The geochemical behaviour of selected chalcophile trace elements in soils from the Bloemfontein Region, South Africa
Clark, John Herbert Attlee
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An early study was done on heavy metal contamination in the soils across the eastern portion of the city of Bloemfontein. One hundred and forty seven samples were collected for the study: there were 22 dust samples, 4 soil profiles, 112 urban soil samples and 9 background samples taken 10 km north, south, east and west of the power station. Contamination was believed to be caused by the coal-burning power station found in Bloemfontein. Heavy metal/metalloids that were under investigation in the study area were the following: antimony, arsenic, bismuth, cadmium, mercury and selenium. Initial results from an earlier study indicated that there was no major issue with the metals/metalloids in the area and the project was abandoned. This is an update to that research. The research indicates that there is a possible contamination of the soils with the heavy metals/metalloids. The ranges of concentrations for the different studied elements are as follows: antimony has a range of 3.44 ppm to 21.13, arsenic has a range of 1.33 ppm to 14.59 ppm, bismuth has a range of 0.12 ppm to 6.86 ppm, cadmium has a range of 0.11 ppm to 21.15, mercury has a range 0.06 ppm to 2.14 ppm, and selenium has a range 0.24 ppm to 1.22 ppm. By comparing these concentrations to background levels found on Earth and comparing them to other areas that have been confirmed to have high amounts of contamination, it can be concluded that elements such as antimony, cadmium and mercury contain high enough concentrations to be considered contaminated. Arsenic and bismuth can be concluded to having very little to no contamination in the study area. Selenium concentrations indicate that there is a deficiency of the element in the area which may lead to other possible problems to the local population. The possible sources for the contamination of the elements in the soils were blamed on the release of ash from the power station that may contain trace amounts of the elements. But because the highest concentration levels are found in the industrial areas of the study area, it can be concluded that the power station is a possible source for contamination but it can also be concluded that the industrial area is also a major source for the contamination.