*3.4.1 The degree of contamination Cd*

**Table 5** shows the contamination factor *C <sup>i</sup> <sup>f</sup>* of the substances in the sediments from the Liaohe River. In Håkanson's research, seven metals (Hg, Cd, As, Cu, Pb, Cr, and Zn) and one organic pollutant (PCBs) were considered. However, in this study, there are only seven metals considered. Therefore, the *Cd* classification thresholds are modified. According to Håkanson's approach, the threshold for the "low degree of contamination" is 7, corresponding to the number of substances (7). The classification of *C <sup>i</sup> <sup>f</sup>* and *Cd* are classified in **Table 6**.

**Table 5** shows that the *C <sup>i</sup> <sup>f</sup>* values of sampling sites range from 0.32 to 25.00. The average *C <sup>i</sup> <sup>f</sup>* value of each element and the percentage of that in *Cd* are in the following

**Figure 3.**

**81**

*Contamination factors (C<sup>i</sup>*

*<sup>f</sup> ) of different elements detected in sediments.*

*Water Quality Ecological Risk Assessment with Sedimentological Approach*

*DOI: http://dx.doi.org/10.5772/intechopen.88594*

L1 111.11 6.97 1.99 1.90 2.41 1.34 0.42 126.14 L2 148.15 12.84 2.84 2.15 3.12 1.05 0.49 170.64 L3 592.59 8.22 3.92 2.34 2.81 0.87 1.15 611.90 L4 601.85 4.39 2.85 1.87 2.17 0.73 1.07 614.93 L5 629.63 5.68 4.33 2.36 3.29 0.63 1.22 647.14 L6 583.33 8.07 5.38 2.86 3.96 1.24 1.47 606.31 L7 546.30 3.90 3.31 1.71 1.80 0.71 0.81 558.54 L8 175.95 13.33 3.15 2.20 3.21 1.67 1.02 200.53 L9 166.67 13.79 10.38 2.95 6.89 1.77 1.00 203.45 L10 203.70 16.36 7.44 2.87 6.56 1.98 0.84 239.75 L11 166.67 13.14 5.03 2.57 4.11 1.65 0.79 193.96 L12 157.41 12.69 3.43 2.28 3.53 1.38 0.67 181.39 L13 194.44 10.68 5.86 2.50 4.52 1.67 0.71 220.38 L14 130.56 9.13 3.99 1.90 2.93 0.98 0.42 149.91 L15 297.22 11.56 2.98 2.70 2.36 0.94 0.53 318.29 L16 175.00 11.06 2.85 2.33 2.04 0.92 0.50 194.70 L17 402.78 15.91 7.26 3.50 3.79 1.26 0.57 435.07 L18 750.00 20.03 2.85 3.60 2.34 0.98 0.58 780.38 L19 325.00 15.65 5.68 3.01 3.96 1.26 0.76 355.32 Min 111.11 3.90 1.99 1.71 1.80 0.63 0.42 126.14

**Elements (***St<sup>i</sup>* **value) Cd As Cu Pb Ni Cr Zn**

**30 10 5 5 5 2 1**

*ERI* <sup>¼</sup> <sup>P</sup>**<sup>7</sup>** *i*¼**1** *Ei r*


#### **Table 6.**

*Classification of the potential ecological risk.*

*Water Quality Ecological Risk Assessment with Sedimentological Approach DOI: http://dx.doi.org/10.5772/intechopen.88594*

**Figure 3.**

**3.3 Methods**

**3.4 Results**

average *C <sup>i</sup>*

*Ci*

1 ≤ *C<sup>i</sup>*

3 ≤ *C<sup>i</sup>*

*Ci*

*Ei*

40 ≤ *E<sup>i</sup>*

80 ≤ *E<sup>i</sup>*

160 ≤ *E<sup>i</sup>*

*Ei*

**Table 6.**

**80**

*3.4.1 The degree of contamination Cd*

*Water Quality - Science, Assessments and Policy*

The classification of *C <sup>i</sup>*

**Table 5** shows that the *C <sup>i</sup>*

**Table 5** shows the contamination factor *C <sup>i</sup>*

*<sup>r</sup>* < 40 *Ei*

*<sup>r</sup>* ≥ 320 *Ei*

*Classification of the potential ecological risk.*

*<sup>r</sup>* < 80 30 ≤ *E<sup>i</sup>*

*<sup>r</sup>* < 160 60 ≤ *E<sup>i</sup>*

*<sup>r</sup>* < 320 120 ≤ *E<sup>i</sup>*

The potential ecological risk index is used to assess the ecological risk of the Liaohe River. The computational formula was shown as Eqs. (1)–(4). The *T<sup>i</sup>*

from the Liaohe River. In Håkanson's research, seven metals (Hg, Cd, As, Cu, Pb, Cr, and Zn) and one organic pollutant (PCBs) were considered. However, in this study, there are only seven metals considered. Therefore, the *Cd* classification thresholds are modified. According to Håkanson's approach, the threshold for the "low degree of contamination" is 7, corresponding to the number of substances (7).

