Sources and Factors contributing towards AMD generation
Before going into the aspects related to the causes and impact that AMD has on the environment, it is important to understand the sources and factors that drive AMD generation. The sources of AMD can be two-fold: primary and secondary (Akcil and Koldas, 2006). The primary and secondary sources are presented in Fig.1.
Similarly, there are a number of factors that play a role in AMD generation. Akcil and Koldas (2006) have listed the factors that play an important role in acid generation in AMD. They are as follows: (1) Microbial activity; (2) Activation energy (chemical) required to initiate acid generation; (3) Activity of ferric iron; (4) Degree of saturation with water; (5) Concentration of oxygen in water phase; (6) Content of oxygen in the gas phase (if saturation is less than 100%); (7) pH; the surface area of metal sulphide exposed to air or water and (8) Temperature.
Fig.1. Sources of AMD (adapted with modification from Akcil & Koldas, 2006)