| 贵州施秉白云岩喀斯特区水化学和溶解无机碳稳定同位素特征 |
| 摘要点击 2881 全文点击 1713 投稿时间：2014-11-17 修订日期：2014-12-19 |
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| 中文关键词 白云岩喀斯特 水化学 溶解无机碳稳定同位素 特征 贵州施秉 |
| 英文关键词 dolomite karst hydrochemistry dissolved inorganic carbon stable isotope characteristics Shibing, Guizhou |
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| 中文摘要 |
| 对贵州施秉白云岩喀斯特世界自然遗产地49个水点进行采样,分析地表水和地下水水化学特征及控制因素,并探讨溶解无机碳(DIC)稳定同位素的分布特征和来源. 结果发现,研究区地表水和地下水pH值呈中性到碱性,溶解质较低,水中阳离子以Ca2+、Mg2+为主,阴离子以HCO3-为主,水化学类型为重碳酸-钙镁型(HCO3-Ca·Mg). 北部上游页岩分布区外源水水中Cl-、NO3-、SO42-的比重相对白云岩区喀斯特水水点的高,Si的含量也明显高于白云岩地区喀斯特水; 外源水的SIc和SId值为负,而流经白云岩区后均大于0. 水化学数据表明研究区水化学受降水和人为活动影响很小,Gibbs图显示水中离子组成主要受岩性的控制. 研究区喀斯特地表水中δ13CDIC值变化范围为-8.27‰~-11.55‰,平均为-9.45‰,地下水的δ13CDIC值范围为-10.57‰~-15.59‰,平均为-12.04‰,地表水δ13CDIC值比地下水偏重. DIC的δ13CDIC值在杉木河支流上整体表现为河流上游相对于下游偏轻,而杉木河干流上河水DIC的δ13CDIC值的变化则比较复杂. 根据同位素质量平衡,利用DIC的δ13CDIC实测值,计算了喀斯特区地下水DIC来自土壤CO2和白云岩矿物溶解的比例,计算结果为51.2%来自于土壤CO2,矿物本身的贡献约为48.8%. |
| 英文摘要 |
| Totally 49 water samples were collected in Shibing Dolomite Karst World Natural Heritage Site in Guizhou Province to analyze the characteristics and controlling factors of both the surface and underground waters, as well as the features and their origins of the dissolved inorganic carbon isotope. It was found that the pH of the study area was neutral to alkaline with low concentrations of total dissolved solids. The cations were dominated by Ca2+, Mg2+and anions by HCO3-, featured by HCO3-Ca·Mg type water. The ratios of Cl-, NO3- and SO42- in the allogenic water from the shale area in the northern catchment were higher than those in autogenic water from the dolomite karst area, so did the concentration of Si. The SIc and SId of the allogenic waters in the shale area were negative. After the waters entered into and flew by the dolomite karst area, both the SIc and SId increased to over 0. It could be told by the water chemistry that the hydrochemistry was little impacted by the rainfall and human activities. The Gibbs plot revealed that the chemical composition of the waters was mainly controlled by rock weathering. The δ13CDIC of the surface waters ranged from -8.27‰ to -11.55‰, averaging -9.45‰, while that of the underground waters ranged from -10.57‰ to -15.59‰, averaging -12.04‰, which was lighter than that of surface water. For the distribution features, it was found the δ13CDIC of the upper reaches of branches of Shangmuhe River was lighter than that of the lower reach, while that of the main river Shangmuhe River was relatively complex. Based on the mass balance of stable isotopes and the δ13CDIC, the ratio of the origin of DIC of the ground water was calculated. It was found that 51.2% was from soil CO2 and 48.8% was from the rock itself. |
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