A reactive transport model for mercury fate in soil – Application to different anthropogenic pollution sources
Bertrand LETERMEa, Philippe BLANCb and Diederik JACQUESa
aPerformance Assessments, Institute for Environment, Health, and Safety, Belgian NuclearResearch Centre (SCK•CEN), Boeretang 200, 2400 Mol, Belgium
bD3E/BGE, Bureau de Recherches Géologiques et Minières (BRGM), Av. C. Guillemin 3, BP6009, 45060 Orleans, France
Corresponding author : Bertrand LETERME (; tel. +3214333124)
Supplementary Material
Selection of the Hg species for the Thermoddem database
The selection for mercury species thermodynamic data was processed according to guidelines described by Blanc et al.(2012). In the present case, the selection process is fully detailed inBlanc (2013), but this appendix gives a brief overview of the selection process and the verification of the database obtained.
The main sources for the selection of thermodynamic data were:
-the CODATA(Cox et al. 1989) selection, for primary master species and the element entropies;
-the Hg-O-H2O system was refined by taking into account the contributions of Baes and Mesmer (1976), Bessinger and Apps (2005) and finally Shock et al. (1997);
-sulfur was added to the chemical system investigated. The main source of data then was from Bessinger and Apps (2005);
-finally, we could extend the investigation to the Cl, P2O5, CO2 and SO3 components thanks to the compilation of Powell et al. (2005).
In the Thermoddem selection process, internal consistency was first ensured by selecting elements entropies from the CODATA review, which is already consistent. Thereafter, the verification was held on essentially by drawing predominance diagrams.Thus, the selection of Hg species was actually done in a relatively large chemical system, but the verification wasperformed on restrained chemical sub-systems.In this way, it is possible to detect the contradictions or the errors with respect to literature results.
In the verification of the Hg-Cl-O-H2O sub-system for example, the diagram obtained at 25°C (Fig. 1) is essentially consistent with Powell et al. (2005)calculations in the same context. The diagramincludes the HgOHCl(aq) complex, which stability domains appears between those of HgCl2(aq) and Hg(OH)2(aq) in the 3.5-9 pH range, consistently with the calculations of Baes and Mesmer (1976).
Fig.1 Predominance diagram in the Hg-O-Cl-H2O sub-system, at 25°C, [Cl]T = 10-2M. Source: Blanc (2013)
A few properties were refined because of a lack of experimental data. The solubility of HgO(cr) was investigated as a function of temperature in order to check the properties of both this solid phase and the main aqueous complex Hg(OH)2(aq). As reported by Baes and Mesmer (1976) the solid has three polymorphs: yellow and red orthorhombic and hexagonal forms. In Fig. 2, the LogK(T) function of HgO(cr) is calculated by using the CODOTA selection based on calorimetric measurements for the red orthorhombic HgO phase. The experimental solubilities are gathered inFig. 2 without any polymorph distinction. Indeed, the scattering of the experimental points is not related to the polymorph type and it would prevent to make an accurate distinction. Concerning the aqueous complex Hg(OH)2(aq),based onFig. 1 we were able to slightly adjust the thermodynamic properties from Bessinger and Apps (2005), with a modification of the equilibrium constant from −6.17 to −6.08 and of its entropy from 162 to 156J/mol.K.
Tables 1 and 2gather the properties collected from the literature or calculated for internal consistency. In Table 1, the a1, a2, a3, a4, c1, c2 and ω correspond to the HKF parameters (Helgeson et al. 1981). In Table 2, the a, b and c coefficient are related to a Maier-Kelley polynomial expression for the Cp(T) function were Cp(T) = a + bT + c/T².
