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Table 5 Enrichment factor (EF) of heavy metals in sediments of lakes along a rural to urban gradient in central China and grade standards for EF (Birth 2003)

From: Heavy metal gradients from rural to urban lakes in central China

Group

EF

         

Grade standards for EF

Mn

Cu

Zn

As

Ni

Cd

Pb

Co

Cr

Fe

Value

Enrichment status

A

3.7 ± 0.8

6.9 ± 3.5

4.0 ± 0.6

1.7 ± 0.9

2.9 ± 1.0

7.9 ± 2.5

3.1 ± 0.9

3.9 ± 0.7

4.9 ± 2.9

3.0 ± 0.7

< 1

No enrichment

B

1.3 ± 0.1

4.5 ± 3.2

3.3 ± 0.2

1.2 ± 0.1

1.8 ± 0.2

4.7 ± 0.9

2.8 ± 1.0

1.4 ± 0.1

2.0 ± 0.6

1.5 ± 0.1

1–3

Minor enrichment

C

2.0 ± 0.7

3.4 ± 1.2

3.4 ± 1.0

1.9 ± 1.1

3.2 ± 1.4

8.4 ± 4.8

2.5 ± 1.0

2.6 ± 1.2

2.7 ± 1.2

2.5 ± 1.0

3–5

moderate enrichment

D

2.4 ± 0.7

4.8 ± 2.7

4.3 ± 1.8

2.1 ± 1.2

3.4 ± 1.7

5.5 ± 1.8

2.8 ± 1.2

2.8 ± 1.4

2.9 ± 1.3

2.6 ± 1.2

5–10

Moderately severe enrichment

E

2.1 ± 1.3

4.2 ± 2.1

4.3 ± 2.0

2.5 ± 1.2

4.4 ± 1.8

5.9 ± 3.3

3.0 ± 1.2

3.7 ± 1.6

3.8 ± 1.5

3.4 ± 1.2

10–25

Severe enrichment