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2017 Vol. 36, No. 5

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Technical key points of 1∶50，000 hydrogeological and environmental geology surveys in karst areas of South China
XIA Riyuan, ZOU Shengzhang, TANG Jiansheng, LIANG Bin, CAO Jianwen, LU Haiping
2017, 36(5): 599-608. doi: 10.11932/karst20170501
Abstract PDF(10455KB) icon2229 icon2407
Abstract:
The karst area in South China is about 520,000 square kilometers, which is controlled by the rock properties, group structure types, geological structural framework, topography and hydrodynamic conditions. The development and distribution of karst in the area is quite uneven. The special subsurface-underground double-deck structure leads to the lack of surface water and deep buried underground water. With the influence of global climate change and irrational human activities, rocky desertification, drought and flood disasters, groundwater pollution and other major environmental geological problems have occurred in karst areas of South China. These natural and man-made factors have seriously restricted the sustainable development of regional social economy, making many karst areas become one of the poorest areas in the country. In order to promote the economic development, ecological civilization construction and poverty alleviation of the karst areas in South China, it is necessary to further clarify the karst hydrogeology and environmental geology conditions, providing a basis for the development and utilization of resources, offering water resources guarantee for the residents and economic development of areas with serious water shortage, and technical support for the protection and control of ecological environments.By summarizing the six research results on the comprehensive investigations of hydrogeology and environmental geology and groundwater development and utilization in the karst areas of South China, this study suggests 10 characteristics of hydrogeological and environmental geology conditions in karst areas of South China, which are stated below, the comprehensiveness of karst development controlled by the strata structure, geologic structure frames and hydrodynamic conditions; heterogeneity of karst groundwater distribution; multiplicity of karst water-bearing media by pores, gaps, joints, pipes and holes; multiphase characteristics of karst groundwater flow; variability of karst groundwater dynamics; seasonal distribution of karst groundwater resources; alternation of drought and flood; concealment of karst groundwater pollution; big buried depth of karst groundwater; and correlation between karst groundwater and ecological economy. At the same time, this study discusses the technical points of investigations and research on the 8 key scientific problems, including carbonate rock group structure, tectonic evolution and development period of karst, karst-form combination relationship, surface karst zones, karst groundwater systems, karst underground river, the main problems of environmental geology, and development and utilization of karst water resources.
Exploitation models for different types of underground rivers in karst mountain areas of southwestern China
CAO Jianwen, XIA Riyuan
2017, 36(5): 609-617. doi: 10.11932/karst2017y27
Abstract PDF(5638KB) icon2092 icon1234
Abstract:
The karst development of karst mountain areas in southwestern China is complicated, which brings difficulties to the development and utilization of underground rivers there. Based on the results of geological surveys in these regions recent years, this work makes a systematic summary on the characteristics of karst landforms and karst development, and proposes 6 typical exploitation modes of underground rivers, i.e.(1)karst depression reservoirs in peak-cluster depression areas,(2) reservoirs formed by subterranean stream blocking in deep karst valley areas,(3) surface-underground combined reservoirs in karst valley areas,(4) water diversion by digging tunnels in karst ridge fold zones, (5) leading groundwater by motor-pumped wells in peak forest-plain areas, and(6) Reservoirs by combined surface-subsurface underground streams in edges of fault-depression basins. These 6 models provide a practical reference for treatment in accordance with local conditions, reasonable and efficient development and utilization of groundwater resources, and can effectively serve the national strategy of precise poverty alleviation.
