Vulnerability,pressures, and protection of karst caves and their speleothems in Ha Long Bay,Vietnam

This paper presents the results of morphological and microclimatic surveys and speleothem analyses of ten karst caves located in different isles in Ha Long Bay, a famous tourist attraction in Vietnam. Characteristically, the caves have enormous entrances, roomy interiors, but short length, typical of karst caves in tropical climates. The cave microclimate was found to be significantly dependent on the outside atmosphere and human activities. There was a clear spatial variation in macro features and fabrics of speleothems from entrance (porous, microcrystalline) to rear (solid, macrocrystalline) of the caves. Microstructure analysis with the use of an environmental scanning electron microscope shows a gradual decrease of biological activity and microclimate instability from outside to the innermost parts of the caves are the causes for this spatial variation. Past and present deterioration of caves and speleothems directly due to tourist activities and vandalism has been observed. On the other hand, there are signs of speleothem regrowth in the caves where tourism has been stopped. This study has proved that caves and their speleothems in Ha Long Bay are highly dynamic and understanding of their environment requires immediate methodological attention. Based on the analytical results, it is recommended that regulation of visitor frequency and removal of lamp-flora are necessary for sustainable development of the show caves and their speleothems.     

A simplified methodology for mapping groundwater vulnerability and contamination risk, and its first application in a tropical karst area, Vietnam

A simplified methodology for mapping groundwater vulnerability and contamination risk is proposed, and the first application of the methodology, in a mountainous tropical karst area, is presented. The test site is the Tam Duong area, one of the poorest and remotest regions in northern Vietnam. The methodology requires a minimum of input data, which makes it particularly useful for developing countries. Vulnerability is assessed on the basis of two factors, which take into account the duality of recharge processes in karst aquifer systems: the overlying layers (O) and the concentration of flow (C). The risk map is obtained by putting together the vulnerability map and a simplified hazard assessment. The resulting maps provide a basis for groundwater protection zoning and land-use planning. Tracer tests and microbiological data confirmed the vulnerability and risk assessment in the test site.     

An approach for estimating sustainable yield of karst water in data sparse regions

This study presents an approach for transferring the qualitative analysis of groundwater sustainability for development to quantitative evaluation by an analogy of two similar regions. A concept of groundwater exploitation sustainability (GES), which is an evaluation index based on water supply capability, eco-geo-environment maintaining capability and the harmony between water and society, is put forward. The fuzzy analytic hierarchy process method is applied to calculate the GES for the Xiangshan and Dianchang karst groundwater sources in the Huaibei city, Anhui Province, China. The GES of the Xiangshan karst system was calculated to be 0.53 and represents medium exploitation sustainability, while that for the Dianchang is relatively high with a value of 0.70. These two karst systems are separate units but have similar hydrogeological conditions. The Dianchang area had limited groundwater observation data, while the Xiangshan area had long series of observation data, which enabled the computation of the sustainable yield. The sustainable yield of the Xiangshan karst area was used to calibrate the GES, and develop a linear equation between the GES and sustainable yield, which was used to calculate the sustainable yield of the Diangchang karst area as 40.4 million m³.     

地质雷达探测技术在岩溶地形勘察中的应用

岩溶地形的有效勘察是保证岩溶地区工程施工安全与质量的重要因素.从应用条件来看,地质雷达方法较其它地球物理方法更适应浅层复杂岩溶地形的勘察.这里介绍了地质雷达在岩溶地形勘察中的工作原理和方法,分析了在岩溶地区雷达波的传播特点与曲线特征,结合工程实例,探讨了地质雷达在岩溶地形勘察中的应用.经分析认为,该技术能够有效地完成岩溶地区的工程地质勘察工作,有较好的发展前景和应用价值.     

水化学特征在岩溶水系统分析中的应用——以山西晋城长河流域岩溶水系统为例

通过对长河流域岩溶水矿化度、Ca^2＋／Mg^2＋、Ca／Sr及Mg／Sr等的特征分析,长河流域岩溶水系统从补给区到径流区、排泄区矿化度、Can／Mgn、Ca／Sr及Mg／Sr变化具有明显的规律性,岩溶水的流动方向则与以上各水化学指标质量浓度的变化方向一致,即研究区在东、北部灰岩裸露区直接接受大气降雨补给渗漏及部分半裸露区间接补给渗漏,向西以泉水形式排泄到沁河河谷地带,形成沁河河谷排泄带,地下水径流方向为南西西方向。并分析岩溶地下水的径流特征,富水强弱,水岩作用强弱及岩溶裂隙发育规律特征。     

