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Urban Omnibus

From Brownfields to Greenfields: A Field Guide to Phytoremediation

by Kaja Kühl
November 10th, 2010

Underutilized or vacant space in the city can be a source of creative inspiration for urban agriculture, public 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.

Field Guide to Phytoremediation | Vacant Lots

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. Click to enlarge. 

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

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.

A Field Guide to PhytoremediationClick to enlarge. 

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 costs associated with remediating lead contamination on a 2,500sf lot through phytoextraction using Indian Mustard can be reduced to 10% of those using common methods of excavation and fill.The costs associated with remediating lead contamination on a 2,500sf lot through phytoextraction using Indian Mustard can be reduced to 10% of those using common methods of excavation and fill. 


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.

Collect a Soil Sample 1. COLLECT A SOIL SAMPLE
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.
Send it to a Lab 2. SEND IT TO A LAB
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 labson 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.
Create a Remediation Strategy 3. CREATE A REMEDIATION STRATEGY
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.
Start Planting 4. START PLANTING
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.
Harvest and Re-plant 5. HARVEST AND RE-PLANT
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.
Dispose as Hazardous Waste 6. DISPOSE AS HAZARDOUS WASTE
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.
Re-test your Soil 7. RE-TEST YOUR SOIL
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.
Get a Green Property Certificate 8. GET A GREEN PROPERTY CERTIFICATION
The New York City Office of Environmental Remediation, which oversees the City’s brownfield clean-up program, offers Green Property Certifications. This certificate signifies that a property has been investigated, cleaned, and is protective of both public health and the environment. To qualify, you can sign up for the NYC Brownfield Cleanup Program.


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.

A Field Guide to Phytoremediation 


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!


This project was originally submitted to the One Prize: From Mowing to Growing competition in May 2010. Lisa Brunie, Erik Facteau and Jay Tsai assisted in research for the field guide.


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 an urban designer and principal of youarethecity, a research, design and planning practice interested in creating dialogue about the urban environment. She is an Adjunct Associate Professor at Columbia University.

The views expressed here are those of the author only and do not reflect the position of Urban Omnibus editorial staff or the Architectural League of New York.


Written by James Thomas

09/01/2011 at 21:12

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