Structural Features and Function of the Karst Critical Zone

1 Major achievements of IGCP 661 The IGCP661 project"Processes,Cycle,and Sustainability of the Critical Zone in Karst Systems(2017-2021)"has been carried out for two years.Besides five International karst meetings and two training courses for karst that have been held,some scientific achievements include the basic roles of the function and structural evolution of the karst critical zone have been determined.In various types of karst critical zone,the different forms of calcite and HCO3-cycling were determined.

A circular zone counting method of identifying a Duffing oscillator state transition and determining the critical value in weak signal detection

Identifying state transition and determining the critical value of the Duffing oscillator are crucial to indicating external signal existence and have a great influence on detection accuracy in weak signal detection. A circular zone counting （CZC） method is proposed in this paper, by combining the Duffing oscillator＇s phase trajectory feature and numerical calculation for quickly and accurately identifying state transition and determining the critical value, to realize a high- efficiency weak signal detection. Detailed model analysis and method construction of the CZC method are introduced. Numerical experiments into the reliability of the proposed CZC method compared with the maximum Lyapunov exponent （MLE） method are carried out. The CZC method is demonstrated to have better detecting ability than the MLE method, and furthermore it is simpler and clearer in calculation to extend to engineering application.

The importance of non-carbonate mineral weathering as a soil formation mechanism within a karst weathering profile in the SPECTRA Critical Zone Observatory, Guizhou Province,China

Soil degradation, including rocky desertification,of the karst regions in China is severe. Karst landscapes are especially sensitive to soil degradation as carbonate rocks are nutrient-poor and easily eroded. Understanding the balance between soil formation and soil erosion is critical for long-term soil sustainability, yet little is known about the initial soil forming processes on karst terrain. Herein we examine the initial weathering processes of several types of carbonate bedrock containing varying amounts of non-carbonate minerals in the SPECTRA Critical Zone Observatory, Guizhou Province, Southwest China. We compared the weathering mechanisms of the bedrock to the mass transfer of mineral nutrients in a soil profile developed on these rocks and found that soil formation and nutrient contents are strongly dependent upon the weathering of interbedded layers of more silicate-rich bedrock(marls). Atmospheric inputs from dust were also detected.

A review of POPs in the fragile critical zone of the Tibetan Plateau: transport and transformation

The near-surface environment of the Tibetan Plateau is a fragile critical zone. Our understanding of the transport and transformation of persistent organic pollutants(POPs) in the ecosystem has significantly improved with research conducted in recent decades. In the current study,POP concentrations in soils logarithmically decreased and fractionated with increasing distance from the source area,patterns attributed to air–soil exchange. Transport from soils resulted in the enrichment of POP concentrations in plants and sediments. The enantiomeric fraction indicated that transformation of POPs in soils was significantly correlated with altitude. At the same time, the chiral signature of POPs in soils was maintained from soils to sediments, while the chiral transformation from soils to plants was found to be complex.

Role of hydro-geochemical functions on karst critical zone hydrology for sustainability of water resources and ecology in Southwest China

Focusing on sustainability of water resources and ecology in the complex karst critical zone, we illustrated functions of the hydro-geochemical analysis on hydrology from the aspects of connection and interaction among hydrology–vegetation–soils/rock fractures along the karst subsurface profile. We reviewed isotopic and geochemical interpretations on tracing water sources for plant uptake, quantifying watershed outlet flow composition and residence times, and evaluating long-term evolution among climate–landscape–hydrology in the karst critical zone. In this paper, the application of the hydro-geochemical analysis on the above aspects in the karst areas of southwest China was summarized.

Geochemical characteristics and growth suitability assessment of Scutellaria baicalensis Georgi in the Earth's critical zone of North China

Geochemical differentiation of soils has a series of consequences on plant and places pressure on the ecological environment.The quantitative evaluation of element migration in the Earth’s critical zone is a challenging task.In this study,two demonstration study areas of Scutellaria baicalensis Georgi were selected,and multiple chemical weathering indexes,chemical loss fraction,mass migration coefficients and biological enrichment coefficient method were used to assess the ecological and geochemical suitability.The results show that for the element of Fe,Zn,Se,Cu,Co,Ni,Mo and Ge,the degree of weathering and soil maturation,were greater in the rhyolitic tuff area than in the Plagioclase gneiss area.In both research sites,the heavy metal level of samples in Scutellaria baicalensis Georgi did not exceed the standard limits.The plagioclase gneiss region’s surface soil environment was more alkaline,and the content of soil organic matter was lower,resulting in a higher bioenrichment intensity of Ge,Co,Cu,and Se elements in Scutellaria baicalensis Georgi than in the rhyolite-tuff area.The elements of Cd,Nb,Mo,Pb and As are considerably enriched in the soil of the plagioclase gneiss area but lost by leaching in the soil of the rhyolite tuff area,which is connected to the interplay of elemental abundance and human impact in the parent materials.This study provides a good example of how to assess growth suitability of Chinese medicinal materials in the Earth’s critical zone.

