中国岩溶

Diel aqueous chemistry and biogeochemical processes in streams of karst areas

ZHANG Cheng

2015, 34(1): 1-8. doi: 10.11932/karst20150101

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Study on diel cycling of stream hydrochemistry can help to reveal relatively rapid biogeochemical processes in natural water (processes of in stream flows) and discriminate drainage basin processes in recharge areas. Existing research shows that biological processes(photosynthesis and respiration), geochemical processes(bicarbonate equilibrium, and calcite precipitation) are the main controlling factors on diel variations of pH values, specific conductivity(SpC), concentrations of Ca2+ and HCO3- in streams. Furthermore, stream orders and types and even microenvironments of the riverbed all have remarkable influence on diel aqueous chemistry. The pH value and dissolved oxygen(DO) are mainly controlled by photosynthesis which is closely related to air temperature. In high-alkalinity and calcium-rich streams, representing carbonate-rich basins, calcification and acid secretion of organisms may play an important role in aquatic plant photosynthesis, thus resulting in diel hydrochemical cycling with daytime decrease(up to a 20% to 30% decline) and nighttime increase of concentrations of Ca2+and HCO3-. Diel DIC cycling downstream caused by photosynthesis and its changes along the stream flow indicate that the stream is losing inorganic carbon along its flow path. It converts to organic carbon, such that inorganic C storage in streambeds will be an important net DIC sink in small productive streams. The effect of diel cycling of biogeochemistry on interpretation of carbon cycling, sink and source, especially on clarification of karst carbon sink stability and net carbon sink estimation trends becomes increasingly important in karst aquifer systems. Diel variability has implications for the design of long-term surface water monitoring programs and interpretation of water quality trends.

Characteristics of δ13C in typical aquatic plants and carbon sequestration by plant photosynthesis in the Banzhai catchment,Maolan of Guizhou Province

LI Rui, YU Shi, SUN Ping-an, HE Shi-yi, YUAN Ya-qiong, XIONG Zhi-bin

2015, 34(1): 9-8. doi: 10.11932/karst20150102

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Aquatic plants play a key role in study of the carbon cycle by using inorganic carbon as a source for photosynthesis. The object of this work is to figure out the contribution of aquatic vegetations to carbon sequestration with the Banzhai catchment in Guizhou as study area. The biomass of typical aquatic plants both in summer and winter was measured. Meanwhile, the δ13C of 4 kinds of aquatic plants, which grew at sampling sites, were tested. The results show that the biomass in summer is less than that in winter. Besides, the obtained values of δ13C for emergent aquatic plants range from -33.59 ‰ to -27.05 ‰, with an average of -30.32 ‰, for floating plants from -35.45 ‰ to -24.62 ‰, with an average of -29.96 ‰, respectively, and for submerged plants it was measured a value of -27.89 ‰. The mean δ13C values of various plants in descending order are emergent plants, floating plants, and submerged plants. Additional to this results the double-meta model was used, by this model the percentage of HCO3- uptake from water by aquatic photosynthesis can be estimated. The calculated HCO3- carbon consumption by photosynthesis was 19.52 tC/(a?km2), HCO3- used by aquatic plants for photosythesis accounted for almost 47.84 % of the total uesd inorganic carbon in Banzhai river, and this part of HCO3- was converted into organic carbon and fixed in aquatic plants. The results indicate that the contribution of aquatic plants to carbon sequestration, especially to the net carbon sink estimation in karst regions cannot be neglected.

