Index | Equation | Classification | References |
CF |
| CF < 1 (low CF) 1 ≤ CF < 3 (moderate CF) 3 ≤ CF < 6 (considerable CF) CF ≥ 6 (very high CF) | [18] [23] |
PLI |
| PLI = 0 (perfection) PLI = 1 (baseline levels of pollutants present) PLI > 1 (progressive deterioration of site) | [24] |
CD |
| CD < 6 (low CD) 6 ≤ CD < 12 (moderate CD) 12 ≤ CD < 24 (considerable CD) CD ≥ 24 (very high CD) indicating alarming anthropogenic contamination | [23] [18] |
EF |
| EF: 2 - 5 (moderate enrichment) EF: 5 - 20 (significant enrichment) EF: 20 - 40 (very high enrichment) EF > 40 (extremely high enrichment) | [25] [26] |
Igeo |
| Igeo < 0 Class 0 (uncontaminated) 0 < Igeo < 1 Class 1 (uncontaminated to moderately contaminated) 1 < Igeo < 2 Class 2 (moderately contaminated) 2 < Igeo < 3 Class 3 (moderately to heavily contaminated) 3 < Igeo < 4 Class 4 (heavily contaminated) 4 < Igeo < 5 Class 5 (heavily to extremely contaminated) Igeo ≥ 5 Class 6 (extremely contaminated) | [3] [27] [28] |
PERI |
| < 30 (low risk) : 30 - 60 (moderate risk) : 60 - 120 (considerable risk) : 120 - 240 (high risk) > 240 (significantly high risk) PERI < 110 (low risk) PERI: 110 - 220 (moderate risk) PERI: 220 - 440 (high risk) PERI > 440 (significantly high risk) | [29] [23] |