【作者】 吕保樱；

【导师】 刘再华；

【作者基本信息】 广西师范大学 ， 无机化学， 2007， 硕士

【摘要】 本文采用仪器自动记录、野外长期人工监测、野外取样以及室内样品分析等相结合的方法,基本弄清了云南白水台钙华景区泉水、池水和人工渠道水的水化学、微量元素以及碳氧同位素变化的规律:对钙华池和人工渠道现代沉积的钙华碳氧同位素、白水台地区降雨量以及雨水的氧氘同位素进行了综合的分析;对钙华碳氧同位素所包含的环境温度、降雨信息应用于古环境重建进行了初步的讨论。对白水台钙华景区源头1号泉长期监测的数据分析,可以看出,白水台1号泉并不具备表层岩溶泉动态多变的特征,其水温较高且常年稳定,CO₂分压达到70000ppmv以上,[Ca²⁺]和[HCO₃^-]分别大于190mg/L和720mg/L,这些为钙华的沉积提供了基本的化学背景条件。对比在白水台钙华景区池水和人工渠道水进行水温长期的监测数据发现:池水和渠道水都有非常明显的昼夜温差变化,说明池水和渠道水都受外界气温的影响。受流速和流量较小的影响,池水的昼夜温差比渠道水大1²倍。由于水中二氧化碳的逸出白水台渠道水中CO₂分压沿水流逐渐降低,pH升高,这使得水中的方解石达到过饱和,导致钙华沿途沉积,[Ca²⁺]和[HCO₃^-]降低（电导降低）。但水流到中下游后,CO₂分压基本保持不变,并有下降趋势。这是钙华沉积达到一种新的平衡的结果。同样地,钙华景区池水也有相似的规律。进入雨季后,渠道水和主要由其补给的1～5号钙华池池水的Ca²⁺、Mg²⁺、HCO₃^-、SO4^2-和Sr浓度都不同程度地被雨水稀释,而K+浓度则升高。特别是Sr元素,将其与降雨量进行线性拟合后,发现渠道水中Sr含量与降雨量有较好的负相关关系,从一定程度上反映了降雨量的大小。但对于泉水而言,泉水受降雨的影响并不大,有着稳定的水化学性质和微量元素组成。受泉水补给的影响,6～10号钙华池池水受降雨的影响也不是很大,相比1～5号钙华池池水而言变化幅度小。池水和渠道水除了受降雨的影响外,还具有空间变化规律。对于Sr元素而言,从上至下浓度依次减小。主要原因是在钙华沉积的过程中,微量元素Sr吸附于CaCO₃表面。降雨的稀释作用不但对水中的元素有影响,同时也影响了水及其沉积的钙华的稳定同位素组成。通过实验室对雨水氧氘同位素的分析,作出了白水台地区的地区雨水线。相比全球雨水线,白水台地区的雨水线斜率为12.56和截距54.88,比全球雨水线的斜率8以及截距10.34大。通过对雨水中氘剩余值d的计算,表明雨季降雨效应来自季风带来的云团,而水体δ¹⁸O的蒸发效应不明显。分析发现,雨水的氧同位素与降雨量有着很好的负相关关系。随着雨季降雨量的增加,雨水的氧同位素将会降低,这也影响了补给源主要是雨水的渠道水和池水,使得渠道水和池水的氧同位素在雨季出现了减小,并且水中沉积的钙华也有着相似的变化规律,即钙华氧同位素与降雨量有着一定的线性负相关关系。除了氧同位素,碳同位素同样也有相似的变化规律。雨水的“稀释”作用使得水中和钙华中的碳同位素降低,并且钙华碳氧同位素的变化比较同步,有着较好的线性关系,反映了两者相似的控制机理。渠道水、池水和钙华稳定同位素除了有时间变化规律外,空间变化规律也相当明显。随着取样点从上游到下游,白水台渠道水和池水中沉积的钙华碳氧同位素都有增加的趋势。碳同位素增加的主要原因是由于含轻碳同位素的CO₂从水中逸出,使水中相对富集重的碳同位素,而在钙华沉积的过程中,重的碳同位素又相对富积在钙华中,这就相当于重碳同位素在钙华中有两次富集。总之,水中的Sr元素和钙华中的氧同位素与降雨量的线性相关关系的发现,为下一步将钙华用于古气候环境重建提供了一定的理论和实验基础。然而要将这些相关关系应用到古环境重建中还需要做进一步的样品分析和数理统计分析。更多还原

