The effect of rehabilitation measures on ecological infrastructure in response to acid mine drainage from coal mining

Water treatment is an important ecosystem service in natural systems and wetlands are well-known to have increased functionality in this regard. The rehabilitation of productive wetlands plays an important role in improving this functionality in degraded wetlands, but it is not well-known to what extent these activities improve acid mine drainage impacted waters. The aim of this study was to evaluate the significance of the effect of such interventions on the ecological functioning of a test wetland affected by acid mine drainage. A degraded wetland influenced by acid mine drainage in the Mpumalanga Province of South Africa was identified for the case study. This site was rehabilitated using a variety of hard (e.g., weirs/dams) and soft (e.g., earth berms) structures and examined to determine whether its ecological functioning (i.e., the improvement of water quality) and biotic community structures have improved. From the results it was evident that a substantial improvement in water quality occurred below the rehabilitated area, even though the wetland still continued to receive acid mine drainage. This was observed through the decrease in metal pollution in conjunction with an increase in pH and alkalinity levels. This resulted in increased productivity, reduced toxicity (embryotoxicity and teratogenicity), as well as changes in the biotic community structures which were a reflection of a less polluted environment. The study has shown that the rehabilitation of ecological infrastructure can be used to mitigate the effect of coal mining related pollution such as acid mine drainage. In the face of ever increasing land use activities that occur globally to meet the demands of growing populations, this information can be useful to mitigate negative residual influences resulting from these activities, e.g. acid mine drainage. (C) 2016 Elsevier B.V. All rights reserved.