【作者】 衣成城；

【导师】 王建力；

【作者基本信息】 西南大学 ， 第四纪地质学， 2010， 硕士

【摘要】 洞穴次生沉积物已成为研究岩溶地区古气候变化的重要载体,尤其体现在高分辨率、短时间尺度研究上。利用洞穴次生沉积物中的稳定碳氧同位素重建古气候,并采用高精度的U／Th测年技术对一系列的气候突变事件进行对比研究是当今古气候研究的重点。但是,在利用洞穴次生沉积物进行古气候重建的过程中,也有一些研究注意到其记录与古气候变化不一致的现象,对洞穴滴水的研究有助于我们对洞穴沉积物的古气候信息进行精确解译。本文选取重庆武隆芙蓉洞作为对象,在洞内选取两处滴水(1#,3#)、两处池水(2#,4#)以及洞外6#泉水进行3个水文年的定点定时监测,以获得其离子和元素地球化学特征。监测指标包含了山顶泉水、洞内滴水及池水的滴率(仅滴水)、电导、pH、水温以及Ca2+、Mg2+、K+、Na+、Sr2+、Ba2+、SO42-、HCO3-、Cl-、离子浓度等。同时对洞内环境指标(如温度,湿度,CO2浓度等),洞外山顶的环境指标(如植被,土壤,岩性等)也进行了长期的动态监测。通过上述的工作,结合芙蓉洞当地气象站的器测数据,主要得到以下初步研究结果：(1)通过对芙蓉洞2006年3月～2009年2月期间滴水、池水、泉水的地球化学和水化学指标监测,结合当地的器测数据,初步认为洞穴滴水中的Sr2+、Ca2+、Mg2+浓度及其比值既取决于环境降水和温度的变化,也受到水文地质条件变化的影响。(2)芙蓉洞洞穴滴水、池水中的Ca2+、Sr2+、Mg2+、SO42-和Cl-的浓度变化范围和均值都比较相近。洞外泉水受外界环境影响较大,变化复杂。本研究区域的岩溶水在洞顶运移形成洞穴滴水之前,达到了很好的均质化效果。芙蓉洞外山上的6#泉水Ca2+平均浓度为45.81 mg／L,洞内1#、3#滴水Ca2+的平均浓度增加到64.59 mg／L,Ca2+在2#和4#池水中沉积,浓度下降到24.74mg/L,下降了大约61.7%。Mg2+和Sr2+的浓度在泉水、滴水和池水中的变化规律与Ca2+基本一致。各种水体中Cl-的浓度变化幅度较小,平均浓度为1.72±0.2 mg/L。(3)岩溶水与基岩作用时间长短以及运移过程中Ca2+的前期沉积作用对各元素与离子含量变化具有重要作用。在2006年7、8月大旱后,洞穴滴水和池水中SO42-和Cl-的浓度分别在2007年2月达到了谷值,同时Ca2+的浓度也达到了3年中的最小值,并且Mg／Ca与Sr／Ca出现峰值。这些指标的共同变化是对2006年夏季大旱的一个很好的反映,表明了芙蓉洞洞穴水的水化学特征对干旱事件比较敏感。在2007年夏季洪涝过后1～2个月期间,SO42-和Cl-的浓度先升后降,Ca2+的浓度则一直下降,Mg／Ca与Sr／Ca也出现了相应的波动。这些指标的同步变化受到了土壤淋溶、基岩溶蚀和强降水稀释作用的共同影响。旱季Ca2+的前期沉积作用和雨季基岩的溶蚀及雨水的稀释作用主导着岩溶水中Mg/Ca与Sr／Ca的变化,这些指标能对干旱和洪涝等极端气候事件做出响应。然而,离子浓度和元素比值与当地降水的非同时性变化表明芙蓉洞岩溶系统水循环的滞后期需要更深入的研究。(4)通过对5个采样点的Ca2+,Mg／Ca与Sr/Ca的相关性分析表明,虽然芙蓉洞上覆岩层厚达数百米,但是在岩溶水的运移过程中,Mg2+与Sr2+的浓度呈现一种反相关的变化,Ca2+的溶蚀和沉积则是按照一种近似指数变化的模式进行,具有一定的规律性。更多还原

