Table 2 Traditional and modified contamination factors of heavy metals (HMs) by sampling area (measured concentrations are expressed in mg/kg dry weight).

From: Inclusion of key soil parameters in the modified contamination factor (MCF) model as a tool for assessing heavy metal pollution in agricultural soils

Parameter

Sampling area

Heavy metals

Cd

Cr

Cu

Co

Fe

Mn

Ni

Pb

Zn

Measured (Cᵢ)

Rural

0.13

12.16

15.19

3.91

5166.65

460.92

10.77

9.75

35.63

Urban

0.29

34.86

22.74

8.91

7820.07

633.22

25.30

42.66

88.96

Industrial

0.71

59.35

33.33

14.34

10,415.80

913.87

31.83

81.86

187.60

Background reference (Bᵢ)

–

0.30

40.00

20.00

10.00

38,000.00

500.00

30.00

25.00

70.00

Traditional CF

Rural

0.43

0.30

0.76

0.39

0.14

0.92

0.36

0.39

0.51

Urban

0.96

0.87

1.14

0.89

0.21

1.27

0.84

1.71

1.27

Industrial

2.37

1.48

1.67

1.43

0.27

1.83

1.06

3.27

2.68

Adjustment factor (f)

Rural

0.67

0.67

0.67

0.67

0.67

0.67

0.67

0.67

0.67

Urban

0.74

0.74

0.74

0.74

0.74

0.74

0.74

0.74

0.74

Industrial

1.02

1.02

1.02

1.02

1.02

1.02

1.02

1.02

1.02

Modified CF

Rural

0.29

0.20

0.51

0.26

0.09

0.62

0.24

0.26

0.34

Urban

0.72

0.65

0.85

0.66

0.15

0.94

0.63

1.27

0.95

Industrial

2.42

1.52

1.70

1.47

0.28

1.87

1.08

3.35

2.74

  1. Background values for HMs were derived from41,42,50, along with international standards provided by the FAO and USEPA. CF = contamination factor (measured concentration / background). CF classification: CF < 1 = low; 1 ≤ CF < 3 = moderate; 3 ≤ CF < 6 = considerable; CF ≥ 6 = very high. MCF = CF × f (adjusted for soil retention; f derived from pH, OM, CEC). Regulatory permissible limits (Table 1) are concentration-based and differ conceptually from enrichment-based CF categories.
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