Groundwater occurrence characteristics and drilling well models in karst peak forest areas, Guangxi, China
QIN Xiaoqun, SONG Kaiben, HUANG Qibo, LAN Funing, HUANG Chunyang, HUANG Hui
2017, 36(5): 618-625. doi: 10.11932/karst2017y28
Abstract PDF(6943KB) icon1833 icon1021
Abstract:
Based on drilling well data for fight against drought recent years in karst peak forest areas of Guangxi, this work analyzed the relations between hydrogeologic conditions and drilling wells. The results show that structure, lithology and karst development horizons are the main control factors for drilling wells. The water-bearing structures such as fault fracture zones, synclines or anticlines and contact zones between aquifers and relative water-resisting layers are favorable drilling sites to find groundwater. The carboniferous strata (C1, C2) and the upper Devonian system strata (D3) are the main drilling formations, occupying 55.24% of the total number of wells with the mean water yield of 261 m3·d-1 for each single well. Groundwater extraction depth is 37.67 m on average. Through the analysis of the occurrence characteristics and law of karst waters, six types of drilling well models are suggested. Meanwhile several common landform features are considered as marks for water search.
Experiences of well drilling for water search in karst areas of southeastern Yunnan Province：An example of the Zhulin area, Guangnan county
ZHANG Gui, ZHOU Cuiqiong, WANG Bo, GU Weifang, DAI Wenmin, ZHANG Wenjun
2017, 36(5): 626-632. doi: 10.11932/karst20170504
Abstract PDF(3685KB) icon1972 icon1013
Abstract:
The Zhulin area of Yunnan is located in the watershed area of the Qingshuijiang river, Pumeihe river and Xiyangjiang river, tributaries of the Nanpanjiang river water system, with elevations 1,200 m to 1,960 m above sea level. Its geomorphology is dominated by peak cluster-depressions, karst valleys and karst hill-depressions. The karst is obviously stratified in vertical direction. Due to the extremely heterogeneous distribution and big burial depths of karst water in watersheds, it is a challenge to drill successful wells in this area. Based on the experiences of drilling at 9 wells from 1996 to 2012 in this area, this paper summarized the work processes for well drilling in karst watershed areas. It is suggested that in watersheds with weak runoffs, the targets should be chosen at the upper ends of large karst depressions on paleo-karst platforms close to watershed zones. In gentle slope zones with relatively strong runoffs, the effort should focus on the perched karst water above the suspension weak permeable layer which has relatively large area and gentle occurrence. In steep slope areas, groundwater in karst windows and shafts are the priority. Determining the locations of wells should follow such procedures as, first regional hydrogeological survey and then detailed hydrogeological investigations around well locations, with aid of some geophysical prospecting to improve the ratio of well drilling success. The wells to be drilled should not be located at discharge areas, strong runoff zones, or peak cluster-depressions, neighboring areas of big karst springs and groundwater flow, or bottoms of the negative landforms. The application of geophysical prospecting results should be closely combined with the results of hydrogeological surveys.
Reanalysis of spring water and its pollution causes of the Niangziguan spring in Shanxi
LIANG Yongping, ZHAO Chunhong, TANG Chunlei, SHEN Haoyong, WANG Zhiheng, GUO Fangfang
2017, 36(5): 633-640. doi: 10.11932/karst20170505
Abstract PDF(3870KB) icon1780 icon1218
Abstract:
As one of the largest karst spring in North China, the Niangziguan spring in Shanxi well known one in the world, with an average annual natural flux of 12.6 m3/s. This work was based on the 1∶50，000 project of hydrogeology and environmental geology investigation to this spring and adjacent areas. The purpose was to reanalyze the two issues,(1) The genesis of the Niangziguan spring water；(2) The causes of its pollution. Exploration data show that the Wulong and Weizeguan springs, located at the south bank of the Mianhe river, mainly receive the recharge of karst water from the middle and upper Cambrian water-bearing formation rather than the recharge karst water from the upper middle Ordovician to lower Ordovician aquifers as suggested by previous studies. In combination with hydrogeological conditions, analysis of isotopes considers that part of the coal mine gob water flow is the primary cause for accelerating pollution of the spring in recent years.