基于CRITIC-TOPSIS法的极端热湿气候区溶液再生器运行优化研究

再生器是溶液除湿系统中的关键部件之一,提高再生器综合性能是解决极端热湿气候区高湿问题的有效手段。将指标相关法(CRITIC,Criteria Importance Through Intercriteria Correlation)和优劣解距离法(TOPSIS,Technique for Order Preference by Similarity to Ideal Solution)联合,建立CRITIC-TOPSIS模型,用于再生器运行入口参数(空气质量流量、溶液质量流量、温度)的选择评价。以永暑岛礁地区为例,通过再生器处理模型得到基础数据以及4个指标的评价体系,采用CRITIC法求得权重后使用TOPSIS法对220种运行入口参数的组合方案进行评价得到最优解。结果表明,空气质量流量为0.1 kg/s、溶液质量流量为0.3 kg/s、溶液温度为56℃时得分0.885,为永暑地区再生器综合性能最优解;再生量指标的权重为0.4,可作为永暑地区再生器综合性能的代表性指标。

Background and Research Prospect of Geo-ecological Survey and Monitor in the Critical Zone of Black Soil

The American Science journal,on the occasion of its 125 publication anniversary,in 2016,released 125 of the most challenging scientific issues(Kennedy et al.,2005)to the world.According to the basics,breadth and the influence,25 of the issues which considered to be the most important were screened,including"How many people can the Earth carry?"(Stokstad,2005;Dailyg et al.,1992;Cohen,1995)and"How high will the greenhouse effect make the earth temperature?

A new statistical model of wave heights based on the concept of wave breaking critical zone

When waves propagate from deep water to shallow water, wave heights and steepness increase and then waves roll back and break. This phenomenon is called surf. Currently, the present statistical calculation model of surf was derived mainly from the wave energy conservation equation and the linear wave dispersion relation, but it cannot reflect accurately the process which is a rapid increasing in wave height near the broken point. So, the concept of a surf breaking critical zone is presented. And the nearshore is divided as deep water zone, shallow water zone, surf breaking critical zone and after breaking zone. Besides, the calculation formula for the height of the surf breaking critical zone has founded based on flume experiments, thereby a new statistical calculation model on the surf has been established. Using the new model, the calculation error of wave height maximum is reduced from 17.62% to 6.43%.

Seasonal shifts in the solute ion ratios of vadose zone rock moisture from the Eel River Critical Zone Observatory

One of the greatest challenges in critical zone studies is to document the moisture dynamics, water flux,and solute chemistry of the unsaturated, fractured and weathered bedrock that lies between the soil and groundwater table. The central impediment to quantifying this component of the subsurface is the difficulty associated with direct observations. Here, we report solute chemistry as a function of depth collected over a full year across the shale-derived vadose zone of the Eel River Critical Zone Observatory using a set of novel sub-horizontal wellbores,referred to as the vadose zone monitoring system. The results of this first geochemical glimpse into the deep vadose zone indicate a dynamic temporal and depth-resolved structure. Major cation concentrations reflect seasonal changes in precipitation and water saturation, and normalized ratios span the full range of values reported for the world's largest rivers.

Comparing mineral weathering and elemental transport between earth's critical zone with different parent rocks in Yanshan Mountain,Hebei province,China