Characteristics of cave drip water and modern carbonate (CaCO3) deposits caused by underground river artificial recharge and landscape restoration

ZHANG Mei-liang, ZHU Xiao-yan, WU Xia, ZHANG Bi-yuan, PAN Mou-cheng

2015, 34(1): 17-26. doi: 10.11932/karst20150103

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The landscape of carbonate (CaCO3) deposits in the karst tourism caves is susceptible to pollution and weathering on carbonate sediments. To ensure the sustainable development of the karst tourism caves, it is necessary to study the methods to repair such contaminated or damaged sediments in these caves. To attain this purpose, continuous monitoring and analysis for four years were made to chemical properties of the underground river, cave drips, and modern carbonate sediments in the No.15 branching cave of Seven Star Cave, Guilin, Guangxi Province. The results show that the change trends of conductivity, Ca2+ and HCO3- from the underground river and cave drip water are basically the same during this period. The conductivity, Ca2+ and HCO3- of cave drip water decreased significantly and the rainfall dilution effect is obvious during rainfall seasons. The modern carbonate (CaCO3) deposits in the cave have obvious seasonal variations, where cave drip water amount, drip rate and calcium carbonate deposit rate during rainy seasons accelerate. The largest amount of deposit is 0.8 g/ half month. The largest amount of calcium carbonate deposit from rapid drip water from the cave entrance to about 150 m within the cave passage is up to 2-4 g/half month. The carbonate deposit rate during dry seasons reduces with the maximum only 0.4 g half month. The recharge of cave drip water by extracting the karst underground river can enhance the conductivity, [Ca2+], [HCO3-] and CaCO3 saturation of cave drip water, rapidly prompting a large number of carbonate (CaCO3) deposits, and realizing restoration of the cave landscape damaged. Besides, new calcium carbonate deposit can also rebind bedrock fissures and damaged / broken speleothem and cave stalactites, which is favorable for the stability of the cave.

Structure and evolution of the Shihua Cave in Beijing

LIU Hong, ZHENG Ming-cun, DUAN Hong-wu, CHEN Hai-jian, WANG Fang, CAI Bing-gui

2015, 34(1): 27-34. doi: 10.11932/karst20150104

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Of the known karst caves in northern China, the Shihua Cave in Beijing has the greatest scale and most kinds of secondary carbonate sediments. It is one of the most important caves in northern China in terms of its landscape sightseeing and scientific values. To determine its size and structure, a complete investigation including survey was conducted in July 2013. This work followed international survey standards and used various instruments including Leica laser rangefinders and Sunnto compasses and clinometers, in conjunction with Onstation and ArcMap 10 software. The results show that the Shihua Cave extends from NWW to SEE along the strike of the Ordovician limestone, indicating that the cave development is primarily controlled by strata. NE and NW-striking faults have influenced cave development to a less extent. The cave has a total length of 5,639 m and a floor projection area of 37,096 m2. In the vertical direction, the highest and lowest positions within the cave are 14 m above and 158 m below the entrance, respectively. The cave system consists of five levels of passages, of which the elevation is 249 m, 211 m, 154 m, 111 m and 95 m above sea level, respectively. Each level indicates a period of stable local base level, suggesting that this cave experienced five stages of development. The lowest level of it has a 1,638 m passage,which is characterized by seasonal water flow with three windows into a perennially inundated phreatic level. The seasonal underground river flows southeastward during the summer flood season. The downstream passage forks, one branch terminating in a sump pool while the other consists of chambers with a large amount of breakdown, implying the end of the underground river.The underground river may connect the Shihua Cave with Silver Fox cave to the northwest and the Kongshui Cave to the southeast. Exploration of nearby caves and tracer tests should be conducted to verify this connection in the future.

Karst abnormal development and origin of the Tianxingzhou carbonate rook belt in the Wuhan area

