How to Deal with Contaminated Soil
If your urban garden has high levels of heavy metals and you still want to be able to grow edible produce, Jouraeva says to start off by “growing away from the road and away from buildings where the quality of the soil is probably better.” Then there are three solutions you can use to deal with contaminants in the soil there:
1. Physically remove the contaminated soil.
You will probably need to hire a professional contractor to do this, which Shayler says may be prohibitively expensive and “doesn’t solve the problem, it only moves it.”
2. Cover up and start over.
Clear the area of any visible paint chips and cover the contaminated soil with raised beds or landscape fabric and a new layer of fresh soil. Heavy metals do not move or seep upwards, so as long as the old and new soils don’t mix, you can simply cover up the dangerous soil with good healthy soil and start over fresh. “This will actually allow you to grow your plants in a better environment,” encourages Shayler.
3. Add a coating of organic matter to your soil.
“This will bind the contaminants and make them less available to the plant,” says Shayler. You should add one-third as much organic matter as there is contaminated soil. Compost, non-acidic peat and manure are all good sources of organic matter. “Even just adding extra compost will dilute the concentration of contaminants and make the soil better off,” she concludes.
Research is also currently being done on a process called bioremediation, which essentially grows the heavy metals out of the soil and into plants that can absorb the toxins. Then the heavy metal-ridden plants are harvested and removed so that only clean soil is left underneath. This process is thought to be useful for the removal of cadmium, zinc and copper, but is currently not viable for lead and is therefore not a great option for city dwellers.
If you think your property might contain problematic soil, call your local environmental agency and ask where you can have your soil tested. “It’s better to make informed decisions so you can remain proactive and don’t have to be worried,” says Shayler. Better to be safe than sorry. Good luck with your urban garden project, and let us know how it goes!