Soil amendments
Adding sand to the soil will
decrease the overall cation exchange capacity since sand does not bind
cations. The problem with this is that the CEC of the clay is still the
same and since it is not being removed, the net gain in availability
of metals is small.
Organic matter is commonly added
to soil to lower pH. This is seemingly a good way to increase Cd bioavailability,
but could actually backfire since Cd binds to organic matter with high
affinity (Street, 1977). Thus, addition of organic matter could actually
decrease Cd bioavailability, despite the decrease in pH conferred.
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