【Abstract】 The method of combining of hydrogeochemical automatic data logging,in-situ perennial observation and analytic sampling in lab was used to study the rule of hydrogeochemistry,trace element and carbon and oxygen stable isotopes and varity of spring water,pool water and channel water.And combing the result of analysing for carbon and oxygen stable isotopic modern travertine deposited in pool and channel and the rainfall in baishuitai area and oxygen and deuterium stable isotopes of rain, we can gain some relationship between the environment and the travertine. At the same time,the message of environment temperature and rainfaull involeved in paleoenvironment reconstruction with carbon and oxygen isotopes of the travertine is discussed.Through analysing of the data in No.1 spring which is the source of the pond water, we can find that No.1 spring didn’t have the charicterictics of variations of typical epikarst springs.The temperature of this spring is so stable in the whole year. The pressure of CO₂ is up to about 70000 ppmv. And the concentration of Ca²⁺ and HCO3- is above 190mg/L and 720mg/L. These all are the basic chemistry background which is applied for travertine. Compareing the automatic temperature data of pool and man-made channel, it can be found that pool water and channel water have various changing temperature day and night.It means that pool water and channel water are both influenced by temperature.And because of the velocity and flux of flow,the temperature fluctuations in pool is more than one or two times above in channel.Rapid CO₂ degassing from the water is triggered by the higher partial pressures than that of the surrounding air.Cosequently,as the water flows downstream of the spring the CO₂ partial pressures gradually decreases,the pH increased.The water becomes supersaturated with respect to calcite,and travertine is deposited, which brings on the decrease of concentration of calcium and bicarbonate.As the water flows from the middle to the end, the CO₂ partial pressures become to be stable and decrease appreciably.This is the result of new balance of deposited travertine.The travertine in pool has the similar rule.When in monsoon,the concentration of Ca²⁺,Mg²⁺,HCO₃^-,SO₄^2- and Sr in channel water and No.1～5 pool water which is derived from channel water is decreased by the rainfall except of K+.It is a good linear negative correlation betweent the concentration of Sr in water and the total of rainfall.It is reflected the total of the rainfall at a certain extent.but for the spring,it is so stable in hydrogeochemistry and trace element.Becauce of the influence of the stable spring,the rain effect in No.6～10 pool is not obviously.The pool water and channel water also has the space diversification.As the Sr for example,it is decreased from upstream to downstream.the reason is Sr is adsorbed by CaCO₃ when the travertine is deposited.Diluted effect of rainwater not only impacts the elements in water but also affects stable isotopes in water and travertine. Through analyzing oxygen and deuterium stable isotopes of the rain we work out Local Meteoric Water Line in baishuitai area. Comparing with Global Meteoric Water Line, the slope and intercept of Local Meteoric Water Line is 12.56 and 54.88. It is higher than the Global Meteoric Water Line which is 8 and 10. The value of deuterium excess shows that the precipitation source in baishuitai area is coming from oceanic air mass by monsoon. And the evaporation effect of oxygen isotopes in water is not obviously. It is show a good negative correlation betweent the oxygen isotopes in rainwater and rainfall. When the total of the rain is increasing, the oxygen isotopes of the rain is decreased. It affects the channel water and pool water which is replenishment from rainwater. The oxygen isotopes in channel water and pool water is decreased.and the rule of travertine deposited has the similar rule--- linear negative correlation betweent the oxygen isotopes in travertine and rainfall. The carbon isotopes in water and travertine is decreased by Diluted effect of rainwater. And variation of carbon and oxygen isotopes in travertine is synchronization.it is show the similar controlled mechanism.The stable isotopes in channel water, pool water and travertine has not only the rule of temporal variety,and also has thr rule of space variety.Carbon isotopes of travertine in channel and pool in baishuitai area gradually increased along the flow path.the main reason is that as the CO₂ degasses from water,isotope fractionation happens.The carbon isotopes is enriched in water.And when the travertine is deposited,the carbon isotopes is enriched in travertine.It is means that the heavy carbon isotopes is enriched twice.In a word, the base of theoretics and experimentation for paleoenvironment reconstruction from travertine is applied by the correlation between the trace element of Sr in water, oxygen stable isotopes in travertine and rainfall.But we should do more sample and symbolic Statistic analyzed in order to use this correlation for paleoenvironment reconstruction.更多还原