Table 3 Element species (%) and Saturation Index (SI) for the ARDs

Element species / ARD
DWS from the Ursk tailings / DWS from the Belovo clinkers / DWS from the Belovo sludge pond
Na+ / 94.88 / 96.02 / 97.55
NaSO4- / 5.12 / 3.98 / 2.45
K+ / 93.53 / 94.86 / 96.75
KSO4- / 6.47 / 5.14 / 3.25
Ca2+ / 57.74 / 61.80 / 68.33
CaHSO4+ / 0.34 / 0.02 / -
CaSO40 / 41.93 / 38.20 / 31.65
Mg2+ / 54.74 / 58.56 / 65.33
MgHSO4+ / - / - / -
MgSO40 / 45.27 / 41.46 / 34.66
Cl- / - / 98.72 / 99.51
SO42- / 43.69 / 55.94 / 65.89
HSO4- / 1.78 / 0.19 / 0.05
Fe2+ / 57.10 / 66.08 / 71.85
FeCl+ / - / 0.23 / 0.24
FeHSO4+ / 0.32 / 0.02 / -
FeSO40aq / 33.78 / 33.49 / 27.79
FeOH2+ / 0.56 / 0.05 / 0.09
Fe(OH)2+ / 0.06 / 0.09 / -
Fe2(OH)24+ / 0.06 / - / -
FeSO4+ / 6.13 / 0.03 / -
Fe3+ / 0.49 / - / -
FeHSO42+ / 0.04 / - / -
Fe(SO4)2- / 1.46 / - / -
Al3+ / 16.40 / 18.35 / 20.03
AlOH2+ / 0.03 / 0.55 / 4.21
Al(OH)2+ / - / 0.02 / 0.81
AlHSO42+ / 0.01 / - / -
AlSO4+ / 62.21 / 64.24 / 64.62
Al(SO4)2- / 21.36 / 16.88 / 10.27
Zn2+ / 48.58 / 54.37 / 63.21
ZnCl+ / - / 0.31 / 0.36
ZnSO40 / 39.98 / 37.91 / 33.28
Zn(SO4)22- / 11.44 / 7.43 / 3.13
Cu2+ / 58.16 / 61.93 / 68.18
CuCl+ / - / 0.35 / 0.38
CuCl2- / - / - / 0.03
CuSO40aq / 41.85 / 37.73 / 31.34
CuOH+ / - / - / 0.02
Cu2(OH)22+ / - / - / 0.02
Cd2+ / 41.47 / 42.86 / 50.89
CdCl+ / - / 10.27 / 11.62
CdCl20aq / - / 0.17 / 0.17
CdSO40aq / 42.33 / 37.01 / 33.12
Cd(SO4)22- / 16.21 / 9.72 / 4.18
Ni2+ / - / 63.10 / 69.28
NiCl+ / - / 0.40 / 0.42
NiSO40aq / - / 36.46 / 30.26
Ni(SO4)22- / - / 0.05 / 0.02
Saturation Index
Al(OH)3 / -5.71 / -3.58 / -1.24
Alunite (KAl3(SO4)2(OH)6) / -1.06 / 3.97 / 8.23
Anhydrite (CaSO4) / -0.41 / -0.32 / -0.53
Antlerite (Cu3(SO4)(OH)4) / - / -1.69 / -0.017
Atacamite (Cu2Cl(OH)3) / - / -2.65 / -1.2
Basaluminite (Al4(SO4)(OH)10·5(H2O)) / - / -3.02 / 4.45
Brochantite (Cu4SO4(OH)6) / - / -3.12 / -0.35
Diaspore (α-AlO(OH)) / -1.77 / 0.36 / 2.70
Ferrihydrite ((Fe3+)2O3·0.5H2O) / -0.86 / -3.59 / -2.81
Gypsum (CaSO4·2H2O) / -0.17 / -0.088 / -0.30
Gibbsite (Al(OH)3) / -2.98 / -0.85 / 1.50
Goethite (FeO(OH)) / 4.85 / 2.16 / 2.97
Jarosite K (KFe3+3(OH)6(SO4)2) / 4.44 / -4.92 / -5.18
Jurbanite (AlSO4(OH)·5H2O) / 0.76 / 0.45 / 1.10
Tenorite (CuO) / - / -2.15 / -1.01