沙漠区地下水化学特征及碳循环——以乌兰布和沙漠东部区为例

doi:10.13866/j.azr.2025.05.03

摘要/Abstract

摘要： 沙漠地下水赋存量大且溶解无机碳（Dissolved Inorganic Carbon，DIC）含量高，揭示沙漠区地下水中碳的迁移转化机制对深入理解全球碳循环具有重要意义。本文基于地下水流动系统理论，在乌兰布和沙漠东部区采集地下水样50个，利用统计分析、Piper三线图、Gibbs图和水文地球化学模拟等方法，对研究区地下水化学特征及其径流过程中碳的迁移转化机制进行研究。结果表明：研究区整体水环境呈弱碱性，潜水为微咸水，承压水为淡水和微咸水；水化学类型以Cl-Ca∙Mg型水和Cl-Na型水为主，地下水水化学组分主要受蒸发浓缩作用和水-岩相互作用影响。乌兰布和沙漠东部区潜水总固碳量为4.26~5.39 g·m^-2·a^-1，其中水-岩相互作用过程中吸收的碳量为1.14 g·m^-2·a^-1，由降水经包气带补给地下水的碳量为3.12~4.25 g·m^-2·a^-1。上述结果表明乌兰布和沙漠东部区地下水具有显著的“碳汇”效应，为全球碳循环中沙漠地下水的作用提供了实证。

关键词: 地下水, 碳循环, 水化学特征, 水-岩相互作用

Abstract:

The desert groundwater exhibits a substantial storage capacity and a high concentration of dissolved inorganic carbon (DIC). Understanding the mechanisms governing carbon migration and transformation in desert groundwater is crucial for gaining deeper insights into the global carbon cycle. Based on groundwater flow system theory, this study collected 50 groundwater samples from the eastern part of the Ulan Buh Desert, Inner Mongolia, China. A combination of statistical analysis, Piper three-line diagram, Gibbs diagram, and hydrogeochemical modeling was employed to investigate the hydrochemical characteristics of groundwater in the study area and the mechanisms of carbon migration and transformation during groundwater flow. The results indicate that the groundwater in the study area is generally weakly alkaline. Unconfined water is classified as brackish, whereas confined water ranges from fresh to brackish. The dominant hydrochemical types are Cl-Ca∙Mg and Cl-Na. The groundwater chemistry is primarily influenced by evaporation concentration and water-rock interactions. The total carbon sequestration flux of phreatic water in the eastern Ulan Buh Desert ranges from 4.26-5.39 g·m^-2·a^-1. Among this, carbon uptake via water-rock interactions accounts for 1.14 g·m^-2·a^-1, while carbon input from precipitation recharge through the vadose zone contributes 3.12-4.25 g·m^-2·a^-1. These findings suggest that groundwater in the eastern Ulan Buh Desert exhibits a significant “carbon sink” effect, providing empirical evidence for the role of desert groundwater in the global carbon cycle.

Key words: groundwater, carbon cycle, hydrochemical characteristics, water-rock interaction

季亚新, 李璐, 杨学东, 厚富来, 张萌, 董少刚. 沙漠区地下水化学特征及碳循环——以乌兰布和沙漠东部区为例[J]. 干旱区研究, 2025, 42(5): 800-809.

JI Yaxin, LI Lu, YANG Xuedong, HOU Fulai, ZHANG Meng, DONG Shaogang. Chemical characteristics of groundwater and carbon cycle in desert areas: A case study of the eastern region of Ulan Buh Desert[J]. Arid Zone Research, 2025, 42(5): 800-809.

