RESUMEN
The development of a waste discharge charge system (WDCS) in South Africa has been proposed to promote waste reduction and water conservation. The WDCS is based on the polluter pays principle and is designed such that the management of waste discharges achieves resource quality objectives (RQOs) at the minimum total cost to the catchment. Two charges are distinguished: first a charge for optimising use of the resource (incentive charge); and secondly, a charge for development and operation of mitigation measures in the resource (mitigation charge). The WDCS is applied to both point sources and non-point sources (NPS) of contamination. In the inclusion of NPS, the charge system distinguishes between registered and non-registered NPS, with the charge applied to the former group only, in the first instance. This paper introduces the WDCS by describing the principles and the theoretical basis of the WDCS, highlighting the link to RQOs as the benchmark of acceptable externalities. The paper explores the inclusion of NPS in the WDCS, describing: first, the principles of NPS inclusion in the WDCS; secondly, the types of NPS included in the present version of the WDCS; thirdly, the methodology for charge estimation; and finally, non-registered NPS and their potential inclusion in future editions of the WDCS. The paper concludes with remarks and challenges facing the first edition of the WDCS.
Asunto(s)
Conservación de los Recursos Naturales/métodos , Contaminación del Agua/prevención & control , Conservación de los Recursos Naturales/economía , Sudáfrica , Contaminación del Agua/análisis , Abastecimiento de Agua/análisis , Abastecimiento de Agua/economíaRESUMEN
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.