Discussion on the characteristics of karst water systems in the Xishan area of Beijing
ZHAO Chunhong, LIANG Yongping, WANG Weitai, TANG Chunlei, SHEN Haoyong
2017, 36(5): 641-647. doi: 10.11932/karst2017y49
Abstract PDF(6277KB) icon1953 icon1216
Abstract:
Beijing is located in the north of the North China platform, where 3 second-order tectonic units meet, i.e. the Shanxi uplift, North China faultdepression, and Yanshan fold belt. In geomorphology, it lies at the conjunction of the Taihang Mountains, Yanshan Mountains and the North China plain. The study area is Xishan area of Beijing, part of the Taihangshan Mountains. The terrain is generally high in the northwest and low in the southeast, and the main rivers are the Dashi river and the Yongding river. The karst groundwater is dominated by cycles of the relatively independent karst groundwater system in the Xishan region of Beijing. The hydrogeological conditions, the system structure model and the importance of water resources of the karst groundwater in this area have certain representativeness in the north. It has abundant groundwater resources and good water quality and is one of the important groundwater supply sources for Beijing City. The karst water in the area receives atmospheric precipitation，and seepage from the Yongding river and the Dashi river. At the same time, there is a transformation relationship between the partial area and the piedmont covering loose pore groundwater and coal measure strata fissure groundwater. The resource elements of constitute are many and the transformation relationship is complex. The carbonate aquifers of the Xishan area include the thick layer of upper Proterozoic karst aquifer group, carbonate intercalation of the middle upper Cambrian-lower Cambrian karst water-bearing rock group and the huge thick layer of Cambrian-Ordovician carbonate water-bearing rock group, which cover most of karst aquifers in North China. According to the definition of karst water systems, the karst water bearing system, surface hydrology system, topography and geomorphology, geological structure and aquifer medium structure, previous study divided the karst water system in the Xishan area of Beijing into 6 systems, which are the Yuquanshan, Gaozhuang-Ganchi, Yugudong, Heilongguan, Mapao and Shangqingshui karst water systems. This paper takes the Yugudong, Heilongguan and Yuquanshan karst systems as the research objects. From the karst aquifer structure, groundwater circulation and geologic structure, we summarize the characteristics of karst water system as follows, double-layer aquifer structure, multiple subsystems and multiple points discharge, complicated and various karst water transformation relationships, and the concentration of karst water and system boundaries in thrust faults.
A quantitative analysis of tracing tests for the Maocun subterranean river basin of Guilin during rainy and dry seasons
HUANG Fen, YIN Weilu, HU Xiaonong, CAO Jianhua
2017, 36(5): 648-658. doi: 10.11932/karst2017y32
Abstract PDF(7161KB) icon1763 icon1273
Abstract:
This paper selected the typical underground river basin in Maocun village of Guilin, Guangxi for quantitative tracer tests in rainy and dry seasons based on online high-resolution monitoring to depict fine characteristics of groundwater aqueous media. According to the tracer test results and groundwater runoff and distribution characteristics, the Maocun underground river system is divided into Shegengyan and Bianyan underground river, Dachongli-Beidiping sub-system and Dayanqian sinkholes-Maocun outlet sub-system, which are distributed in upstream and downstream of the Maocun basin, respectively. The experimental tracer study shows that the breakthrough curves (BTC) are featured by steep upward and steep drop pinnacles, which suggest that the conduits are relatively simple, and have no large turnouts and karst tams developed. Each section of the underground river is generally turbulence which is dominated by convection; the flow velocity and flux in rainy seasons are larger, the average travel time is shorter, and the tracer recovery rates are higher than in dry seasons. The aqueous medium in the middle region is relatively uniform, and has no conduit developed. Groundwater is mainly stored in karst cracks.
