The studies of the oxgen and carbon isotopes of the rainwater in Guilin area, the drip water and the present carbonate deposit in Panlong cave of Guilin show that: (i) as to the general characteristics of the oxygen i...The studies of the oxgen and carbon isotopes of the rainwater in Guilin area, the drip water and the present carbonate deposit in Panlong cave of Guilin show that: (i) as to the general characteristics of the oxygen isotopes of the rainwater within a year and between years, the δ18O values decrease with an increase of air temperature and the rainfall, and the correlation between δ18O values and the mean monthly air temperature is much better than that between δ18O values and the rainfall, and the δ18O values of the rainwater during the summer monsoon are much smaller than those during winter monsoon; (ii) δ18O values of the drip water have a quite good correlation with the δ18O values of the rainwater in the same period; (iii) when the conditions are appropriate, δ13C can be used as an environmental proxy, that is, the smaller δ13C of speleothems is, the larger the proportion of C3 plants is and the more plentiful the rainfall is. On the contrary, C4plants may be prevailing or the environment may be a stony desert caused by climate changes or human activity.展开更多
sources of cave drip water, time scales of drip water re- sponding to precipitation, and processes of water dynamics in four caves of Pearl watershed in Guizhou, China (Liang- feng cave in Libo, Qixing cave in Duyun, ...sources of cave drip water, time scales of drip water re- sponding to precipitation, and processes of water dynamics in four caves of Pearl watershed in Guizhou, China (Liang- feng cave in Libo, Qixing cave in Duyun, Jiangjun cave in Anshun and Xiniu cave in Zhenning). Because of the variety of karst cave surroundings, interconnections of water trans- porting ways, water dynamics processes etc., time scales of drip-water in four caves responding to rainfall is 0—40 d. According to the characteristics of water transport in cave roof, pathways of water movement, types of water head etc., drip water of four caves can be divided into five hydrody- namics types. The differences of time scales, and ways of water-soil and water-rock interaction during water trans- porting in cave roof make it difficult to correctly measure speleothem record and trace material sources. In addition, there exist great differences in water dynamic conditions among the four caves. So the interpretation of the paleoenvi- ronment records of speleothem must be supported by the understanding of hydrodynamics conditions of different drip sites. Based on the data got from drip sites in four caves, drip conductivity accords with precipitation, which indicates that element contents in speleothem formed by drip water record the change of karst paleoenvironment. But results of multi-points study are needed to guarantee the correctness of interpretation.展开更多
According to systemically monitoring results of oxygen(hydrogen) isotope compositions of precipita-tion,soil waters,soil CO2,cave drip waters and their corresponding speleothems in Liangfeng Cave(LFC) in Guizhou Provi...According to systemically monitoring results of oxygen(hydrogen) isotope compositions of precipita-tion,soil waters,soil CO2,cave drip waters and their corresponding speleothems in Liangfeng Cave(LFC) in Guizhou Province,Southwest China,it is found that local precipitation is the main source of soil waters and drip waters,and that the amplitudes of those δ 18O values of three waters(precipitation,soil water and drip water) decrease in turn in the observed year,which are 0‰ to -10‰, -2‰ to -9‰ and -6‰ to -8‰,respectively.Moreover,the δ 18O values for three waters show a roughly simultaneous variation,namely,that those values are lighter in the rainy seasons,weightier in the dry seasons,and that the average δ 18O value of drip waters is about 0.3‰ weightier than that of precipitation,which is modified by surface evaporation processes.We also find that oxygen isotope equilibrium is reached or neared in the formation processes of speleothems in LFC system,and that it is feasible to reconstruct paleotemperature and paleoprecipitation by using δ 18O values of speleothems.However,it should be noted that surface evaporation would affect the oxygen isotope values in the study area.展开更多