*<sup>f</sup>* and *Cd* are classified in **Table 6**.

**Threshold Modified threshold Degree of risk**

*<sup>f</sup>* < 3 / Moderate

*<sup>f</sup>* < 6 / Considerable

*<sup>f</sup>* ≥ 6 / Very high

*Cd* < 8 *Cd* < 7 Low 8 ≤ *Cd* < 16 7 ≤ *Cd* < 14 Moderate 16 ≤ *Cd* < 32 14 ≤ *Cd* < 28 Considerable *Cd*≥ 32 *Cd*≥ 28 Very high

ERI < 150 ERI < 60 Low 150 ≤ ERI < 300 60 ≤ ERI < 120 Moderate 300 ≤ ERI < 600 120 ≤ ERI < 240 Considerable ERI ≥ 600 ERI ≥ 240 Very high

*<sup>f</sup>* < 1 / Low

*<sup>f</sup>* value of each element and the percentage of that in *Cd* are in the following

As, Cu, Pb, Ni, Cr, and Zn are 30, 10, 5, 5, 5, 2, and 1, respectively [7, 22].

*<sup>r</sup>* for Cd,

*<sup>f</sup>* of the substances in the sediments

*<sup>f</sup>* values of sampling sites range from 0.32 to 25.00. The

*<sup>r</sup>* < 30 Low

*<sup>r</sup>* < 60 Moderate

*<sup>r</sup>* < 120 Considerable

*<sup>r</sup>* < 240 High

*<sup>r</sup>* ≥ 240 Very high

*Contamination factors (C<sup>i</sup> <sup>f</sup> ) of different elements detected in sediments.*



is 58, so the classification threshold of ERI could be 60. The classification of *Ei*

**Table 7** illustrates the potential ecological risks of the heavy metals in the

potential ecological risk. Cd at L1 posed a considerable potential ecological risk (111.11), while at other sampling sites, it shows high or very high potential ecolog-

extremely severe pollution. The ERI values for the sampling sites range from 126.14 to 780.38. According to the listing of the ERI values (**Table 6**), the lowest ERI value for site L1 is over 120; therefore, all the sampling sites all have the considerable or very high potential ecological risk. The mean value of ERI (358.35) for the sediments in the Liaohe River indicates very high potential ecological risk (**Figure 4**).

The Liaohe River is used as a case study to illustrate this approach. The investigation of seven heavy metals (Cd, As, Cu, Ni, Pb, Cr, and Zn) in the sediments suggest that the Liaohe River is dominated by the pollution of Cd which contributes

Because of the "toxic-response" factor, compared with other approaches, the potential ecological risk index can distinguish the differences among substances and aquatic systems. Therefore, this approach has outstanding advantages to assess the risk of water system as a widely used approach which can provide a better overall ecological risk to the aquatic system. However, two main problems are neglected in

given to the BPI value. Different aquatic systems have different sensitivities to toxic substances. According to Eq. (3) and **Table 4**, the effect of BPI value on the results depends on the degree of contamination of the aquatic system. If the pollution of the study aquatic system is serious, the BPI value will have large effect on the index calculation. Ecological risks can be evaluated more accurately by measuring the BPI value of the study aquatic system. (2) According to Håkanson's research [7, 23], the classification thresholds should be modified for different assessments. In this chapter, a reasonable suggestion for modification is suggested as well as applied. For *Cd*, the threshold for the "low risk" is modified by the number of substances. For *Ei*

elements. There are still other problems deserve researchers concerns in the application of this approach, for example, the determination of accumulation areas in the

*<sup>r</sup>* is replaced by *Sti*

ranked as: Cd (93.39%) > As (3.13%) > Cu (1.26%) > Ni (0.97%) > Pb (0.70%) > Cr (0.34%) > Zn (0.22%). All elements except cadmium have low potential ecological risk. According to the ERI results, due to the serious pollution of cadmium, all the sampling sites have the considerable or very high potential ecological risk. Thus, it is important to control the pollution of cadmium. This study assesses the risk of Liaohe River by the modified risk classification criterion. Therefore, the results are different from [11], the risks assessed by this study are more serious. It is worth discussing how to use the risk classification criterion. This study

(93.39%) > As (3.13%) > Cu (1.26%) > Ni (0.97%) > Pb (0.70%) > Cr

*Water Quality Ecological Risk Assessment with Sedimentological Approach*

ERI are classified in **Table 6**.