Bedrock weathering performs a significant influence on the evolution of Earth’s critical zone.Carbonate rock(dolostone),metamorphic rock(gneiss),and sedimentary rock(sandstone)geological formations in Yanshan Mountain,Hebei Province,are taken as objects to probe the controlling of geological formations on weathering characteristics,migration,and enrichment of elements as well as structure of Earth’s critical zone under the identical climate conditions through geological field survey,analysis on minerals component,element distribution in the weathering profile.The dolostone geological formation(DGF)is lithologically dominated by dolostone,characterized by the strongest and predominant chemical weathering.During bedrock weathering and pedogenesis,DGF is marked by significant depletion of CaO,Mg O,S,Mn,Mo and enrichment of N,K,Fe_(2)O_(3),and Zn with concentrations of P,Cu,and B keeping stable.Shortage of soil-forming materials and significant loss are driven by soil erosion,which results in thin regolith and soil.The soil thickness is less than 10 cm,and the regolith thickness is less than 30 cm.The vegetation community is predominantly rock arbor or brush,which is calcivorous and tolerant of barrenness.Plagiogneiss is a dominant rock type of gneiss geological formation(GGF),characterized by the weakest weathering and fast chemical and physical weathering rate.GGF is masked by significant depletion of P,K,CaO,MgO,Fe_(2)O_(3),Mn,Cu and enrichment of N,S,Mo,and B,with contents of Zn keeping stable.Both soil and regolith developed in GGF are relatively thick for one of the reasons that biotite expands during weathering.The soil thickness is more than 50 cm,and the regolith thickness ranges from 100 to 200 cm.The vegetation community is predominantly high-quality economic forests and various arbors because of the enrichment of nutrients in GGF.Sandstone is primarily a rock type of sandstone geological formation(SGF),characterized by moderate weathering degree and slow chemical weathering rate.SGF is marked by significant depletion of P,K,CaO,MgO,Fe_(2)O_(3),and enrichment of N,S,Mn,Cu,Zn,and Mo,with fluctuant changes of Zn and B.The thickness of soil developed in SGF varies between that of DGF and GGF.The soil thickness ranges from 30 to 50 cm,and the regolith thickness ranges from 50 to 100 cm.Chinese pines are widely spread on the shady slopes of SGF.Research provides theoretical support for screening dominant ecological resource areas,ecological industry development and ecological protection and restoration for Yanshan Mountain,Hebei Province.

Carbon,nitrogen and phosphorus coupling relationships and their influencing factors in the critical zone of Dongting Lake wetlands,China

Wetland is a transition zone between terrestrial and aquatic ecosystems,and is the source and sink of various biogenic elements in the earth’s epipelagic zone.In order to investigate the driving force and coupling mechanism of carbon(C),nitrogen(N)and phosphorus(P)migration in the critical zone of lake wetland,this paper studies the natural wetland of Dongting Lake area,through measuring and analysing the C,N and P contents in the wetland soil and groundwater.Methods of Pearson correlation,non-linear regression and machine learning were employed to analyse the influencing factors,and to explore the coupling patterns of the C,N and P in both soils and groundwater,with data derived from soil and water samples collected from the wetland critical zone.The results show that the mean values of organic carbon(TOC),total nitrogen(TN)and total phosphorus(TP)in groundwater are 1.59 mg/L,4.19 mg/L and 0.5 mg/L,respectively,while the mean values of C,N and P in the soils are 18.05 g/kg,0.86 g/kg and 0.52 g/kg.The results also show that the TOC,TN and TP in the groundwater are driven by a variety of environmental factors.However,the concentrations of C,N and P in the soils are mainly related to vegetation abundance and species which influence each other.In addition,the fitted curves of wetland soil C-N and C-P appear to follow the power function and S-shaped curve,respectively.In order to establish a multivariate regression model,the soil N and P contents were used as the input parameters and the soil C content used as the output one.By comparing the prediction effects of machine learning and nonlinear regression modelling,the results show that coupled relationship equation for the C,N and P contents is highly reliable.Future modelling of the coupled soil and groundwater elemental cycles needs to consider the complexity of hydrogeological conditions and to explore the quantitative relationships among the influencing factors and chemical constituents.

Fractured zone height of longwall mining and its effects on the overburden aquifers

As mining depth becomes deeper and deeper,the possibility of undermining overburden aquifers is increasing.It is very important for coal miners to undertake studies on the height of fractured zone during longwall mining and the effects of longwall mining on the underground water while mining under surface water bodies and underground aquifers.In order to study this problem,piezometers for monitoring underground water levels were installed above the longwall panels in an American coalmine.Large amounts of pre-mining,during mining and post-mining monitoring data were collected.Based on the data,the heights of fractured zones were obtained and the effects of longwall mining on the underground water were studied.The results demonstrate that when the piezometer monitoring wells had an interburden thickness of less than 72.7 m,the groundwater level decreased immediately to immeasurable levels and the wells went dry after undermining the face of longwall.The height of the fractured zone is 72.7-85.3 m in the geological and mining conditions.The results also show that the calculated values of fractured zones by the empirical formulae used in China are smaller than the actual results.Therefore,it is not always safe to use them for analyses while mining under water bodies.