LUO Xiao-jie

2015, 34(1): 35-42. doi: 10.11932/karst20150105

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This work studied the characteristics of the Tianxingzhou carbonate zone adjacent to the Xiangfan-guangji fault, located at the middle-north Wuhan. A comparison was made to this rock zone and the Daqiao and Baishazhou carbonate zones to the south in some aspects including rock chemical and mineral composition，lithology and the degree of karst development，karst cave scale，burial depth of karst cave roof under bedrock surface，karst vertical zoning and cave fillings. The results show great differences among them. The development of karst in the Tianxinzhou zone was associated with the activity of the Xiangfan-guangji fault. The first karstification of this zone took place during Late Triassic and Jurassic period. In the Cretaceous and Paleogene period，the extension dominated by the Xiangfan-Guangji fault resulted in fractures and cracks, providing channels for the basaltic magma eruption and tectonic hydrothermal activity. Because of widespread tectonic hydrothermal dolomitization and silicification，the raw rock of the Tianxingzhou carbonate zone suffered reformation，leading to rock combination dominated by dolomite containing silicite with weak dissolution. At the same time，the karstification interrupted due to the broad coverage of red beds. Neogene and early Pleistocene，the carbonate rock zone once again exposed on the surface，suffered second karstification. Due to change of lithology and weakened solubility, the karstification of the Tianxingzhou rock zone became diminished compared with other carbonate belts.

Progress of research on the response of information of karst cave drip water to ground conditions

LIU Zi-qi, XIONG Kang-ning, Lü Xiao-xi, ZHANG Qian-zhu, FU Chao-fan

2015, 34(1): 43-51. doi: 10.11932/karst20150106

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By reviewing domestic and foreign research progress on the response of information of karst cave drip water to ground conditions, coupled with the research background of global climate change, karst environmental evolution and drip water's physical and chemical indicators, this paper divides the history of this research into three stages: initial stage, slow development stage and rapid growth stage. This paper also systematically summarizes the research results and understandings of drip water's regular monitoring indicators, stable isotopes, major elements, trace elements, and so on. Meanwhile, it concluded the research progress of drip water's response to atmosphere, vegetation, soil and bedrock. It is suggested that the material resource and the hydro-geochemical process of drip water should be explored, the research for drip's sensitivity to indicate environment should be enhanced, the environment response mechanism of drip's information should be deeply probed and comprehensive environment elements of cave systems should be monitored. It is also pointed out that the research on the rocky desertification by drip water's indicators remains relatively weak now, which should be the focused topic in the future.

Spatial-temporal distribution and causes of karst collapse in the Xuzhou area

WEI Yong-yao, SUN Shu-lin, HUANG Jing-jun, JIANG Su, MIAO Shi-xian

2015, 34(1): 52-57. doi: 10.11932/karst20150107

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Xuzhou is the only city in the Jiangsu Province to use the karst underground water as the municipal water. Due to the long-term absurd use of the Karst underground water, karst collapse often happens in the Xuzhou region. This paper looks into the distribution of bare karst and covered karst in the Xuzhou region in northern Jiangsu Province and the special and temporal distribution of karst collapse in the history, and summarizes rules of the karst collapse. Firstly, as controlled by the fault zone of the ancient Yellow River, the Karst developed more intensive when closer to the ancient Yellow River and vice versa. Secondly, the collapse occurs in sections with shallow well developed karst, mostly in Ordovician limestone and a few in the Cambrian limestone. Thirdly, the collapse is concentrated within the ancient channel. Most collapse happens in the sand soil monolayer, some in the clay sand-clay layer. Lastly, all collapse is in the cone of depression due to the extraction of karst water. In combination with the correlation between the timing of karst collapse and the dynamics of ground water, this paper comprehensively analyzes the causes of ground collapse. Though the overlap section of the ancient watercourse and the fault zone of the ancient Yellow River provides favorable condition for the karst underground collapse, its final occurrence is resulted from human engineering activities, which change the karst water level significantly and causes rapid decline in volatility. The results of this study would provide scientific basis for prevention of karst collapse hazards in the Xuzhou city in the future.

