Soil contamination poses a threat to both ecosystems and public health, particularly in urban and park environments. This article explores major U.S. cleanup efforts and highlights innovative biological solutions for sustainable soil restoration.
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The Hidden Dangers Beneath Green Spaces
Soil contamination is an environmental and public health issue across the United States, and it’s particularly concerning in parks and green spaces. These areas serve two critical purposes: recreation and supporting biodiversity.
State and national parks have largely been protected from soil contamination. However, there are many public lands with significant contamination from nearby dumping or industrial operations. The National Park Service has an ongoing program for purchasing contaminated park-adjacent lands and remediating them3.
For the most part, urban parks are assumed to be safe, clean spaces. However, they are increasingly found to contain soil contaminants, including heavy metals such as lead and arsenic. In fact, contaminated soils are believed to be the primary source of lead found in children living in urban areas1. Lead exposure in children can result in neurodevelopmental deficits, decreased IQ, behavioral issues, and physical effects such as kidney damage and reduced bone density, even at low levels of exposure2. These contaminants can persist in soils for decades and pose significant risks, especially to children who spend significant time playing outdoors1.
Recent high-profile remediation projects in both kinds of US parks reveal both the challenges and evolving strategies for tackling contaminated soils.
Contaminated Soil and Its Removal in US Parks
Soil contaminants typically stem from industrial operations or improper waste disposal practices. Contamination often goes unnoticed for years, only being discovered due to a public health crisis, new construction, or happenstance.
A striking example of undetected soil contamination emerged in 2018 when the National Recreation and Park Administration (NRPA) selected Sandorf Park in Indianapolis as its “Park Build” site, an annual city park selection for volunteer-driven upgrades and renovations. The $2 million project came to an abrupt halt when soil testing revealed dangerous concentrations of arsenic and lead. Testing showed that the park sat atop industrial fill and foundry slag from mid-twentieth-century manufacturing, with high levels of toxic metals that posed health risks to nearby children.2 The park was subsequently closed for three years while remediation teams excavated and replaced contaminated soil.
When soil contamination is known, it often takes significant time and resources to clean it up. One of the largest cleanup projects in a US park was converting a former dump site into a thriving wetland inside Ohio’s Cuyahoga Valley National Park. As part of an ongoing effort to naturalize commercial or industrial land adjacent to national parks, the National Park Service purchased the former Krejci dump site in 1985 and incorporated it into the adjacent Cuyahoga Valley National Park. The 45-acre site had operated as a junkyard and hazardous waste dump from 1948 to 1980, holding thousands of leaking barrels of toxic chemicals and scrap metal. Six companies, including Ford and General Motors, were identified as responsible for soil pollution at the dump and required to pay between $50 and $60 million each for the cleanup3.
That money funded what is regarded as the largest cleanup in National Park Service history. Organized by Ford, the removal of approximately 375,000 tons of contaminated soil involved machines digging out soil up to 25 feet deep3. In 2012, nearly three decades after the dump was acquired, the park service started naturalizing the space, converting it into 3.5 acres of seasonal wetlands stocked with native plants. Today, the former dump is home to a natural ecosystem that includes salamanders, woodpeckers, bald eagles, and more3.
Emerging Solutions and Future Outlook
While soil excavation remains the dominant remediation approach, it is costly, carbon-intensive, and disruptive to soil ecosystems. Scientists are now exploring more sustainable alternatives that harness the natural processes of soil itself.
One of the most promising developments is microbial iron mining, a bio-geochemical approach that leverages naturally occurring microbes to clean contaminated soils. In wetlands and other iron-rich environments, microbes drive iron cycling that produces tiny iron nanoparticles. These particles can trap and transform pollutants, including lead, arsenic, mercury, and microplastics. By introducing organic residues, such as rice straw, and optimizing soil moisture, researchers can accelerate these microbially mediated reactions, transforming contaminated sites into “self-cleaning biogeochemical reactors”4. The result is a self-sustaining soil system that gradually detoxifies itself, at sustainable cost and with minimal ecological disturbance.
Another promising breakthrough comes in the form of the Chinese brake fern (Pteris vittata), a plant capable of absorbing exceptionally high levels of arsenic. Recent molecular studies have identified three genes, PvGAPC1, PvOCT4, and PvGSTF1, that enable this fern to uptake, transport, and store arsenic safely within its tissues, mimicking bacterial arsenic resistance pathways5. This discovery opens the door to engineering other plants for efficient, low-cost bioremediation. These plant-based systems could one day supplement or even replace heavy-equipment soil removal in contaminated parks and playgrounds.
The success of emerging solutions, and of soil contamination cleanup more broadly, will partly depend on public officials and policy. For example, in Sacramento, Calif., community gardeners attempted to bioremediate lead-contaminated soil in a public park space using ferns. Unfortunately, the garden was later bulldozed by the city and the soil removed in a more conventional but disruptive approach6. The park space remained fenced off and closed for nearly three years after.
Such community-led remediation efforts highlight tensions between ecological innovation and urban development, highlighting how soil and “dirt” are alternately valued as living systems or as disposable material within political and economic agendas6.
The future of soil removal and remediation in US parks will depend on integrating traditional and emerging technologies. While soil excavation will remain the dominant approach, biotechnological solutions, such as microbial remediation and phytoremediation, offer more sustainable methods for maintaining long-term soil health. These innovations, along with others like them, support public safety and biodiversity, as well as more sustainable development.
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Resources
- Filippelli, G. et al. (2010). The Elephant in the Playground: Confronting Lead-Contaminated Soils as an Important Source of Lead Burdens to Urban Populations. Perspectives in Biology and Medicine. DOI:10.1353/pbm.0.0164, https://muse.jhu.edu/article/372294
- Hopkins, E. (2019 April 22). In southeast Indianapolis, the city's industrial past haunts its children. Indystar. (No DOI available) https://www.indystar.com/story/news/2019/04/22/sandorf-park-industrial-waste-leaves-future/2301418002/
- Bohle, S. (2022 May 2). It was a toxic wasteland. Now it’s a national park. National Geographic. (No DOI available) https://www.nationalgeographic.com/travel/article/it-was-a-toxic-wasteland-now-its-a-national-park
- Shenyang Agricultural University. (2025 October 24). Microbial iron mining: turning polluted soils into self-cleaning reactors. EurekAlert! (No DOI available) https://www.eurekalert.org/news-releases/1103333
- Chao, C. et al. (2019 May 20). Three Genes Define a Bacterial-Like Arsenic Tolerance Mechanism in the Arsenic Hyperaccumulating Fern Pteris vittata. Current Biology 29(10):1625–1633. DOI:10.1016/j.cub.2019.04.040, https://www.cell.com/current-biology/fulltext/S0960-9822(19)30427-0
- Cutts, B. (2017 May 11). Moving dirt: soil, lead, and the dynamic spatial politics of urban gardening. Local Environment 22:998–1018. DOI:10.1080/13549839.2017.1320539, https://www.tandfonline.com/doi/full/10.1080/13549839.2017.1320539
[Further Reading: Sustainable Agriculture]
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