**1. Introduction**

The mining of minerals such as gold, coal, titanium and other natural resources plays several roles in South Africa's emerging economy with many positive outcomes as well as negative consequences. Till date, the mining sector remains the largest employer of labour. Mining of various minerals is a common sight in the country but of late has become a public menace due to land degradation and contamination of major water bodies through the discharge of waste materials such as overburdens, waste rocks, tailings, slags, mine water and gaseous wastes.

The resource being mined, geology of an area and technology adopted are some of the factors that influence the nature, characteristic properties and level of mine waste generated at specific mines. Mining companies in South Africa, due to legislations and regulations pertaining to general waste management at mining sites, endeavour to manage waste generated during their operations in a bid to avoid the release of contaminants into the environment [1]. Unfortunately, some level of contaminants, which constitute crushed, sand-like materials, still finds their way into the ecosystem.

By definition, mine dumps, also known as residue stockpiles, refer to any debris, discard, tailing, slimes, screening, slurry, waste rock, foundry sand, beneficiation plant waste, ash or any other product derived from or incidental to a mining operation and which is stockpiled, stored or accumulated for potential reuse, or which is disposed of, by the holder of a mining right, mining permit, production right or an old order right [2, 3]. Generally, mine wastes are unwanted, currently uneconomic, solid and liquid materials found at or near mine sites that largely constitute one of the world's major waste streams due to their composition of high concentrations of elements and compounds that impact negatively on humans and animals, the surrounding environment and plants alike [4]. An alarming number of mine dumps often characterised by a complex mixture of metals and dust particles are located at several jurisdictions of the country. This implies that during windy conditions, exposure to dust could be high for close-by inhabitants. Other challenging issues associated with mine wastes include environmental impacts such as the loss of agricultural lands because of their conversion to waste storage facilities and the successive introduction of sediments and other impurities into adjoining surface and groundwater from water running over exposed chemically reactive wastes [5–8].

Most mine wastes have heavy metals (HMs) as a major component, and their continued circulation in soil and water puts the world in a nerve-wracking situation due to their toxic and deleterious effects [9]. HMs such as cadmium (Cd), thallium (Ti), zinc (Zn), lead (Pb), arsenic (As), mercury (Hg), chromium (Cr), copper (Cu), lead (Pb), iron (Fe) and nickel (Ni) are naturally occurring components of the earth's crust and are often referred to as metallic chemical elements with a relatively high density—at least five times the specific gravity of water [10]. At trace concentrations, HMs such as Cu, Cr + 3, Zn, Mn, Co and molybdenum (Mo) are of biological significance; however long-term exposures and high concentrations impact negatively on several biomolecules. It is noteworthy to mention that at very low concentrations, Hg, Cd, Cr + 6, As and Pb stand to be very toxic [11].

Sediments are vital components of aquatic habitat as they can retain contaminants that are not bioavailable to humans [12]. Pollutants are released into water bodies via processes such as sediment resuspension, desorption and redox reactions of sorptive substances. This further explains why sediments despite being reservoirs could at the same time act as likely source of pollutants in the aquatic system [12, 13]. Mine tailings (MT) having the possibilities of containing some HMs are seen in different areas of Blesbokspruit in Ekurhuleni Municipality, South Africa. Over the years, these mine tailings solidify, leaving mountainous structures made of very fine sand particles. Several agents of erosion such as wind and surface run-off after heavy rainfall transport sediments to surrounding water bodies (rivers). These rivers are major sources of water supply to agricultural lands and may constitute diverse environmental problems to humans, animals and plants [14].

A comprehensive understanding of the physicochemical features of soil and water pollutants provides a platform for careful soil management aimed at reducing the adverse effect of the pollutants on the ecosystem. Heavy metals from mine tailings in ionic solutions sometimes contaminate groundwater via leaching and are absorbed by plants; thus it is introduced to the food chain [15]. In another instance,

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tory for storage at 4o

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

animals drink from stream waters containing these HMs. The final consumption of

South Africa's agricultural sector had suffered immense setbacks in the recent past, owing to issues of water shortages and the problem of acid mine drainage (AMD), amongst others. These issues over the years have impacted adversely on the quality and quantity of farm produce. Due to irregular municipal water supply, farmers suffer economically in the quest for portable water; thus, they end up relying on surrounding stream water for their animals and crops. Following the growing numbers of small-scale farming in the Blesbokspruit area of Ekurhuleni, this study seeks to investigate the physicochemical features of selected stream waters and sediments from an abandoned gold mine tailing site with the goal of assessing the distribution of HMs in stream water and sediments from surrounding mining

Due to outraging scarcity of water resources, South Africa is referred as a semi-arid nation. Study materials were obtained from a mine tailing dump facility located within the Blesbokspruit catchment (26°10′12″S 28°27′52″E), Heidelberg (34°01′59″S 18°52′28″E) and Suikerbosrand (26°29′46″S 28°21′00″E) rivers, respectively, all of which constitute part of the Vaal River Barrage secondary catchment, located in the eastern region of the Gauteng Province. The Blesbokspruit catchment has in it an important and international wetland covering an area of about 1858 km<sup>2</sup> with a Ramsar recognition dated as far back as 1986. This wetland has a gold mine tailing dump located very close to it and provides support and habitat to several species of birds and plants [16]. Extended part of the study area is used for agricultural activities such as cultivation of crops and rearing of animals. The sampling sites (**Figure 1a**) were selected due to what seems to be the ironic presence of an abandoned gold mine tailing dump that has located next to it an artificial wetland. The wetland was supposed to aid in remediation of the discharge from the mines. In addition, an informal settlement characterised with mostly rural–urban dwellers that engage in farming activities was also in proximity. The rivers being considered in this study are to the best of our knowledge the major water sources for farming activities such as irrigation and feeding of local cows. The subsistence farmers within this area created artificial channels in a bid to redirect water from the streams to special reservoirs that service mostly the animals (**Figure 1b**). During rainfall and often windstorms, sediments from the tailing dumps get eroded into the wetland and subsequently into the surrounding rivers as a result of overflow

Using sterile bottles, water samples were randomly obtained from four sampling

C prior to further analysis. Collected soil samples were oven

sites located at various directions and distances within the Blesbokspruit catchment. The water samples were assigned names: wetland (WL), Blesbokspruit (BS), Heidelberg (HB) and Suikerbosrand (SB). Soil samples (mine tailing sediments) were collected using a Teflon-coated soil auger and put in labelled polyethylene bags with clear designation MT1–MT4, respectively. The collected water samples from identified streams were stored in an insulated icebox and transported to the labora-

these plants and animals is of great concern due to danger of HM toxicity.

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

sites and the ecological risks of such HMs.

**2.1 Description of the sampling site**

and surface run-offs (**Figure 1c**).

**2.2 Collection of samples and pretreatment**

**2. Sampling and samples**

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

animals drink from stream waters containing these HMs. The final consumption of these plants and animals is of great concern due to danger of HM toxicity.

South Africa's agricultural sector had suffered immense setbacks in the recent past, owing to issues of water shortages and the problem of acid mine drainage (AMD), amongst others. These issues over the years have impacted adversely on the quality and quantity of farm produce. Due to irregular municipal water supply, farmers suffer economically in the quest for portable water; thus, they end up relying on surrounding stream water for their animals and crops. Following the growing numbers of small-scale farming in the Blesbokspruit area of Ekurhuleni, this study seeks to investigate the physicochemical features of selected stream waters and sediments from an abandoned gold mine tailing site with the goal of assessing the distribution of HMs in stream water and sediments from surrounding mining sites and the ecological risks of such HMs.
