Heavy metal Permissible concentration within soils (mg/kg) Threshold limit (Adagunodo et al., 2018) mg/kg
Cadmium 3-6 1
Chromium 100-180 100
Lead 300 60
Arsenic 50 5
Mercury 1 -
Cu 140-200 100
Zn 200-300 200
Ni 75 50