*2.3.3 The toxic factor Sti*

In this risk index approach, the toxic factor (St<sup>i</sup> Þ primarily provides two important pieces of information—the threat to man and the threat to the aquatic ecological system. Håkanson calculated the "toxic-response" factor based on "abundance principle" and "sink-effect". The potential biotoxicity of a metal element is inversely proportional to its abundance.

3.The "relative abundance" in each media is calculated by comparing the highest mean concentration with others in each media. For example, the value of Zn is 80 times higher than that of Pb in land animals, so Pb should be given 80. The

**Element Igneous rocks Soils Freshwater Land plants Land animals** As 1.8 6.0 0.0004 0.2 ≤0.2 Cd 0.2 0.06 <0.08 0.6 ≤0.5 Cr 100 100 0.00018 0.23 0.075 Cu 55 20 0.01 14 2.4 Hg 0.08 0.03–0.8 0.00008 0.015 0.046 Pb 12.5 10 0.005 2.7 2.0 Zn 70 50 0.01 100 160

*Water Quality Ecological Risk Assessment with Sedimentological Approach*

**Land plants**

56-Cr 500-As 2130-Cr

125-Hg 6670-Hg 3480-Hg

Cr 1.0 1.0 56 435 2130\* 2623 493.0 110.0 Zn 1.4 2.0\* 1.0 1.0 1.0 6.4 4.4 1.0 Cu 1.8 5.0 1.0 7.1 67\* 81.9 14.9 3.4 Pb 8.0 10 2.0 37 80\* 137 57.0 13.0 As 56 17 25 500 800\* 1398 598 140.0 Cd 500 1670\* 31 167 320 2688 1018 230.0 Hg 1250 240 125 6670\* 3480 11,765 5095 1160.0

*) [16].*

**Land animals** P**5 1**

P**4 1**

**Abundance number**

4.The "abundance numbers" are determined by the sum of the five relative

balance the effect of extreme "abundance numbers" and to avoid the inappropriate weight to the "abundance numbers", the largest value marked "\*" for each element should be omitted. The results of every element are given

by division by the value of 4.4 (the value of Zn). For example, the "abundance

<sup>1</sup> column. To

<sup>1</sup> . In the end, the "abundance numbers" are obtained

abundance numbers for each element. It is shown in the P<sup>5</sup>

*\*To avoid the inappropriate weight to the sum, the largest value for each element should be omitted.*

results of relative abundance are given in **Table 2**.

in the column marked P<sup>4</sup>

**Table 1.**

**Table 2.**

**75**

**Order Igneous rocks**

6 500-Cd 240-

7 1250-Hg 1670-

*The abundance of various elements in different media (<sup>10</sup><sup>6</sup>*

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

Hg

Cd

*Relative abundance of elements in different media [17].*

**Soils Fresh water**

1 1.0-Cr 1.0-Cr 1.0-Zn 1.0-Zn 1.0-Zn 2 1.4-Zn 2.0-Zn 1.0-Cu 7.1-Cu 67-Cu 3 1.8-Cu 5.0-Cu 2.0-Pb 37-Pb 80-Pb 4 8.0-Pb 10-Pb 25-As 167-Cd 320-Cd 5 56-As 17-As 31-Cd 435-Cr 800-As

To evaluate the "abundance principle", the following methodology has been used:


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


**Table 1.**

(e.g., Ni, V, Mo, Co). Fe, Mn, and P are unsuitable as sediment parameters in this approach because their concentration is often influenced by physical or chemical

*<sup>f</sup>* ), single elements, *C <sup>i</sup>*

), Håkanson chose preindustrial

*n*

*<sup>f</sup>* are classified as follows:

*n*, for example, the national standards and the back-

background reference values as PCB = 0.01, Hg = 0.25, Cd = 1.0, As = 15, Cu = 50, Pb = 70, Cr = 90, and Zn = 175 (ppm). Different researchers [13–15] have selected