Fig.2 HgO,cr – Hg(OH)2(aq) equilibrium as a function of temperature
1
Table 1 Thermodynamic properties for aqueous complexes
Specie / G°fkJ/mol / H°f
kJ/mol / S°
J/mol.K / Cp
J/mol.K / a1*10-2
J/mol.bar / a2
J/mol / a3*10-4
J.K/mol.bar / a4
J.K/mol / c1
J/mol.K / c2*10-4
J*K/mol / *10-5
J/mol / References
Hg,aq / 37.12 / 12.50 / -6.65 / 410.74 / 17.93 / 11.21 / 19.71 / -12.09 / 263.83 / 70.97 / -0.22 / (a)
Hg+2 / 164.67 / 170.21 / -36.19 / -2.20 / -38.00 / 39.00 / -10.10 / 75.60 / -10.80 / 4.80 / (b), (c)
Hg2+2 / 153.57 / 166.87 / 65.74 / 16.80 / 8.60 / 20.70 / -12.00 / 91.20 / -0.90 / 3.40 / (b), (d)
Hg(OH)+ / -53.07 / -32.38 / 69.87 / 5.20 / -19.70 / 31.70 / -10.80 / 151.40 / 26.90 / 1.30 / (d), (e)
Hg(OH)2,aq / -274.94 / -351.18 / 156.00 / 73.00 / 45.30 / 78.00 / -6.50 / -14.90 / 67.00 / 2.10 / -0.20 / This work, (a)
HHgO2- / -189.17 / -119.91 / 9.62 / 7.60 / -14.00 / 29.60 / -11.00 / 15.70 / -37.60 / 6.70 / (d), (e)
Hg2(OH)+3 / -55.03 / (f)
Hg3(OH)3+3 / -180.08 / (e)
HgOHCl,aq / -226.87 / -282.70 / 129.76 / (e)
HgCl+ / -7.71 / -21.84 / 48.83 / 10.40 / -7.10 / 26.80 / -11.30 / 136.00 / 20.60 / 1.60 / (e), (g)
HgCl2,aq / -177.57 / -58.39 / 103.09 / 25.20 / 28.90 / 12.70 / -12.80 / 203.50 / 49.60 / -0.20 / (e), (g)
HgCl3- / -314.95 / -103.80 / 127.65 / 43.90 / 74.70 / -5.30 / -14.70 / 326.50 / 76.20 / 4.90 / (e), (g)
HgCl4-2 / -448.22 / -159.22 / 118.66 / 65.20 / 126.70 / -25.80 / -16.90 / 458.40 / 100.40 / 11.70 / (e), (g)
Hg(HS)2,aq / -37.79 / -56.50 / 207.94 / 59.11 / 111.78 / -19.70 / -16.25 / 110.52 / 17.31 / -0.16 / 59.11 / (a)
HgS(HS)- / -2.80 / -38.52 / 150.88 / 43.14 / 72.79 / -4.42 / -14.64 / 98.44 / -1.87 / 4.50 / 43.14 / (a)
HgS2-2 / 44.58 / (h)
HgSO4,aq / -587.33 / (i)
HgCO3,aq / -503.56 / (i)
Hg(OH)CO3- / -706.48 / (i)
HgHCO3+ / -528.27 / (i)
HgHPO4,aq / -981.55 / (i)
HgPO4- / -949.87 / (i)
HgF+ / -126.37 / -165.34 / -18.77 / -0.21 / -33.05 / 37.02 / -10.26 / 156.06 / 24.24 / 2.60 / (g)
(a) Bessinger and Apps (2005); (b) Cox et al. (1989); (c) Shock and Helgeson (1988); (d) Shock et al. (1997); (e) Baes and Mesmer (1976); (f) Arnek and Kakolowicz (1967); (g) Sverjensky et al. (1997); (h) Benoit et al. (1999); (i) Powell et al. (2005)
1
Table 2 Thermodynamic properties for mercury bearing minerals and gases
Species / G0fkJ/mol / H0f
kJ/mol / S0
J/mol.K / Cp 25°C
J/mol.K / a
J/mol.K / b*103
J/mol.K² / c*10-5
J/mol/K / V
cm3/mol / References
Hg,l / 0.000 / 0.00 / 75.90 / 20.98 / (a), (b)
Hg,g / 31.84 / 61.38 / 174.97 / 20.79 / (a)
HgO,cr / -58.52 / -90.79 / 70.25 / 44.06 / 42.09 / 21.93 / -4.06 / 19.32 / (a), (b)
HgS,cr
Cinnabar / -45.73 / -53.35 / 82.82 / 48.41 / 46.22 / 15.52 / -2.17 / 28.42 / (c)
HgS,cr
Metacinnabar / -43.53 / -48.98 / 89.68 / 46.37 / 49.21 / 11.95 / -5.69 / 30.17 / (c)
HgCl2,cr
Calomel / -210.73 / -265.37 / 191.60 / 101.97 / 97.19 / 26.28 / -2.71 / 32.94 / (a), (d)
Hg2SO4 / -625.78 / -743.09 / 200.70 / 132.33 / 103.97 / 131.08 / -9.53 / 65.77 / (a), (e)
HgCO3.2HgO,cr / -799.96 / (f)
Hg3(PO4)2,cr / -1838.38 / (f)
(HgOH)3PO4,cr / -1367.06 / (f)
HgHPO4,cr / -1006.09 / (f)
Hg(CH3)2,g / 146.10 / 94.39 / 306 / 83.30 / (g)
(a) Cox et al. (1989); (b) Chase (1998); (c) Helgeson et al.(1978); (d) Chase et al. (1985); (e) Barin et al. (1977); (f) Powell et al. (2005); (g) 1982 Wagman et al. (1982)
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