CHAPTER 3 STUDY AREA AND METHODOLOGY
South Africa is a country rich in minerals and Limpopo province is one of the provinces with the widest range of minerals deposits (Citizen, 2004). Due to the large number of these deposits, there is a high possibility of groundwater contamination in Limpopo province and this is one of the factors which prompted the choice of the province as a study area. The majority of the province comprises of rural areas where groundwater is the only source of water for plants, animals and humans.
This chapter describes the methodology by which the research was conducted. The study comprised of three objectives. The methods used to achieve each are discussed in the sections below.
OBJECTIVE 1: TO IDENTIFY POTENTIALLY CONTAMINATED AREAS IN LIMPOPO PROVINCE.
This objective was achieved in two stages, as outlined in sections 3.1.1 and 3.1.2.
Step 1: Preliminary identification of study areas
The first step was to identify the broad areas where As, Hg and Pb contamination may occur based on geological characteristics. A geological maps showing the spatial distribution of minerals and the location of mines in Limpopo is presented as Figure 3.1.
According to Fig. 3.1, mineral deposits are widespread throughout the Limpopo Province with clusters of heavy mineralization occurring in the vicinity of Musina (L1); in an east-west band extending from the south-eastern corner of the Bochum district to Giyani (L2); around Gravelotte and Phalaborwa in the Namakgale districts (L3); around Mokopani (A4); and to the west of Bela-Bela (Warmbaths) (L5).
These five areas represent the possible study areas. Areas where all three toxic elements were located were obvious choices for selection as study areas. Where there was little or no coincidence, research areas were identified using random selection methods.
Areas with potential Hg contamination
Careful perusal of Fig. 3.1 shows only one area with mercury-containing deposits. That is the area in the vicinity of Gravelotte.
Gravelotte in area L3 is one of the rural areas in Limpopo that is very rich in minerals. Among the 57 listed minerals found in this area are gold and mercury. The presence of these minerals suggests that there could be the possibility of arsenic and lead contamination. It is thus obvious that Gravelotte should be included as a study area.
Areas with potential As contamination.
As mentioned in Chapter 2, arsenic-bearing minerals are primarily associated with geological settings where sulphide mineralization has taken place. Arsenic is usually present in areas where gold, silver, copper, nickel, zinc, lead and cobalt are found (Sami & Druzynski, 2003).
The majority of the areas of heavy mineralization shown in Fig 3.1, with the exception of those near Musina and in the Namakgale districts, coincide with those identified by Sami and Druzynski (2003) as potentially high risk areas (Fig 3.2) using borehole data. Groundwater in these areas showed As concentrations ranging from 0.01 to 0.1 mg/l. The areas so identified included the surrounds of Mokopane (L4), Leeupoort (L5), Vivo (L2), and almost the whole of the Nebo district.
In order to delineate the second study area, one of the areas shown on Fig 3.2 was selected randomly by assigning numbers to the areas and picking one number out of hat. The region so selected was L1, i.e. the region to the west of Bela-Bela, in the vicinity of Leeupoort.
Areas with potential lead contamination
According to Lurie (1977), zinc and lead minerals generally occur together in deposits. Lead ore minerals include Galena (PbS) and cerussite (PbCO3). A number of old mines related to the Bushveld Complex produced Zn and Pb in the past. Numerous lead deposits also occur in Transvaal dolomite.
Perusal of Fig 3.1 indicates the presence of Pb in the area near Gravelotte as well as to the south of Leeupoort. It was therefore assumed that the two previously selected areas would also exhibit some potential for lead contamination.
Step 2: Final selection of study areas
In order to select the specific areas to be studied, the actual villages where the research would be conducted had to be identified. Prerequisites for this selection were that the villagers were dependent upon subsistence farming, that goats were reared in the communities and that goat’s milk was consumed.
A geographical grid was superimposed over the selected regions in Fig 3.1. The “Leeupoort” grid occupies the area between 24°37’30 » and 25°00’00 » South and 27°42’00 » to 28°00’00 » East (2427DC). This area is henceforth referred to as study area
A. The area around Gravelotte lies between the latitudes 23°45’00 » to 24°00’00 » South and longitudes 30°30’00 » to 30°45’00 » East (2330DC) (study area B).
In order to select sample villages, all villages in the two study areas were listed. The villages in study area A are: Buffelskraal, Rooiberg, Doornfontein, Leeupoort, Weihoek, Driefontein, Rooikrans, Koperfontein and Ruin, while the villages study area B are Kwagga, Salwana, Malete, Mpageni, Gravelotte, Mashororo, Mawa, Waterbok, Kondowi, Haartebeest, Grootfontein, Mabete, Eden, Thiergarten, Murchison, Bettie, Bosbok, Allonbridge and Leysdorp.
