Acid Drainage of Coal Mining in Cundinamarca Department, Colombia

Abstract

Coal in Cundinamarca is exploited by small and medium operations that use underground systems, and they have not involved appreciable levels of technology in none of the mining stages. As main negative environmental effects can be mentioned acid drainage generation, taken place by sulfides oxidation (pyrite present in the mineralized body); particulate matter production (coal dust) that is emitted to the atmosphere, surface waters, soils, biota and to the labor force (health and safety risk). Also it is important the improper disposal of coal wastes, that affect soils, waters and biota; biota and soils affectation as product of vegetal cover removal, and over use of forest resources. As positive socioeconomic effects can be mentioned employment and royalties generation, as well as impulse to the economy. pH and conductivity measurements allowed to evidence acid mine drainage occurrence (AMD), which contains high levels of ions in solution, possibly heavy metals (toxic) leached from the mineralized body. Along the carboniferous area, acid mine drainages (pH 2.6-5.5) with high values of conductivity (up to >3000 rtS/cm) were detected. Previous datas (INGEOMINAS, 1981, 1985, 1992), showed that although total sulfur contents in Cundinamarca's coal are quite low (0.84%), correlation among acidity generation (AMD) and sulfur concentrations (pyrite FeS) in the exploited coal exists. Although the AMD causes economic losses and they produce affectation on the biota, soils and waters, studies do not exist about their characterization. AMD characterization study is recommended in this area, as basis to propose mitigation and remediaci6n plans for those affected mining areas.