Application of seismic velocity tomography in investigation of karst collapse hazards,Guangzhou, China

This paper describes seismic velocity tomography applied to the investigation and assessment of karst collapse hazards to facilitate accurate characterization of geological conditions of karst sinkhole formation. In the survey areas of Xiamao, Guangzhou, China, and Huangchi, Foshan, China, seismic velocity tomography was used to explore the structures of rock and soil associated with karst collapse. The results show that sand intercalated with clay or clay intercalated with soft soil dominates the cover of these two areas. The overburden is 20–33 m thick and underlain by Carboniferous limestone. In the limestone, there are well-developed karst caves and cracks as well as highly fluctuating bedrock surfaces. The seismic velocities are less than 2500 m/s in the cover, 2500–4500 m/s in the karst fracture zones and caves of Xiamao, and 1500–2000 m/s in the Huangchi collapse area. The karst fracture zones, relief of bedrock surfaces, and variations of soil thicknesses revealed by seismic velocity tomography are well constrained and in agreement with those in the drilling borehole profiles. This paper demonstrates that seismic velocity tomography can delineate anomalies of rock and soil with the advantages of speed, intuitive images, and high resolution.     

Hydrogeological controls of variable microbial water quality in a complex subtropical karst system in Northern Vietnam

Karst aquifers are particularly vulnerable to bacterial contamination. Especially in developing countries, poor microbial water quality poses a threat to human health. In order to develop effective groundwater protection strategies, a profound understanding of the hydrogeological setting is crucial. The goal of this study was to elucidate the relationships between high spatio-temporal variability in microbial contamination and the hydrogeological conditions. Based on extensive field studies, including mapping, tracer tests and hydrochemical analyses, a conceptual hydrogeological model was developed for a remote and geologically complex karst area in Northern Vietnam called Dong Van. Four different physicochemical water types were identified; the most important ones correspond to the karstified Bac Son and the fractured Na Quan aquifer. Alongside comprehensive investigation of the local hydrogeology, water quality was evaluated by analysis for three types of fecal indicator bacteria (FIB): Escherichia coli, enterococci and thermotolerant coliforms. The major findings are: (1) Springs from the Bac Son formation displayed the highest microbial contamination, while (2) springs that are involved in a polje series with connections to sinking streams were distinctly more contaminated than springs with a catchment area characterized by a more diffuse infiltration. (3) FIB concentrations are dependent on the season, with higher values under wet season conditions. Furthermore, (4) the type of spring capture also affects the water quality. Nevertheless, all studied springs were faecally impacted, along with several shallow wells within the confined karst aquifer. Based on these findings, effective protection strategies can be developed to improve groundwater quality.     

山东省菏泽凸起地热田岩溶地热水水化学水平演化特征

在前人研究成果的基础上,选择A-A'和B-B'两条路径,采用Piper三线图解、Schoeller图解、Na-K-Mg平衡图解、饱和指数计算评价等方法,研究山东菏泽凸起地热田地热水沿路径上的循环演化特征.结果表明:沿A-A'、B-B'剖面岩溶冷水→岩溶热水,水化学类型由SO4?HCO3-Ca?Mg?Na或SO4?HCO...     

贵州岩溶水充水矿井涌水量预测探讨

贵州绝大多数煤矿井是以岩溶水充水为主，矿井排水量与大气降水密切，地面塌陷与淹井事故也屡见不鲜，因此矿井涌水量预测是个非常复杂的问题，作者根据在本地工作的多年工作经验，介绍了一种适用的简易的矿井涌水量与突水量计算方法。     

山东羊庄岩溶水系统地下水环境演化趋势评价

羊庄岩溶水系统地下水是山东枣庄滕州市、山亭区和薛城区城市供水及部分工业用水的主要来源。基于地下水环境演化趋势评价指标体系的羊庄岩溶水系统地下水环境演化趋势的研究,对地区饮用水安全、工农业生产和经济社会可持续发展具有重要意义。以羊庄岩溶水系统地下水为研究对象,用地下水环境演化趋势评价指标体系对系统地下水环境演化趋势进行研究,结果显示,除山亭断块和辛召断块部分低山丘陵区以波动平衡演化为主以外,其他地区地下水环境演化趋势以劣向演化为主,约占系统总面积的2/3,亟需采取相关措施抑制这一趋势。     

