Heavy metals in the soils of Bloemfontein, South Africa: concentration levels and possible sources

摘要

The possible heavy metal and metalloid contamination in the soils around a coal-generated power station, situated on the eastern end of the central business district of Bloemfontein, central South Africa, was investigated. One-hundred and thirty-three samples (22 dust samples collected inside buildings and 111 soil samples) were collected for the study and analysed for As, Se, Cd, Sb and Hg. The results indicated generally elevated levels for Cd, Sb and Hg, and some localised contamination of As, but no significant increases in the non-metal Se. In fact, Se levels indicated a deficiency of the element in the study area. In general, the dust samples showed elevated levels of all elements (except Se) relative to the soils. A possible source for the enrichment might have been the release of ash, containing trace amounts of these elements, from the local power station; however, because the highest concentration in soils was found in the industrial areas, other processes could have contributed or even have been the sole cause of the elevated levels. High levels of As occur at an abandoned horse race course and were probably caused by the questionable practice of administering As-containing tonics to the horses shortly before they run a race.