New York City Wants the Dirt on Urban Soils

April 19, 2011 at 7:13 pm Leave a comment

Wise people never take their health for granted.  Wise city farmers and gardeners go one step further:  They never take their — or their soil’s — health for granted.

Contaminants such as lead and other metals may lurk in urban soils that pose risk to human health.  In fact, the soil quality in many urban areas throughout New York State is unknown.

But that is about to change.  A team of scientists and researchers from Cornell University has teamed up with the New York State Department of Health, New York City gardening group GreenThumb, and a host of other organizations to look into the issue.   The multi-year project —called Healthy Soils, Healthy Communities (HSHC) — aims to assess the level and nature of soil contamination in community gardens throughout the city and the state.

“We aim to help gardeners and others make informed decisions with the help of science-based resources,” states the HSHC project team in a slide presentation.

The team members conducted an initial pilot study of 44 food-producing gardens from 2008 – 2010.  The study found that 13 of the gardens had levels of lead that were above the guidance values developed by the New York State Department of Environmental Conservation and the New York State Department of Health for remediating brownfield sites. Though the guidance values were not developed specifically for community gardens, they were the closest points of reference available.

The pilot survey found that some beds in the 13 gardens had lead levels that exceeded the guidance value of 400 parts per million, or ppm.  This means that there were 400 parts of lead for every 400 million parts of soil.

Beds in 14 gardens exceeded guidance values for barium. Five had beds above guidance values for arsenic.

The HSHC team stressed that the guidance values were not benchmarks to red-flag problem gardens.  They merely offered guidance to help interpret levels of chemicals in soil and assess the potential related risks to human health and the environment.

The initial results were better than those in other cities.  Of the 414 samples of New York City garden soil tested, less than 10 percent had levels above 400 ppm.  In Indianapolis, by contrast, nine in 10 gardens tested had problems with lead in the soil, according to this article on NPR’s web site.

Still, community gardens need to be vigilant, the HSHC project team advised.

Since the pilot study, the team has surveyed 30 additional food-producing gardens, the results of which are being analyzed.  The group is at a stage where it will begin to study the link between what’s in the soil and what’s picked up in food crops, said Véronique Lambert, extension associate at Cornell University Cooperative Extension.

The project team encourages gardeners to follow best practices.  They urge gardeners to use raised beds with fresh soil and compost, noting that gardens with fewer beds growing directly in the ground had lower lead levels. They also strongly encourage the mulching of beds and other areas of the garden to reduce the effects of soil splash and dust, which might carry contaminants. They also recommend, among other things, maintaining a good soil nutrient balance and a pH balance near neutral.

With time and care, even the most contaminated gardens can be made whole.  Shawn Spencer, deputy director of the Land Restoration Project at GreenThumb, recalled a Brooklyn site that he and his team were asked to remediate.  It tested 3,000 ppm for lead.  The team closed half the garden, tilling the soil and working in partially degraded wood chips to absorb the toxins.  On the other side of the garden, they built elevated beds.  Within a year the lead level fell to 1,600 ppm.  Within three years, the garden was well below the threshold where it is safe to plant, said Spencer, noting that it now has a lead level of 220 ppm.

“It’s completely functional,” he said.


Entry filed under: City Farmers, Community Gardens, Local Food Production, Urban Agriculture. Tags: , , , , , , , .

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