pH ≤ 5.5 (4 points)

Cd

Hg

As

Pb

Cr

Max

0.16

0.06

13.90

33.23

495.25

Min

0.10

0.01

7.76

20.73

30.81

Mean

0.14

0.03

11.04

25.56

159.67

Coefficient of variation

0.14

0.67

0.22

0.19

1.22

Risk value

0.30

1.30

40.00

70.00

150.00

5.5 < pH ≤ 6.5 (21 points)

Cd

Hg

As

Pb

Cr

Max

0.20

0.11

23.80

36.36

66.81

Min

0.07

0.005

3.34

19.45

28.16

Mean

0.13

0.03

10.52

26.16

45.94

Coefficient of variation

0.31

1

0.45

0.15

0.21

Risk value

0.30

1.80

40.00

90.00

150.00

6.5 < pH ≤ 7.5 (45 points)

Cd

Hg

As

Pb

Cr

Max

0.28

0.14

20.85

37.76

84.24

Min

0.08

0.007

3.77

20.40

24.53

Mean

0.14

0.03

10.17

27.52

52.56

Coefficient of variation

0.29

0.67

0.38

0.14

0.22

Risk value

0.30

2.40

30.00

120.00

200.00

pH > 7.5 (37 points)

Cd

Hg

As

Pb

Cr

Max

0.26

0.17

34.44

39.41

76.71

Min

0.08

0.00

3.88

20.49

29.80

Mean

0.15

0.03

10.10

28.80

54.90

Coefficient of variation

0.27

1

0.50

0.14

0.19

Risk value

0.60

3.40

25.00

170.00

250.00