Hydraulic interaction between groundwater and surface-water at Zengpiyan site in Guilin, China
WANG Ziyan, JIANG Guanghui, GUO Fang, YUAN Xiaoyu, ZENG Xinru
2017, 36(5): 659-667. doi: 10.11932/karst2017y34
Abstract PDF(6065KB) icon2085 icon1092
Abstract:
Zengpiyan is located in the Guilin Peak forest plain. The stability of this site is threatened by groundwater scouring due to the change of hydrodynamic conditions of karst groundwater. In order to examine the characteristics of groundwater leakage process, and to reveal the transformation process of groundwater and surface water in the protected areas of the site, this study analyzed the dynamic characteristics of water level. The tank model and water level decay equation were constructed according to the water balance elements of karst water system. Then the difference between the simulated water level and the actual water level was compared to explain the relationships between rainfall, surface water and groundwater. The results show that there are various differences between the pond and the groundwater, such as the water level, the start rising point, the decay rate and the lag time of the peak. The difference in dynamic processes reflects the strong communication capacity of karst media. The leakage process of the pond is controlled by seepage capacity. Groundwater recharging to surface water reservoirs is dominated by concentrating supplies through main runoff zones. The hydraulic interaction between groundwater and surface water shows strong dynamic patterns, especially in the high-permeability karst areas. The hydraulic interaction of groundwater and surface water is beneficial to alleviate the erosion and damage of groundwater to the cover layer.
Sedimentary record of metal elements in the Dashiwei sinkhole section of Bailang underground river, Guangxi 
KONG Xiangsheng, LUAN Rijian, HONG Tao, QIN Xiaoqun, QI Shihua
2017, 36(5): 668-677. doi: 10.11932/karst2017y38
Abstract PDF(3681KB) icon1643 icon1002
Abstract:
In this work, the concentration of metal elements and sediment organic matter (SOM) in sediment cores of the Dashiwei sinkhole section from the Bailang underground river has been studied, and the pollution history of the river basin from 1932 to 2007 has been reconstructed by combining the 210Pb dating and historical records. The results show that concentrations of main toxic heavy metals Cd and Hg in the sediment cores are high, which are 3.4 and 0.6 times than the soil background values of Guangxi, respectively, even more than 11.2 and 2.7 times of the soil background value throughout China, respectively. On the whole, the distributions of heavy metal elements have a similar increase tendency in the sediment cores. The vertical distribution of metal elements in the sediment cores shows that metal element pollution in the underground river were associated with many events in history, such as peasant movement, the war of AntiJapanese, Great Leap Forward age, the early stage of reform and opening up , and the rapid development of economy. Especially，the vertical variation of Ca and Mg in the sediment core records indicates that a new construction climax has begun in this karst mountain area since 1983. Correlation and clustering analyses show that, (1) Cr and Pb came mainly from natural environment, (2) Cu, Ni, Zn, As and MgO originated from natural environment and artificial sources, (3) Cd, Hg, Mn, CaO and SOM stemmed from artificial pollution sources. Correlation analysis with polycyclic aromatic hydrocarbons suggests that part of Zn, Cd and As came from coal combustion. In a nutshell, metal elements in the sediment cores better recorded pollution history of the Bailang underground river.
Enrichment environment and sources of strontium of groundwater in Xintian county, Hunan Province
SU Chuntian, HUANG Chenhui, ZOU Shengzhang, XIE Daixing, ZHAO Guangshuai, TANG Jiansheng, LUO Fei, YANG Yang
2017, 36(5): 678-683. doi: 10.11932/karst2017y42
Abstract PDF(4577KB) icon1705 icon965
Abstract:
This work attempts to better understanding the enrichment environment and sources of strontium in groundwater in Xintian county, Hunan Province. Groundwater and rocks on geological profiles were sampled and analyzed. The results showed that, (1) Rich-strontium groundwater is present in the strata of D3s, with contents in order for strata, D3s＞C1y＞D3x1＞D2q; (2)The average contents of strontium element of springs and shafts are 376.57μg·L-1 and 2,756.87 μg·L-1, respectively, 1.88 times and 13.78 times the natural mineral water, respectively. Strontium element contents of shafts are much higher than that of descending springs, 7.32 times the descending spring; (3)The lithology of D3s is medium-thick or thin layers of light grey marls, intercalated with limestone and shale, in which strontium contents are generally more than 300 mg·kg-1, with the highest was 838 mg·kg-1, which is the primary source of strontium in groundwater; (4) Many conditions have contributed to the formation of rich strontium in groundwater, such as gentle strata, the low coefficient of precipitation infiltration, planar supplies, and scattered seepage.