【Abstract】 Secondary cave sediments had become an important carrier of the records, which show the ancient climate change of the karsts area, especially reflected in the high-resolution、short-time scale studies. Using the stable carbon and oxygen in the secondary cave sediments to reconstruct the ancient climate, and using high-precision U/Th dating techniques on a series of comparative study of abrupt climate change events is the focus of today’s ancient climate research. However, in the use of secondary cave sediments in ancient climate reconstruction process, there are some study notes that its records are inconsistent with the ancient climate change, the study of the cave drips help us to accurately interpret the cave sediments’ ancient climate information.This article choose the Furong cave in Chongqing Wulong as the study object, select drip water in two place(1#,3#),pool water in two place(2#,4#)inside the cave,and the water of the spring 6 # outside the cave for three hydrologic years’regular monitoring, in order to obtain their ionic and elemental geochemistry.monitoring indicators include the peak springs, cave drip water and pool water drip rate (just dripping),conductivity, pH, temperature, and the ionic concentration of Ca2+ Mg2+、K+、Na+、Sr2+、Ba2+、SO42-、HCO3-、Cl- and so on. At the same time, there is also a long-term dynamic monitoring about the environmental indicators(such as temperature, humidity, concentration of CO2, etc.) inside the cave, the environmental indicators(such as vegetation, soil, litho logy, etc.)of the peak outside the cave.Through this work, combined with instrumental data measured by the local weather station in Furong cave, mainly got the following preliminary findings:(1)Through monitoring the geochemistry and water chemistry indicators about dripping water, pool water and spring water from Mar.2006 to Feb.2009, combined with the local instrumental data,preliminary considered that the concentration and the ratio of the Sr2+、Ca2+、Mg2+in the cave drip water not only depends on environment precipitation and temperature changes, but also by the effects of changes in hydro-geological conditions.(2) The changing range and mean of the concentration of Ca2+、Sr2+、Mg2+、SO42-、and Cl" in cave drip water and pool water are quiet similar. Spring water outside the cave are more influenced by the external environment, changes in the complex. The study area of karst water in the study area achieved a good homogenization effect, before it moving on the top of the cave and coming into cave drip water. The average concentration of the Ca2+ in the 6 # spring water on the hill which outside the Furong cave is 45.81 mg/L, the average concentration of the Ca2+ in the 1#、3# cave drip water increased to 64.59 mg/L,Ca2+ deposited in the 2# and 4# pool water, its concentration dropped to 24.74 mg/L, declined by about 61.7%. The concentration changes of Mg2+ and Sr2+ in the spring water、drip water and pool water is basically same as the Ca2+, The concentration of Cl" changes a lesser extent in variety of waters, with an average concentration is 1.72±0.2 mg/L.(3) The contacting time between karst water and bedrock as well as prior calcite precipitation play an important role in the change of elements and ions. After the drought in July and August 2006, the concentrations of the SO42- and Cl- in the cave drip water and pool water respectively reached the valley in February 2007, at the same time the concentration of the Ca2+ also reached the minimums value, while the Mg/Ca and Sr/Ca reached the peak value. These indicators common change is a good reflection of the drought in the summer of 2006, showing that the chemical characteristics of the water in the Furong cave is sensitive to drought events. During the one to two month after the flooding in the summer of 2007, the concentrations of SO42" and Cl- went up first and then decreased, the concentration of Ca2+ has been declining, Mg/Ca and Sr/Ca also appeared corresponding fluctuations, simultaneous changes in these index are effected by the leaching of soil，bedrock dissolution and strong dilution.The pre-deposition of the Ca2+ during the dry season, the bedrock dissolution during the rainy season and the Rainwater dilution dominant the change of the Mg/Ca and Sr/Ca in the karst water, these index can response to the extreme climate events, such as drought and flood. However, the non-contemporary change between the ion concentrations and element ratios and local precipitation show that the residence time of water cycle in Furong cave karst system needs further study.(4) Through the correlation analysis of the Ca2+,Mg/Ca and Sr/Ca in the five sampling sites showed that, although the overlying rock in the Furong cave is a few hundred meters thick, however, during the migration process of karst water, the concentration of Mg2+ and Sr2+ showed an anti-related changes, the corrosion and sedimentation of Ca2+ is according to an approximate index change, with a certain regularity.更多还原