Soil Contamination

Considering our site is located in the heart of brooklyn, which is an obviously very developed and urban area, it is crucial that we check the soil for heavy metal, lead, or other contamination.  We have brought a soil sample from our backyard to Brooklyn College’s soil testing lab, and are awaiting the results with bated breath.

In the mean time, I’ve been looking into some possible steps of remediation we can take once we find out what exactly our soil is contaminated with.  Better safe than sorry.

The first thing I came across was this write up from the University of Minnesota:

http://www.extension.umn.edu/distribution/horticulture/DG2543.html

Of particular interest was the following:

“To minimize absorption of lead by plants a number of control measures may be taken:

  1. Maintain soil pH levels above 6.5. Lead is relatively unavailable to plants when the soil pH is above this level. If needed, add lime according to soil test recommendation. Lead is also less available when soil phosphorus tests are high. For information about obtaining a routine soil test, contact your local Extension office.
  2. Add organic matter to your soil. In soils with high lead levels, adding one-third by volume organic matter will significantly reduce lead availability. Organic compounds bind lead and make it less available to the plant. When adding organic matter, the pH should also be maintained above 6.5. Good sources of organic matter include composted leaves, neutral (non-acid) peat, and well-rotted manure. Avoid leaf mulch obtained along highways or city streets as it may contain higher than normal lead levels.
  3. Locate your garden as far away from busy streets or highways and older buildings as possible.
  4. Because of the possibility of bare soil exposure to children through hand to mouth activity, soils with lead levels exceeding 100 ppm should not be used for gardening. If soil exposure to children is not a concern, then plants can be safely eaten from soils with soil lead levels up to 300 ppm.”

So that’s interesting.  Basically all we have to do to ensure the least amount of lead exposure, if it’s there, is to maintain the right pH, add organic matter, and keep the kids from eating the dirt.  Not a problem!

The next minute, a light bulb went off in my head, and I immediately grabbed my copy of Mycelium Running by Paul Stamets, an incredibly useful and interesting book which talks about so many of the recently discovered wonderfully useful properties of the fungi kingdom, including mycopesticides, mycoforestry, and the topic relevant to our discussion, mycoremediation.  According to Mycelium Running, mycoremdiation is “the use of fungi to degrade or remove toxins from the environment.”

Outlined in this book are methods of using mushrooms to treat contaminated soils, containing tables with which mushrooms cleanse the soils of what contaminants, and in what concentration.  Some are more effective at certain compounds than other.  One particularly interesting case study was the use of oyster mushrooms to treat petroleum contaminated soil.  This method was compared against other chemical and biological methods of remediation.  At the end of it, the mushroom pile had reduced the hydrocarbons from 20,000 to 200 ppm. The book also outlines a number of cultivation methods, mostly on the beginner level and very easy to understand.

So so far, our option for treating our soils is first, the use of mushrooms, mixed into the soil, and once the mushrooms have fruited, removing them and second, putting in only fruiting plants, such as apples and berries, and planting the herb and salad garden in containers with soil of a known origin and free of contaminants.

So overall, it doesn’t look like it would be too much work to free our soils.  Hopefully our soil tests will come back as safe for all plant growth, but if not, at least now we know what steps we will have to take to make it useable.

Until next time!

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