From Brownfields to Greenfields: A Field Guide to Phytoremediation

Underutilized or vacant space in the city can be a source of creative inspiration for urban agriculturepublic parks, housing, community space, and the occasional mini-golf course. But prior to any contemplation of productive interventions into these sites, their environmental health and safety must be considered. Contaminated lots are known as brownfield sites, and the remediation necessary before development can take place is often a lengthy and expensive process. In PlaNYC, Mayor Bloomberg has identified brownfield remediation as a key initiative to the healthy development of New York, but urban designer Kaja Kühl (and her fellow researchers Lisa Brunie, Erik Facteau and Jay Tsai) was interested in finding smaller scale, cost-effective approaches to the problem. Here, Kühl presents A Field Guide to Phytoremediation, a handbook on how to remove contaminants from land using plants. Read on, and if you have property that might benefit from this approach, contact Kühl to help turn her research into action. –V.S.

According to the Department of City Planning’s most recent data, 7.1% of New York City’s land is vacant and, for the most part, underutilized. This is a rate much lower than the national average of 15% (in some cities the rate of vacant land is as high as 45%). However, taken together, these properties amount to approximately 11,000 acres of underutilized land — roughly the size of Manhattan (not counting streets). Imagine: across the five boroughs there is enough available land to fill Manhattan, with the potential to grow fresh food, create new parks or build affordable housing. But many of these vacant sites are potentially contaminated by previous industrial uses or leftover building materials, especially lead-based paint. Contamination and the potential health hazards to people who live, work or play on or near such sites become subject to oversight and regulation only in the event of a rezoning permitting residential uses. In those cases, a site receives an e-designation, which identifies it as potentially hazardous due to previous industrial uses. Once designated, site owners are obligated to submit to a process of site investigation and clean up.

50% of all vacant lots in New York City are smaller than 2,500sf and are owned by individuals.
50% of all vacant lots in New York City are smaller than 2,500sf and are owned by individuals.

In May of 2009, Mayor Bloomberg signed the New York City Brownfield and Community Revitalization Act, a milestone in the City’s commitment to cleaning up brownfields for productive reuse in accordance with PlaNYC. Citing the scarcity of land in New York City and the anticipated influx of one million new residents by 2030, PlaNYC identified the importance of cleanup and redevelopment of properties that are abandoned and underutilized due to the presence or perceived presence of contamination. As part of this effort, the City has created the Office of Environmental Remediation, which oversees the environmental review of brownfield sites and offers assistance to property owners on the path to a Green Property Certification and potential redevelopment.

50% of all vacant properties in the city are smaller than 2,500sf and individually owned. 80% are smaller than 5,000sf. Remediation, typically in the form of excavation of the contaminated soil, is costly, despite programs, assistance and grants now available. As a result, these small properties lie vacant for years, underutilized and toxic, their value further diminished by the appearance of abandonment and potential contamination.

Brownfields to Greenfields | A Field Guide to Phytoremediation
Brownfields to Greenfields | A Field Guide to Phytoremediation

We created a Field Guide to Phytoremediation to illustrate how property owners can use these years to their advantage and initiate a slow but cost-effective clean-up process using nature as their ally to add 11,000 acres of productive, usable land to the City‘s healthy environment.

Phytoremediation is the use of plants to remove contaminants from the environment. By harnessing the natural capabilities of plants we can remediate toxic soils, groundwater, surface water, and sediments. Phytoremediation is a low-cost alternative to traditional brownfield clean-up. Instead of removing tons of toxic soil and filling the site with new clean soil, plants remove contaminants from the soil and store it within their plant tissue. In some cases, the plants themselves then have to be removed as hazardous waste, other plants break down the toxins and eliminate them altogether.

Contaminants successfully removed in field studies have included heavy metals, radionuclides, chlorinated solvents, petroleum hydrocarbons, polychlorinated biphenyls (PCBs), pesticides and explosives. In order to successfully remediate toxins in soil or water, the appropriate plant groups have to be planted and monitored. Different plants have different remediative qualities. Plants offer an aesthetic as well as an environmental value to the city beyond the phytoremediation process. Improved air quality and reduction of storm water run-off are among the additional benefits of planting on sites that would otherwise be underutilized until funding for soil removal becomes available.