750.00. The consequence of *Ei*

(0.34%) > Zn (0.22%). The *Ei*

According to the category of *Ei*

ical risk. The very highest *E<sup>i</sup>*

**4. Discussion**

sediments from the Liaohe River. The *Ei*

*DOI: http://dx.doi.org/10.5772/intechopen.88594*

around 94% potential ecological risk. The *Ei*

suggests using the modified risk classification criteria.

threshold for the "low risk" is modified by the *T<sup>i</sup>*

For ERI, the threshold for the "low risk" is modified by the sum of *T<sup>i</sup>*

the application of this method. (1) *T<sup>i</sup>*

**83**

*<sup>r</sup>* and

*<sup>r</sup>* values of sampling sites range from 0.42 to

*<sup>r</sup>* means of the remaining sites are

. More attention should be

*<sup>r</sup>* value of the most toxic element.

*<sup>r</sup>* of all

*<sup>r</sup>*, the

*<sup>r</sup>* (mean) of the 7 heavy metals are ranked as: Cd

*<sup>r</sup>* (**Table 6**), these six heavy metals have a low

*<sup>r</sup>* value is observed for Cd (750.00) at L18, indicates

*<sup>r</sup>* value of As, Cu, Pb, Ni, Cr, and Zn are all below 30.

**Table 7.**

*The potential ecological risk factor (Ei <sup>r</sup>) of different elements detected in sediments [11].*

order: Cd (70.74%) > As (7.12%) > Cu (5.71%) > Zn (5.01%) > Ni (4.39%) > Cr (3.84%) > Pb (3.18%). Every *C <sup>i</sup> <sup>f</sup>* value of Pb and Cr is less than 1.0. For the average *C i <sup>f</sup>* value, Cd and As have a very high and moderate contamination factor, respectively. Whereas, Cu, Zn, Ni, Cr, and Pb have low contamination factors.

The resulting *Cd* values of each sample site ranged from 6.75 to 29.83. According to the category of *Cd* (**Table 6**), only sample L1 has the low degree of contamination. Ten sampling sites are classified as moderate and 7 sampling sites as having high contamination factors, sample L19 is classified into very high contamination factor. **Figure 3** clearly shows that Cd has the highest contamination factor. That means the Liaohe River is dominated by the pollution of one element—Cadium.

#### *3.4.2 The potential ecological risk Ei <sup>r</sup> and ERI*

If the classification thresholds of *Cd* are modified, the *Ei <sup>r</sup>* and ERI should also be modified. The first level of *E<sup>i</sup> <sup>r</sup>* is fixed by the *T<sup>i</sup> <sup>r</sup>* value of the most toxic element. This means that the results of the given water body are compared with a reference lake which has no contamination (*C <sup>i</sup> <sup>f</sup>* = 1). Similarly, the first level of ERI is fixed by the sum of *T<sup>i</sup> <sup>r</sup>* value of all the elements.

In the Liaohe River case study, the most toxic element is Cd and the *T<sup>i</sup> <sup>r</sup>* of Cd is 30. Therefore, the classification threshold of *Ei <sup>r</sup>* is 30. The sum of *T<sup>i</sup> <sup>r</sup>* of all elements

*Water Quality Ecological Risk Assessment with Sedimentological Approach DOI: http://dx.doi.org/10.5772/intechopen.88594*

is 58, so the classification threshold of ERI could be 60. The classification of *Ei <sup>r</sup>* and ERI are classified in **Table 6**.

**Table 7** illustrates the potential ecological risks of the heavy metals in the sediments from the Liaohe River. The *Ei <sup>r</sup>* values of sampling sites range from 0.42 to 750.00. The consequence of *Ei <sup>r</sup>* (mean) of the 7 heavy metals are ranked as: Cd (93.39%) > As (3.13%) > Cu (1.26%) > Ni (0.97%) > Pb (0.70%) > Cr (0.34%) > Zn (0.22%). The *Ei <sup>r</sup>* value of As, Cu, Pb, Ni, Cr, and Zn are all below 30. According to the category of *Ei <sup>r</sup>* (**Table 6**), these six heavy metals have a low potential ecological risk. Cd at L1 posed a considerable potential ecological risk (111.11), while at other sampling sites, it shows high or very high potential ecological risk. The very highest *E<sup>i</sup> <sup>r</sup>* value is observed for Cd (750.00) at L18, indicates extremely severe pollution. The ERI values for the sampling sites range from 126.14 to 780.38. According to the listing of the ERI values (**Table 6**), the lowest ERI value for site L1 is over 120; therefore, all the sampling sites all have the considerable or very high potential ecological risk. The mean value of ERI (358.35) for the sediments in the Liaohe River indicates very high potential ecological risk (**Figure 4**).
