An assessment of heavy metal pollution near an old copper mine dump in Musina, South Africa

Abstract

Heavy metal pollution in water and soil is a serious concern to human health and the associated environment. Some heavy metals have bio-importance but the bio-toxic effects of many of them in human health are of great concern. Hence, there was a need for proper understanding of the concentration levels of these heavy metals in ground water and soil around the community residing in the vicinity of the defunct mine. Mining has become prominent in this area because of the existence of copper lodes, veins and veinlets. It was therefore necessary to assess these selected metals associated with copper mining as their concentration has a tendency to affect the environment and human health. The objective of this study was to establish the levels of lead (Pb)-zinc (Zn)-copper (Cu)-arsenic (As)-nickel (Ni) metals in ground water and soil associated with an old copper mine in the vicinity of the township and to compare them with the South African and international standards in order to safeguard the health of the community using such water for drinking purpose. Clean sampling plastic bottles were used to collect water from five water boreholes being used at present. Water samples were filtered using membrane filtration set LCW (0.45 μm). The samples were digested sequentially with different procedures for the total metal concentration. Concentrations of four metals commonly associated with Cu mining were examined at five different water boreholes which are used for drinking and industrial purposes. Flame Atomic Absorption Spectrophotometer (Perkin Elmar S/n 000003F6067A, Singapore) was used to analyze metals in water samples at Eskom Ga-Nala Laboratory: pH, electrical conductivity and turbidity were analyzed using an auto titrator meter (AT- 500,Japan), conductivity meter (Cole-parmer® YO-19601-00) and turbidity meter (AL 250TIR, Agua lytic, German) respectively. Soil samples were collected from the selected areas where human health is of a serious concern, and a hand held auger drill was used to recover samples, while shovels were used to prepare the sampling area. The samples were sieved up to 63.0 μm particle size and digested with aqua-regia. Flame Atomic Absorption Spectrophotometer (Model: AA400; Year: 2008; Manufacturer: Perkin Elmer; Germany; Serial no: 201S6101210) was used at the University of Venda Laboratory to analyze soil from the study area for possible heavy metal contamination due to the defunct Cu mine in the area. v The results showed variation of the investigated parameters in water samples as follows: pH, 6.0 to 7.51; EC, 70.0 to 96.40 μS/cm and turbidity, 1.05 to 4.56 NTU. The mean concentration of the metals increased in the followed order: Pb<Cu<As<Ni. Ni is the most abundant in the ground water determined with value of (6.49 μg/g). The observations have confirmed that most ground water contains an appreciable quantity of Ni. The mean value of As in water is (4.20 to 4.84 μg/g), Pb and Cu have (2.13 to 2.58 μg/g) and (1.52 to 2.52 μg/g) respectively. For soil samples, the mean concentration of the metals increased in the following order: Pb<Cu<Zn<As<Ni. Pb ranged from (0.023 to 0.036 μg/g) followed by Cu (0.28 to 0.45 μg/g) then Zn (0.026 to 0.053 μg/g), the mean range of As in soil ranged from (0.054 to 0.086 μg/g). However, some studies show much higher contamination of As from the natural sources and Ni with (0.057 to 0.144 μg/g) lastly. Accumulation of heavy metals in soil is of concern due to their toxic effects on human and animals. The quality of ground water from the five boreholes studied was satisfactory with turbidity (T), electrical conductivity (EC) and heavy metals (HM’s) below the WHO limit. The water therefore may, according to the WHO Standards be safely used as a drinking water. The concern lies on pH which was slightly (0.5) below the standard. There is a serious need to monitor the ground water which is now used for drinking purposes. This study revealed that heavy metal pollution in soil from the abandoned Cu mine in Musina is a threat to the health of the community. Although pollution was between medium and low in the contamination index, it is therefore important for the Musina Municipality or mine owner of Musina (TVL) Development Co Ltd copper mine to advocate possible remedial actions which will safeguard the environment and human health. The tailing at Musina’s old Cu mine have high pH and they lack normal soil stabilization processes, as a result the tailing does not develop a good plant cover. Pollution of the ground water resources is also evident in the study area where there is seepage or ingress of polluted water to the underground aquifers. Small-scale mining in Musina is causing further degradation to the environment but it supports the South African Waste Hierarchy by promoting the reuse and recycling of the tailing and mine dumps for the production of bricks. Mine workers are exposed to the above mentioned toxic heavy metals daily. Medicine will not help stop the poisoning. The only way to stop the metal poisoning is to stop being exposed to the heavy metals.