Critical Soil Phosphorus Values for Yield Reduction in Intensive Agricultural Systems

Phosphorus(P)is an essential element for agricultural production.Over-fertilization during decades caused an accumulation of P in soils leading to eutrophication in regions characterized by intensive agriculture.These environmental concerns together with the non-renewability of P resources have led to a more sustainable P use.Knowledge about the P need of crops is essential for a sustainable agriculture thereby minimizing P losses to the environment without lowering the yield substantially.Therefore,in this study,critical soil P values for yield reduction(PCrit)were determined based on fertilizer trials conducted between 1970 and 1988 and more recent fertilizer trials(2016-2017).At rotational level a common PCrit value of 109 mg P/kg dry soil(in an ammonium lactate and acetate extract)was determined.Crop specific PCrit values were also determined for seven crops(potato,winter wheat,barley,rye,maize,sugar beet and temporary grassland).These critical values ranged from 59 mg P/kg dry soil to 164 mg P/kg dry soil with winter wheat the least and maize the most sensitive towards P deficiency.The diversity in PCrit values among crops can mainly be explained by the root intensity but also rooting depth,exudation of organic acids and phosphatases may influence the PCrit value.The soil pH also influenced the P availability significantly.Soils with a favorable pH had a significantly higher availability(i.e.,lower PCrit value)for all crops compared to soils with a suboptimal pH.Critical soil P values might help to set up new or to evaluate current soil P in target zones used for P fertilizer recommendations.

Influence of train speed and its mitigation measures in the short-and long-term performance of a ballastless transition zone

The ballastless track is nowadays the most popular railway system due to the required low number of maintenance opera-tions and costs,despite the high investment.The gradual change from ballasted to ballastless tracks has been occurring in Asia,but also in Europe,increasing the number of transition zones.The transition zones are a special area of the railway networks where there is an accelerated process of track degradation,which is a major concern of the railway infrastructure managers.Thus,the accurate prediction of the short-and long-term performance of ballastless tracks in transition zones is an important topic in the current paradigm of building/rehabilitating high-speed lines.This work purposes the development of an advanced 3D model to study the global performance of a ballastless track in an embankment-tunnel transition zone considering the influence of the train speed(220,360,500,and 600 km/h).Moreover,a mitigation measure is also adopted to reduce the stress and displacements levels of the track in the transition.A resilient mat placed in the tunnel and embank-ment aims to soften the transition.The behaviour of the track with the resilient mat is evaluated considering the influence of the train speed,with special attention regarding the critical speed.The used methodology is a novel and hybrid approach that allows including short-term and long-term performance,through the development of a powerful 3D model combined with the implementation of a calibrated empirical permanent deformation model.

典型喀斯特白云岩小流域土壤-表层岩溶带厚度空间异质性特征

土壤-表层岩溶带厚度是喀斯特地球关键带的关键指标,明确其空间异质性特征对于理解地球关键带结构演化机理以及评估水源涵养功能具有重要意义。在广西环江木连小流域1.4 km 2范围内,通过高密度电法(ERT)探测45条样线,共获取1731个样点的土壤-表层岩溶带厚度及环境因子数据资料,研究了土壤和表层岩溶带厚度的空间分布格局及其影响因素。结果表明,土壤和表层岩溶带厚度平均值分别为1.15 m和6.44 m,且分别呈现强变异程度和中等变异程度。地统计分析结果表明球状模型和指数模型分别可以反映土壤和表层岩溶带的空间结构特征。土壤厚度呈现中等空间自相关性,变程长,空间连续性好;而表层岩溶带呈现强烈的空间自相关性,变程短,空间依赖性强。土壤厚度受到环境因子(地形湿度指数、垂直曲率、曲率、坡向、坡度、高程、覆盖度、出露基岩率和植被归一化指数)的多重影响,而表层岩溶带厚度受部分环境因子影响的同时,与土壤厚度和植被类型的相关性更高。研究结果有助于喀斯特区土壤-表层岩溶带演化机理认识,并为土壤-表层岩溶带厚度的空间预测提供科学依据。