Development characters of karst collapse in the Gele mountain area

ZHANG Hai-tan, LI Qing-hua, DENG Shu-jin

2015, 34(1): 58-63. doi: 10.11932/karst20150108

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The trough valley zone of the Gele mountains is largely covered by limestone, with a hill landform and complex geological environment. Influenced by the subtropical monsoon climate, the rainfall of the rainy season (from May to October) in this area reaches 881.40 mm, accounting for 80 percent of the total annual precipitation, resulting in nonuniform distribution of rainfall between the rainy and dry seasons. With the increasing human engineering activity in recent years, karst collapse occurs frequently, which have become the main geological disaster in this region. This work collected and analyzed relevant data of previous surveys and related data of existing hydrological boreholes with long-term observations, and made a special investigation of environmental geology and geological disasters on scales of 1∶2 000～1∶10 000. The purpose was to determine the number and distribution of karst collapse and human engineering activity status in this region. The survey area is 60 a.km2. The results show that the number of karst collapse has an increasing trend year by year, which are mainly distributed in those places where the karst developed well, the groundwater level changed significantly, more calcium carbonate are present, and the thickness of the loose cover ranges from 3 to 8 meters. It divided the process of collapse development into early stage, middle stage and late stage and analyzed the characteristics of these developmental stages. By analysis of the types and function of collapse forces in the process above, it suggests that the latent erosion is the primary mechanism for the collapse. To sum up, the number of karst collapses increases year by year, which mostly occur in rainy seasons. There is an obvious characteristic pattern of spatial distribution as well as stage-wise development of karst collapse, and the latent erosion is the dominant mechanism.

Risk assessment of karst collapse areas based on the improved fish bone model: An example of the Liuzhou area in Guangxi Province

CUI Yu-liang, WANG Gen-hou, LI Zhi-yong

2015, 34(1): 64-71. doi: 10.11932/karst20150109

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Taking the karst collapse area in Liuzhou of Guangxi as an example, this study conducted field investigations and analysis to the major controlling and influencing factors of the karst collapse. Considering the relationship of these factors in the fish bone model and the grading influence of fractures, we established the grading buffers of fractures, and thus determined five feature layers of those comprehensive factors. Based on the improved fish bone model, we made spatial overlay analysis on the feature layers of each factor's vector data format, and prepared a zoning map of the risk prediction. It is shown that more than 75% of the discovered collapse groups fall in the areas with a high risk or a moderate risk, which approximately account for half of the total research areas and are mainly located in the central and southern portions of the study area. These areas have thin covers, and frequent karst collapse is common. Less than 25% of the discovered collapse groups are in the areas with a low risk or a very low risk, which are mainly distributed in the north and west of the study area. Urban planning and construction should select those areas with a low risk or a very low risk. This study has effectively predicted the risk of karst collapse in Liuzhou city. 

Dealing with overestimates of underground river discharge in karst areas of southwestern China

YI Lian-xing, XIA Ri-yuan, TANG Jian-sheng, SHI Jian, LUO Wei-quan, CHEN Zhen

2015, 34(1): 72-78. doi: 10.11932/karst20150110

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In the karst areas of eight provinces in southwestern of China, the number of underground river and their total discharge are two important parameters that draw mauch attention. The statistics in the 1980s yielded 2 836 underground rivers and total discharge 1 482 m3/s. Whereas in the 1990s, the statistics for all the 8 provinces, corrected by the database in recent years, shows that there are 2 523 underground rivers with total discharge about 1 321.7 m3/s. Of them, there are 120 underground rivers with single discharge more than 2 000 L/s, and their discharge sums 699.7 m3/s accounting for 52.94% of the total. The underground rivers with discharge between 50-500 L/s is the most, occupying 51.55% of the total; next is those less than 50 L/s which is 723 in number and accounts for 22.43% of the total. This paper points out that the statistics above are problematic with over-estimation in karst underground river discharge and large-discharge karst springs. Taking two examples of the Daxiaojing and Zhaidi underground river systems, this paper presents the specific amount of double counting. Based on the old 1∶200 000 hydrogeological survey data, the total re-statistics account for 57.1% and 7.1% separately for the total outlet discharge of the Daxiaojing and Zhaidi river systems, respectively. While these values can be increased separately to 134.3% and 86.1% using the latest survey data. It can concluded further that with increasing coverage of 1∶50 000 hydrogeological surveys, more outlets will be counted, the amount of the bouble counting by the traditional methods will be greater. The primary reason for such an overestimation problem lies in mess of the underground river system and sub-system. Finally, this paper discusses the spatial attributes of karst underground river systems and proposes countermeasures to metigatye the problem of double counting. It would help establish realistic statistics of discharge of underground rivers and major springs of karst areas in southwestern China. 

