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Soil in the city I live in is quite often contaminated with nasty things like arsenic and lead. Levels are sometimes twice or more what's considered acceptable. For this reason, people usually garden in imported soil in raised beds rather than directly in their own backyards.

I'm wondering how risky it would be to use leaves (most commonly maple) from untested soil as mulch or as bedding for vermicomposting worms. Would different varieties of trees be more/less likely to deposit contaminants in their leaves?

J. Musser
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intuited
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1 Answers1

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This study's summary suggests that arsenic in fruit trees ends up mainly in the heartwood. (I don't have access to full text, so I don't know if there are any caveats.)

The book Arsenic, By Assembly of Life Sciences (U.S.). Committee on Medical and Biologic Effects of Environmental Pollutants looks like it may contain the answer to your question, but I can't find it at the moment. A quick reading of a few dozen pages suggests that (a) trees that take up certain forms of arsenic will show signs of toxicity but (b) sometimes you might not be able to tell.

But a general answer may not be what you really want anyway. What I would do:

  • If you're getting leaf compost from an external source (e.g. municipal compost), ask them if they test for heavy metals.
  • If they don't test, or if you're making your own, give your local cooperative extension service a call to see if they will test compost/leaf mulch for heavy metals, and how they recommend taking a sample to send in for testing.
bstpierre
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