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The geoaccumulation index standard classes.
| Grade | Value | Soil quality |
|---|---|---|
| 0 | Igeo  0 |
Practically uncontaminated |
| 1 | 0 < Igeo < 1 | Uncontaminated to moderately contaminated |
| 2 | 1 < Igeo < 2 | Moderately contaminated |
| 3 | 2 < Igeo < 3 | Moderately to heavily contaminated |
| 4 | 3 < Igeo < 4 | Heavily contaminated |
| 5 | 4 < Igeo < 5 | heavily to extremely contaminated |
| 6 | Igeo > 5 | Extremely contaminated |
