**3. Analysis**

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

**38**

**Figure 1.**

*(a) Map of South Africa showing the Blesbokspruit water catchment [17]; (b) study area showing tailing dump* 

*site, wetland and river; (c) transfer mechanism of trace metals/elements.*

### **3.1 Experimental analysis**

Soil samples (tailing sediments) were oven dried at 100o C for 24 hours and mechanically pass through a sieve for particle distribution [18]. Approximately 2 g aliquots of the various soil samples were weighed into a Teflon crucible and then moistened with 100 mL of 1 M HCl acid in a microwave digestion system 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. The solutions were filtered using a Whatman filter paper and the filtrates stored in sterile bottles prior to being analysed for heavy metals using inductively coupled plasma-optical emission spectrometry (ICP-OES, GBC Quantima Sequential).

At very high pressure using a mould, 10 g of each of the representative soil samples were pelletised and then inserted in the sample compartment of an X-ray fluorescence (XRF; Rigaku ZSX PrismusII), to help in analysing the elemental compositions of the various minerals that make up the soil samples.

Morphological and mineralogical phase analyses of the tailing material were carried out using a scanning electron microscope (SEM, Tescan Vega 3 XMU) operated with an Oxford software and X-ray diffractometer (XRD; Rigaku Ultima IV), respectively.

In a soil-to-water suspension (1:2.5, w/w), the pH of representative soil samples was determined, while electrical conductivity (EC) was measured in a 1:5 soil-towater suspension using a Crison multimeter model MM 41. Also carried out was an assessment of the total dissolved solids (TDS) in guidelines as stipulated by standard protocols of APHA [19].

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

For precision analysis, all reagents used were of analytical standards, while apparatus and glassware inclusive were acid-washed with a 5% nitric acid. Multiple levels of calibration standard solutions are prepared from a Certipur ICP multielement standard (Merck KGaA) by diluting the stock multi-elemental standard solution (1000 mg L<sup>−</sup><sup>1</sup> ) in 0.5% (v/v) nitric acid. The calibration curves for all the studied elements were in the range of 0.01–1.0 mg L<sup>−</sup><sup>1</sup> . The conditions of the ICP were the same as described in a similar study as reported by Okereafor et al. [20].

## **4. Results and discussion**

#### **4.1 Particle size distribution of tailing sediments**

**Table 1** highlights the textural characteristics of the tailing sediments as gotten from mechanical sieve analysis. The main fractions of all tailing sediments were fine sand (0.150–0.075 mm) and clay (0.075–0.053 mm) with average composition of 66.03% for fine sand, 23.08% clay and 10.89% silt, respectively. With fine sand constituting a major part of the soil within the tailing dump site which are loose with little or no vegetation cover, wind and soil erosion particularly during continued rainfall are likely to occur with no restriction. The steep and inclined nature of


#### **Table 1.**

*Sieve analysis of the soil from the gold mine tailing.*

the dump will support surface run-off of sediments which end up as discharge into the wetland.

#### **4.2 Physicochemical analysis**

Various indices such as electrical conductivity, pH, moisture, soil organic matter, texture, temperature, etc. contribute to the quality of soil and as such have great influence on its basic functions such as water retention, promotion of biodiversity, flood resistance, landslides, erosion and agricultural support [21]. However, the physicochemical properties of water to a large extent affect water usage. **Table 2** gives a summary of the observed physicochemical properties of water analysed in this study.

#### *4.2.1 pH of stream water and soil samples*

As a physical parameter, pH is a measure of the hydrogen ion concentration in the water/soil samples as ranked on a scale of 1.0–14.0. The lower the pH value of a material (soil/water), the more acidic it is, and the higher the pH value, the basic, or alkaline, it is. Generally, many chemical and biological processes are affected by pH as different organisms flourish better at different ranges of pH. A pH metre (Jenway model 3510) was used to determine the pH levels of the different water samples and sediments obtained from an abandoned golf mine dump. The observed pH values were within the limit of standard irrigation water (6.5–8.4), ranging from 6.31 to 6.35, thus validating the mobility and availability of heavy metals for plant uptake due to the presence of fewer H+ ions [22]. A low pH of 4.21 was recorded for the tailing sediments which supports the heterogenous deposits of sulphidic residues from mining activities. The ability of plants to take up nutrients could be affected by the acidity of tailings, hence the sparse distribution of vegetation at the mine tailing site. The identified heavy metals (Zn2+, Ni2+, Pb2+, AS2+, Cu2+) together with the observed pH of the tailings and wetland could result in acid mine drainage (AMD).

In the long run, the continuous erosion of the tailing sediments to surrounding water bodies could result in damage to metal pipes, tanks and fittings used for irrigation purposes by farmers. Consequently, the alkalinity (acid absorbing potential) of the various water samples based on the reported pH (6.31–6.35) is an indication that most of the available dissolved carbon dioxide have been converted into bicarbonate ion.

**41**

tion pipes.

