. Cai et al. (2007) and Ko et al.
(2008) found in their own studies that in the process of composting,
as the organic matters got decomposed, the heavy metals got enriched, but the complex macromolecules that formed in the humification taking place in the late period of composting, such as humic
acids, chelated Cu, thus reducing its bioavailability, which was the
main reason why the inhibiting effects of the heavy metal Cu on
the activity of the enzymes got weakened at the end of composting.