| 洞穴滴水地球化学的空间和时间变化及其控制因素--以北京石花洞为例 |
| |
| 引用本文： | 王新中,班凤梅,潘根兴.洞穴滴水地球化学的空间和时间变化及其控制因素--以北京石花洞为例[J].第四纪研究,2005,25(2):258-264. |
| |
| 作者姓名： | 王新中 班凤梅 潘根兴 |
| |
| 作者单位： | 南京农业大学农业资源与生态环境研究所,南京,210095;中国科学院地质与地球物理研究所,北京,100029;南京农业大学农业资源与生态环境研究所,南京,210095 |
| |
| 摘 要： | 通过对北京石花洞滴水地球化学一个水文年的观测,揭示了洞穴滴水水文地球化学季节变化与外界气候变化的关系,3个滴水点的滴率随降雨量的增加都有明显的变化,但不同滴水点滞后时间不同。滴水滴率、Mg2+和SO2-4含量的季节变化数据显示,雨季洞穴滴水主要来源于当季降水,但也存在岩层滞留水的混入。滴水中Mg/Ca比值存在明显季节变化,旱季较低而雨季较高,但在雨季初期出现较大的波动。分析洞穴上覆土壤和洞内裂隙土壤数据,认为雨季初期滴水中Mg/Ca比值的波动是由土壤中Mg2+的快速淋溶造成的,上覆土壤结构性质和组分变化均影响滴水地球化学特征。
|
| 关 键 词： | 北京石花洞 洞穴滴水 地球化学 Mg/Ca比值 土壤 |
| 文章编号： | 1001-7410(2005)02-258-07 |
| 收稿时间： | 2004-12-06 |
| 修稿时间： | 2004年12月6日 |
TEMPORAL AND SPATIAL VARIATION OF CAVE DRIPWATER GEOCHEMISTRY IN SHIHUA CAVE, BEIJING,CHINA |
| |
| Wang Xinzhong,Ban Fengmei,Pan Genxing.TEMPORAL AND SPATIAL VARIATION OF CAVE DRIPWATER GEOCHEMISTRY IN SHIHUA CAVE, BEIJING,CHINA[J].Quaternary Sciences,2005,25(2):258-264. |
| |
| Authors: | Wang Xinzhong Ban Fengmei Pan Genxing |
| |
| Institution: | 1. Institute of Resources, Ecosystem and Environment of Agriculture, Nanjing Agricultural University, Nanjing 210095;
2. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029 |
| |
| Abstract: | In recent years there has been a growing interest in cave speleothems as archives of paleoclimate change. An understanding of temporal and spatial variability of cave dripwater geochemistry is thus important in studying the stalagmite records for interpreting the paleoclimatic change. In this paper, the authors reported a monitoring of drip water geochemistry and its response to rainfall and soil water regime in Shihua Cave, Beijing, China from December 2003 to November 2004. As monitored in three drip sites, there was marked temporal and spatial changes in dripping rates, with the lag times varying with the different features of micro-fissure/porosity in the soil and limestone rock above cave the drip site. Spring rainfall water filled the soil cracks developed after a long period of drought in the precedent autumn and winter, and infiltrated into the epikarst zone, passing the karst conduits that fed the cave drip water. Rainfall water migration was predominantly along low-permeability, diffuse flow-routes during periods of low rainfall and correspondingly, low recharge. As rainfall and recharge increased, the capacity of low-permeability diffuse flow-routes was exceeded and groundwater migration along pathways of high-permeability conduit flow-routes increased. The analysis of the seasonal variation of drip rate, Mg 2+ and SO 2- 4 demonstrates that most of the drip water came from the rainfall mixed with older water stored in the pores and micro-fissure network of epikarst zone. The chemical composition of soil above the cave has also been determined to address the role of soil in karst water hydrogeochemistry. There are a considerable amount of soluble Ca 2+ and Mg 2+ in the soil above the cave, which may be leached to the underlying aquifer by rainwater. On the other hand, rainwater contains large amount of CO 2 derived from soil with higher concentration in summer dissolving the underlying carbonate, resulting in the increase of Ca 2+ concentration in drip waters, indicating active deposition of secondary calcite during summer. The observed variability in dripwater Mg/Ca ratio indicates that water-rock interaction processes are neither spatial nor temporal constant. The variation of karst water residence time in the epikarst zone may be interpreted by the drip water Mg/Ca. In the dry season, there could exist a durable contact of rock with moisture, probably resulting in an increased Mg/Ca ratio of the solution due to quicker saturation of calcite than dolomite. Furthermore, calcite precipitation prior to dolomite occurred along the flow path due to degassing of CO 2 from fissure solution, resulting in depletion of Ca 2+ and relative enrichment of Mg 2+ in drip water. This process is highly sensitive to temperature both of water and the soil above cave. While variation of speleothem Mg/Ca ratio with temperature is insignificant for the temperature in the Shihua Cave is relatively constant within a year, variation of speleothem Mg/Ca ratio could be indirect indicator of drip water Mg/Ca ratio and, in turn, an indicator of the epikarst environmental conditions affecting the hydro-geochemical flow in the cave. However, precise and accurate interpretation requires more detailed and long term monitoring and calibration of Mg/Ca ratio variation to climate conditions. |
| |
| Keywords: | cave drip water geochemistry Mg/Ca ratio soil epikarst zone |
| 本文献已被 CNKI 维普 万方数据 等数据库收录！ |
| 点击此处可从《第四纪研究》浏览原始摘要信息 |
| 点击此处可从《第四纪研究》下载免费的PDF全文 |
|