The thresholds are determined by the number of substances. Eight substances were analyzed in Håkanson's research; therefore, the threshold is 8 for the low degree of contamination. *Cd* classification thresholds should be modified for different assessments. For example, if there are five substances analyzed in an assessment, then the threshold for the low degree of contamination should be 5.

tant pieces of information—the threat to man and the threat to the aquatic ecological system. Håkanson calculated the "toxic-response" factor based on "abundance principle" and "sink-effect". The potential biotoxicity of a metal element is

To evaluate the "abundance principle", the following methodology has been

abundance of various elements in igneous rocks, soils, fresh water, land plants,

2.Relative abundance of elements in different media are shown in **Table 2**. The value of 1.0 is given to the element with the highest mean concentration in each media. For example, Zn has the highest value in land animals, so Zn

1.The basic data for the evaluation is given in **Table 1**. It illustrates the

*<sup>f</sup>* are classified as

*<sup>f</sup>* , which accounts for

Þ primarily provides two impor-

processes in the sediments.

other reference values for *C<sup>i</sup>*

*2.3.2 The degree of contamination Cd*

the total of the sediment pollution. *C <sup>i</sup>*

*Cd* <8, low degree of contamination;

8≤ *Cd* <16, moderate degree of contamination; 16≤ *Cd* < 32, considerable degree of contamination;

*Cd* ≥32, very high degree of contamination.

In this risk index approach, the toxic factor (St<sup>i</sup>

inversely proportional to its abundance.

should be given the value of 1.0.

ground reference value.

*2.3.3 The toxic factor Sti*

and land animals.

used:

**74**

follows: *C i*

1≤ *C <sup>i</sup>*

3≤ *C <sup>i</sup>*

*C i*

According to the contamination factor (*C <sup>i</sup>*

*<sup>f</sup>* ≥6, very high contamination factor.

For the preindustrial reference condition *C<sup>i</sup>*

*<sup>f</sup>* <3, moderate contamination factor;

*<sup>f</sup>* <6, considerable contamination factor;

The degree of contamination value (*Cd*) is the sum of all *C <sup>i</sup>*

*<sup>f</sup>* <1, low contamination factor;

*Water Quality - Science, Assessments and Policy*

*The abundance of various elements in different media (<sup>10</sup><sup>6</sup> ) [16].*


#### **Table 2.**

*Relative abundance of elements in different media [17].*


numbers" of Cr is obtained by dividing 493.0 (the sum of 1.0, 1.0, 56, and 435 in the line of Cr) by 4.4. The results of the "abundance numbers" are following: Zn < Cu < Pb < Cr < As < Cd < Hg.

determined using the standard Kjeldahl method [19]. The IG value is the ignition loss of dried sediment samples (550°C for 1 h). The N value and IG value are given in mg/g and % ds (ds = dry substance), respectively. After Håkanson's analysis, the

It is should be noted that the thresholds of low potential ecological risk are

The comprehensive potential ecological risk index (ERI) is the sum of all *Ei*

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

contaminants. The thresholds of ERI value are determined similarly. ERI values are

It could consider that there is a reference lake in which each substance's *C <sup>i</sup>*

**Substance** *St<sup>i</sup>* **value** *T<sup>i</sup>*

Cd <sup>30</sup> <sup>30</sup>�

Cu <sup>5</sup> <sup>5</sup>�

Pb <sup>5</sup> <sup>5</sup>�

Cr <sup>2</sup> <sup>2</sup>�

Zn <sup>1</sup> <sup>1</sup>�

As 10 10

PCB 40 40�BPI/5 Hg 40 40�5/BPI

values which is used to express the potential ecological risk for a given aquatic

ERI < 150, low potential ecological risk for the water system.

ERI ≥600, very high ecological risk for the water system.

*r*

*r*

*<sup>r</sup>* values are classified as follows:

*<sup>r</sup>* value of substances. This means that even though there

*<sup>r</sup>* values are determined by the number and type of

*<sup>r</sup>* values of every substance in an assessment.