Two villages were selected within each of the study areas by means of random selection. The names of all the villages in the specific area were written on different piece of paper, folded and placed in container. The folded papers were drawn randomly. Two villages were selected for sampling from each study area. The two from study area A were Rooiberg and Leeuport while Gravelotte and Kwagga were selected for study area B.
The final selection was confirmed after site visits to each of the villages to ascertain that those selected actually fulfilled the four criteria namely that:
There is high potential for contamination of groundwater due to geology.
Rural communities are dependent on groundwater as main water source.
Villagers are dependent on subsistence farming.
Infants are fed on goats’ milk once they are weaned from mothers’ milk.
All four selected villages (Rooiberg, Leeupoort, Gravelotte and Kwagga) were found to fulfill these criteria and depend exclusively on subsistence farming. Figures 3.3 and 3.4 depict the topographical maps of the study areas showing the location of rural villages.
Characteristics of the study areas
Tin mines were located at Rooiberg and Leeupoort. According to Lurie (1977: 94), the Rooiberg tinfield lies about 60 km west of Bela-Bela. In this area mineralization occurs in sediments of the Pretoria Group. Minerals found in the area include tourmaline, cassiterite, carbonates and a variety of sulphides (pyrrhotite, pyrite, chalcopyrite, bismuthinite, sphalerite and galena (Leube & Stumpfl, 1963). The minerals contain gold, copper, iron, tin, tungsten, lead, zinc, molybdenum, bismuth and arsenic (Lurie, 1977). In the 1970s there were three working mines over a curves strike of 20 km at Rooiberg, Nieupoort and Leeupoort. A number of dormant workings are also located in the area.
Gravelotte is located on the Murchison Range, which represents a remnant of Swaziland rocks. It is well known for its rich deposits of antimony and gold. This metal is used for pigments and detonators, matches and flame-proofing chemicals (Lurie, 1977, 83). Currently South Africa is one of the largest producers of antimony.
Antimony and related minerals are found in mineralized quartzites and schists in Archaean granites. The general geological structure consists of steeply folded parallel anticlines and synclines. The rocks form a line of hills running in an ENE direction for about 55 km from Leydsdorp and is known amongst geologists as the ‘Antimony Line’ (Lurie, 1977).
Gravelotte Mines also exploit the gold-bearing reefs of the Witwatersrand and Transvaal Supergroups. Gold mineralization was formed under conditions of partially closed systems, where various mineral-forming processes developed (metasomatism, crystallization of true solutions and gels, gel metasomatism, dispersion of crystalline phases, segregation of mineral particles, formation of early minerals, etc.) (Safonov and Prokof’ev, 2006).
Interestingly, perusal of geological and mineral maps of South Africa (Fig 3.1), indicate that mercury deposits are also found in the vicinity of Gravelotte. This is the only place where such deposits are indicated. According to Prof Morris Viljoen in the Department of Geology, University of the Witwatersrand (Wits) (pers. Comm.), mercury was mined in the vicinity of Gravelotte during the war, but the mercury mines have subsequently closed down.
OBJECTIVE 2: TO DESCRIBE THE EXTENT OF ENVIRONMENTAL CONTAMINATION IN THE SELECTED AREAS.
This objective was achieved by collecting and analyzing groundwater, soil and plant samples in the selected areas.
A member of each community who had been working with the local government in these areas over the years was identified as the contact persons in each of the areas. In study area A, Mr. Morris was the contact person (Fig. 3.5) while in area B; Mrs Shishenga was the contact person. The purpose of the research was explained to them and they in turn conveyed it to the community. This method assisted in obtaining the cooperation of the communities.
Collection of water samples
The major source of water for Leeupoort, Gravelotte and Kwagga are boreholes while at Rooiberg the source of water is a dam.
The samples (water, plants and milk) were collected in plastic containers which had been washed with detergent, rinsed and then re-rinsed again with distilled water to avoid any external contamination.
Plastic containers were used in order to prevent the adherent of the element unto the container which could affect the integrity of the samples.
The first set of water samples were collected in the winter season (July), 2007. These were collected from the dam at Rooiberg and the borehole at Leeupoort, respectively, since these are the major water supplies for domestic purposes in the villages. One liter samples were collected from each village. The water sample was collected at a depth of 10 cm depth from the dam in Rooiberg after the container has been rinsed with the same water from the dam to avoid contamination at about. At Gravelotte and Kwagga water samples are taken from the boreholes that were located outside the villages using the same procedure as that of Leeupoort. The samples were taken to the Agricultural Research Council (ARC), Pretoria, for analysis.
