Relationship of historical copper mining to the transport and accumulation of trace metals and salts in semi-arid environments : an example from Buffels River, Northern Cape, South Africa
Date
2016-03
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : Stellenbosch University
Abstract
ENGLISH ABSTRACT: The town of Kleinzee, located in the Northern Cape, South Africa exists solely to mine alluvial diamonds
found in the Buffels River. Given the very low precipitation of the area (generally <150mm/yr)
groundwater is the principal supply of domestic and industrial water to the town. In an effort to
increase the water supply needed, the town installed an underground membrane across the Buffels
River approximately 5.5km upriver from the town. However, climatic conditions, long term copper and
diamond mining and poor groundwater management practices have combined to produce very poor
quality groundwater within the Buffels River Valley. The purpose of this study is to look at the impact
of the membrane on the quality of both the shallow groundwater system as well as the soils within the
river bed. To do this, 46 sites were selected for soil analysis starting below the membrane and
continuing above the membrane upriver for a distance of approximately 5 km. Additionally, a further
15 groundwater samples were collected at the end of the wet season in October when groundwater
was available. Cation and anion analysis of the shallow groundwater and the saturated paste extracts
shows significant peaks in SO4
2- and Mg2+ immediately above the membrane in the sediments in
addition to Na+ and Cl-, diminishing upstream away from the membrane. Cu2+ and Zn2+ did not show
an elevated concentrations in the groundwater or sediments above the membrane as originally
thought. Experiments on atacamite, a Cu2+-hydroxide, which forms naturally in the Spektakel soils
within the Buffels River Valley, indicates that although generally stable at moderate pH, large rain
events may increase the solubility of atacamite resulting in its transport downstream. However, the
source of sulphate is probably linked to processing of Cu2+ ores further up the river valley. The transport
mechanism of the groundwater salts and trace metals is via dissolution mobilization. The membrane
is accumulating trace metals and salts in sediments behind the membrane and not in groundwater
found behind the membrane. Thus accumulation is due principally to evaporative concentration.
AFRIKAANSE OPSOMMING: Nie beskikbaar nie.
AFRIKAANSE OPSOMMING: Nie beskikbaar nie.
Description
Thesis (MSc)--Stellenbosch University, 2016.
Keywords
Groundwater -- Quality -- South Africa -- Kleinzee, UCTD, Soils -- Copper content -- South Africa -- Kleinzee, Copper mines and mining -- Environmental aspects -- South Africa -- Kleinzee, Metals -- Environmental aspects -- South Africa -- Kleinzee, Trace elements in water -- South Africa -- Kleinzee, Soils -- Quality -- South Africa -- Kleinzee, Water salinization -- South Africa -- Kleinzee