Mining in the early days took place at a time when environmental impacts were not as well understood and most importantly, not a matter of significant concern. During these times, primarily before the 1970s, the mining cycle did not necessarily include closure activities specifically designed to mitigate environmental or social impacts. As a result, historical mine sites may still have un-reclaimed areas, remnants of facilities, and untreated water. This inherited legacy of environmental damage from mining is not indicative of the mining cycle today. Now, mine closure and a number of activities to mitigate the social and environmental impacts of mining are an integral part of mine planning and mineral development from the discovery phase through to closure (Adapted from Hudson et. al, 1999).
Environmental Impacts of Mining (Adapted from Aswathanaryana, 2003; Carr and Herz, 1989; and Nilsson and Randhem, 2008):
- Lithosphere: Depending on the type of mining conducted and the site of mining there are several types of impacts on the lithosphere. The results range from formation of ridges, depressions, pits and subsidence on the surface as well as underground cavities affecting the stability of the ground. Furthermore, both the area for mining and the area used for waste dumps, occupy and degrade land that could be used for farming, agriculture or other economic activity.
- Hydrosphere: Impacts on the hydrosphere resulting from mining include lowering of the groundwater table, mine water discharge into rivers, seas and lakes, leakage from settling tanks and evaporators that have a negative effect on the groundwater quality and pumping of water into the ground for the extraction of a mineral. Significantly lowered groundwater levels can result in significant surface depressions and drained rivers and lakes with serious impacts on surrounding agriculture for example. Furthermore, depending on the chemical composition of the rock, the drained water usually becomes highly acidic with the resulting capability of taking into solution a variety of toxic and heavy metals.
- Atmosphere: Atmospheric emissions during mining occur not only from internal combustion engines in mining machinery but dust and gases are also released from blasts and rocks and mineral masses. One tonne of explosives produces about 40-50 m3 nitrogen oxides and huge amounts of dust. Also, smelters are commonly used for mineral purification and emissions from these processes include particulate matter and gases such as sulfur dioxide, carbon monoxide and carbon dioxide. Although some installations use different kinds of flue gas purifications, these are never completely effective.
- Biosphere: The biosphere is adversely affected by mining mainly by pollution and by degradation of land and vegetation resulting in loss in biodiversity. Mining can also have impact on local microclimate.
- Public Safety: Old mining sites are inherently interesting to people, but potentially dangerous as well. They may have surface pits, exposed or hidden entrances to underground workings, or old intriguing buildings. Another safety consideration at some mine sites is ground sinking or “subsidence.”
Key Mining Related Environmental Issues (Adapted from Environmental Law Alliance Worldwide, 2010):
- Greenhouse Gases: Reduction in greenhouse gas emission as an initiative for minimizing the heat retention caused by the accumulation of greenhouse gases around the earth.
- Acid Rock Drainage (ARD): When the sulfides in the rock are excavated and exposed to water and air during mining, they form sulfuric acid. This acidic water can dissolve other harmful metals in the surrounding rock. If uncontrolled, the acid mine drainage may runoff into streams or rivers or leach into groundwater.
- Toxicity: Humans and the surrounding ecosystem can be impacted by not only the physical effects of mining, but also the toxicological impacts of minerals mined, chemicals used, and byproducts of the overall refining process.
- Biodiversity: Biodiversity is the variation of organisms within a given species, ecosystem, and/or biome. The number of species and the variety of genetic material available within a population determines the diversity within an ecological system. Biodiversity promotes species adaptation and evolution.
- Erosion and Sedimentation: Though erosion and sedimentation are naturally occurring processes, mining and mine-related activities amplify their effect, and may negatively affect the surrounding environment. In the absence of adequate prevention and control strategies, erosion can carry excessive amounts of sediment into streams, rivers, and other surface waters and aeolian movement can affect broader terrestrial ecosystems.
- Water and Groundwater Supply: Large volumes of groundwater are either discharged, or are used by the mining and associated supporting operations. Also, drawing down the water table and diverting runoff to other watersheds may reduce the volume of water available for other uses (e.g., fisheries).
- Tailings Management: Tailings are the rejected materials after the process of separating the valuable fraction from the uneconomic fraction of an ore. Tailings management is an important aspect in the design and operation of mining projects and needs to balance a variety of considerations, including potential environmental, social, economic, public health and safety impacts.
Although mining can have significant impact on environment, as scientific and technological advances increase the understanding of the physical and chemical processes that cause undesired environmental consequences, mines and related beneficiation or smelting facilities apply this understanding to improve prevention and solve environmental problems (Adapted from Langer et. al., 2004).
Society’s requirement for mineral resources establishes a strong link between our standard of living, the Earth, and science. By understanding key concepts of the process of mining, citizens should be prepared for the necessary discussions and decisions concerning society’s increasing need for mineral resources and the related environmental tradeoffs. Decisions about the development and use of Earth’s mineral resources affect the economic, social, and environmental fabric of societies worldwide (Adapted from Hudson et al., 1999).
What is the most important mining related environmental issue? Are there the good practices for addressing this concern?
Follow me on twitter @rcrdossantos
Hudson, T. L., Fox, F. D. and Plumlee, G. S. “Metal Mining and The Environment”. American Geological Institute, Alexandria, Virginia (1999).
Langer, W. H., Drew, L. J. and Sachs, J. S. “Aggregate and The Environment”. American Geological Institute, Alexandria, Virginia (2004).
Hatch Ltd “Environmental Analysis of the Mining Industry in Canada”, Canadian Mining Innovation Council, Canada (2013). Last accessed on 07/27/2016 at http://www.cmic-ccim.org/wp-content/uploads/2013/07/HatchScopingReport.pdf
Nilsson, J. A. and Randhem, J. “Environmental Impacts and Health Aspects in the Mining Industry, A Comparative Study of the Mining and Extraction of Uranium, Copper and Gold”, Master of Science Thesis in the Master Degree Programme Industrial Ecology, Department of Energy and Environment, Chalmers University of Technology, Sweden (2008).
Aswathanarayana, U. “Mineral resources management and the environment”, A.A. Balkema. Tokyo, Japan. ISBN 978-90-5809-545-9. (2003).
Carr, D. D. and Herz, N. “Concise Encyclopedia of Mineral Resources”. Oxford: Pergamon Press. (1989).
Hartman, H. L. and Mutmansky, J. M. “Introductory Mining Engineering”, Published by Wiley, Hoboken, NJ, USA, (August, 2002).
Environmental Law Alliance Worldwide “Guidebook for Evaluating Mining Project EIAs”, Environmental Law Alliance Worldwide. Eugene, OR 97403 U.S.A. (July, 2010) Last accessed on 07/27/2016 at https://www.earthworksaction.org/files/pubs-others/Evaluating-Mining-EIAs-ELAW.pdf
Feature: USGS hydrologist Greg Clark measures streamflow on Government Gulch Creek, a tributarty to the Coeur d’Alene River in northern Idaho. Author: U.S. Geological Survey
Figure 1: Dedicated camera for environmental monitoring. Author: Jim Barton
Figure 2: Iron hydroxide precipitate (orange) in a Missouri stream receiving acid drainage from surface coal mining. Author: D. Hardesty, USGS Columbia Environmental Research Center
Figure 3: Bento Rodrigues dam disaster Author: Brazilian Senate
Figure 4: Head-on view of a snapping turtle (Chelydra serpentina) hidden near the St. Lawrence River in northern New York state. Author: User:Moondigger
Figure 5: Land reclamation – restored land at the Seneca Yoast coal mine. Author: Peabody Energy, Inc.