Background concentrations | Cu | Zn | Pb | Cd | Ni | Fe | References |
World average shale | 45 | 95 | 20 | 0.30 | 68 | 4.70 | [34] |
Lowest concentration in the present study | 9.66 | 66.61 | 2.57 | 0.58 | 11.37 | 1.89 | Present study |