The strontium isotopic compositions (87Sr/86Sr) of samples including soils, bedrock, soil waters, drip waters and their corresponding speleothems in the Qixing Cave (QXC), Guizhou Province, China, were systemically me...The strontium isotopic compositions (87Sr/86Sr) of samples including soils, bedrock, soil waters, drip waters and their corresponding speleothems in the Qixing Cave (QXC), Guizhou Province, China, were systemically measured and analyzed. The results indicate that there are significant Sr isotopic differences among samples. The mean 87Sr/86Sr ratios in drip water for the samples 1#, 4# and 9# were 0.709568, 0.709139 and 0.708761, respectively, which possibly result from different flow paths, residence times, and other hydrogeological processes in the unsaturated zone overlying QXC. Meanwhile, levels of 40.8%, 57.6% and 72.4% of Sr in drip waters for 1#, 4# and 9#, respectively, were derived from bedrock dissolution, which was calculated by the mixture model of the two end-members (soil and bedrock). There is, however, no positive correlation between the relative proportion from bedrock dissolution (δ13C value is 1.8‰) and drip water δ13CDIC values. The mean drip water δ13CDIC value in 1# is the heaviest (–4.5‰) with the lowest contribution rate of bedrock dissolution, whereas the value in 9# is the lightest (–9.3‰) with the highest contribution rate of bedrock dissolution. The proportion from host rock dissolution in 4# is higher than that in 1# and lower than that in 9#, while its mean drip water δ13CDIC value (–8.6‰) is higher than that of 9# and lower than that for 1#. This suggests that the prior calcite precipitation (PCP) processes in the unsaturated zone overlying the cave are responsible for the δ13CDIC value differences between different drip waters, and not bedrock dissolution. Furthermore, this study also demonstrates that the 87Sr/86Sr ratios of speleothems in the 1# and 4# mainly reflect the variation in the relative proportions from the soil system (soil water) and bedrock dissolution overlying the cave. It is, therefore, feasible to use the strontium isotopic signals of speleothems as an indicator for soil chemical weathering intensity, and consequently as a monsoon proxy in the s展开更多
文摘The studies of the oxgen and carbon isotopes of the rainwater in Guilin area, the drip water and the present carbonate deposit in Panlong cave of Guilin show that: (i) as to the general characteristics of the oxygen isotopes of the rainwater within a year and between years, the δ18O values decrease with an increase of air temperature and the rainfall, and the correlation between δ18O values and the mean monthly air temperature is much better than that between δ18O values and the rainfall, and the δ18O values of the rainwater during the summer monsoon are much smaller than those during winter monsoon; (ii) δ18O values of the drip water have a quite good correlation with the δ18O values of the rainwater in the same period; (iii) when the conditions are appropriate, δ13C can be used as an environmental proxy, that is, the smaller δ13C of speleothems is, the larger the proportion of C3 plants is and the more plentiful the rainfall is. On the contrary, C4plants may be prevailing or the environment may be a stony desert caused by climate changes or human activity.
基金This work was supported by the Key Project of the Knowledge Innovation Engineering of the Geochemistry Institute of Chinese Academy of Sciences and the National Nalural Science Foundation of China(Grant No.90202003).
文摘sources of cave drip water, time scales of drip water re- sponding to precipitation, and processes of water dynamics in four caves of Pearl watershed in Guizhou, China (Liang- feng cave in Libo, Qixing cave in Duyun, Jiangjun cave in Anshun and Xiniu cave in Zhenning). Because of the variety of karst cave surroundings, interconnections of water trans- porting ways, water dynamics processes etc., time scales of drip-water in four caves responding to rainfall is 0—40 d. According to the characteristics of water transport in cave roof, pathways of water movement, types of water head etc., drip water of four caves can be divided into five hydrody- namics types. The differences of time scales, and ways of water-soil and water-rock interaction during water trans- porting in cave roof make it difficult to correctly measure speleothem record and trace material sources. In addition, there exist great differences in water dynamic conditions among the four caves. So the interpretation of the paleoenvi- ronment records of speleothem must be supported by the understanding of hydrodynamics conditions of different drip sites. Based on the data got from drip sites in four caves, drip conductivity accords with precipitation, which indicates that element contents in speleothem formed by drip water record the change of karst paleoenvironment. But results of multi-points study are needed to guarantee the correctness of interpretation.
