Background Image 3 - (Coppi, 1992)
Figure 7 - (Burbano, 2013)
Figure 8 - (Atkin, 2005)
|
|
Figure 9 - (van Zeijst, 2010)
Figure 10 - (National Nuclear Security Administration, 2006)
|
|
Figure 11 - (Liefferink, 2016)
|
Both Surface and Subsurface WatersAcid mine drainage, or AMD, can be triggered quickly from leaching from surface waste dumps (sometimes within a year) (Salomons, 1995) or through groundwater flowing through underground mines where after being exposed to oxygen from ventilation, sulphides such as chalcopyrite can produce sulphuric acid (Sengupta, 1993).
AMD is a problem on an international scale, in the US alone there are approximately (2–5)x10^4 mines producing AMD and in 1982 the entire planet produced more than 4.5 gigatonnes of mine waste. Techniques used to extract resources that asteroids could provide already have a legacy of heavy metal contamination; mercury, used in extracting gold, has left a lasting legacy in Brazil and Indonesia. The main issue for these resources is the fact that the metals are often found in ore bodies containing sulphur–based minerals such as in the case of silver, which while often found as a native metal, it can be found as silver sulfosalts and as silver substitutions in tetrahedrite [(Cu,Fe,Ag)12Sb4S13] as in many Mexican mines (Blowes et al., 2003) which would be the primary contributors to AMD, along with any other sulphide minerals present. AMD can increase the concentration of iron dissolved in waters such as in Mahoney Creek in Pennsylvania, USA (Fear, Dowling and Neumann, 2011). Or simply decrease the pH level such as during low flows in the Kawcrong River catchment area (Bougainville Island, Papua New Guinea) when most of the flow originates from groundwater flow from surface dumps in the flood plains, this groundwater has low pH and high amounts of dissolved copper which severely decrease the quality of the water (Salomons, 1995). |
Figure 12 - (McBride, 2015)
|
Case Studies for the HydrosphereA case study that presents the legacy of mining activity could be the Gold king Mine disaster of 2015 where the EPA punctured a wastewater impoundment whilst testing for pollutants. This mistake caused one million gallons of wastewater rich in lead, arsenic, cadmium, and aluminium to flow into the Animas River, raising the concentrations to the point where it was unsafe for human contact (Schlanger, 2015).
Another case study, this time from the Summitville Mine in Colorado shows the importance of a managed mine legacy. In 1994 the EPA declared the site a superfund site (the common name for a site requiring extensive clean-up and/or a site with a high toxic spillage risk (Pollutionissues.com, 2016)). In addition to the natural geologic factors that caused natural acid rock drainage, the dike holding back the cyanide leaching solution was not built high enough for snowmelt and a French drain below the leaching pad resulted in cyanide contaminated solutions to leak into the surrounding watershed and area streams (McKinley, 2016). |