Contrast study of Ca2+ and HCO3- concentration in karst-water samples between field test and laboratory test values
ZHOU Changsong, ZOU Shengzhang, ZHU Danni, XIE Hao, CHEN Hongfeng, YU Jianguo
2017, 36(5): 684-690. doi: 10.11932/karst2017y33
Abstract PDF(1729KB) icon1609 icon1007
Abstract:
In order to grasp the differences of Ca2+and HCO3- concentration in karst water between field test and laboratory test values, 85 groundwater samples collected from Zunyi, Hechi and Loudi City were analyzed. The results show that 88.2% of the sample sites of Ca2+ have field values greater than the experimental values, while 64.7% of the sample sites of HCO3- have field values greater than the experimental values. Using the ratio method, (CaY/CaS) is of an average value of 1.11, mainly concentrating between 1.0 and 1.2, accounting for 70% of the total, and (HCO3Y/HCO3S) with a average value of 1.02, mainly concentrated in between 0.95 and 1.1, accounting for 75% of the total. Under certain conditions of the laboratory test error, artificial random error has some impact on the result of the test. The results provide basic data to improve the quality of field surveys of underground water.
Analysis on the hydrogeological influence of the Huangniya tunnel in Nanchuan district of Chongqing
CAO Rui, Lyu Yuxiang, PEI Jianguo
2017, 36(5): 691-696. doi: 10.11932/karst2017y35
Abstract PDF(5116KB) icon1857 icon985
Abstract:
It is certain that tunnel construction can bring great impacts on the hydrogeological environment in karst areas. Taking the Huangniya tunnel project in Nanchuan district of Chongqing as an example, this paper uses ground investigation, tracer tests, long-sight monitoring and numerical simulation to analyze the influence of tunnel engineering on the hydrogeological environment. The results show that the Huangniya tunnel project has changed the groundwater flow field in the tunnel area, drained the groundwater, exacerbated drought and water shortage, and led to a new artificial water point-tunnel of gushing water. At the same time, the tunnel project destroyed the water resource allocation pattern and reduced the utilization rate of water resources.
Hydrogeochemical characteristics of karst groundwater in southern Nanchuan district of Chongqing
FAN Lianjie, PEI Jianguo, ZOU Shengzhang, DU Yuchao, LU Li
2017, 36(5): 697-703. doi: 10.11932/karst2017y61
Abstract PDF(2960KB) icon1977 icon1035
Abstract:
This work focused on the karst groundwater in southern Nanchuan District of Chongqing city. We have analyzed hydrochemical components and trace heavy metals in 149 pieces of samples. The results indicate that the hydrochemical types of groundwater are dominated by HCO3-Ca Mg , HCO3-Ca and HCO3·SO4-Ca. Most major chemical components of groundwater are Ca2+，Mg2+，HCO3-and SO42-，which show the corresponding relation with the water-bearing rock groups, i.e. carbonate karst water > carbonate rock and clastic rock water > clastic rock water. The ratio of Mg2+/Ca2+ in underground water shows that the co-dissolution of calcium carbonate and dolomite is dominant in the groundwater runoff process. The content of trace heavy metals is generally on the low side in groundwater. Most of the water quality is within the category III of water standard, only a few contaminated spots lead to some heavy metals on the high side.
Variation of water quality of underground rivers in uncovered karst regions during the process of urbanization
LUO Wei, YANG Xiuli, ZOU Shengzhang, NING Liyuan
2017, 36(5): 704-712. doi: 10.11932/karst2017y40
Abstract PDF(3826KB) icon1396 icon903
Abstract:
Underground rivers are the primary form of water resources as well as the most important landscape resources in karst regions in southern China. Their water quality was constantly deteriorated recently by human activities changing. Taking the Shangzhai underground river as an example, this paper addresses this issue based on historical monitoring data. The water quality of this river has experienced stage-wise changes with urbanization, and became the worst in rural-urban conjunctions. The relatively high contribution rates to over standard components are attributed to Mn,NH4+,F- and NO2-. Contaminants come mainly from aquaculture，life，food processing, smelting and manufacturing. Organic contaminants were detected since 2003, and BaP was found over-standard from 2015. The increasing of population and enterprises, the random discharge of waste water and waste residue have led to severe pollution of surface water. The vulnerable antipollution ability of underground river systems in uncovered karst regions are the main reason for underground water deterioration.
