Arsenic concentration in groundwater: Archetypal study from South Africa

• Published in: Groundwater for sustainable development 2019-10, Vol.9, p.100246, Article 100246
• Main Authors: Abiye, Tamiru A., Bhattacharya, Prosun
• Format: Article
• Language: English
• Subjects: Arsenic; Crystalline aquifer; Geodesi och geoinformatik; Geodesy and Geoinformatics; Groundwater; Land and Water Resources Engineering; Mark- och vattenteknik; South Africa; Water quality
• ISSN: 2352-801X; 2352-801X
• DOI: 10.1016/j.gsd.2019.100246

South Africa does not have significant surface water resources, which is often easily affected by unpredictable and rapidly changing climatic variables, due to its location in the arid and semi-arid climatic setting. In large part of the country, groundwater from weathered and fractured crystalline rocks plays pivotal role in sustaining the livelihood, often it contains toxic metals released from the host rocks. The host rocks that are responsible for arsenic release in groundwater are primarily enriched due to metamorphism and igneous processes that resulted in the enrichment of economic minerals. Preliminary assessment indicates that the main arsenic containing minerals are arsenopyrite (FeAsS), arsenical oxide, sulpharsenide, arsenopyritical reefs, leucopyrite, löllingite (FeAs2) and scorodite (FeAsO4·2H2O). Owing to the release of arsenic from highly mineralized rocks that constitute the aquifers, arsenic concentration in the groundwater reaches up to 253 μg/L (Namaqualand), 6150 μg/L (west of Johannesburg), about 500 μg/L in the Karoo aquifers, considerably higher than the WHO guideline value of 10 μg/L. Acid mine drainage from coal and gold mining is also found to be an important source of arsenic and other toxic metals in groundwater. [Display omitted] •Groundwater in South Africa contains high levels of arsenic.•Mineralization of the rocks due to metamorphism is responsible for high arsenic concentration.•Leaching and redox reactions facilitated the concentration of arsenic in groundwater.•Gold and coal mining areas contain high level of arsenic.