*<sup>r</sup>* can reach a value of 40 [20].

� � is used to express the poten-

*r*

*f*

*<sup>r</sup>* **value**

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 5*=* ffiffiffiffiffiffiffiffi *BPI* <sup>q</sup> <sup>p</sup>

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 5*=* ffiffiffiffiffiffiffiffi *BPI* <sup>q</sup> <sup>p</sup>

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 5*=* ffiffiffiffiffiffiffiffi *BPI* <sup>q</sup> <sup>p</sup>

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 5*=* ffiffiffiffiffiffiffiffi *BPI* <sup>q</sup> <sup>p</sup>

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 5*=* ffiffiffiffiffiffiffiffi *BPI* <sup>q</sup> <sup>p</sup>

relationships between the BPI value and *Sti* are the following (**Table 4**).

*Water Quality Ecological Risk Assessment with Sedimentological Approach*

*2.3.5 The monomial potential ecological risk factor Ei*

*<sup>r</sup>* <40, low potential ecological risk;

*<sup>r</sup>* ≥320, very high ecological risk.

system. ERI values are classified as follows:

The thresholds of *Cd* and *Ei*

determined by the sum of all the *T<sup>i</sup>*

*<sup>r</sup> of elements [7].*

tial ecological risk for a substance. *Ei*

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

*Ei*

*Ei*

**Table 4.** *The St<sup>i</sup> and T<sup>i</sup>*

**77**

40≤ *Ei*

80≤ *Ei*

160≤ *E<sup>i</sup>*

determined by the largest *T<sup>i</sup>*

is no contamination (*C <sup>i</sup>*

The monomial potential ecological risk factor *Ei*

*<sup>r</sup>* < 80, moderate potential ecological risk;

*<sup>r</sup>* < 320, high potential ecological risk;

*<sup>f</sup>* <sup>¼</sup> 1), the *Ei*

*2.3.6 The comprehensive potential ecological index ERI*

*<sup>r</sup>* <160, considerable potential ecological risk;

5.The "corrected abundance numbers" are closely related to the toxicity coefficient, but it cannot represent "toxic-response" factor directly. Håkanson modified the "abundance numbers" by multiplying it by the "sink-factors", where the sink factor is determined as:

Sink factor <sup>¼</sup> Natural background concentration in fresh water Preindustrial reference value for lake sediments

**Table 3** lists the data of natural background values for freshwater and preindustrial reference values. This results in the following "corrected abundance numbers": Zn = 57, Cr = 220, Cu = 680, Pb = 920, As = 3780, Cd = 46,000 and Hg = 371,200.

6. In order to match the dimensions of the contamination factors, first, divide all "corrected abundance numbers" by 57 (the value of Zn), then to take the square root of these figures, and then round off the values. This gives the following results: Zn = 1, Cr = 2, Cu = 5, P b = 5, As = 10, Cd = 30, and Hg = 80. The result of Hg is too high compared to Cd, therefore the toxic factor of Hg was determined as 40 by Håkanson. In addition, Håkanson hypothesized that the sedimentological toxic factor for PCB should be the same magnitude as that of Hg. Therefore, the *Sti* value for PCB was given 40. This gives the following *Sti* : Zn = 1, Cr = 2, Cu = 5, Pb = 5, As = 10, Cd = 30, Hg = 40, and PCB = 40.

#### *2.3.4 The "toxic-response" factor T<sup>i</sup> r*

It is well known that the sensitivity of organisms to the toxic substances is related to the biological characteristics of the aquatic systems [18]. This section describes sensitivity to toxic substances and how it varies from lake to lake. Håkanson uses the bioproduction index (BPI) value to represent the sensitivity. The BPI value is calculated by measuring the ignition loss (the IG value) and the nitrogen content (the N value) of sediment samples. The BPI value is defined as the nitrogen content on the regression line for IG = 10%. The nitrogen content is


**Table 3.** *Sink factors of elements [16].*

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

determined using the standard Kjeldahl method [19]. The IG value is the ignition loss of dried sediment samples (550°C for 1 h). The N value and IG value are given in mg/g and % ds (ds = dry substance), respectively. After Håkanson's analysis, the relationships between the BPI value and *Sti* are the following (**Table 4**).

