Heavy metals

Not polluted

Moderately polluted

Heavily polluted

Present study

Shell value

Continental crust value

Mn

<300

300 - 500

>500

478 - 2211

850

750

Fe

ND

ND

ND

14,787 - 95,464

47,200

35,900

Cr

<25

25 - 75

>75

99 - 290

90

71

Cu

<25

25 - 50

>50

23 - 133

45

32

Ni

<20

20 - 50

>50

23 - 65

68

49

As

<3

3 - 8

>8

55 - 105

13

10

Zn

<300

300 - 600

>600

44 - 205

95

129

Pb

<40

40 - 60

>60

4

20

0.3

Cd

-

<6

>6

BDL

0.3

16