Analysis of variation characteristics of karst groundwater quality in Guiyang City
YANG Xiuli, LUO Wei, PEI Jianguo, YOU Jun
2017, 36(5): 713-720. doi: 10.11932/karst20170515
Abstract PDF(2639KB) icon1784 icon963
Abstract:
The aim of this study is to understand the longtime underground water quality variation characteristics in karst regions. Choosing karst underground water of central Guiyang city as the object, the variation characteristics of karst underground water quality of Guiyang in 30 years were analyzed using 48 samples collected in 1984 and 2014, respectively. The results show that the ground water quality is good as a whole, while having a tendency to deteriorate. Only 9 sampling sites of 1984 were not suitable for drink directly, which was mainly caused by primary background environment. In 2014, 14 sampling sites were not suitable for drink, most of which was caused by human activities. The hydrochemical types of underground water have changed greatly over the 30 years, about half of the controlling points were changing into the HCO3·SO4 type from the type of HCO3 Underground water was getting sulfation obviously. Underground water quality in old and new city zones were getting better, and that in rural-urban conjunctions was easily polluted. Due to the low degree of human activities , the water quality in agricultural areas were changing gently. In the work of groundwater resources development and environmental protection, karst hydrogeology conditions and human activities characters in different areas should be considered synthetically and the objective-oriented evaluation of monitoring and management should be carried out. Aiming at the phenomenon of groundwater salinization in the work area, the comprehensive improvement of the urban-rural conjunctions should be strengthened to facilitate comprehensive protection of the groundwater environment in agricultural areas, so as to curb the trend of groundwater pollution and prevent the occurrence of groundwater pollution incidents.
Comparative tracing of two common dyes in conduits with silt: A case study of the Dingqi underground river
YI Lianxing, ZHAO Liangjie, LU Haiping, WANG Zhe
2017, 36(5): 721-726. doi: 10.11932/karst2017y46
Abstract PDF(2451KB) icon1970 icon940
Abstract:
The study area is located in the upstream Dabang river, a branch of the Beipanjiang river in Dingqi town, Zhenning county, Guizhou Province. The strata of this place comprise lower Triassic limestone, dolomite and landform, with landforms of dissolution hills and valleys. It hosts underground rivers A19, A30 and A10, with silt deposits and buried depths less than 30 m. This study focused on the comparison of tracer experiments for two materials of Uranine and Rhodamine B, and discussion on the rationality of the recovery rates by the two methods. The results show that,(1) The recovery rate of Uranine is 53.91%, which is higher than Rhodamine B of 40.72%;(2) Uranine’s recovery intensity for maximum concentration is 2.95 times than that of Rhodamine B; (3) It is relatively easy to notice some complete wave crests in the attenuation section of the Rhodamine B concentration curve. It is concluded that，(1) in the underground rivers with silt deposition, Uranine and Rhodamine B have higher adsorption rates, and there may be some problems in the tracer test technology with higher recovery rates; (2) For the analysis of conduit structure or hydrogeological conditions, Uranine is superior to Rhodamine B; (3) The accuracy of recovery rates depends on fluorimeter calibration, flow monitoring, and closely related to environmental factors, such as water-turbidity and sediments.