山东省枣庄盆地岩溶塌陷形成条件及易发区划分方法探讨

枣庄市是碳酸盐岩分布较广的地区之一，也是以开发利用岩溶地下水为主的城市。20a来，岩溶塌陷灾害比较严重，在山东省较为突出，已成为当地发展经济的制约因素和社会不安定因素之一。为防治灾害的发生、发展，在研究岩溶塌陷形成条件、影响因素的基础上，依据岩溶塌陷形成、发育的地质环境条件、规模和强度等，采用袭扰系数法对岩溶塌陷易发性进行分区，划分出高易发区、中易发区、低易发区和不发育区。对高、中易发区提出了监测、勘查、工程和水资源合理开发利用等措施，有的放矢地预防岩溶塌陷灾害，使地质环境与经济协调发展。     

贵州河流河水的锶同位素与喀斯特地区化学风化作用

贵州省地处世界岩溶发育最复杂、类型最齐全、分布面积最大的东亚岩溶区域中心, 也是我国碳酸盐岩分布面积最大、岩溶最发育的省区, 同时也是我国水土流失严重的地区之一。由于河水的地球化学反映了流域盆地的化学风化、气候和上地壳的化学组成的重要信息, 本工作对贵州喀斯特地区两条主要水系(乌江水系、沅江水系)河流的主要阴、阳离子和Sr2＋离子及锶同位素组成变化进行了系统研究, 对河水地球化学组成变化特征及其控制因素进行了解释。 贵州喀斯特地区两条主要水系河流的水化学组成代表了典型碳酸盐岩地区河流的相应化学组成, 显示了与世界主要河流不同的水化学特征, 反映了喀斯特环境地表化学风化作用的特点。     

山西长治辛安泉域岩溶水硫酸盐污染来源分析

辛安泉域核心区域工农业相对发达,人类活动强烈,逐渐出现岩溶地下水位下降、泉流量减小和水质污染等水环境问题。硫酸盐污染是泉域岩溶水的主要污染物之一,通过科学手段进行污染来源分析和识别,可为泉域保护提供决策依据。硫氧同位素是地下水领域应用较广的一种环境同位素方法,不仅技术成熟且识别精度高。本次研究将硫氧同位素方法与水化学方法结合,在辛安泉域采取岩溶泉水、岩溶地下水、孔隙水、裂隙水和河水五类水样,测试硫同位素δ34S、氧同位素δ18O和硫酸根离子SO42-含量,以分析辛安泉域岩溶水硫酸盐污染来源。结果显示,辛安泉域岩溶水水质的硫酸盐大部分符合地下水III类标准,硫酸盐含量较高的区域主要集中在西部滞流缓流区与襄垣和长治子系统的分界处、长治子系统和平顺-壶关子系统南部等地区。西部滞流缓流区硫酸盐主要来源于石膏、硬石膏的溶蚀,人类活动影响较小。泉域南部岩溶水中硫酸盐主要来源是煤矿开采的影响,大气沉降也是重要来源之一。     

珠琳地区岩溶水分布规律及找水经验

本文在研究区域水文地质条件的基础上，分析了珠琳地区岩溶水的分布规律，认为新构造运动的间歇性和持续上升、弱透水层的存在是造成自分水岭至排泄区岩溶水的富水性由弱到强及岩溶发育均匀程度由高到低，地下水埋深呈阶梯状降低的主要因素。总结提出了高原斜坡地带岩溶石山区找水要在古溶蚀台面上接近分水岭的地段、溶蚀洼地的扬起端寻找表层带岩溶水，以及悬托的弱透水层之上寻找滞水型岩溶水；不宜在强迳流区、负地形最低部位布井。     

城镇化进程下裸露岩溶区地下河水质变迁——以贵阳上寨地下河系统为例

为查明城镇化进程中裸露型地下河系统水质变化特征,以贵阳上寨地下河为例,基于历史水质监测数据,对比研究区城镇化进程,分析总结水质变化情况与成因。结果显示:上寨地下河水质随城镇化进程呈明显阶段性变化,1987年前基本未受影响,1988-1995年仅轻微影响,1996-2014年即城乡结合部期间污染最严重;无机超标组分历年贡献率以锰、氨氮、氟化物和亚硝酸盐最高,来源以养殖、生活、食品加工为主,冶炼、制造次之;有机污染物主要为苯系物和苯并[a]芘,2003年后开始有机污染物检出,2015年首次出现苯并[a]芘超标。从1981年至今研究区经历了从农村-城郊-城镇的发展过程,尤其是城乡结合部期间,区内人口、企业激增,但基础设施建设滞后,社会管理未能跟上,导致废水废渣无序排放,地表水体污染严重,加上裸露岩溶区地下河系统脆弱的防污性能,是地下河污染的主要原因。建议尽快开展区内排污管网建设、加强对生猪养殖场、食品工业园等污染源控制、启动区域地表水体污染的综合修复治理,以遏制上寨地下河的污染现状。      

