Formation of Groundwater Based on Inverse Geochemical Modeling: A Case Study from the Sixian County, Anhui Province

doi:10.19657/j.geoscience.1000-8527.2019.02.19

Abstract

Abstract:

Based on regional hydrogeological conditions, the hydrogeochemical characteristics, water type and spatial distribution of groundwater in Sixian County,Anhui Province were analysed and discussed. According to the characteristics of hydrodynamic field under groundwater exploitation, three paths were selected to simulate. The hydrogeochemical simulation was carried out using PHREEQC, and the formation and evolution of groundwater were quantitatively analysed. The results showed that the halite, gypsum and illite were dissolved; kaolinite, quartz, dolomite, calcite, fluorite were precipitated; calcic montmorillonite did not participate in the reaction; NaX desorption or CaX₂ adsorption occurred in Path Ⅰ. Halite, gypsum, illite, quartz were dissolved; calcic montmorillonite and calcite were precipitated; NaX desorption and CaX₂ adsorption occurred in Path Ⅱ. Reactions of Paths Ⅰ and Ⅲ are largely the same; the difference is the presence of dolomite dissolution in Path Ⅲ. The reason for this difference may be that dolomite dissolution is affected by precipitation CO₂ and precipitation hysteresis in groundwater runoff. The results show that the groundwater composition is mainly influenced by dissolution of rock salt and gypsum, Ca-Na ionic exchange and calcic montmorillonite, calcite in groundwater mining conditions of Sixian County.

Key words: inverse geochemical modeling, groundwater, formation, space distribution, Sixian County

CLC Number:

P642

LIU Hai, KANG Bo, SHEN Junhui. Formation of Groundwater Based on Inverse Geochemical Modeling: A Case Study from the Sixian County, Anhui Province[J]. Geoscience, 2019, 33(02): 440-450.

Figures/Tables 12

Fig.1 Hydrogeological map of bedrock in the study area

Fig.2 Hydrogeological profile of I-I'

Fig.3 Groundwater depth zoning and simulated paths in the study area

Table 1 Data of hydrochemical parameters

指标	极小值	极大值	均值	标准差	变异系数/%
pH	7.400	8.670	7.670	0.240	3.1
Na⁺	25.990	207.770	126.160	62.890	49.8
K⁺	0.340	5.810	1.460	1.090	75.0
Ca²⁺	36.220	128.890	65.697	18.006	27.4
Mg²⁺	21.520	70.970	36.996	12.054	32.6
N $H 4 +$	0.010	0.110	0.038	0.021	56.0
$HCO 3 -$	221.230	538.200	445.940	61.616	13.8
Cl^-	7.920	171.220	70.620	45.777	64.8
$SO 4 2 -$	6.220	303.870	117.040	85.096	72.7
F^-	0.230	2.130	0.904	0.367	40.6
$NO 3 -$	0.100	22.300	3.144	4.842	154.0
TDS	374.000	1 113.000	726.310	211.870	29.2

Table 1 Data of hydrochemical parameters

指标	极小值	极大值	均值	标准差	变异系数/%
pH	7.400	8.670	7.670	0.240	3.1
Na⁺	25.990	207.770	126.160	62.890	49.8
K⁺	0.340	5.810	1.460	1.090	75.0
Ca²⁺	36.220	128.890	65.697	18.006	27.4
Mg²⁺	21.520	70.970	36.996	12.054	32.6
N $H 4 +$	0.010	0.110	0.038	0.021	56.0
$HCO 3 -$	221.230	538.200	445.940	61.616	13.8
Cl^-	7.920	171.220	70.620	45.777	64.8
$SO 4 2 -$	6.220	303.870	117.040	85.096	72.7
F^-	0.230	2.130	0.904	0.367	40.6
$NO 3 -$	0.100	22.300	3.144	4.842	154.0
TDS	374.000	1 113.000	726.310	211.870	29.2

Fig.4 Ternary Piper diagram of water samples

Fig.5 Spatial distribution characteristics of different hydrochemical types of groundwater

Fig.6 Gibbs diagram of groundwater from the study area

Fig.7 Activity diagrams for Na+/H+-SiO2 (a), Ca2+/H+-SiO2 (b) and K+/H+-SiO2 (c)

Table 2 Chemical compositions of the starting and ending paths

离子及相关参数	模拟路径Ⅰ(L07→L05)		模拟路径Ⅱ(L02→SJ05)		模拟路径Ⅲ(L22→L19)
离子及相关参数	起点	终点	起点	终点	起点	终点
pH	7.74	7.68	7.40	7.49	7.51	7.63
Na⁺	118.33	199.09	36.90	148.08	33.86	191.26
K⁺	0.69	5.81	0.40	1.93	0.69	0.96
Ca²⁺	52.71	75.74	128.89	72.24	78.51	84.21
Mg²⁺	48.00	68.50	25.62	37.11	29.45	49.17
$HCO 3 -$	538.20	457.55	456.43	423.92	412.19	493.46
Cl^-	23.40	154.98	57.52	127.84	7.92	109.24
$SO 4 2 -$	101.82	303.87	51.39	147.73	52.14	236.72
F^-	1.40	0.78	0.75	0.92	0.45	1.20
SiO₂	38.86	40.45	0.00	42.06	32.21	28.17
钠吸附比	3.99	5.62	1.10	4.97	1.17	5.77
TDS	909.19	1 113.00	427.35	822.00	432.00	856.00
水化学类型	HCO₃-Na·Mg	HCO₃·SO₄-Na·Mg	HCO₃-Mg·Ca·Na	HCO₃·SO₄-Mg·Na	HCO₃-Ca·Mg	HCO₃·SO₄-Na·Ca