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		K⁺	Na⁺	Ca²⁺	Mg²⁺	Cl^-	SO₄^2-	HCO₃^-	NO₃^-	F^-	TDS	pH
潜水	均值	12.66	131.84	57.90	47.20	135.45	199.33	242.89	43.53	0.75	764.84	8.30
	标准差	35.18	69.19	38.79	35.31	88.76	153.61	101.40	58.03	0.36	437.89	0.72
	极小值	1.20	34.90	8.00	8.50	39.00	38.40	103.70	0.00	0.18	252.40	7.66
	极大值	156.40	283.90	140.30	170.10	340.30	744.00	433.20	241.40	1.44	2299.45	10.67
	变异系数	2.78	0.52	0.67	0.75	0.66	0.77	0.42	1.33	0.49	0.57	0.09
承压水	均值	3.86	144.60	48.51	41.23	162.97	177.77	227.62	12.41	0.72	716.56	8.25
	标准差	1.81	101.00	30.49	25.23	121.29	103.88	110.04	16.37	0.58	372.92	0.40
	极小值	0.80	29.70	12.00	7.30	42.50	28.80	67.10	0.00	0.18	246.50	7.66
	极大值	7.80	383.90	140.30	111.80	549.50	422.40	494.20	64.49	3.20	1562.30	9.18
	变异系数	0.47	0.70	0.63	0.61	0.74	0.58	0.48	1.32	0.80	0.52	0.05

矿物名称	饱和指数范围	平均值	矿物溶解方程
白云石	2.37~5.01	3.901	CaMg(CO₃)₂=Ca²⁺+Mg²⁺+2CO₃^2-
方解石	1.12~2.43	1.894	CaCO₃=Ca²⁺+CO₃^2-
石膏	-0.23~1.30	0.534	CaSO₄·2H₂O=Ca²⁺+SO₄^2-+2H₂O
岩盐	-4.56~-1.54	-3.643	NaCl=Na⁺+Cl^-
石英	1.07~2.55	1.958	SiO₂+2H₂O=H₄SiO₄

矿物名称及化学式	路径
矿物名称及化学式	1-5	6-7	10-11	15-14	21-23
钠长石NaAlSi₃O₈	-1.35E-04	1.04E-03	-2.61E-05	1.01E-03	-1.40E-03
钙长石CaAl₂Si₂O₈	-5.27E-08	1.01E-03	-1.13E-05	1.38E-03	-1.79E-03
方解石CaCO₃	1.63E-03	-7.52E-04	-9.63E-04	1.78E-03	9.82E-04
二氧化碳CO₂	-2.04E-04	1.30E-03	1.73E-03	7.95E-04	-1.36E-03
白云石CaMg(CO₃)₂	-8.28E-04	-2.58E-04	7.25E-04	-1.41E-03	1.01E-03
钾长石KAlSi₃O₈	2.05E-05	-1.79E-04	4.86E-05	-3.84E-05	1.02E-05
蒙脱石Al₂O₉Si₃	4.90E-05	-1.24E-03	1.58E-04	-1.60E-03	2.13E-03
石膏CaSO₄·2H₂O	-1.62E-03	-1.50E-04	-1.50E-04	2.10E-03	2.50E-04

路径	水量/（10⁵ m³)	方解石/(t·a^-1)	白云石/(t·a^-1)	CO₂/(t·a^-1)	钠长石/(t·a^-1)	钙长石/(t·a^-1)	钾长石/(t·a^-1)	蒙脱石/(t·a^-1)	石膏/(t·a^-1)
1-5	61.75	1007.10	-940.50	-55.370	-217.75	-0.09	35.12	85.38	-1403.02
6-7	196.20	-1475.63	-929.96	1119.680	5320.39	5519.85	-977.43	-6838.63	-412.85
10-11	36.45	-351.09	486.26	277.109	-24.89	-11.43	49.26	161.98	-76.59
15-14	31.50	561.38	-818.47	110.128	836.93	1209.45	-33.62	-1424.96	926.18
21-23	26.06	255.81	483.73	-156.260	-955.03	-1298.01	7.42	1567.98	91.27
合计		-2.43	-1718.94	1295.290	4959.66	5419.77	-919.25	-6448.26	-875.00

矿物相	消耗或排放CO₂/(t·a^-1)	净碳量/(t·a^-1)
方解石	（4149.300）	1131.627
白云石	（-1182.041）	-298.509
CO₂	（3488.516）	951.413
钠长石	（757.789）	1230.624
钙长石	（1826.310）	249.042
钾长石	（-142.749）	-58.397