Sources of SO42- and NO3- and Their Disturbances to Water Rock Processes in Karst Cave Systems
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摘要: 为揭示洞穴系统中SO42-和NO3-离子来源及其对洞穴碳酸盐溶解的影响,通过对麻黄洞6个水点自2018年8月至2019年7月进行为期一个完整水文年的系统监测,对于监测结果进行综合分析.结果表明:(1)麻黄洞洞穴水水化学类型为HCO3-Ca·Mg以及HCO3·SO4-Ca·Mg型;(2)通过实地调查与元素比值法综合分析可知,麻黄洞NO3-与SO42-各水点来源存在一定差异,其中麻黄洞NO3-主要源于农业活动和大气N沉降,而SO42-主要以农业活动、石膏溶解为主要来源,SO42-和NO3-均参与了岩溶作用,加速了基岩的溶蚀,这一过程主要受离子浓度、径流大小以及补给模式影响;(3)基于水化学计量法和稳定同位素技术估算可知,SO42-和NO3-洞穴水DIC的贡献为0.05~0.61,释放DIC的同时改变了水中离子浓度,对于岩溶作用形成扰动,总体呈现出旱季>雨季、滴水>裂隙水的特征.同样,由于岩溶区的复杂和不可知,在对其进行系统研究时应当注重多种方法的结合与比较,提高研究精度与可信度.
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关键词:
- 岩溶洞穴 /
- 水岩作用 /
- SO42-和NO3- /
- 麻黄洞 /
- 水文地质
Abstract: In order to reveal the source of SO42-and NO3-in the cave water and their influence on the hydrogeochemical process, a complete hydrological year monitoring was carried out at six monitor points in Mahuang Cave from August 2018 to July 2019. The results showed as follows: (1)The cave waters hydrochemical types are HCO3-Ca·Mg and HCO3·SO4-Ca·Mg; (2)SO42- and NO3- are mainly derived by agricultural activities, atmospheric deposition and gypsum dissolution, and their sources are different at different drip points. NO3- in the Mahuang cave is mainly caused by agricultural activities and atmospheric N deposition, while SO42- is supplemented by agricultural activities and gypsum dissolution; The SO42- and NO3- both participate in the karstification and accelerate the dissolution of bedrock; (3)Based on the estimation of hydrochemistry method and stable isotope technique, the contribution of DIC of SO42- and NO3-cave water ranges from 0.05 to 0.61. The release of DIC also changes the ion concentration in the water, causing disturbance to karstification and presenting a general pattern of Dry season > Rainy season and dripwaters > fissure water. Similarly, due to the complexity and unknowability of karst area, the combination and comparison of various methods should be paid attention to in the systematic study of karst area, so as to improve the accuracy and credibility of the study.-
Key words:
- Karst caves /
- water-rock process /
- SO42-and NO3- /
- Mahuang Cave /
- hydrogeology
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表 1 洞穴水点基本参数
Table 1. General parameters of cave water in the Mahuang cave
序号 样号 水样类型 滴水类型 沉积物类型 顶板厚度(m) 距洞口距离(m) 1 MH1# 钟乳石滴水 慢速常年性滴水 石钟乳 99.979 107.27 2 MH2# 钟乳石滴水 慢速常年性滴水 石笋、石钟乳 107.826 173.47 3 MH3# 裂隙水 快速常年流水 石幔、石钟乳 123.5 427.40 4 MH4# 壁流水 季节性流水 石幔 96.7 523.75 5 MH5# 地下河流水 常年流水 石幔 86.9 720.68 6 MH6# 钟乳石滴水 慢速常年性滴水 石笋、石钟乳 107.6 1169.73 表 2 SO42-、NO3-对洞穴基岩溶蚀贡献估算比例.
Table 2. Estimation of the contribution ratio of SO42- and NO3- to cave bedrock dissolution of the cave water samples in the Mahuang Cave
MH1# MH2# MH3# MH4# MH5# MH6# 201808 0.29 0.54 0.32 0.08 0.41 0.42 201809 0.60 0.29 0.31 0.45 0.47 0.49 201810 0.57 0.56 0.40 0.31 0.34 0.61 201811 0.47 0.31 0.50 0.39 0.29 0.53 201812 0.51 0.56 0.51 0.51 0.46 0.74 201901 0.41 0.16 0.24 0.26 0.37 0.39 201902 0.35 0.17 0.08 0.19 0.11 0.25 201903 0.04 0.35 0.16 0.12 0.42 0.26 201904 0.26 0.41 0.00 0.00 0.00 0.24 201905 0.24 0.06 0.14 0.04 0.08 0.05 201906 0.28 0.19 0.17 0.37 0.10 0.36 201907 0.23 0.00 0.00 0.00 0.00 0.23 Average 0.36 0.30 0.24 0.23 0.25 0.38 Cv 0.46 0.64 0.74 0.80 0.72 0.50 表 3 SO42-、NO3-对洞穴水DIC贡估算比例.
Table 3. The ratio of contribution of SO42- and NO3- to DIC in of the cave water samples in the Mahuang Cave
MH1# MH2# MH3# MH4# MH5# MH6# 201808 0.23 0.32 0.15 0.15 0.22 0.39 201809 0.21 0.31 0.10 0.07 0.15 0.11 201810 0.26 0.38 0.11 0.09 0.26 0.29 201811 0.24 0.38 0.21 0.26 0.46 0.41 201812 0.22 0.40 0.27 0.42 0.57 0.45 201901 0.27 0.42 0.37 0.46 0.60 0.42 201902 0.32 0.42 0.39 0.47 0.61 0.42 201903 0.33 0.39 0.36 0.42 0.58 0.40 201904 0.25 0.36 0.17 0.07 0.10 0.34 201905 0.28 0.32 0.15 0.11 0.23 0.30 201906 0.25 0.30 0.14 0.08 0.09 0.40 201907 0.19 0.29 0.10 0.05 0.05 0.39 Average 0.25 0.36 0.21 0.22 0.33 0.36 Cv 0.16 0.13 0.53 0.78 0.67 0.25 -
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