Thursday, April 30, 2009

Lead Belly

This is the soil under my vegetable planters

I have received my soil test results from the ESAC. I had a sense that things weren't good over in the side garden, but I didn't think it would be as bad as it is. Although I suppose it could've been worse. I didn't test the front yard mostly because I do not plant veggies over there, but now I am thinking I will test it. In addition to the side yard analysis, I sent in my planter box compost, which is a mixture of Farfard product and an "I can't remember brand" of seaside compost I bought from Gowanus Nursery last year. I did this as a sort of control group, something to compare the yard earth to.

The good Dr. Cheng analyzed my soil himself. Below are the results, please click on the image to zoom in.

These numbers will mean little to you as they do me until they are put into context. Dr. Cheng has agreed to provide that context but asked me not to post that until some final details are worked out. Comparing the side yard soil under my gardening feet to the store-bought compost kept in pots:
  • Arsenic is 3 x greater in the side yard

  • Lead is 50 x greater in the side yard

  • Cadmium is 3 x greater in the side yard

  • Chromium is 2 x greater in the side yard

  • Mercury is 9 x greater in the side yard

  • Soil PH is a bit more acid in the side yard (expected and compost near neutral 7)

  • Organic content (humus) is a low 8 percent of soil in the side yard

  • Soluble Salts were half what they are in the compost (not sure what this means)

In regards to nutrients:
  • Calcium (Ca) is 5 x greater in the compost (probably because of sea life in it)
  • Magnesium (Mg) is 4 x greater in the compost
  • Phosphates (P) are 24 x greater in the compost
  • Iron (Fe) and Potassium (K) are just a bit more in the compost
  • Manganese (Mn) is 3 x greater in the compost
  • Copper (Cu) is about 23 % less in the compost
  • Zinc (Zn) is about 95 % less in the compost
What does all this mean? Well, we can see that the compost has a greater nutrient load than the common soil. It also has a balance PH compared with the common soil. Only copper and zinc are lower in the compost over the side yard soil.

Clearly the side yard soil has much elevated Lead (Pb). Close to 1/10 of a percent of the analyzed soil is lead or put another way, for every 10000 particles of soil, there is one particle of lead.

EPA guidelines put Lead safely at 400 ppm, my soil is well over 900 ppm. Then there's the Mercury, Cadmium, Chromium, and really, who knows what else?


  1. Yikes! Now what? Is there an abatement protocol?

  2. Abatement in this case is simply not using it for veggies. Truth is alot of people have at least the lead (pb) in their soil around the house. Maybe the other items too. Its disconcerting, but I try not to let it disturb me too much as there is little I can do about it.

  3. Wow. This is scary. Maybe you can piggyback on the Gowanus Canal Superfund?!

    We have to ASSUME there is lead in urban soils. But quantifying it is also important to managing any risks. Do I need to simply wash my hand after working in my soil, or do I need to wear a hazmat suit? Abatement may also mean ensuring that the soil is never converted to dust, so keeping it mulched constantly is important to mitigate the risk.

    I just started my Soil Management class this week. I'll be sampling and testing my soil and having my results sometime this summer.

  4. Caught between leaded exhaust years ago and chipping house paint, our front yards are a repository of lead. Its worth washing anytime you touch the garden soil, if not only because of cat poo. As for the other metals, I cannot say what their affect is, but it is worth knowing so you can make informed decisions.

    As for my plot, I'm still gardening. But as we green the cities, as we plant more vegetables, we need to have solutions to the soil contaminants. I grow veggies in planters. Make sure they are deep enough for striving roots.
    The perennials do not seem to mind the metals.

    Remember too that my soil sample was taken from 6-10 inches beneath the surface. I mulch the top, but more so it is not muddy than for any other reason.


If I do not respond to your comment right away, it is only because I am busy pulling out buckthorn, creeping charlie, and garlic mustard...