**1. Introduction**

Although South Africa was the biggest producer of gold globally, the industry has been experiencing several drawbacks such as mine closure of older mines and shafts, declining mineral production, exhaustion of gold reserves, global low gold prices, the high energy requirement for deep-level mining, high wage demands and social unrests as well as the generation of acid mine drainage from the mines and tailings storage facilities [1]. The cessation of the large mining operations has detrimental effects as access to gold reserves are far underground, and mining operations resorted to dewatering activities to keep the groundwater level away from the mining operations [2]. Cessation of mining further resulted in flooding of the voids, a substantial cause of groundwater and surface water contamination by acidic water [3]. The acidic Sulfur rich wastewater or effluent from mining and industrial environments has greater consequences for Acid Mine Drainage in both actively operating and abandoned mines [4]. During the active mining process, the extraction of the gold-bearing conglomerate layer is crushed and gold become extracted [5]. Once the gold is extracted, the crushed rock is deposited on heaps known as slimes or tailings dumps, and generally, the gold-bearing conglomerates contain approximately 3% pyrite which gets deposited in slimes and tailings dumps. AMD is defined as a natural process (more correctly termed "acid rock drainage", or ARD) that occurs when sulfurcontaining minerals become exposed to water and oxygen, in the presence of bacteria known as the *Acidithiobacillus* and *Ferrooxidans* [6]. Sulfides in pyrite rock (Fool's gold) then react with oxygen and water and leading to the production of sulfuric acid.

The sulfuric acid percolates through the slimes dam and dissolves some of the heavy metals. The resultant acidic, net acidic, and saline plume enters the surrounding soils, and eventually enters the groundwater and surface water bodies. AMD is a slow process characterized by low pH and high salinity levels with higher concentrations of sulfate, iron, aluminum, manganese, and the possibility of radionuclides [7]. The dark, reddishbrown and low pH water (often lower than 2.5) is difficult to rectify. The most important salts and heavy metals associated with AMD pose serious contamination threats to the environment and human health [8]. Metals such as Fe, Mn, Al, and other heavy metals as well as metalloids such as arsenic [9]. Heavy metals such as mercury and metalloid such as arsenic can become toxic and pose additional risks to the environment even when they are introduced to the water system in minute amounts [10].

Factors such as pH, redox potential, and soil types have a greater impact on the uptake of the element in the sediments. Soil types have a significant effect on the uptake of metals. In addition, clay soils, in particular, have higher sorption capacity which in turn reduces the availability of metals. Clay soils with high organic content enhance the conditions that favor successive precipitation of sulfides, and this can reduce the available elements at the lower depths. In addition, soils with less organic matter content tend to release elements from the sediments and improve metals uptake, a requirement of plant growth. Salinity levels also improve the rates of metal uptake especially Cr, Ni, and Zn [11]. According to [12], variations in water pH affect the ability of elements to be soluble. Furthermore, this also impacts the deposition ability of metals in the sediments as well as in the water column. The concentrations of Zn, Mn, and Ni in sediment have a direct bearing on the increased uptake of elements by plants [13].

Many aquatic macrophytes are classified as heavy metal accumulators and they are known to accumulate metals to various degrees and store them in below-ground tissues (rhizomes, roots) or above-ground tissues (leaves, stems). In some cases, aquatic macrophytes have been found to absorb higher concentrations of metals than are found in the water [14]. Plant species differ in their ability and tolerance to metal uptake and accumulation. Some plant species can accumulate high concentrations of a single metal and translocate it to the roots, rhizomes, stems, and/or leaves, while others can accumulate more than one element in different parts. Another category of

*The Evaluation of the Macrophyte Species in the Accumulation of Selected Elements… DOI: http://dx.doi.org/10.5772/intechopen.105708*


#### **Table 1.**

*Descriptive summary of the study sites.*

plants is known as the excluders and can tolerate metal-rich environments by reducing the number of elements translocated from the below-ground parts to the aboveground parts. For plants to survive, they must adapt to the chemical and physical characteristics of the soil, water, atmosphere, and climate. Plants that grow and survive in metal-contaminated environments (metallophytes) have the distinct characteristic of tolerance. Plants also may be categorized as metal excluders, indicators, accumulators, or even hyperaccumulators [15]. Hyperaccumulators can translocate metals to their above-ground organs, and thereby extract and accumulate quantities that exceed any other species in the same environment (**Table 1**) [25].

#### **1.1 Study methods**

The study area is found in the Gauteng Province, Southern Johannesburg, Under the Westonaria Municipality, **Figure 1**. The area is also called the West Wits, it is located in Carletonville, and it is situated along the 15 kilometers (km) Varkenslaagte drainage line, also known as the old canal of the West Wits Operations (AngloGold Ashanti). The area is divided by a rocky ridge called Gatsrand. It covers approximately 3785.5 ha and approximately 38.58% which equates to 14,604 ha under deep mining (Mponeng, Tautona, and Savuka mine). The rest of the area is occupied by miningrelated infrastructures such as tailing dams, mining plants, shafts, related operations, and residential wells as excavations. The Northern part of the mining area has been

**Figure 1.** *Map of South Africa showing the location of Western Deep Levels in Carletonville.*


#### **Table 2.**

*Some herbaceous plants used in mine sited for phytoremediation.*

converted into agricultural land and mining activities while only a small portion of the area is still in its natural state as shown in **Figure 1**.

The study site consisted of 17 artificial wetlands and only five selected wetlands were studied these were artificial wetlands 1, 2, 4, 5, and 7, and regarded as site 1, site 2, site 3, *The Evaluation of the Macrophyte Species in the Accumulation of Selected Elements… DOI: http://dx.doi.org/10.5772/intechopen.105708*

**Figure 2.** *Some* P. communis *species with AMD water flowing between the plants.*

#### **Figure 3.**

*Metal precipitation on the soil crusts with some metals sticking to the basal part of the* S. corymbosus *and* P. communis *species.*

site 4, and 5 in this study. The summary of the investigated sites is presented in **Table 2**. The selected five sites out of the seventeen, were due to clear observations made in terms of growth and development of the macrophytes and other physical characteristics (algae growth and tadpoles occurring) on these sites when compared to the rest of the other sites. Accessibility was also another factor considered when conducting sampling at those sites. The effectiveness of rehabilitation was much clearer on these sites. The wetlands were grown with macrophyte species of *Typha Capensis*, *Schoenoplectus Corymbosus*, and *Phragmites Communis*.

#### **Figure 4.**

*Some metal precipitates at the edge of the artificial wetland with some precipitates attached to the lower parts and leaves of the* P. communis *spp that fall off often become covered by the salts.*

**Figure 5.** *Some AMD and metal precipitation of the floodplain of the right side adjacent to the canal.*