The second set of water samples were taken in the summer time (November, 2007). This was the rainy season and all the water sources were full to capacity. The same procedure as the first collection was adopted for the collection of the second samples. Samples were also analysed at the ARC laboratory, in Pretoria. Fig. 3.7 below shows the dam at Rooiberg and Fig 3.8 illustrates the collection of the water.
Collection of soil samples
The soil samples were collected from the area surrounding the dam at Rooiberg. Not only is dam water consumed by the locals, but goats forage on the vegetation surrounding the dam. The soils were collected in two different areas. Samples of the top soil plus A and the B horizons to a depth of around 30 cm, were collected and stored in separate bags. The samples were taken to the ARC in Pretoria for analysis.
Collection of plant samples
The commonest plants and shrubs eaten by the goats were identified through the information given by the goats’ owners. These plants were collected in the morning in the month of February, 2006 (during summer) by cutting the foliage of the plants. Plant samples were placed in plastic bags, were labeled and were taken to the ARC laboratory for treatment and analysis.
The second set of plant samples were taken in the summer time (November, 2007). This was during the rainy season.
Another set of water, soil and plant samples were collected from Rooiberg during August 2009 using the same procedures.
OBJECTIVE 3: TO DETERMINE THE EXPOSURE PATHWAY TO HUMANS IN CONTAMINATED AREAS.
In order to achieve this objective, all the sources and pathways had to be identified by which As, Pb and Hg reach infants in the study area.
Fig 1.3 in Chapter 1 indicated that the main sources of contamination of infants by ingestion are dust from the soil, water and food. The collection of water and soil samples has been discussed in the previous section. The following sections describe the collection and analysis of goat’s milk and mother’s milk. With this information, it is possible to trace the path of contamination through the food chain from groundwater to humans and thus to determine whether mercury arsenic and lead pose a health hazard to human in the selected parts of Limpopo.
Collection and analysis of goat’s milk
In the study areas, goats are reared intensively i.e. they are confined to a specific area. In the mornings, the goats are allowed out of their pens to forage and drink from any available water sources.
All the female goats with kids were numbered and two were randomly selected for milking. The udders of the goats were first washed thoroughly with alcohol and water. With the assistance of the owner of the goats, they were milked. A 20 ml sample of milk was taken from each of the goats. The samples of the milk were taken to the ARC laboratory for analysis.
Figure 3.8 and 3.9 shows the herd from which the milk were taken and the milk of the selected goats respectively.
Human milk sampling
The human milk samples were obtained from the clinic that was closest to the villages and which is attended by the pregnant women. The consent of the mothers was obtained via the village contact person who explained the purpose of the research and the possible environmental benefit for the entire communities to the mothers and the nursing sisters at the clinics. The milk was collected from nursing mothers who had just given birth and who originated from the villages. The breasts of the mothers were washed with water before the extraction of the milk into a plastic container. This was done with the assistance of Dr. Arajuwa Peterson of outpatient department in Thabazimbi district Hospital. The milk sample was taken to the ARC for analysis.
ANALYSIS OF SAMPLES
Samples were analyzed by the ICWS at the ARC laboratories in Pretoria. The total metal as well as the arsenic, lead and mercury content were determined using inductively coupled plasma source atomic emission spectroscopy (ICP-AES).
The results of the analyses are presented in Chapters 4 and 5.
TABLE OF CONTENT
TABLE OF CONTENT
LIST OF TABLES
LIST OF FIGURES
1.2 Justification for the Study
1.3 Research Framework
1.4 Chapter Layout
2. LITERATURE REVIEW
1.5 Hazards of Toxic Minerals
2.2 Toxic Mineral Contamination in South Africa Lead
2.5 The Environmental and Health Impact of Arsenic
2.6 Milk as a Source of Contamination
3 STUDY AREA AND METHODOLOGY
3.1 Objective 1: To Identify Potentially Contaminated Areas In Limpopo Province.
3.2 Objective 2: To Describe the Extent of Environmental Contamination in the Selected Areas.
3.3 Objective 3: To Determine the Exposure Pathway to Humans in Contaminated Areas.
3.4 Analysis of Samples
4 ENVIRONMENTAL ASSESSMENT
4.2 Overview of Arsenic (As) Contamination in the Environment
4.3 Pathways of Mercury in the Environment.
4.4 Lead in the Environment
5 EXPOSURE PATHWAYS OF ARSENIC, MERCURY AND LEAD TO INFANTS
5.2 Exposure to Arsenic
5.3 Exposure to Mercury
5.4 Exposure to Lead
5.6 Summary of the Three Toxic Elements Hazard Effect
6 SUMMARY, CONCLUSION AND RECOMMENDATIONS
6.1 Summary and Conclusion
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