135 Figure 2 – Hyperspectral Remote Sensing Applications in Mining Water Management 3. Current Challenges in Water Management for the Mining Industry 3.1 Acid Mine Drainage: The Persistent Challenge Acid Mine Drainage (AMD) occurs when sulfide minerals are exposed to oxygen and water, producing sulfuric acid, and mobilizing heavy metals. The problem is particularly acute because of their impact in the long-term due to persistence. Modelling studies indicate AMD can persist for 30+ years without active intervention, with some sites showing contamination for over 100 years [6]. Complex geochemistry also plays a role since multiple interacting processes involving over 20 different chemical reactions make prediction and control difficult [12]. Legacy impacts are part of the challenge since historical mining operations continue to generate AMD decades after closure, with treatment costs exceeding $1 billion annually in North America alone [12]. Table 3 summarizes a quantitative analysis of AD generation and persistence. Table 3 – AMD Generation and Persistence Mine Type Initial pH Range Metal Concentrations mg/L Predicte d Duration years Treat ment Cost USD per m3 Affect ed Area km2 Ann ual Volu me ML Coal 2.5-3.5 Fe: 50-200, Al: 10-50, Mn: 5-25, SO4: 500-2000 20-50 2-5 5-50 1005000 Copper 2.0-3.0 Cu: 20-100, Fe: 100-500, Zn: 10-80, SO4: 10008000 30-80 3-8 10200 5001500 0 Gold 2.8-4.0 As: 5-25, Fe: 20-150, Cu: 5-30, SO4: 800-3000 25-60 4-10 2-100 502000 Iron Ore 3.5-4.5 Fe: 200-800, Mn: 10-40, 15-40 1-4 20- 1000
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