ABSTRACT
It is very clear from this chapter that acid mine drainage (AMD) effluents deserve special attention given that AMD is associated with numerous undesirable components such as low pH (high acidity), (2) high metal concentration, (3) elevated sulphate levels and (4) excessive suspended solids and/or siltation (AMRC, 2020). This chapter focused particularly on the effects of heavy metals and acidity on plants, aquatic species and human health. A collection of documented studies in the chapter has shown that heavy metals are toxic to soil, plants, aquatic life and human health if their concentrations are high. Heavy metals exhibit toxic effects towards soil biota, for example, by affecting key microbial processes and decrease the number and activity of soil microorganisms. Several reports have indicated that even low concentrations of heavy metals may inhibit the physiological metabolism of plant. Furthermore, the uptake of heavy metals by plants and aquatic species such as fish and the subsequent accumulation along the food chain is a potential threat to animals and humans. More specifically, contaminations of the aquatic systems by heavy metals can stimulate the production of reactive oxygen species (ROS) that can damage fishes and other aquatic organism. Heavy metals toxicity to humans has proven to be a major threat and there are several health risks associated with them including interference with metabolic processes. The need for proper balance of the soil pH was also emphasised in the chapter since pH is influential on the availability of nutrients and on the growth of different kinds of plants. The knowledge of pH associated changes in aquatic ecosystems is also important. For example, acidification affects the structure and functioning of ecosystems, causes damages to forests and causes the extinction of aquatic organisms. Much of the effect of AMD acidity on humans is indirect. For example, the depletion of aquatic organisms affected by AMD acidity has domino effects up the ecosystem by reducing the food sources available for animals at the top of the marine and human food chain.