The steps below describe a one-year process of testing, planting, monitoring and harvesting. Depending on the level of contamination, this cycle can be repeated for several years until levels of metal or PCBs in the soil reach the minimum recommended by the NYS Department of Environmental Conservation.

Gather soil samples by taking them from at least 4 different areas per every 400sf of space. Samples should come from approximately 6 inches below the surface and should not contain any gravel, grass, trash, etc. You can mix the samples to form a composite sample of your entire lot.

Gather soil samples by taking them from at least 4 different areas per every 400sf of space. Samples should come from approximately 6 inches below the surface and should not contain any gravel, grass, trash, etc. You can mix the samples to form a composite sample of your entire lot.

Brooklyn College and Cornell University provide inexpensive soil testing services (approximately $30 for heavy metal tests). The NY State Department of Health also offers a list of certified professional labs on its Wadsworth Center website. Fill a zip-lock bag with your soil and send it to the lab together with information about your site. You will get a report in about 2 weeks.

From the test results, determine if and how you should remediate contaminants. See the chart at the end of this post to determine which plants would best help you clean up your lot and how many you will need.

Most of the seeds you will need are sold online. Sow and germinate them in a small container and water them regularly. Transplant them to your site when they are about 3“ high and after the last spring frost. Manage them as garden plants and watch them grow.

After about fourteen weeks, your plants will be saturated with heavy metals, PCBs or other toxins. Harvest the entire plant, including the roots, stems and leaves, and repeat this growing cycle as often as climate permits.

Some plants are hyperaccumulators. They store the toxins within their plant tissue and, after this process, will themselves be toxic. Check for the location of the Special Waste Drop-Off site in your borough and dispose of them as hazardous waste. Keep them away from children and animals.

At the end of the growing season, re-test the soil to track the improvements. You can also test the plant material if you are curious about the change. Depending on the level of contamination at the site, this planting process may have to be repeated over 2-3 years.

The table below gives examples of levels of acceptable soil contamination for certain recreational, residential or food production uses (as recommended by the NY State Department of Environmental Conservation) and suggests plant material most effective in remediating each contaminant.

We would love to help and put this research into action. So, whether you are an individual property owner or community group with little budget but plenty of energy and a vacant lot that might be contaminated, get in touch!

1. US Environmental Protection Agency. “Re: Contaminant Focus.” Contaminated Site: Clean-Up Information. US EPA Office of Superfund Remediation and Technology Innovation, Washington, DC, 7 Jan. 2010. Web. 22 Apr. 2010.
2. New York State Department of Environmental Conservation. “Re: 375-6-8 Soil Cleanup Objective Tables.” Subpart 375-6: Remedial Program Soil Cleanup Objectives. NYS DEC, Albany, NY, 14 Dec. 2006. Web. 22 Apr. 2010.
3. Wikipedia, The Free Encyclopedia. “Re: Hyperaccumulators Table – 1 and 3.” Redirected from, Phytoremediation, Hyperaccumulators. Wikimedia Foundation, Inc. San Francisco, CA, 14 Apr. 2010. Web 22 Apr. 2010.
4. U.S. EPA. 1996. Soil Screening Guidance: User‘s Guide. Office of Emergency and Remedial Response, Washington, DC. EPA/540/R95/128.
5. Schippers, R.R. & Mnzava, N.A. Brassica juncea (L.) Czern. [Internet] Record from Protabase. van der Vossen, H.A.M. & Mkamilo, G.S. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. 2007. Web. 22 Apr. 2010.
6. Duke, James A. Brassica juncea (L.) Czern. Handbook of Energy Crops. unpublished. Center for New Crops & Plant Products, Purdue University, 1983. Web. 22 Apr. 2010.
7. Shayler, Hannah, Murray McBride and Ellen Harrison. “Re: Guide to Soil Testing and Interpreting Results.” Cornell Waste Management Institute. Department of Crop & Soil Sciences, Ithaca, NY, 15 Apr. 2009. Web. 22 Apr. 2010.
8. Environmental Science Analytical Center. Soil Testing Brochure. Department of Geology, Brooklyn College, Web. 22 Apr. 2010.
9. Washington State Department of Ecology.  Dirt Alert – Soil Sampling Guidance for Owners, Operators and Employees of Small Properties Where Children Play. Publication #06-09-099. Olympia, WA, Sep. 1999. Web. 22 Apr. 2010.
10. New York City Department of City Planning (Land use summary, 2007)
11. Michael A. Pagano and Ann O’M. Bowman: Vacant Land in Cities, Brookings Institution Report, 2001

