds in the nine experiment plots in the voracious New Orleans environment. The Seedballz didn’t perform well; the hot summer sun baked the clay into a hard ball, and birds picked out the seeds as the balls sat on top of the soil. “Figuring out how to get them to germinate was the real success,” noted Brice. Eventually they ended up burying the seedballs and also planting a crop of black oil sunflower seeds in an effort to not tie the project to one specific patented product, one donation.

Additionally, there was no record of the type of sunflowers in the Seedballz, and type of sunflower does seem to be an important variable in lead uptake. Researchers in Zurich, Switzerland examined the toxic metal accumulation in fifteen sunflower cultivars grown in a field contaminated with sewage sludge (Nehnevajova et. al). Because some metal uptake also varies with the kind of fertilizer used to reduce the pH, they used two different soil amendments, ammonium sulfate and ammonium nitrate. Surprisingly, they reported a wide variety in lead accumulation — almost 10 percent. The most lead, 26.5 mg/kg Dry Weight, accumulated in the Salut cultivar, when the plants were fertilized with ammonium sulfate, while the least amount of lead, only 2.8 mg/kg Dry Weight, was found in the cultivar Alzan, also grown with ammonium sulfate. To make matters more confusing, some cultivars accumulated more lead with the ammonium nitrate fertilizer than they did with ammonium sulfate. Neither of the varieties used in New Orleans, the Giant and Black Oil sunflowers, were included in the study, which used varieties widely available in Switzerland.

Despite the difficulties and multiple variables in the project, Brice said their preliminary results indicate a promising reduction in soil lead content. The study opens the door for future research with a New Orleans, community-based focus. “A lot of people have said they don’t want to use phytoremediation because they say it’s too slow,” he pointed out, “but we thought the results from 1-2 crops were promising enough to possibly use it. Also, the growing season here is longer than a lot of places. If you started first thing in the spring, you could maybe get four crops of sunflowers in. But in a place in the Northeast where they said it was too slow, they probably only got one crop in. All these things are things to look into in the future.” There are other questions as well: “When do you harvest them to get optimum efficiency? Is there lead in the seeds? Are animals eating the seeds, are people eating the seeds?… The simple thing we want to know is, did it take the lead out, and if so, is the first step that you can plant [sunflowers] and harvest them, and make sure you throw them away. Maybe that is a good start. Like all the Common Ground stuff — if they actually knew there was lead, and they planted all these sunflowers and then harvested them, they certainly didn’t hurt anything, and they probably made it better.”

Community-oriented science

In addition to providing valuable data on sunflowers, this project is a good exercise in community-oriented science. I salute Emily, Brice, and all the other intrepid gardeners who are vastly expanding the field conditions under which phytoremediation is used experimentally. By keeping track of what works under what conditions, and doing soil testing when it’s available, we can turn our DIY efforts into a solid body of knowledge created by the communities it serves. This is an excellent example of science working for the people. While we build bridges with sympathetic members of the scientific establishment, we can work towards organizing our own radical science infrastructure, like accessible soil testing labs. Let’s free bioremediation from the clutches of bureaucracy and academia! Bioremediation is a natural chemical process. No doubt there are other tools in the ground that we can use to repair the effects of industrialization, if we take the time to understand them.

Thank you to Emily and Brice for the interviews!


Toolbox for Sustainable City Living, Scott Kellogg and Stacy Pettigrew, South End Press

Gardener’s Remediation Guide, EPA (just being published; contact

Common Ground Relief,

People’s Environmental Center, Brice White, Operations Manager,


Hetland, M., Gallagher, J., Daly, D., Hassett, D., and Heebink, L. 2001. Processing of plants used to phytoremediate contaminated sites. In Phytoremediation, Wetlands, and Sediments, Leeson, A. et al. eds. Battelle Press.

Henry, Jeanna. 2000. An Overview of the Phytoremediation of Lead and Mercury. EPA,

Feigl, J. et al. A resource guide: The phytoremediation of lead in urban, residential soils.

Madejon, P., Murillo, J.M., Maranon, T., Cabrera, F., and Soriano, M.A. 2003. Trace element and nutrient accumulation in sunflower plants two years after the Aznacollar mine spill. Sci.Total.Environ. 307, 239-257.

Nehnevajova, E., Herzig, R., Federer, G., Erismann, K.-H., and Schwitzguebel, J.-P. 2005. Screening of sunflower cultivars for metal phytoextraction in a contaminated field prior to mutagenesis. Internat. Journal of Phytoremediation, 7: 337-349.