#### *2.3.5 The monomial potential ecological risk factor Ei r*

numbers" of Cr is obtained by dividing 493.0 (the sum of 1.0, 1.0, 56, and 435

coefficient, but it cannot represent "toxic-response" factor directly. Håkanson modified the "abundance numbers" by multiplying it by the "sink-factors",

Preindustrial reference value for lake sediments

: Zn = 1, Cr = 2, Cu = 5, Pb = 5, As = 10, Cd = 30, Hg = 40, and

**Sink factor (10**�**<sup>3</sup> )** **Abundance number**

**Corrected abundance numbers**

Sink factor <sup>¼</sup> Natural background concentration in fresh water

6. In order to match the dimensions of the contamination factors, first, divide all "corrected abundance numbers" by 57 (the value of Zn), then to take the square root of these figures, and then round off the values. This gives the following results: Zn = 1, Cr = 2, Cu = 5, P b = 5, As = 10, Cd = 30, and Hg = 80. The result of Hg is too high compared to Cd, therefore the toxic factor of Hg was determined as 40 by Håkanson. In addition, Håkanson hypothesized that the sedimentological toxic factor for PCB should be the same magnitude as that of Hg. Therefore, the *Sti* value for PCB was given 40. This gives the

**Table 3** lists the data of natural background values for freshwater and preindustrial reference values. This results in the following "corrected abundance numbers": Zn = 57, Cr = 220, Cu = 680, Pb = 920, As = 3780, Cd = 46,000 and

*r*

It is well known that the sensitivity of organisms to the toxic substances is related to the biological characteristics of the aquatic systems [18]. This section describes sensitivity to toxic substances and how it varies from lake to lake.

Håkanson uses the bioproduction index (BPI) value to represent the sensitivity. The BPI value is calculated by measuring the ignition loss (the IG value) and the nitrogen content (the N value) of sediment samples. The BPI value is defined as the nitrogen content on the regression line for IG = 10%. The nitrogen content is

> **Preindustrial reference value for lake sediments**

Cr 0.2 90 2 110.0 220 Zn 10 175 57 1.0 57 Cu 10 50 200 3.4 680 Pb 5 70 71 13.0 920 As 0.4 15 27 140.0 3780 Cd 0.2 1 200 230.0 46,000 Hg 0.08 0.25 320 1160.0 371,200

in the line of Cr) by 4.4. The results of the "abundance numbers" are

5.The "corrected abundance numbers" are closely related to the toxicity

following: Zn < Cu < Pb < Cr < As < Cd < Hg.

where the sink factor is determined as:

*Water Quality - Science, Assessments and Policy*

Hg = 371,200.

following *Sti*

*2.3.4 The "toxic-response" factor T<sup>i</sup>*

**Element Background**

**Table 3.**

**76**

*Sink factors of elements [16].*

**concentration in fresh water**

PCB = 40.

The monomial potential ecological risk factor *Ei r* � � is used to express the potential ecological risk for a substance. *Ei <sup>r</sup>* values are classified as follows:

*Ei <sup>r</sup>* <40, low potential ecological risk; 40≤ *Ei <sup>r</sup>* < 80, moderate potential ecological risk; 80≤ *Ei <sup>r</sup>* <160, considerable potential ecological risk; 160≤ *E<sup>i</sup> <sup>r</sup>* < 320, high potential ecological risk; *Ei <sup>r</sup>* ≥320, very high ecological risk.

It is should be noted that the thresholds of low potential ecological risk are determined by the largest *T<sup>i</sup> <sup>r</sup>* value of substances. This means that even though there is no contamination (*C <sup>i</sup> <sup>f</sup>* <sup>¼</sup> 1), the *Ei <sup>r</sup>* can reach a value of 40 [20].
