OVERVIEW OF THE IMPACT OF MINING ON THE ... - IIED pubs

• Small-scale (non artisan) gold mines not being able to adequately manage their cyanidation processes and
causing localized cyanide pollution.
6.1.4 Salinity impacts
The most important issues associated with impacts caused by salinity (or total dissolved salts) relate to the
potential for deterioration water quality for other water users and the aquatic environment. In particular, acid
mine drainage is often closely associated with increased salinity levels and decreased fitness for use of the
water.
Specific areas of concern around salinity impacts are:
• Reduced crop yields when the salinity of irrigation water is increased due to contaminated by mining and
metal processing operations such as those experienced in areas affected by AMD. Specific examples are
those experienced in the middle reaches of the Olifants River downstream of the Witbank and Highveld
coalfields, and the middle reaches of the Crocodile River downstream of the Thabazimbi iron ore mines.
• Flocculation of clay particles in soils irrigated with high salinity water such that the soil structure is adversely
affected. Examples of this feature can be seen along the Middle and Great Letaba rivers where increasing
salinities have exacerbated the dispersive characteristics of some soils near Letaba Ranch.
• Adverse osmotic effects on aquatic plants and animals caused by increased salinity levels and altered
sodium : potassium ratios. In turn, this reduces the ability of aquatic plants to withstand adverse
temperature effects during the summer months, prevents completion of seed-setting and germination
processes, disrupts aquatic plant life cycles and interferes with nutrient transformation processes in the
aquatic environment. Examples of this can be seen in the upper reaches of the Riet, Steenkool and Olifants
rivers where benthic algal communities have been altered by increased salinities and lowered pH values
associated with AMD.
• Decreased rates of photosynthesis in aquatic plants exposed to increased salinity levels leads to reduced
productivity and altered community structures in aquatic ecosystems. Examples of this can be seen in the
lower reaches of the Olifants River where benthic algal communities have disappeared from certain
habitats.
6.1.5 Impacts due to suspended solids
The most important impacts associated with increased suspended solids levels are the often very visible
changes that occur to aquatic habitats and the aquatic biota. Specific areas of concern are:
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