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Table 1 Pollutions indices [33]

From: Data analysis of heavy metal content in riverwater: multivariate statistical analysis and inequality expressions

Indexes Used formulas Values
Contamination Factor (CF) CFn = Cn sample/Cn background CF<1 low contamination
1 ≤ CF<3 moderate contamination
3 ≤ CF<6 considerable contamination
CF ≥ 6 very high pollution
Enrichment Factor (EF) EFn = (Cn/Fe) sample/(Cn/Fe) background EF<2 natural variability
2<EF<5 moderate enrichment
5<EF<20 significant enrichment
20<EF<40 very high enrichment
EF>40 extremely high enriched
Geochemical Index (Igeo) \(\text{I}_{\text{geo}}=\log 2(\text{C}_{\text{n}}/ 1.5\text{B}_{\text{n}})^{***}\) Igeo<0.42 unpolluted
0.42<Igeo<1.42 low unpolluted
1.42<Igeo<3.42 moderately polluted
3.42<Igeo<4.42 strongly polluted
Igeo>4.42 extremely polluted
  1. CF (metal) is the ratio between the content of each metal and the background value in sediment and water samples of the study area [35].
  2. C/Fe (sample) and C/Fe (background) represent the heavy metal-to-Fe ratios in the study and in the background sample, respectively [35].
  3. Cn expresses the content of the toxic metal n, Bn expresses background data of the toxic metal n, 1.5 is a a factor of possible lithological changes [37].