**3. Analysis**

### **3.1 Experimental analysis**

20 representative tailing samples of about 5 g each were oven dried at 100°C for 24 hours and passed through a 2 mm sieve. Aliquots of approximately 2 g of the various tailing samples were weighed into a Teflon crucible and moistened with 100 mL of 1 M HCl acid for the determination of the HCl-soluble fraction of heavy metals. The mixtures were covered and placed on a shaker for 12 hours at 130 rpm.

*Evaluation of Trace Elemental Levels as Pollution Indicators in an Abandoned Gold Mine Dump… DOI: http://dx.doi.org/10.5772/intechopen.89582*

The solutions were filtered through a Whatman filter paper, and the filtrates were stored in sterile bottles prior to analysis of minerals using inductively coupled plasma-optical emission spectrometry (ICP-OES).

10 g each of the representative tailing samples were pelletized using a mold at very high pressure and then placed in the sample compartment of the X-ray fluorescence spectrometer (XRF; Rigaku ZSX PrismusII). This was done to analyze the major and trace element oxides of the tailing samples.

Physicochemical properties such as pH and EC (electrical conductivity) of the soil samples (tailings) were measured in a soil-to-water suspension (1,2.5, w/w) and a 1:5 tailings-to-water suspension using a Crison multimeter (model MM 41) respectively [23]. Loss on Ignition (LOI) analysis was used to determine the organic matter content (% OM) of the various tailing's samples [24]. The grain size distribution of tailing samples was determined using the hydrometer method [25].

## **3.2 Quality assurance and quality control**

Apparatus and glassware used were acid-washed with 5% nitric acid for precision analysis while reagents were of analytical standard. The trace metals were determined using ICP-OES (Model - GBC Quantima Sequential) operated under specific conditions of 1300 W RF power, 15 L min�<sup>1</sup> plasma flow, 2.0 L min�<sup>1</sup> auxiliary flow, 0.8 L min�<sup>1</sup> nebulizer flow, 1.5 mL min�<sup>1</sup> sample uptake rate. Multiple levels of calibration standard solutions prepared from a Certipur ICP multi-element standard (Merck KGaA) was used in the calibration of the ICP-OES. Metal determination was done using Axial view, while 2-point background correction and 3 replicates were employed in the measurement of analytical signal. The emission intensities were determined for the most sensitive lines free of spectral interference. By diluting the stock multi-elemental standard solution (1000 mg L�<sup>1</sup> ) in 0.5% (v/v) nitric acid, the calibration standards were prepared. The calibration curves for all the studied elements were in the range of 0.01 to 1.0 mg L�<sup>1</sup> .

#### **3.3 Data analyses**

sampling site located along Outeniqua Road & Cloverfield Weg in Springs,

**Station no. Latitude (S) Longitude (E)**

28<sup>0</sup> 27<sup>0</sup>

28<sup>0</sup> 35<sup>0</sup>

28<sup>0</sup> 40<sup>0</sup>

28<sup>0</sup> 44<sup>0</sup>

28<sup>0</sup> 50<sup>0</sup>

29<sup>0</sup> 10<sup>0</sup>

29<sup>0</sup> 15<sup>0</sup>

290 20<sup>0</sup>

29<sup>0</sup> 35<sup>0</sup>

290 42<sup>0</sup>

29<sup>0</sup> 47<sup>0</sup>

29<sup>0</sup> 50<sup>0</sup>

29<sup>0</sup> 53<sup>0</sup>

30<sup>0</sup> 10<sup>0</sup>

30<sup>0</sup> 15<sup>0</sup>

30<sup>0</sup> 25<sup>0</sup>

30<sup>0</sup> 29<sup>0</sup>

30<sup>0</sup> 35<sup>0</sup>

300 40<sup>0</sup>

30<sup>0</sup> 48<sup>0</sup>

1 26<sup>0</sup> 10<sup>0</sup>

*Trace Metals in the Environment - New Approaches and Recent Advances*

2 26<sup>0</sup> 15<sup>0</sup>

3 260 04<sup>0</sup>

4 26<sup>0</sup> 17<sup>0</sup>

5 260 21<sup>0</sup>

6 26<sup>0</sup> 30<sup>0</sup>

7 260 00<sup>0</sup>

8 260 27<sup>0</sup>

9 26<sup>0</sup> 09<sup>0</sup>

10 260 38<sup>0</sup>

11 26<sup>0</sup> 43<sup>0</sup>

12 26<sup>0</sup> 34<sup>0</sup>

13 260 13<sup>0</sup>

14 260 19<sup>0</sup>

15 26<sup>0</sup> 48<sup>0</sup>

16 260 36<sup>0</sup>

17 260 40<sup>0</sup>

18 260 14<sup>0</sup>

19 260 23<sup>0</sup>

20 260 54<sup>0</sup>

*Location of the Blesbokspruit gold mine tailings sediment samples.*

In a bid to assess the level of trace metal contamination in the mine tailings, about 2 kilograms of 20 representative tailing samples were obtained from the dump. Preceding the removal of top tailing samples (2 cm) using an auger, samples were taken at a depth of 10 cm for every 50 m horizontal interval for a wider coverage. The collected soil samples (tailings) were kept cool in an icebox (<4°C) and transported to the laboratory for further analyses in sterile plastic bags.

