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Table 1 Igeo, CF, Er, DC, PLI, and PRI classes

From: Soil characterization and heavy metal pollution assessment in Orabi farms, El Obour, Egypt

Index type Value Environmental risk grade Reference
Single indices I geo Igeo ≤ 0 Practically uncontaminated (Muller 1979)
0 < Igeo ≤ 1 Uncontaminated to moderately contaminated
1 < Igeo ≤ 2 Moderately contaminated
2 < Igeo ≤ 3 Moderately to heavily contaminated
3 < Igeo ≤ 4 Heavily contaminated
4 < Igeo ≤ 5 Heavily to extremely contaminated
Igeo > 5 Extremely contaminated
CF CF < 1 Low contamination (Hakanson 1980)
1 ≤ CF < 3 Moderate contamination
3 ≤ CF < 6 Considerable contamination
CF ≥ 6 High contamination
Er Er < 40 Low potential ecological risk (Hakanson 1980)
40 ≤ Er < 80 Moderate potential ecological risk
80 ≤ Er < 160 Considerable potential ecological risk
160 ≤ Er < 320 High potential ecological risk
Er ≥ 320 Very high ecological risk
Integrated indices DC DC < 5 Low contamination (El-Bady and Samy 2014)
5 ≤ DC < 10 Moderate contamination
10 ≤ DC < 20 Considerable contamination
DC ≥ 20 High contamination
PLI PLI < 1 Not polluted (Tomilson et al. 1980)
PLI = 1 Baseline levels of pollutants
PLI > 1 Polluted
PRI PRI < 150 Low contamination (Hakanson 1980)
150 ≤ PRI < 300 Moderate contamination
300 ≤ PRI < 600 Considerable contamination
PRI ≥ 600 High contamination