Geogene Versus Anthropogene Origin of Trace Metals in Sediments in Cua Luc Estuary and Ha Long Bay, Vietnam

In the present study, the geochemistry of 49 surficial-bed and 101 core sediment samples is investigated to clarify the origin of trace metals in the Cua Luc Estuary and Ha Long Bay, which is a famous World Natural Heritage Site in Vietnam. Moreover, the potential mobility of trace metals is also assessed and their relationship with reference elements (Al, Fe, and Ca) and organic matter is established in order to make recommendations for sediment management and monitor future pollution. Generally, trace metals display higher concentrations in Ha Long Bay compared to the Cua Luc Estuary. However, this is controlled by the distribution of the fine (clay?+?silt) fraction, and hence the concentrations of Al, Fe, Ca, and organic matter (OM). The comparison of concentrations of trace metals (normalized towards Al) between the surficial sediments and the subsurface core sediments based on ¹³⁷Cs datings indicates that almost all surficial-sediment data fall inside or deviate slightly from the 95 % prediction interval of a background regression line. In addition, as determined by a Community Bureau of Reference three-step extraction, trace metals mainly dominate in the residual fraction (assumed to relate to crystal lattice of primary and secondary minerals), and this fraction does not change much in recent sediment layers. Therefore, trace metals are supposed to be derived from natural bio/geochemical processes and are characterized by a low potential mobility. Consequently, the established linear regression relationships of trace metal vs. Al or multiple regression relationships of trace metal vs. multi-elements (Al, Fe, Ca, and OM) are useful for the prediction of background levels of trace metals in sediments in future pollution monitoring and assessment programs.     

天然电场选频法在充水岩溶勘查中的试验与分析

探讨了天然电场选频法在岩溶水灾害勘查中的地质效果和异常成因。在四川古叙煤田观文煤矿选定4处试验点,共敷设选频法测线11条,通过对各测线上采集结果的处理和分析,结合现场地形地质条件,推测各点地下充水溶洞的分布情况。根据选频法的解释结果与矿山前期地勘成果及后期运输巷道实际开挖情况的对比来看,该方法的解释结果是准确的,可在今后进一步将该方法应用于地下水灾害勘查,以便为矿山排水巷道、排水措施设计和地下水的安全防治提供科学依据。在实践应用的基础上,进一步从麦克斯韦方程组出发,对均匀谐变电磁场中低阻水平圆柱体的感应场进行理论推导和模拟计算,通过感应二次电场水平分量的模拟计算结果与实测曲线的对比,说明天然电场选频法的异常成因主要是由二次感应电场所致。     

生态系统变化对湘西岩溶水资源的影响

本文在分析岩溶山区典型生态系统类型及其演化特征和岩溶水资源特点的基础上,通过湘西20年来的生态系统变化的对比,就其对岩溶水资源的影响进行了详细的论述.认为生态的恶化是引起岩溶石山区水资源短缺的一个重要因素 ,生态系统变化对岩溶水资源的影响主要是通过对岩溶水的补给、迳流、排泄等的影响,使岩溶水资源产生水质和水量的变化.明确生态系统变化是如何影响岩溶水资源的质与量这一重大问题,将有助于岩溶水循环机制的深入研究,为揭示岩溶水资源的形成、演化规律及控制机理,建立岩溶水资源评价、开发利用和保护的系统理论,探索岩溶水资源可持续利用模式提供科学的依据.     

广西典型岩溶区土壤水分含量空间自相关分析

以广西壮族自治区马山县为研究区,在野外调查、室内实验测试获取182个土壤水分含量数据的基础上,采用半方差函数和Moran’s I统计量对研究区域土壤水分含量的空间自相关关系、空间相关尺度和空间分布规律进行了研究。结果表明:(1)研究区域土壤水含量平均值为16.97%,受结构性因素和随机因素共同作用,土壤水分含量具有中等强度的空间异质性;(2)研究区域土壤水分含量Moran’s I指数为0.423,表明研究区内土壤水分含量存在空间自相关性,在0~21 km和31~34 km范围内土壤水分含量自相关性为正,在21.7~31 km和34~45 km范围内自相关性为负;(3)Lisa聚类图表明,土壤水分含量空间聚集区和空间孤立区相伴存在,其中“高—高”空间聚集主要分布在马山县东北部,“低—低”聚集区主要分布在东南部。“低—低”聚集区和“高—低”孤立区土壤水分含量缺乏风险大。