20 representative tailing samples of about 5 g each were oven dried at 100°C for 24 hours and passed through a 2 mm sieve. Aliquots of approximately 2 g of the various tailing samples were weighed into a Teflon crucible and moistened with 100 mL of 1 M HCl acid for the determination of the HCl-soluble fraction of heavy metals. The mixtures were covered and placed on a shaker for 12 hours at 130 rpm.

Ekurhuleni are illustrated in **Table 1**.

**2.2 Sampling (material) description**

**3. Analysis**

**84**

**Table 1.**

**3.1 Experimental analysis**

The history and degree of trace metal pollution in an environment can be ascertained from the surrounding sediments by comparing the pollutant metal concentration with an unpolluted reference material. The average shale concentration as an International standard reference for unpolluted sediment was utilized [26]. This study applied pollution indices such as (i) metal contamination factor, (ii) contamination degree, (iii) index of geoaccumulation, and (iv) pollution load index to assess heavy metal contamination.

#### *3.3.1 Assessment according to contamination factor*

By calculating the ratio of the concentration of a specific trace metal in the study area and the concentration of the background concentration of the corresponding metal, the contamination factor was determined. **Table 2** shows the various terminologies in describing contamination factor class and level [27]. CF is an effective tool for monitoring pollution over a period and for the respective metals was calculated using the equation as prescribed by [28].

$$\text{CF} = \frac{(\text{Mean metal concentration at contaminant} \times \text{Gm})}{(\text{Level of pre} - \text{individual concentration of individual metal } (\text{Cbackground}))}$$


#### **Table 2.**

*Terminologies used to describe contamination factor [27].*

*3.3.2 Assessment according to contamination degree*

Contamination degree (CD) refers to the sum of all the contamination factor (CF) values of a specific sampling site. It is a diagnostic tool aimed at providing a measure of the degree of overall contamination in surface layers in a sampling site or core. In this study, CD was assessed using Eq. (2).

$$\text{CD} = \sum\_{i=0}^{n} \mathcal{G} \tag{2}$$

*3.3.4 Assessment according to pollution load index*

*Classification for the geoaccumulation index (Igeo) [30].*

*DOI: http://dx.doi.org/10.5772/intechopen.89582*

root from the n-CFs that was obtained for all the metals.

the number of metals.

**Table 4.**

background level [32].

various criteria.

**Table 5.**

**87**

Pollution load index, which is a useful tool in heavy metal pollution evaluation, refers to the number of times by which each heavy metal concentrations in the sediments (tailings) exceeded the background concentration in the soil, and it provides a summary of the overall level of heavy metal toxicity in a sample. The world average concentrations of metals using shale was used as background for identified heavy metals in this study [26]. The PLI can provide an estimate of the various metal contamination status and precautionary steps to be taking [31]. Using Eq. (4) as developed by [26], the PLI of the study site was calculated by obtaining the n-

**Igeo Value Class Contamination Level** Igeo ≤ 0 0 Uncontaminated

 < Igeo < 2 2 Moderately contaminated < Igeo < 3 3 Moderately/strongly contaminated < Igeo < 4 4 Strongly contaminated < Igeo < 5 5 Strongly/extremely contaminated < Igeo 6 Extremely contaminated

0 < Igeo < 1 1 Uncontaminated/moderately contaminated

*Evaluation of Trace Elemental Levels as Pollution Indicators in an Abandoned Gold Mine Dump…*

where CF is the contamination factor, CFn is the CF value of metal n, and n is

Interpretation of PLI values are categorized into two levels; polluted (PLI > 1) and unpolluted (PLI < 1) whereas PLI = 1 indicate trace metal loads close to the

The potential contamination of the tailing's sediments was evaluated using the

**Metal Not polluted Moderately polluted Heavily polluted Present study** Cd — — >6 7.1 Cr <25 25–75 >75 860.3 Cu <25 25–50 >50 0.1 Pb <40 40–60 >60 121.9 Zn <90 90–200 >200 3.9

*USEPA guidelines for sediments (mg/kg dry weights) in comparison with gold mine tailings sediments.*

*3.3.5 Assessment according to the United States environmental protection agency*

proposed sediment quality guidelines by USEPA [19] **Table 5**. Illustrated the

PLI <sup>¼</sup> ð Þ CF1 � CF2 � CF3 � … � CFn <sup>1</sup>*=*<sup>n</sup> (4)

A list of terminologies as prescribed by [29] used in describing the contamination degree of the site under investigation is summarized in **Table 3**.

