清江神女洞岩溶洞穴沉积物的磁学研究

通过对清江神女洞岩溶沉积物的磁学研究,得出有关该洞沉积物形成环境的下列判断：岩溶洞穴沉积物形成于早更新世至中更新世;岩溶洞穴沉积物形成于湿暖、干冷交替的环境;岩溶洞穴沉积物形成于ＮＥ５６°流向的古水流中。     

喀斯特区域的水化学不稳定性——以黔中地区为例

黔中地区是岩溶作用发育的喀斯特区域.1993年秋和1994年春末采自该地区不同类型水样的水化学分析表明:碳酸盐岩裂隙泉水呈中偏碱性,为[C]Ca-Ⅱ型;秋季离子总量、HCO₃-及Ca2+浓度大于春季.裂隙泉水流经地表一定距离后,HCO₃-降低,pH及SO₄2-、Cl-、K+、Na+明显增高.黄果树的天星桥、水帘洞及落水潭三个部位河水的SO₄2-、Na+以及Fe3+、NO₃-等浓度的季节性变化也更加明显.春季因瀑布暴气,CO₂的逸出,钙华生成更强烈一些.红枫湖作为喀斯特区域地表水的汇集地,HCO₃-与SO₄2-的当量比值仅2.1～2.4;Ca2+与Mg2+比值上升为2.4～4.2,Cl-浓度较碳酸盐岩裂隙泉水增高1倍;Na+浓度增高一个数量级.说明流域内地表土层溶蚀及人为污染影响的增强.土层孔隙水属强矿化水,而湖水呈现过渡特征.碳酸盐沉淀作用、硫酸盐矿化作用及固氮氨化作用,导致水质组成的显着差异.     

The role of anthropogenic activities in karst spring discharge volatility

The traditional hydrological time series methods tend to focus on the mean of whichever variable is analysed but neglect its time‐varying variance (i.e. assuming the variance remains constant). The variances of hydrological time series vary with time under anthropogenic influence. There is evidence that extensive well drilling and groundwater pumping can intercept groundwater run‐off and consequently induce spring discharge volatility or variance varying with time (i.e. heteroskedasticity). To investigate the time‐varying variance or heteroskedasticity of spring discharge, this paper presents a seasonal autoregressive integrated moving average with general autoregressive conditional heteroskedasticity (SARIMA‐GARCH) model, whose the SARIMA model is used to estimate the mean of hydrological time series, and the GARCH model estimates its time‐varying variance. The SARIMA‐GARCH model was then applied to the Xin'an Springs Basin, China, where extensive groundwater development has occurred since 1978 (e.g. the average annual groundwater pumping rates were less than 0.20 m³/s in the 1970s, reached 1.20 m³/s at the end of the 1980s, surpassed 2.0 m³/s in the 1990s and exceeded 3.0 m³/s by 2007). To identify whether human activities or natural stressors caused the heteroskedasticity of Xin'an Springs discharge, we segmented the spring discharge sequence into two periods: a predevelopment stage (i.e. 1956–1977) and a developed stage (i.e. 1978–2012), and set up the SARIMA‐GARCH model for the two stages, respectively. By comparing the models, we detected the role of human activities in spring discharge volatility. The results showed that human activities caused the heteroskedasticity of the Xin'an Spring discharge. The predicted Xin'an Springs discharge by the SARIMA‐GARCH model showed that the mean monthly spring discharge is predicted to continue to decline to 0.93 m³/s in 2013, 0.67 m³/s in 2014 and 0.73 m³/s in 2015. Copyright © 2014 John Wiley & Sons, Ltd.     

Variation of δ18O, δD and 3H in karst springs of south Kashmir,western Himalayas (India)

Water samples were collected from cold and warm karst springs for stable isotopes (δ¹⁸O and δD) and ³H from SE of Kashmir valley (western Himalayas) to distinguish the sources of recharge and infer their recharge areas. The spring water samples were most depleted in heavier isotopes in May (average δ¹⁸O: ?8.87‰ and δD: ?50.3‰) and enriched in September (average δ¹⁸O: ?7.58‰ and δD: ?48.1‰). The depleted ¹⁸O and ²H of spring waters bear the signatures of winter precipitation while as the enriched ¹⁸O and ²H of spring waters bear the signature of summer rainfall. D‐excess and ³H corroborate with the stable isotope results that the spring flow in spring season (May) and autumn (September) is dominantly controlled by the melting of winter snowmelt and summer rainfall, respectively. The results showed that unlike δD, the δ¹⁸O value in the karst spring waters decreases in January suggesting δ¹⁸O shift. The spring water samples also fall above the Local Meteoric Water Line and Global Meteoric Water Line indicating the δ¹⁸O shift due to interaction of groundwater with the host carbonate rocks during its traverse. The mean elevation of the recharge areas of the springs using δ¹⁸O and δD tracers was also estimated. Copyright © 2014 John Wiley & Sons, Ltd.     

