Groundwater pollution on the Zambian Copperbelt: deciphering the source and the risk.
The protection of groundwater resources is of great importance in many semi-arid and sub-tropical environments. The Copperbelt of Zambia is one such environment and due to the high proportion of tailings impoundments, residue heaps, high-density informal settlements and extensive sulfidic ore deposits in the region, its groundwater resources are under threat of anthropogenic or geogenic pollution. One such pollutant plume is investigated in this study, to determine its origin, rate of progression and the environmental and health risk it poses. Geological and geochemical investigation strongly suggests an upslope tailings impoundment as the source of contaminants, with the edge of the pollution plume lying 500-700 m downstream of the impoundment. Although cobalt, nickel and zinc concentrations were elevated within the polluted groundwater, the concentrations are low as a result of sulfide precipitation and adsorption within the aquifer, and meets guidelines for drinking water quality. Attenuation of heavy metals is linked to tailings dam and aquifer pH, with the high buffering capacity of each implying that these processes of attenuation are likely to continue removing harmful metals from the aquifer. Thus, it appears unlikely that the contaminated groundwater will present a major environmental risk at this site. However, tailings impoundments are widespread throughout the Copperbelt: sites with low tailings dam buffer capacity and in catchments on crystalline bedrock geology, groundwater pollution through tailings dam leachate may liberate high concentrations of heavy metals into the shallow groundwater, potentially posing a serious human health risk to the communities using the water resources and an environmental risk to the downstream ecosystems.
von der Heyden
C J
CJ
School of Geography and the Environment, Oxford University, Oxford OX1 3TB, UK. constantin.vonderheyden@geography.oxford.ac.uk
New
M G
MG
D003247:Conservation of Natural Resources; D004784:Environmental Monitoring; D005618:Fresh Water / Q000032:analysis*; D019216:Metals, Heavy / Q000032:analysis*; D008906:Mining; D025341:Principal Component Analysis; D012987:Soil / Q000032:analysis*; D014872:Water Movements; D014876:Water Pollution / Q000032:analysis*; D015024:Zambia
D019216:Metals, Heavy; D012987:Soil