基金National Basic Research Program of China (Grant No. 2006CB403200)the International Partnership Project and the Orientation Project of Knowledge Innovation Program of Chinese Academy of Sciences (Grant No. kzcx2-yw-306)National Natural Science Foundation of China (Grant No. 90202003)
文摘According to systemically monitoring results of oxygen(hydrogen) isotope compositions of precipita-tion,soil waters,soil CO2,cave drip waters and their corresponding speleothems in Liangfeng Cave(LFC) in Guizhou Province,Southwest China,it is found that local precipitation is the main source of soil waters and drip waters,and that the amplitudes of those δ 18O values of three waters(precipitation,soil water and drip water) decrease in turn in the observed year,which are 0‰ to -10‰, -2‰ to -9‰ and -6‰ to -8‰,respectively.Moreover,the δ 18O values for three waters show a roughly simultaneous variation,namely,that those values are lighter in the rainy seasons,weightier in the dry seasons,and that the average δ 18O value of drip waters is about 0.3‰ weightier than that of precipitation,which is modified by surface evaporation processes.We also find that oxygen isotope equilibrium is reached or neared in the formation processes of speleothems in LFC system,and that it is feasible to reconstruct paleotemperature and paleoprecipitation by using δ 18O values of speleothems.However,it should be noted that surface evaporation would affect the oxygen isotope values in the study area.
基金supported by the Orientation Project of Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-YW-306)the International Partnership Project of the Chinese Academy of Sciences, the National Basic Research Program of China (2006CB403200)+1 种基金the National Natural Science Foundation of China (90202003)the Personnel Training Project (Western Doctor) of West Light Foundation of the Chinese Academy of Sciences
文摘The strontium isotopic compositions (87Sr/86Sr) of samples including soils, bedrock, soil waters, drip waters and their corresponding speleothems in the Qixing Cave (QXC), Guizhou Province, China, were systemically measured and analyzed. The results indicate that there are significant Sr isotopic differences among samples. The mean 87Sr/86Sr ratios in drip water for the samples 1#, 4# and 9# were 0.709568, 0.709139 and 0.708761, respectively, which possibly result from different flow paths, residence times, and other hydrogeological processes in the unsaturated zone overlying QXC. Meanwhile, levels of 40.8%, 57.6% and 72.4% of Sr in drip waters for 1#, 4# and 9#, respectively, were derived from bedrock dissolution, which was calculated by the mixture model of the two end-members (soil and bedrock). There is, however, no positive correlation between the relative proportion from bedrock dissolution (δ13C value is 1.8‰) and drip water δ13CDIC values. The mean drip water δ13CDIC value in 1# is the heaviest (–4.5‰) with the lowest contribution rate of bedrock dissolution, whereas the value in 9# is the lightest (–9.3‰) with the highest contribution rate of bedrock dissolution. The proportion from host rock dissolution in 4# is higher than that in 1# and lower than that in 9#, while its mean drip water δ13CDIC value (–8.6‰) is higher than that of 9# and lower than that for 1#. This suggests that the prior calcite precipitation (PCP) processes in the unsaturated zone overlying the cave are responsible for the δ13CDIC value differences between different drip waters, and not bedrock dissolution. Furthermore, this study also demonstrates that the 87Sr/86Sr ratios of speleothems in the 1# and 4# mainly reflect the variation in the relative proportions from the soil system (soil water) and bedrock dissolution overlying the cave. It is, therefore, feasible to use the strontium isotopic signals of speleothems as an indicator for soil chemical weathering intensity, and consequently as a monsoon proxy in the s
文摘为探究岩溶关键带碳循环机制,揭示洞穴通风对洞穴环境变化的响应机制,在2018年国庆期间对贵州绥阳大风洞洞内空气环境指标(温度、湿度、CO 2浓度)和滴水水化学指标(温度,pH值,EC,Ca 2+,HCO-3)进行为期7 d的连续自动监测,并运用系统分析方法对各要素进行了综合分析。结果表明:(1)受游客数量、洞道结构的影响,洞穴空气CO 2浓度表现出明显的昼夜变化特征;与2#(神泉玉露)点相比,1#(夜明珠)点位于大风洞主洞道,洞腔体积较大,洞道较宽,洞穴空气CO 2浓度增加幅度及变化幅度表现为2#>1#。(2)洞穴通风效应与洞穴滴水水化学相关性显著。洞穴通风与lg P CO 2(w)呈反相关,与pH值,SIc和SId为正相关;受监测点洞道结构、通风效应和滴水水量的影响,洞穴通风与1#点的Ca 2+和HCO-3浓度变化呈反相关关系,与2#点的相关性不显著。(3)不同通风模式下,不同监测点的水气CO 2分压差及沉积环境存在差异。当ΔT v>0时,洞穴属于积极通风状态,洞穴空气CO 2浓度降低,ΔP CO 2>0,有利于洞穴景观的沉积;反之,洞穴沉积物趋向于产生溶蚀作用。
