| Model # | Independent variable(s) | Predictive Model | R2 value |
| 57. | As | = 0.85 As – 43.14 | 90.8% |
| 58. | Cd | = 0.99 Cd + 21.91 | 92.4% |
| 59. | Co | = 0.96 Co – 5.76 | 93.5% |
| 60. | Cr | = 0.89 Cr + 13.18 | 94.0% |
| 61. | Fe | = 0.03 Fe + 3.11 | 30.0% |
| 62. | Pb | = 0.47 Pb – 25.97 | 37.9% |
| 63. | Sb | = 0.56 Sb – 85.51 | 55.6% |
| 64. | Cd, Co, Cr, & Fe | = 0.91 Cd + 0.01 Fe + 5.07 | 94.7% |