人地耦合视角下喀斯特石漠化地区生态系统服务提升

针对喀斯特石漠化治理转型面临恢复效果区域差异大、生态功能稳定性弱、忽视社会系统与生态系统的协同等问题,系统梳理了当前我国石漠化治理存在的主要挑战与科技需求,提出从侧重自然生态系统转向社会-生态系统的整体性视角,以区域生态系统服务整体提升为目标,聚焦喀斯特关键带地上-地下耦合过程,加强石漠化与社会-生态过程的互馈机制、功能微生物-钙协同促进土壤碳氮高效固持机理、基岩生境植被恢复关键带水分养分保障机制等研究,突破喀斯特社会-生态系统耦合、岩溶多界面蓄水-保土协同增效、岩土组构与生态位互补的植被群落改造、生物固氮与有机废弃物高效利用的种养协调、生态-岩溶过程协同的固碳能力提升等关键技术,形成喀斯特生态产品供给能力提升与农业产业转型协同的绿色发展模式,有助于实现喀斯特区域人地耦合与生态系统服务整体提升,为西南喀斯特地区石漠化治理工程与乡村振兴提供科技支撑。

河流下综放工作面覆岩破坏特征和陷落柱防水煤柱留设研究

目的长平矿Ⅲ2317工作面在开切巷处揭露陷落柱,地表丹河流向与工作面推进方向一致,受采动影响,陷落柱内部水体及河水可能通过开采裂隙导入回采空间,从而造成工作面突水。针对以上问题,方法本文采用理论分析、数值模拟和现场观测等方法,对回采工作面覆岩“两带”高度、覆岩破坏特征和陷落柱煤柱留设宽度进行研究。结果结果表明:工作面顶板垮落带与导水裂隙带最大发育高度分别为18.38,93.85 m,河水对工作面不构成突水威胁;无煤柱开采时,陷落柱一侧顶板裂隙沿陷落柱胶结面向上高度发育;结合理论计算和数值模拟分析,确定煤柱宽度为35 m。工作面在留设35 m煤柱条件下安全完成回采,地表变形特征符合预期,最大下沉量达到4000 mm,回采过程中工作面未发生突水事故。结论研究结果可为类似条件下的煤层安全开采提供理论和经验支撑。

煤矿采动覆岩离层水害致灾因素勘查与预测评价

采动覆岩离层突水在我国各地矿区均较为常见且危害性较大,现有的规范中鲜有针对离层水害的具体工程地质和水文地质勘查方法。探索煤矿离层水害工程地质水文地质勘查与评价方法,能够推动我国矿井水害防治水平进一步提升。首先从煤矿采动覆岩高位离层水害孕灾机制出发,分析了离层水害从孕灾到致灾的工程地质条件,将我国现有的离层水害归纳为3种典型类型:离层动力突水、离层静水压涌突水和离层携泥砂突水。然后,确定了“水源”“通道”“力源”和“物源”为控制离层水害类型与强度的关键隐蔽致灾因素,将位于传统导水裂隙带以上,可发生离层突水的复合层位称为采动覆岩“突水离层带”,并提出了煤矿采动覆岩“突水离层带”的判别流程,划分勘查阶段,指明勘查要点。煤矿离层水害采前勘查应包括2个阶段:①开展覆岩基本工程地质和水文地质条件勘探,评估勘探区离层水害的可能性并确定潜在“突水离层带”的层位;②将“突水离层带”和“物源”层作为勘查目标层,开展离层水害致灾因素专项勘查,评定离层水害类型和强度。回采期间对水动力条件和覆岩裂隙演化进行探查。最后,基于离层水害致灾因素互馈演化致灾机制,建立了适用于采动覆岩离层水害的矿井区域预测综合评价模型,提出了全矿井/采区尺度的区域危险性分区、采前工作面突水位置判定及涌水量预计的煤矿采动覆岩离层水害预测评价方法。

深埋煤层开采对河流安全性的影响评价

以文家坡煤矿4105工作面深埋覆水煤层开采为例,采用相似材料模拟和数值模拟方法,研究覆岩破坏和裂隙带发育规律,探究深埋煤层开采对红岩河安全的影响。研究表明:当工作面不断推进,采空区面积随之增加,覆岩在重力作用下发生弯曲变形,形成离层;当重力超过岩石变形极限时,覆岩会破坏变形,部分离层垮落消失,在垮落体上部发育新离层,两侧形成裂隙;4105工作面垮落带高度稳定在164 m;随着工作面的不断推进,导水裂隙带高度逐步上升,最终稳定在244 m;地裂缝自地表向下延伸32 m;导水裂隙带上方存在414 m的岩层做保护层,未导通地表,未与地裂缝沟通,因此红岩河不会发生渗漏,煤层的开采不会对红岩河产生影响。