Aquifer structure of karst areas derived from borehole pumping and tracer tests
Lyu Quanbiao, HU Xiaonong, CAO Jianhua, HUANG Fen, ZHU Hao
2017, 36(5): 727-735. doi: 10.11932/karst2017y29
Abstract PDF(3574KB) icon1825 icon1310
Abstract:
Karst aquifers have strong heterogeneity and anisotropy. The investigation and understanding of their spatial structure are the important foundation for research of groundwater flow and contaminant migration. However, hydrogeology surveys are very difficult to conduct in karst areas due to their special geologic structure. To tackle this problem, this work conducted pumping tests and multiple tracer experiments (sodium fluorescein and rhodamine, fluorescent whitening agent) at the same. Using the Theis standard curve comparison, we analyzed pumping test data and calculate the permeability tensors of test sites. The structure properties of aquifers were determined by the results of the tracer tests. The calculated coefficient of transmissibility in the main direction of permeability tensor in the study area are: 0.297 m2·h-1 and 0.028 m2·h-1, specific yield is 1.19e-04 and predominant direction is east by south 18.47°. Tracer recovery rates in the tracer tests under the pumping condition for three kinds of traces are: fluorescein sodium 97.98%, rhodamine B 47.34%, and fluorescent whitening agent 39.54%. The average flow velocities are 0.378 m2·h-1, 0.3 m2·h-1 and 0.14 m2·h-1, respectively. They reflect the karst pores and fractures are small in the study area, tracer migration is slow and needs long time. The BTC curve of fluorescein sodium and fluorescent whitening agent is of unimode type, the BTC curve of rhodamine B is multi-peak, showing the development of single dominant fractures and relatively uniform fractures in the study area. At the same time, the direction of maximum recovery of the tracer is in accordance with the main direction of the permeability tensor from pumping tests. The results can provide a method and basis for precise description of karst aquifer characteristics and the determination of physical parameters of hydrological models.
Numerical modeling of the influence of karst-conduit structure on variation of spring flow
JIAO Youjun, PAN Xiaodong, ZENG Jie, REN Kun
2017, 36(5): 736-742. doi: 10.11932/karst2017y48
Abstract PDF(2549KB) icon1950 icon1279
Abstract:
The spring hydrograph, such as variation of flow, can be used to extract information on the structure of karst conduits, while the complexity of these conduits makes such study not very successful. To solve this problem, this work employs a numerical model of the known karst conduit structure to reveal the relationship between the spring hydrograph and the conduit structure, which will help address this issue for real cases. This conduit flow model is built with MODFLOW-CFP to study the karst aquifer response in a storm period. The basic features of the karst aquifer of this simplified model are taken from a deeply-cut valley of the Liuchong river in Guizhou Province. This karst aquifer consists of a single conduit and a fracture network which is treated as an equivalent continuous porous medium. The valley is regarded as the river boundary of the karst water system, and the water level of the river is higher than the location of the spring outlet, so the conduit can be saturated with water. In the modeling spring hydrograph, the peak flow value is chosen as the dependent variable in the analysis of the karst conduit, and 4 parameters of the conduit structure and the recharge ratio of sinkhole are studied, respectively. The results show that the pipe diameter, wall permeability and the concentrated recharge of the sinkhole are characterized by positive correlation with the spring flow peak, of which the wall permeability has the greatest effect on the flow peak. When pipe bending is smaller, the spring flow becomes bigger, while the growth of the flow peak is limited by the tortuous flow path. The water flow status experiences two abrupt changes at the two critical Reynolds number of conduit-wall roughness, leading to twice of sudden variations of flow peak.