#### *3.3.3 Assessment according to geoaccumulation index*

To quantify the level of heavy metal contamination associated with the study site, the geoaccumulation index (I-geo) was adopted. The Igeo is an important method used for the interpretation of the quality of sediments in the sampling site. It is used to assess impacts due to anthropogenic activities and was determined using Eq. (3) as prescribed by [30].

$$\mathbf{I}\_{\text{geo}} = \log\_2 \frac{\mathbf{C} \mathbf{n}}{\mathbf{1}.5 \mathbf{B} \mathbf{n}} \tag{3}$$

where Cn is the measure of the metal concentration in the examined metal n in the sediment, Bn is the background concentration of the element (average shale concentration) or reference value of the metal n, and 1.5 is the correction factor due to the lithogenic effect that could result in variations in the background values for a given metal in the environment. There are seven grades (0–6) ranging from unpolluted to highly polluted in the geoaccumulation index scale as described by [30] (**Table 4**).


**Table 3.** *Terminologies used to describe contamination degree for soil [29].* *Evaluation of Trace Elemental Levels as Pollution Indicators in an Abandoned Gold Mine Dump… DOI: http://dx.doi.org/10.5772/intechopen.89582*


**Table 4.**

*3.3.2 Assessment according to contamination degree*

*Terminologies used to describe contamination factor [27].*

**Table 2.**

or core. In this study, CD was assessed using Eq. (2).

*3.3.3 Assessment according to geoaccumulation index*

using Eq. (3) as prescribed by [30].

[30] (**Table 4**).

**Table 3.**

**86**

Contamination degree (CD) refers to the sum of all the contamination factor (CF) values of a specific sampling site. It is a diagnostic tool aimed at providing a measure of the degree of overall contamination in surface layers in a sampling site

CD <sup>¼</sup> <sup>X</sup>*<sup>n</sup>*

tion degree of the site under investigation is summarized in **Table 3**.

**CF Description**

*Trace Metals in the Environment - New Approaches and Recent Advances*

CF < 1 Low contamination factor 1 ≤ CF < 3 Moderate contamination factor 3 ≤ CF < 6 Considerate contamination factor CF ≥ 6 Very high contamination factor

*i*¼0

A list of terminologies as prescribed by [29] used in describing the contamina-

To quantify the level of heavy metal contamination associated with the study site, the geoaccumulation index (I-geo) was adopted. The Igeo is an important method used for the interpretation of the quality of sediments in the sampling site. It is used to assess impacts due to anthropogenic activities and was determined

Cn

Igeo ¼ log <sup>2</sup>

**CD Description**

*Terminologies used to describe contamination degree for soil [29].*

CD < 6 Low contamination degree 6 ≤ CD < 12 Moderate contamination degree 12 ≤ CD < 24 Considerate contamination degree CD ≥ 24 Very high contamination degree

where Cn is the measure of the metal concentration in the examined metal n in the sediment, Bn is the background concentration of the element (average shale concentration) or reference value of the metal n, and 1.5 is the correction factor due to the lithogenic effect that could result in variations in the background values for a given metal in the environment. There are seven grades (0–6) ranging from unpolluted to highly polluted in the geoaccumulation index scale as described by

*cf* (2)

<sup>1</sup>*:*5Bn (3)

*Classification for the geoaccumulation index (Igeo) [30].*

#### *3.3.4 Assessment according to pollution load index*

Pollution load index, which is a useful tool in heavy metal pollution evaluation, refers to the number of times by which each heavy metal concentrations in the sediments (tailings) exceeded the background concentration in the soil, and it provides a summary of the overall level of heavy metal toxicity in a sample. The world average concentrations of metals using shale was used as background for identified heavy metals in this study [26]. The PLI can provide an estimate of the various metal contamination status and precautionary steps to be taking [31]. Using Eq. (4) as developed by [26], the PLI of the study site was calculated by obtaining the nroot from the n-CFs that was obtained for all the metals.

$$\text{PLI} = \left( \text{CF1} \times \text{CF2} \times \text{CF3} \times \dots \times \text{CFn} \right)^{1/\text{n}} \tag{4}$$

where CF is the contamination factor, CFn is the CF value of metal n, and n is the number of metals.

Interpretation of PLI values are categorized into two levels; polluted (PLI > 1) and unpolluted (PLI < 1) whereas PLI = 1 indicate trace metal loads close to the background level [32].

#### *3.3.5 Assessment according to the United States environmental protection agency*

The potential contamination of the tailing's sediments was evaluated using the proposed sediment quality guidelines by USEPA [19] **Table 5**. Illustrated the various criteria.


**Table 5.**

*USEPA guidelines for sediments (mg/kg dry weights) in comparison with gold mine tailings sediments.*