Kaja Kühl is principal of youarethecity, a research, planning, and design practice, and adjunct professor of Urban Design at Columbia University. She previously worked as an urban designer at the New York City Department of City Planning.

The views expressed here are those of the authors only and do not reflect the position of The Architectural League of New York.


john parker November 22, 2010

“Contaminated lots are known as brownfield sites, ”

actually i believe that “brownfield” indicates “previously developed” as opposed to greenfield which means yet to be developed. Contamination may also exist there, but certainly does not have to. Equally, a greenfield site could be contaminated, but undeveloped… hate to be so pedantic, but I am English…

Varick Shute November 22, 2010


Dictionary definitions are inconsistent in their inclusion or exclusion of contamination. I now realize, after looking up precise definitions to respond to your comment, that this may be a case of American English v. British English. Merriam-Webster defines a brownfield as “a tract of land that has been developed for industrial purposes, polluted, and then abandoned.” The American Heritage Science Dictionary notes brownfields as “often environmentally contaminated.” Meanwhile The Cambridge Advanced Learner’s Dictionary does not include any mention of contamination at all.

In the context of this piece, I think it is reasonable to fold contamination into the definition. But thank you for your meticulous reading of the piece – you’re keeping us honest!

–Varick, Urban Omnibus

ali December 9, 2010

it would be great to develop a city strategy for the hyperaccumulators beyond sending them to the traditional special waste facilities. this is something that i have given thought to in my thesis project as a graduate student in architecture. phytoremediation has so many possibilities beyond brownfields. i understand that rhizofiltration is used for the treatment of water and am curious about phytoremediation applied to air pollution. what if cities were gigantic air filters?

Georgia December 22, 2010

Possible — private — site: oil spill at Washington Square Village NYU housing?

Ian Balcom February 10, 2011

These Field guides are GREAT!. Do you have hard copies?
Regarding Brownfields. The definition includes sites with “perceived” contamination as well as those with actual impacts.

From EPA: “Brownfields are real property, the expansion, redevelopment, or reuse of which may be complicated by the presence or potential presence of a hazardous substance, pollutant, or contaminant.”

Air purification by plants in NYC has been recognized for many years.

see: Smith S: Vegetation a Remedy forthe Summer Heat of Cities. Appleton’s Popular Science Monthly 54:433-450, 1899

All those interested in this subject should consider attending:

The Eighth International Phytotechnologies Conference
When: September 13, 2011, 8:00 am
International Phytotechnology Society Conference “Putting Plants to Work where we Live, Labor, Breathe, and Play” September 13-16, 2011- Hosted by SPROut- the Sustainable Plant Research and Outreach Center
Registration Start Date: January 1, 2011, 12:00 am
Registration End Date: September 16, 2011, 11:00 pm

Anandi September 11, 2013

Where can I find a PDF or hard copy of this guide? I’d love to share with my SustyQ community.

Lennie Araujo, Intl. Assoc. AIA June 6, 2016

Jaja Kühl, AICP

As a NY urbanist architect I worked for over 12 years as consultant in project management and design for creative adaptive urban design of Brownfields and large underused real estate across US.
I was so happy and impressed when I learned about this initiative; if I were to go back to NYC I feel I would be involved in such projects; way to go!

Christin March 27, 2018

Just curious…. Where do the toxic plants go (i.e. where do the Special Waste Dropoffs put the toxic plants)? What’s the difference between having toxic soil and toxic plants? Is there away for plants to break down or neutralize the toxins?