Development characteristics of buried karst under a foundation in Wuxi and sources of karst fillings

LI Xiao-nan, YAN Chang-hong, XU Bao-tian, DUAN Cheng-long, ZHOU Yin-kang

2015, 34(1): 79-85. doi: 10.11932/karst20150111

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The development characteristics of burial karst and sources of the karst fillings are very important for choosing the location of super-high buildings and bearing strata. This study employed the cross-hole seismic CT method to detect the caves and fracture zones of a foundation in Wuxi, and made indoor tests on samples of the karst fillings from the typical karst caves. Combined with the in-situ geological conditions, this paper presents a qualitative analysis of the scale, distribution and development characteristics of the karst and the sources of fillings which are more than 80 meters below the foundation. The results show that the karst is of a small size, the area of most caves is less than 2 m2, and there are many layers in the vertical direction. The rate of cave filling reaches 92.7%, and the caves are mostly filled with hard plastic mud which has a large bearing capacity and can be used as the bearing layer of foundation. XRD analysis of mineral composition shows that the minerals of different cave fillings are generally the same, consistent with those of the overlying bedrock. Thus, the denudation of overlying bedrock is the main source of these fillings. There is no large connective channel between the caves, and the underground water level has dropped below the caves. It is therefore concluded that these caves will not further develop and pose no threat to the stability of the foundation. The results of this study will provide reference for the site selection, design and construction of super-high buildings, karst detection, stability analysis of foundations and the treatment of unfavorable geological bodies in the Suzhou-Wuxi-Changzhou areas, which are located on deep karst foundation.

The effect of land integration on soil microbial biomass carbon, nitrogen and enzyme activity in karst areas：An example of Sanba township, Fengdu county, Chongqing City

QI Le, GAO Ming, YANG Lai-shu, WANG Dan, DENG Wei

2015, 34(1): 86-94. doi: 10.11932/karst20150112

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Land integration is an important measure to build high-standard prime farmland. It can improve production and living conditions of farmers and enhance the comprehensive land productivity. This study takes the land integration project in the karst area of Sanba township, Fengdu county in Chongqing City as an example. It collected 52 points before this project (December 2012) and 28 typical points afterwards (March 2013). Through field sampling and laboratory analysis, this paper have studied the effect of this project on soil microbial structure, soil microbial biomass carbon (SMBC), soil microbial biomass nitrogen (SMBN) and enzyme activity including catalase (CAT), urease (URE), and sucrase(INV) activity of soil microorganisms in the low hilly area. Our objective was to describe the distribution characteristics before and after finishing land integration. The results show that, (1) the implementation of this project has imposed significant effect on soil microbial. After the land integration, the number of actinomycetes decreased in the soil than the previous state, and the number of fungi increased. (2) Land integration reduced overall SMBC and SMBN content in 0 to 20 cm soil, of which SMBC content was decreased by 20.33% and SMBN content decreased by 47.84%, respectively. In vertical distribution, land integration changed the rule that SMBC and SMBN contents vary with soil depth, showing their minimum values 68.34 mg/kg and maximum value 33.58 mg/kg in the subsurface of 20 to 40 cm. (3) In the same soil, land integration has caused significant differences between urease activity and catalase activity in 0 to 20 cm and 20 to 40 cm, while invertase activities were significant different in 0 to 20 cm, 20 to 40 cm and 40 to 60 cm soil levels. After land integration, urease and catalase activity decreased, and invertase activity improved, each in the soil tends to be uniform as well. (4) Organic material is significantly positively correlated with surface SMBC and SMBN contents and urease activity, and pH shows a significant positive correlation with soil enzyme activity. The change of SMBC and SMBN contents and soil enzyme activity can be used as indicators to determine the soil fertility level and soil fertility effect before and after land integration, and it can help to carry out soil improvement and soil fertility work in the area after land integration.

2015 Vol. 34, No. 1

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