Agriculture Reference
In-Depth Information
Soil Contamination
Some soils, especially in urban environments, are contaminated with radionuclides,
chlorinated solvents, petroleum hydrocarbons, PCBs, PAHs, and heavy metals such as lead,
mercury, cadmium and chromium. Many of these come from human activities such as
waste disposal, “inert” ingredients in chemical fertilizers, and industrial mining, agricultur-
al and recreational pollution. To determine if your soil is contaminated, find a local lab that
does this kind of testing.
If you have soil contamination, then comes the task of remediation. Many of the chemic-
al and physical methods of reclaiming polluted soil require a lot of energy and often leave
the soil lifeless and unproductive. Some methods go so far as to remove the soil and treat it
as hazardous waste. Another approach is to work with nature by using microorganisms
(bioremediation) and plants (phytoremediation) to help with the process. Though it takes
longer, these actually improve the soil, while chemical and physical processes can be very
destructive.
Fungi are especially adept at breaking down hydrocarbons such as those found in oil.
Even the oyster mushrooms I've grown in my home are good at this. The topic,
Mycelium
Running
by Paul Stamets is an excellent introduction to using fungi in your garden and for
soil remediation.
Certain plants can pick up nearly all of the heavy metals from a soil. Research, for ex-
ample, suggests that
Brassica juncea
(Indian mustard), can take up lead, cadmium and
nickel from the soil into its above ground parts. It can then be harvested and disposed of
elsewhere. Other common plants such as corn, alfalfa and sunflower can be useful for this
same purpose because of how fast they grow a lot of biomass. Admittedly, this process just
moves the problem elsewhere, but that's the way it is with minerals. They can't be broken
down like organic molecules. Some argue that lead cannot be effectively taken up by
plants, but that fungi may be able to do a good job of removing it.
The specifics of remediation are beyond the scope of this topic because I've never know-
ingly dealt with a contaminated soil, but I believe testing for and fixing contamination is
very important.
