| 岩溶溪流的脱气作用及碳酸钙沉积--以重庆市南川区柏树湾泉溪流为例 |
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| 引用本文： | 周小萍,蓝家程,张笑微,徐尚全.岩溶溪流的脱气作用及碳酸钙沉积--以重庆市南川区柏树湾泉溪流为例[J].沉积学报,2013,31(6):1014-1021. |
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| 作者姓名： | 周小萍 蓝家程 张笑微 徐尚全 |
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| 摘 要： | 以一定间距监测水体中pH、电导率、溶解氧等水化学参数及HCO3-、Ca2+等阴阳离子浓度，揭示了重庆市南川区柏树湾泉及其下游溪水的水化学的空间特征。泉水出露地表后，CO2溢出导致溪流水的水化学特征沿流程发生有规律的变化，并促使溪水达到过饱和状态而产生明显的碳酸钙沉积。研究结果表明，脱气作用导致溪水的HCO3-浓度、Ca2+浓度、电导率（EC）和CO2分压沿流程逐渐递减，pH值及常见碳酸盐矿物的饱和指数逐渐升高。泉水出露时水中CO2浓度与自由大气之间的浓度梯度是影响脱气速率的主要因素，但溪渠的水力坡度也对脱气速率也有一定影响。地下水出露至泉口处的脱气程度，是影响溪流碳酸钙沉积的决定性因素。旱季泉水流量较小，泉口处脱气程度较大，并且溪水的Ca2+浓度含量较高，再加上溪流沿途的水体扰动加速CO2溢出，以及溪渠内的枯枝落叶和其他物质的吸附等，皆有利于碳酸钙沉积。
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| 关 键 词： | 岩溶溪流 脱气作用 碳酸钙沉积 重庆市南川区柏树湾泉 |
CO2 Outgassing and Precipitation of Calcium Carbonate in a Karst Stream: A case study of Baishuwan Spring in Nanchuan,Chongqing |
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| Abstract: | PH, conductivity, dissolved oxygen and concentration of HCO3-, Ca2+ , as well as other anion and cation, was monitored by certain space to explain the evolution of stream water chemistry along the flow path of Baishuwan Spring downstream in Nanchuan, Chongqing, China. After surfacing, stream water chemistry was changed regularly by CO2 outgassing, water became increasingly supersaturated with calcium carbonate and the obviously precipitation occurred. The result shows that, concentration of HCO3-, Ca2+, conductivity(EC) and CO2 partial pressure declined along the flow path, caused by CO2 outgassing, while pH value and saturation index of common carbonate minerals increased. The concentration gradient between atmosphere and water is the main factor affecting the degassing rate, while the creek drainage gradient also has a certain influence. Extent of degassing at the spring vent is decisive factors controlling the carbonate deposition along the flow path. The small flow during dry season, a great degree of degassing, high level of Ca2+ concentration, and the hydraulic disturbance which accelerates CO2 outgassing, as well as the physical adsorption of litter and other substances in the creek drainage, factors above all play active role in deposition of calcium carbonate. |
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