Aquatic plants bioremediation to groundwater contaminated by mines in karst areas
ZHANG Liankai, QIN Xiaoqun, HUANG Qibo, LIU Pengyu, SHAN Xiaojing
2017, 36(5): 743-750. doi: 10.11932/karst2017y47
Abstract PDF(1516KB) icon1809 icon1134
Abstract:
The karst regions in southwest China is an important producing area of nonferrous metals. Long-term extensive mining and waste residue accumulation have made the local environment seriously polluted by heavy metals. Many heavy metal elements enter the underground through surface runoffs and leaching, polluting groundwater aquifers, and pose a significant impact on the vulnerable karst environment. The leachate from the tailings reservoirs enters the groundwater system through karst pipelines and has a serious impact on the downstream ecological in a lead-zinc mine environment. In order to study the treatment technology of heavy metal pollution in karst groundwater and improve the quality of groundwater of this area, Hydrilla verticillata and Spirogyra communis grown in tailing reservoir leachate were selected as the sorbents of heavy metal. Hydrochemistry and enrichment factor analyses were conducted to examine the adsorption capacity of heavy metals of these two aquatic plants. Meanwhile, their heavy metal adsorption mechanism was explored and the feasibility of using these two aquatic plants to control karst groundwater pollution was discussed. Results show that, (1) The contents of heavy metals in these two aquatic plants lived in the mining area are high and the plants are well growing with large biomasses, suggesting these two kinds of aquatic plants have a certain avoidance or resistance to the heavy metals; (2)The bioconcentration factors (BCF) to elements in Hydrilla verticillata are relatively high, with value order as Pb > As > Co > Mn > Cu > Cd > Zn > Ni > Cr > Hg. The BCFs in Spirogyra communis are higher than those in Hydrilla verticillata but their value order is the same as that in Hydrilla verticillata. Although the contents of heavy metals do not reach the critical value of hyper-accumulators, the enrichment coefficients of Cu, Pb, Zn, Cd, Co, Ni, Mn and As in these two kinds of plants are much larger than 1, consistent with the hyper-accumulator enrichment characteristics, showing a co-enrichment feature; (3) Compared with non-karst areas, the content and BCF of heavy metals in these two aquatic plants in karst areas are much higher. Three main enrichment mechanisms of heavy metals in Hydrilla verticillata are suggested, which are enhancement of antioxidant enzyme activity under the stimulating of heavy metals, passive absorption, and ion exchange effect. For Spirogyra communis, its special molecular structure is important for its heavy metal adsorption. As the Hydrilla verticillata and Spirogyra communis are widely distributed in karst areas of southern China, using these two planes as the heavy metal remediation plants in karst polluted water will have a good prospect.
Assessment of water quality risk from karst aquifer recharge with multi-source water in the Yufuhe river, Ji’nan
LI Fengli, WANG Weiping, XU Qiaoyi, WU Shen, ZHANG Zhengxian
2017, 36(5): 751-758. doi: 10.11932/karst2017y30
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Abstract:
Ji’nan is well known for Spring City, while facing huge challenges of spring protection and security of water supply. The aquifer recharge with multi-source water is one of the effective measures to solve these problems. However, the quality of source water is still poorer than karst water, which would caused some risk of health and safety. Comparing the standard of groundwater quality and the background value of karst water quality, this work chose the risk monitoring indicators that exceed the standard in surface water sources or are inferior to background values. And adopting the Australian Guidelines of MAR, we assessed the water quality risk of the aquifer recharge with multi-source water in the Yufuhe river. In 2015, monitoring and index analysis were performed to the water quality of source water, pore well water and karst deep well water when Yellow River water and Wohushan reservoir water recharging the aquifers many times. The results show during the Yellow River water recharging, respectively in source water, pore water and karst water, the standard indexes of average turbidity are 1.4, 1.7 and 0.93, the standard indexes of sulfate’s average content are 0.93, 0.9 and 0.73 and although the content of chloride ion does not exceed the groundwater class III standard, it in the source water content is more than 2 times the groundwater content; during the Wohushan reservoir water recharging, respectively in source water, pore water and karst water, the standard indexes of average turbidity are 2.4, 1.1 and 0.43, the standard indexes of sulfate’s average content are 0.75, 0.84 and 0.66 and the standard indexes of ammonia nitrogen’s average content are 1.14, 1.47 and 1.35. We draw conclusion that the turbidity, sulfate and the movement of pollutants in the aquifers are at critical points for the whole Yufuhe aquifer recharge project. In addition, the risk of salinity should receive attention when the Yellow River water is used as the recharge source. Similarly, the risk of nutrient is also a concerned issue when the Wohushan reservoir water is the recharge source. Based on the above analyses, this paper offers some suggestions, such as limiting the proportion of karst water resources.

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