Nehnevajova, E., Herzig, R., Federer, G., Erismann, K.-H., and Schwitzguebel, J.-P. 2007. Chemical mutagenesis — A promising technique to increase metal concentration and extraction in sunflowers. Internat. Journal of Phytoremediation, 9:149-165.

Rock, S.A. 2003. Field evaluations of phytotechnologies. In Phytoremediation: Transformation and Control of Contaminants, McCutcheon, S. and Schnoor, J. eds. John Wiley and Sons, Inc.

Simple steps to clean toxic soil

These instructions are mostly taken from The New Orleans Residents’ Guide To Do It Yourself Soil Clean Up Using Natural Processes, published by the Meg Perry Healthy Soil Project (2006). The handbook includes great info for general soil cleanup, condensed here for space reasons.

Step 1: Soil evaluation and testing

Research historical contamination on/near the property using city/county records, aerial photographs, building permits, Sanborn fire insurance maps, property deeds, and EPA databases. Get your soil tested by a local agricultural extension or by UMASS Amherst.

Step 2: Soil preparation

If the soil is dead or compacted begin by aerating the soil. Pierce the soil with a garden fork or shovel but don’t turn the soil because this may bring toxic substances to the surface. If grass or other plants are already flourishing you may not need to aerate the soil. Wear at least a paper respirator when working if it’s dusty. Then spray compost tea to increase the amount of beneficial bacteria.

Compost tea: Fill a 5 gal. bucket with non-chlorinated water. (Let city tap water sit out over night to let chlorine volatilize. If your area uses chloramine, like the East Bay, add some citric acid to break it down.) Put an aquarium bubbler in the bucket to aerate the brewing tea. Suspend 1 cup of worm castings or aerobic compost in the water in an old stocking and squeeze it gently. After an hour, add 1/4 cup of food: molasses, humic acid, or fish hydrolase (ideally a mixture). Let the brew bubble for 24-36 hours, not longer or it will go anaerobic and smell! Apply it to damp soil within 4 hours before it goes bad, using a watering can or sprayer.

Step 3: Treating for High Levels of Metals like Lead and Arsenic

Different soil conditions are needed for the removal of metals such as lead (cationic metals) and metals such as arsenic (anionic metals)–that is, they cannot both be removed at once. Soil must be acidic (low pH) for removal of lead and other cationic metals. Soil must be basic (high pH) for removal of arsenic and anionic metals. This means that if you have both lead and arsenic in your soil, you will need to remove the toxins in several steps, rotating between acidic soil conditions and basic conditions.

Start first with the metals that are most highly concentrated. If both arsenic and lead are present, with higher concentrations of lead, for example, lower the pH and plant lots of sunflowers and Indian mustard to absorb lead. When these plants are fully-grown harvest them and throw them away. The next crop of Indian mustard should be in beds of high pH to treat for arsenic. Raising the pH to extract arsenic will also help immobilize lead.

Lead, Antimony, Barium, Cadmium, Copper, Mercury, Thallium, Zinc (cationic metals):

When trying to extract this group of heavy metals, lower the pH level by adding coffee grounds, organic sulfur or pine needles. The best lead absorbing plants are Indian mustard and sunflowers. Indian mustard will also uptake selenium, cadmium, nickel, and zinc. Sunflowers will also uptake cadmium and zinc. Plant seeds as directed, covering the area thoroughly; water and tend normally. When plants are grown spray compost tea around each plant a week before harvesting because this makes metals available to be absorbed by plants. Harvest and carefully discard in plastic bags that will go to the dump or be treated as toxic waste. Do not eat the mustard greens!

Arsenic and Chromium (anionic metals):

Grow Indian mustard in more basic conditions. Use thinly spread Phosphorous in some organic form such as bat guano or agricultural lime to raise the pH.

Step 4: Retesting and Repetition

Retest soils after each harvest or as often as you can. It is impossible to predict how long this will take because of ever-changing soil conditions; it will probably require many repetitions.

Personal Health and Safety:

Avoid direct contact with sediment. Touching sediment with bare hands, getting it in your mouth or eyes, or breathing the dust could be hazardous. Do not bring young children into contaminated areas, where they might touch sediment and then put fingers into their mouths.

Grow mostly fruiting crops (peas, beans, tomatoes, peppers, eggplant, squash, cucumbers, corn, etc.)–these are safest because most plants don’t store toxins in their fruits. Avoid eating the roots, stems or leaves of plants if your soil has high toxin levels. Do not plant greens–broccoli, kale, mustard greens, spinach and lettuce are some of the common greens that take up toxins. Cabbage is the safest of leafy crops.