| Er value | Potential ecological risk | Ri value | Ecological risk index |
| Er < 40 | Low | Ri < 95 | Low |
| 40 ≤ Er < 80 | Moderate | 95 ≤ Ri < 190 | Moderate |
| 80 ≤ Er < 160 | Considerable | 190 ≤ Ri < 380 | Considerable |
| 160 ≤ Er < 320 | High | 380 ≥ Ri | Higher |
| 320 ≥ Er | Higher |
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