*2.3.6 The comprehensive potential ecological index ERI*

The comprehensive potential ecological risk index (ERI) is the sum of all *Ei r* values which is used to express the potential ecological risk for a given aquatic system. ERI values are classified as follows:

ERI < 150, low potential ecological risk for the water system. 150≤ ERI<300, moderate potential ecological risk for the water system. 300≤ ERI<600, considerable potential ecological risk for the water system. ERI ≥600, very high ecological risk for the water system.

The thresholds of *Cd* and *Ei <sup>r</sup>* values are determined by the number and type of contaminants. The thresholds of ERI value are determined similarly. ERI values are determined by the sum of all the *T<sup>i</sup> <sup>r</sup>* values of every substance in an assessment. It could consider that there is a reference lake in which each substance's *C <sup>i</sup> f*


**Table 4.** *The St<sup>i</sup> and T<sup>i</sup> <sup>r</sup> of elements [7].* value = 1.0, BPI value = 5.0. This means that there is no contamination in the reference lake. The data from one's samples would be compared with the reference lake. The ERI classification thresholds are modified for different assessments. For example, if there were eight substances analyzed in Håkanson's research and the sum of all the *T<sup>i</sup> <sup>r</sup>* values is 155, the thresholds of the first level could be 150. Moreover, Håkanson ignores the influence of BPI value on the *T<sup>i</sup> <sup>r</sup>* value because of the *C <sup>i</sup> <sup>f</sup>* value is 1.0. Therefore, he regards the sum of *St<sup>i</sup>* value as the threshold.

**3.1 Description of the study area**

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

**3.2 Data collection and processing**

Cd, Cr, Cu, Ni, Pb, and Zn). The details are found in [11].

River [21].

**Table 5.**

**79**

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

The Liaohe River is located in the south of northeast China (**Figure 2**). It is one of the seven major rivers in China. As an important aquatic ecosystem, it plays an important role in the local economic and social development. Because of anthropogenic activities, the pollution of the Liaohe River is becoming a more serious problem. The Liaohe River has become one of the most polluted rivers in China. Therefore, it is significant to assess the quality of the Liaohe

*Water Quality Ecological Risk Assessment with Sedimentological Approach*

Nineteen superficial sediment samples were collected along the Liaohe River protected area. At each site, three surface sediments were collected and placed into polyethylene bags and sealed. An Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES) was applied for the determination of heavy metals (As,

L1 3.70 0.70 0.40 0.38 0.48 0.67 0.42 6.75 L2 4.94 1.28 0.57 0.43 0.62 0.53 0.49 8.86 L3 19.75 0.82 0.78 0.47 0.56 0.44 1.15 23.97 L4 20.06 0.44 0.57 0.37 0.43 0.37 1.07 23.31 L5 20.99 0.57 0.87 0.47 0.66 0.32 1.22 25.09 L6 19.44 0.81 1.08 0.57 0.79 0.62 1.47 24.78 L7 18.21 0.39 0.66 0.34 0.36 0.36 0.81 21.13 L8 5.87 1.33 0.63 0.44 0.64 0.84 1.02 10.77 L9 5.56 1.38 2.08 0.59 1.38 0.89 1.00 12.86 L10 6.79 1.64 1.49 0.57 1.31 0.99 0.84 13.63 L11 5.56 1.31 1.01 0.51 0.82 0.83 0.79 10.83 L12 5.25 1.27 0.69 0.46 0.71 0.69 0.67 9.72 L13 6.48 1.07 1.17 0.50 0.90 0.84 0.71 11.67 L14 4.35 0.91 0.80 0.38 0.59 0.49 0.42 7.94 L15 9.91 1.16 0.60 0.54 0.47 0.47 0.53 13.67 L16 5.83 1.11 0.57 0.47 0.41 0.46 0.50 9.34 L17 13.43 1.59 1.45 0.70 0.76 0.63 0.57 19.13 L18 25.00 2.00 0.57 0.72 0.47 0.49 0.58 29.83 L19 10.83 1.57 1.14 0.60 0.79 0.63 0.76 16.32 Min 3.70 0.39 0.40 0.34 0.36 0.32 0.42 6.75 Max 25.00 2.00 2.08 0.72 1.38 0.99 1.47 29.83 Mean 11.16 1.12 0.90 0.50 0.69 0.61 0.79 15.77 Reference lake ("unpolluted") 1.00 1.00 1.00 1.00 1.00 1.00 1.00 7.00

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

*C i*

**Cd As Cu Pb Ni Cr Zn**

*<sup>f</sup> Cd*