Table 2 Chemical compositions of the starting and ending paths

离子及相关参数	模拟路径Ⅰ(L07→L05)		模拟路径Ⅱ(L02→SJ05)		模拟路径Ⅲ(L22→L19)
离子及相关参数	起点	终点	起点	终点	起点	终点
pH	7.74	7.68	7.40	7.49	7.51	7.63
Na⁺	118.33	199.09	36.90	148.08	33.86	191.26
K⁺	0.69	5.81	0.40	1.93	0.69	0.96
Ca²⁺	52.71	75.74	128.89	72.24	78.51	84.21
Mg²⁺	48.00	68.50	25.62	37.11	29.45	49.17
$HCO 3 -$	538.20	457.55	456.43	423.92	412.19	493.46
Cl^-	23.40	154.98	57.52	127.84	7.92	109.24
$SO 4 2 -$	101.82	303.87	51.39	147.73	52.14	236.72
F^-	1.40	0.78	0.75	0.92	0.45	1.20
SiO₂	38.86	40.45	0.00	42.06	32.21	28.17
钠吸附比	3.99	5.62	1.10	4.97	1.17	5.77
TDS	909.19	1 113.00	427.35	822.00	432.00	856.00
水化学类型	HCO₃-Na·Mg	HCO₃·SO₄-Na·Mg	HCO₃-Mg·Ca·Na	HCO₃·SO₄-Mg·Na	HCO₃-Ca·Mg	HCO₃·SO₄-Na·Ca

Table 3 Chemical equations of mineral dissolution

矿物	溶解反应方程式
钙蒙脱石	6Ca_0.167Al_2.33Si_3.67O₁₀(OH)₂+60H₂O+12OH^-=Ca²⁺+14Al( OH $) 4 -$ +22H₄SiO₄
高岭土	Al₂Si₂O₅(OH)₄ +6H⁺ = H₂O+2H₄SiO₄+2Al³⁺
石英	SiO₂ + 2H₂O = H₄SiO₄
伊利石	K_0.6Mg_0.25Al_2.3Si_3.5O₁₀(OH)₂ + 11.2H₂O = 0.6K⁺+ 0.25Mg²⁺+2.3Al(OH $) 4 -$ +3.5H₄SiO₄+1.2H⁺
白云石	CaMg(CO₃)₂ = Ca²⁺+Mg²⁺+2 $CO 3 2 -$
石膏	CaSO₄·2H₂O=Ca²⁺+ $SO 4 2 -$ +2H₂O
岩盐	NaCl=Cl^-+Na⁺
萤石	CaF₂=Ca²⁺+2F^-
方解石	CaCO₃= $CO 3 2 -$ +Ca²⁺
阳离子交换	2NaX+Ca²⁺=2Na⁺+CaX₂

Table 3 Chemical equations of mineral dissolution

矿物	溶解反应方程式
钙蒙脱石	6Ca_0.167Al_2.33Si_3.67O₁₀(OH)₂+60H₂O+12OH^-=Ca²⁺+14Al( OH $) 4 -$ +22H₄SiO₄
高岭土	Al₂Si₂O₅(OH)₄ +6H⁺ = H₂O+2H₄SiO₄+2Al³⁺
石英	SiO₂ + 2H₂O = H₄SiO₄
伊利石	K_0.6Mg_0.25Al_2.3Si_3.5O₁₀(OH)₂ + 11.2H₂O = 0.6K⁺+ 0.25Mg²⁺+2.3Al(OH $) 4 -$ +3.5H₄SiO₄+1.2H⁺
白云石	CaMg(CO₃)₂ = Ca²⁺+Mg²⁺+2 $CO 3 2 -$
石膏	CaSO₄·2H₂O=Ca²⁺+ $SO 4 2 -$ +2H₂O
岩盐	NaCl=Cl^-+Na⁺
萤石	CaF₂=Ca²⁺+2F^-
方解石	CaCO₃= $CO 3 2 -$ +Ca²⁺
阳离子交换	2NaX+Ca²⁺=2Na⁺+CaX₂

Table 4 Saturation index along each path

矿物	路径Ⅰ (L07→L05)		路径Ⅱ (L02→SJ05)		路径Ⅲ (L22→L19)
矿物	起点	终点	起点	终点	起点	终点
方解石	0.62	0.58	0.63	0.40	0.50	0.63
CO₂	-2.04	-2.07	-1.77	-1.90	-1.92	-1.98
白云石	1.55	1.45	0.90	0.85	0.93	1.36
萤石	-0.98	-1.43	-1.08	-1.21	-1.92	-0.97
石膏	-1.84	-1.32	-1.74	-1.56	-1.89	-1.35
岩盐	-7.15	-6.12	-7.26	-6.32	-8.15	-6.29

Table 5 Calculated amount of mineral dissolution or precipitation

路径	各矿物溶解沉淀量/(mmol/L)
路径	岩盐	石膏	钙蒙脱石	高岭土
路径Ⅰ(L07→L05)	1.782	1.357	—	-0.039
路径Ⅱ(L02→SJ05)	1.986	1.004	-0.064	—
路径Ⅲ(L22→L19)	2.861	1.924	—	-0.013
路径	各矿物溶解沉淀量/(mmol/L)
路径	方解石	石英	CaX₂	NaX
路径Ⅰ(L07→L05)	—	-0.688	-0.698	1.396
路径Ⅱ(L02→SJ05)	-1.379	0.071	-1.519	3.307
路径Ⅲ(L22→L19)	-0.627	-0.081	-1.984	3.967
路径	各矿物溶解沉淀量/(mmol/L)
路径	伊利石	萤石	白云石
路径Ⅰ(L07→L05)	0.034	0.014	-0.440
路径Ⅱ(L02→SJ05)	0.065	0.004	0.457
路径Ⅲ(L22→L19)	0.012	0.020	0.081

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