宁夏清水河上游浅层地下水咸化作用研究

摘要/Abstract

摘要：

认识干旱区地下咸水的形成机制对水资源管理和规划具有重要意义。在宁夏清水河平原上游采集52组浅层地下水化学样品和8组易溶盐样品,分析了地下水咸化的水文地球化学作用,利用元素质量平衡法计算了各作用对地下水盐分的贡献比率。结果表明:沿径流方向,地下水咸化程度呈增加趋势。咸化作用主要为岩石风化,并具空间分异,在补给区以碳酸盐风化为主,在强径流区硫酸盐风化占优,在弱径流区硫酸盐和岩盐风化共同提供了68%~93%的盐量。随着地下水TDS增加,蒸发岩贡献比率上升,碳酸盐和硅酸盐贡献比率下降。蒸发岩风化是导致浅层地下水咸化的首要因素。

关键词: 地下水咸化, 岩石风化, 蒸发岩, 质量平衡, 宁夏清水河

Abstract:

Research on salinization mechanism of groundwater in arid areas is of great significance for water resources management. Fifty-two groundwater samples and eight rock samples were taken from the upstream Qingshui river plain in Ningxia. Hydrogeochemical processes controlling groundwater salinization were studied and their contribution ratios to salinity were calculated using element mass balance method. The results show that the salinization extent increased along groundwater flow path. The salinization processes mainly depended on rock weathering and had a spatial variation. Carbonate weathering played a dominant role in recharge area and sulfate weathering in strong runoff area. In slow runoff area, 68-93 percents of total salt were supplied by sulfate and halite weathering. The contribution ratios of evaporite increased with groundwater TDS, while carbonate and silicate had an opposite trend, which indicated that evaporite weathering controlled groundwater salinization.

Key words: groundwater salinization, rock weathering, evaporite, mass balance, Qingshui river in Ningxia

中图分类号:

P641

王雨山, 李戍, 孟莹, 程旭学. 宁夏清水河上游浅层地下水咸化作用研究[J]. 现代地质, 2017, 31(01): 191-199.

WANG Yushan, LI Shu, MENG Ying, CHENG Xuxue. Study on the Salinization Mechanism of Shallow Groundwater along the Upstream Qingshui River in Ningxia[J]. Geoscience, 2017, 31(01): 191-199.

图/表 10

图1 研究区水文地质剖面图

Fig.1 Hydrogeological profile in the study area

图2 研究区和取样点位置图

Fig.2 Location map of the study area and sampling sites

表1 地下水主要组分统计(ρB/(mg/L))

Table 1 Major chemical components of groundwater samples(mg/L)

水文地质单元 (样品数)		pH	TDS	Ca²⁺	Mg²⁺	Na⁺	K⁺	HCO₃^-	Cl^-	SO₄^2-	NO₃^-	Si
Ⅰ(12)	最小值	7.80	385.10	52.90	31.80	21.60	2.30	268.50	14.20	32.70	0.88	1.35
	最大值	8.79	710.90	92.50	95.80	80.10	4.30	388.10	31.90	236.30	35.35	8.78
	均值	8.22	571.08	74.58	51.72	45.63	2.78	351.84	20.87	158.08	13.84	6.96
	中位值	8.16	563.85	74.10	47.15	42.50	2.55	367.90	20.60	145.05	13.14	7.85
Ⅱ(16)	最小值	7.72	981.30	28.10	46.20	131.20	2.10	269.70	28.40	212.30	0.00	5.26
	最大值	8.50	3 615.00	193.20	204.90	812.40	14.20	683.40	546.70	1 630.00	69.04	8.71
	均值	8.19	1 618.98	83.63	103.01	321.94	4.63	407.67	195.26	657.81	27.71	6.90
	中位值	8.20	1 388.00	73.15	79.25	265.04	4.30	376.45	156.35	567. 03	18.92	7.29
Ⅲ(19)	最小值	7.80	1 083.60	57.30	74.90	98.20	2.90	236.70	26.20	574.50	3.53	5.22
	最大值	8.65	4 865.30	275.60	255.20	1 199.60	12.90	408.80	1145.30	2 416.20	78.51	8.99
	均值	8.21	2 819.58	150.96	143.87	591.37	5.52	322.93	448.82	1 257.54	33.42	6.85
	中位值	8.20	2 258.32	124.20	141.06	594.00	4.90	308.70	322.60	1 141.00	32.57	6.75

图3 地下水Piper三线图(单位:%)

Fig.3 Piper plot of groundwater

图4 G12钻孔地下水和易溶盐组分垂向变化

Fig.4 Concentrations of soluble ions in rocks and ground-water vs. sampling depths from borehole G12

图5 浅层地下水Gibbs图

Fig.5 Gibbs plot of shallow groundwater

图6 Mg2+/Na+(a)、HCO3-/Na+(b)与Ca2+/Na+关系图

Fig.6 Plots of Mg2+/Na+(a) and HCO3-/Na+ (b) vs. Ca2+/Na+

图7 Na+与Cl-(a)、非岩盐来源阳离子与SO42-(b)、(Na+-Cl-)与HCO3-(c)及(Ca2++Mg2+)与HCO3-(d)关系

Fig.7 Plots of Na+ vs. Cl-(a), non-halite sources cations vs. SO42-(b), (Na+-Cl-) vs. HCO3-(c) and (Ca2++Mg2+) vs. HCO3-(d)

图8 矿物饱和指数沿途变化(a)、岩盐饱和指数与Cl-(b)、石膏饱和指数与SO42-(b)关系

Fig.8 Plots of saturation index(SI) variation for several minerals along flow path(a),SI of halite vs.Cl-(b),and SI of gypsum vs. SO42-(c)

图9 不同作用的贡献比率和TDS关系 a.岩盐和硫酸盐贡献比率;b.蒸发岩、硅酸盐和碳酸盐贡献比率

Fig.9 Plots of contribution ratios of rock weathering vs. groundwater TDS

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