Variable effects of heavy metal contamination on soil enzyme activities due to the metal type, the contamination mode and the contact time have been reported previously.
For example, Dar (1996) found that Cd as sole contaminant decreased the soil enzyme activities when its concentration
was as high as 50 mg kgK1. Moreno et al. (1999) reportedthat high Cd concentrations (O800 mg Cd kgK1) affected
dehydrogenase activity, but not b-glucosidase urease