*Mobility of Trace Element Contaminants from Abandoned Gold Mine Dump to Stream Waters…*

**Sample names pH EC μS/cm TDS mg/L** Wetland (WL) 6.31 948.00 606.72 Blesbokspruit (BS) 6.33 1040.00 665.60 Heidelberg (HB) 6.34 1235.00 790.40 Suikerbosrang (SB) 6.35 488.00 312.32 Mine tailing 4.21 132.00 84.48

The most influential water quality guideline on crop productivity is the water salinity hazard as measured by electrical conductivity (ECw). EC measures salinity from all identified ions dissolved in a sample including negatively charged ions

The values of electrical conductivity were determined by the concentration of ionic species contained in water. Using a standard of 84μS and a Crison multimeter (MM 41), water samples from Heidelberg (HB) recorded the highest electrical conductivity value of 1235 μS followed by (BS) 1040 μS, (WL) 948 μS and (SB)

A value of 132 μS was recorded for the tailing sediments. The higher electrical conductivity recorded could imply the presence of higher dissolved salt or ion concentration which suggests that the samples have higher conductivity.

The observed high ECw water on crop productivity will result in plants' inability to compete with ions in the soil solution for water (physiological drought). The higher EC implies less water is available to plants, despite the soil appearing wet, thus a reduced yield potential. This is because plants can only transpire "pure"

Using the expression 0.64 × EC, a measure of the total dissolved amount of substance was obtained. The lowest value was observed in the MT (84.48 mg/L) with HB recording the highest (790.40 mg/L). WL and BS both had 606.72 mg/L and 665.60 mg/L, respectively, while 312.32 mg/L was recorded in (SB). Crop yield can be adversely affected by the higher concentration of salt in water, thereby leading to soil degradation and pollution of groundwater. This parameter however did not deviate from the international standards, but the high concentrations of dissolved solids could result in some technical effects. Dissolved solids can produce hard water, which leaves deposits and films on fixtures and on the insides of irriga-

The energy-dispersive X-ray (EDX) microanalysis is a technique of elemental analysis associated to electron microscopy based on the generation of characteristic X-rays that reveal the presence of elements present in specimens. EDX technique is useful in the study of environmental pollution as it carries a huge vantage in the detection of heavy metals because they are nonbiodegradable and they can accumu-

).

3) and positively charged ions (e.g., Ca++, Na+

water as usable plant water in soil solution decreases as EC increases.

**4.3 Chemical composition of tailing sediments**

late in ecological systems, thus resulting in pollution.

*DOI: http://dx.doi.org/10.5772/intechopen.90818*

*Physicochemical analysis of sediments and water samples.*

*4.2.2 Electrical conductivity*

*4.2.3 Total dissolved solids*

(e.g., Cl<sup>−</sup>, NO<sup>−</sup>

488 μS.

**Table 2.**

*Mobility of Trace Element Contaminants from Abandoned Gold Mine Dump to Stream Waters… DOI: http://dx.doi.org/10.5772/intechopen.90818*


**Table 2.**

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

No. 100 5.68 No. 140 45.51 No. 200 15.84 No. 270 10.25 PAN 22.72 Total 100 % Sand 67.03 % Silt 10.25 % Clay 22.72

the dump will support surface run-off of sediments which end up as discharge into

**Sieve size (ASTM) % materials, retains (gms)**

Various indices such as electrical conductivity, pH, moisture, soil organic matter, texture, temperature, etc. contribute to the quality of soil and as such have great influence on its basic functions such as water retention, promotion of biodiversity, flood resistance, landslides, erosion and agricultural support [21]. However, the physicochemical properties of water to a large extent affect water usage. **Table 2** gives a summary of the observed physicochemical properties of water analysed in

As a physical parameter, pH is a measure of the hydrogen ion concentration in the water/soil samples as ranked on a scale of 1.0–14.0. The lower the pH value of a material (soil/water), the more acidic it is, and the higher the pH value, the basic, or alkaline, it is. Generally, many chemical and biological processes are affected by pH as different organisms flourish better at different ranges of pH. A pH metre (Jenway model 3510) was used to determine the pH levels of the different water samples and sediments obtained from an abandoned golf mine dump. The observed pH values were within the limit of standard irrigation water (6.5–8.4), ranging from 6.31 to 6.35, thus validating the mobility and availability of heavy metals for plant uptake

tailing sediments which supports the heterogenous deposits of sulphidic residues from mining activities. The ability of plants to take up nutrients could be affected by the acidity of tailings, hence the sparse distribution of vegetation at the mine tailing site. The identified heavy metals (Zn2+, Ni2+, Pb2+, AS2+, Cu2+) together with the observed pH of the tailings and wetland could result in acid mine drainage (AMD). In the long run, the continuous erosion of the tailing sediments to surrounding water bodies could result in damage to metal pipes, tanks and fittings used for irrigation purposes by farmers. Consequently, the alkalinity (acid absorbing potential) of the various water samples based on the reported pH (6.31–6.35) is an indication that most of the available dissolved carbon dioxide have been converted

ions [22]. A low pH of 4.21 was recorded for the

**40**

into bicarbonate ion.

the wetland.

**Table 1.**

this study.

**4.2 Physicochemical analysis**

*Sieve analysis of the soil from the gold mine tailing.*

*4.2.1 pH of stream water and soil samples*

due to the presence of fewer H+

*Physicochemical analysis of sediments and water samples.*
