H-ESD : Environmental and Sustainable Development lectures 2015
Acid Mine Drainage Exercise, 11.11.2015
The following hydrochemical data for drainage from a mine waste deposit shows sulfate release as well as
copper, resulting from weathering of pyrite and traces of chalcopyrite in the ore rock. If there is no natural
attenuation, the amount of acidity in the discharge should correspond to the protons produced by pyrite
weathering. The amount of acidity produced by pyrite weathering can be estimated from hydrochemical
data.
Hydrochemical Analyses of Discharge Water from a Copper Mine Waste Deposit
(mg L-1).
pH
AlT
Na+
3,8
75
46
SO42Cu2+
K+
1310
19
17
Ca2+
FeT
SiT
185
2
19
Mg2+
MnT
Cl-
57
12
27
Note: The subscript T refers to total dissolved concentration
Step 1: Calculate molecular weight of sulfate and list the atomic weight of Copper
Step 2: Calculate molar concentration of Sulfate and Cu in discharge
Step 3: Calculate sulfate release from pyrite, accounting for sulfate release from chalcopyrite (2 S for each
Cu in CuFeS2
Step 4: Calculate protons released from pyrite weathering, 4 protons are produced when pyrite dissolves
to produce sulfate and ochre.
Step 5: Calculate pH from expected proton concentration