Experimental and computational validation and verification of the Stokes–Darcy and continuum pipe flow models for karst aquifers with dual porosity structure

In our previous study, we developed the Stokes–Darcy (SD) model was developed for flow in a karst aquifer with a conduit bedded in matrix, and the Beavers–Joseph (BJ) condition was used to describe the matrix–conduit interface. We also studied the mathematical well‐posedness of a coupled continuum pipe flow (CCPF) model as well as convergence rates of its finite element approximation. In this study, to compare the SD model with the CCPF model, we used numerical analyses to validate finite element discretisation methods for the two models. Using computational experiments, simulation codes implementing the finite element discretisations are then verified. Further model validation studies are based on the results of laboratory experiments. Comparing the results of computer simulations and experiments, we concluded that the SD model with the Beavers–Joseph interface condition is a valid model for conduit–matrix systems. On the other hand, the CCPF model with the value of the exchange parameter chosen within the range suggested in the literature perhaps does not result in good agreement with experimental observations. We then examined the sensitivity of the CCPF model with respect to the exchange parameter, concluding that, as has previously been noted, the model is highly sensitive for small values of the exchange parameter. However, for larger values, the model becomes less sensitive and, more important, also produces results that are in better agreement with experimental observations. This suggests that the CCPF model may also produce accurate simulation results, if one chooses larger values of the exchange parameter than those suggested in the literature. Copyright © 2011 John Wiley & Sons, Ltd.     

江西北部岩溶地貌陆生贝类物种多样性

作者于2013年5月至6月调查了位于江西北部地区岩溶地貌陆生贝类资源,共采得陆生贝类63种及亚种(含5个未定种),分别隶属于12科21属,其中1个新种,即石钟山弯螺(Sinoennea shizhongshanensis sp.nov),优势种为雪土鸥螺(Georissa niva)、细纹喇叭螺(Boysidia gracilis)、囊喇叭螺(Boysidia dorsata)和灰尖巴蜗牛(Bradybaena ravida ravida)。区系成分以东洋界成分为主,占总种类数的61.90%。计算了江西北部地区岩溶地貌陆生贝类多样性指数,其中Margalef丰富度指数(dMA)为2.205~4.273,Shannon-Wiener多样性指数(H′)为1.960~3.374,Pielou均匀度指数(Jsw)为0.448~0.681。与邻近自然保护区比较,江西北部地区岩溶地貌陆生贝类较为丰富,与其他自然保护区物种相似性较低。     

高密度电法在某公路路基下隐伏岩溶探测中的应用

灰岩分布区易发生岩溶塌陷等地质灾害,高密度电阻率法是岩溶地质调查的重要手段。以某一段穿越岩溶发育区的公路为例,应用高密度电法对区内暗河、槽谷型岩溶塘、落水洞等灾害地质体进行了探测,结果显示拟建路段覆盖层厚度大约为2~20 m,基岩内岩溶极发育,岩石地表起伏大,溶沟、溶槽、岩溶塌陷、落水洞发育;岩石中溶蚀裂隙、溶洞发育。表明高密度电阻率法能够有效地判定岩溶的发育情况,可以为地质灾害评估提供科学客观的依据。     

贵阳某些表层岩溶基坑边坡局部失稳机理分析

随着建设活动的日益频繁以及建筑范围的扩大,局部表层岩溶被揭露,出现不同于基坑整体失稳的局部岩溶充填物的失稳现象,此失稳现象往往和地下岩溶水相联系,因为处于局部,不能引起设计人员的重视,在沟槽中岩溶水动力的作用下失稳,可能产生较大的工程问题。     

鄂尔多斯盆地东胜砂岩型铀矿中铀矿物的电子显微镜研究

鄂尔多斯盆地东胜铀矿是我国一个重要的大型砂岩型铀矿床。通过电子显微技术,对该铀矿床中铀矿物的种类、产出特征进行详细的研究。研究确定东胜砂岩型铀矿床中铀矿物主要为铀石和水硅铀矿,两者紧密共生,它们均为表生铀矿物。铀矿物的颗粒十分细小,一般粒度均为微米级。铀石和水硅铀矿往往呈板状、不规则微粒状产出,铀矿物的表面溶蚀现象明显,有的还具纳米级的溶蚀孔。铀矿物的产出与蚀变黑云母、蚀变黄铁矿密切相关,也见到微脉状铀矿物集合体穿切碎屑石英等现象。研究表明在表生作用下,该铀矿床中的铀元素存在溶解(迁移)-沉淀(富集)的反复过程。     

塔河油田奥陶系碳酸盐岩油藏溶洞充填物特征

塔河油田奥陶系缝洞型储层是该区最重要的油气生产层段,古岩溶作用产生的大量溶洞作为油气的存储空间,具有举足轻重的意义。通过对11口井充填溶洞的岩心观察,划分出化学沉(淀)积岩相、搬运型岩相、垮塌型岩相、渗流充填相4大类溶洞充填相。搬运型岩相为溶洞的早期充填产物,当地表岩溶的溶蚀作用发展到一定程度时岩石会发生崩落,崩落的结果就产生了垮塌型岩相,后期的渗流充填相以填隙物的形式充填在垮塌型岩相里。据区内Ta井的典型溶洞充填特征,归纳出其充填序列为上部的溶洞破裂相、中部的塌陷相及下部的海水侵入充填相。溶洞充填物中微量元素、稀土元素等的地球化学特征,证实区内存在海水-淡水混合岩溶,对油田的开发生产具有很好的指导意义。