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Getting Soiled

July 29, 2015

Want to get the inside dirt on your dirt? That’s the mission of the Urban Soils Institute and focus of HII’s most recent workshop, part of our East River State Park Summer Series.

 

Some of the great folks from USI - including Director Tatiana Morin, a French post-doc student studying microbiology in urban soils, and two recent environmental science graduates - came out to lead (pun intended) the workshop. The Urban Soils Institute is the first research center anywhere in the world to focus exclusively on urban soils. Based out of Brooklyn College and also funded by the New York City Soil & Water Conservation District, USDA Natural Resources Conservation Service, and the Gaia Institute, its mission is to advance the scientific understanding and promote sustainable use of urban soils through research, education, and conservation. To learn more, you can email them at tatiana@usi.nyc or call at 646.847.7763.

 

What to do if you want your soil tested? You can send a sample for testing to Brooklyn College’s Environmental Sciences Analytical Center or Cornell’s Soil Health Lab.

 Workshop participants were encouraged to bring soil samples from their backyards, and we also tested the soil for lead and pH in several places in the Park itself. More importantly, I brought a sample from my (tiny) garden terrace for testing, and while we were waiting for the results, I asked Tatiana why are these two numbers are particularly important, and how to test for them.

Pb & J:

Ideal Number: 0ppm

My Result: 39ppm

East River State Park Range: 0-80ppm

 

In sufficient quantities, lead (Pb on the Periodic Table) has been found to be toxic to humans, and particularly harmful to children.While some argue that any level of lead in our soil, water, food, or bodies is unsafe, general recommendations issued by various academic and governmental bodies for lead in soil are:

  • Below 100ppm: no precautions necessary

  • 100-400ppm: follow best-management practices for garden soils (i.e. don’t grow green leafy vegetables or root crops), children should not play in bare soil

  • 400+ppm: soil should not be used for growing food plants, and remedial actions should be taken for residential use

In New York City, sources of lead in our soil can come from industrial sites (e.g. paint manufacturers, old gasoline spills), and can hang around in our soil for quite a while. And while urban farming is a growing (and positive!) phenomenon, it’s important that we test our soils for potentially harmful chemicals before we attempt to grow that artinsal kale.

 

Our lead testing process was simple: our soil samples were x-rayed for lead using this nifty gadget (pictured at left).

 

 

XRF imaging works on the principle that, when excited by an external energy source, atoms emit X-ray photons of a characteristic energy or wavelength, which can be counted, identified and quantitated.

 

pHind out if your soil is acidic or basic

Ideal Range: 6-7

My Result: 5.2

East River State Park Range: 6.5-7.3

 

To test for pH, dig deep into your memories from 7th grade bio, then: combine a 1:1 mixture of soil and water, leave to to settle for 2-5 minutes, then use a pH testing kit (available at all major retail chains).  

 

The pH of a soil does not tell us about its toxicity. However, it can tell us what plants are likely to grow well or poorly in the soil, as well as what kinds of nutrients and/or toxins the plant will be affected by. For instance, the more acidic the soil, the more lead can be absorbed by plants - particularly leafy greens.

 

To adjust the lead in my soil, Tatiana recommended that cycle out some of the existing soil with new topsoil, and place a level of compost or mulch on the top, to prevent lead particulates in the air from landing on my soil and being absorbed by my (struggling) oregano. To make my soil less acidic, she recommended adding lime (the chemical, not the citrus), or crushed eggshells and crushed oyster shells, both of which also contain calcium carbonate, an acid neutralizer.

 

Also good to know: the East River State Park is un-soiled by lead - so feel free to play in the dirt! (and attend one of our upcoming events).  

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