Western Hubei Research Articles

Neoproterozoic extensional basins and its control on the distribution of hydrocarbon source rocks in the Yangtze Craton, South China

• Neoproterozoic source rocks in the Yangtze Craton. • Structural and sedimentary patterns of the extensional basins evaluated. • The source rocks are related to the extensional basins, climate and life evolution. • Favorable areas for the source rock distribution are predicted. Hydrocarbon exploration in the Neoproterozoic extensional basins in the Yangtze Craton of South China has made prominent progresses in the past decades. However, the spatial distribution of source rocks across the craton still remains unclear. Here, we use outcrop observations, borehole data, and reflective seismic profiles to investigate the prototype, distribution and sediment infilling of these basins in the Yangtze Craton during the periods of source rock deposition. The basin prototype is categorized based on its tectonic origin and structural-sedimentary feature as follows. (1) During the deposition of the Datangpo Formation, rift basins extensively developed, band are characterized by a series of graben or half graben structures that consist of basin-controlling normal faults. The source rocks in the Datangpo Formation were deposited as the inner shelf basin or deep shelf facies, obtaining high thickness (i.e., 200 m) in the Wuling rift basin. (2) During the deposition of the Doushantuo Formation, the intracratonic rift basin and passive continental margin basin formed. These basins were controlled by syn-depositional faults that inherited the existing rift fault structures. The source rocks of the Doushantuo Formation were deposited as shelf lagoon, slope to deep-water basin facies. (3) During the deposition of the Dengying Formation, the intraplatform rift basin and passive continental margin basin developed with influence of regional tectonic extension. Not only are these basins affected by the preexisting faults, but also by the newly developed syn-depositional faults. The argillaceous source rocks of the Dengying Formation deposited as slope and deep-water basin facies. Further in-depth analyses revealed that a range of mechanisms may have contributed to the formation and distribution of source rocks in the Yangtze Craton, such as the break-up of the Rodinia Supercontinent, paleaolatitudes, glacial-interglacial geological events, basin extension and sedimentary environments. By integrating the distribution of the source rocks and the late tectonic reworking, this study predicts several targets for the source rock distribution in the Yangtze Craton, including in the central Sichuan, northeastern Sichuan, southern Shanxi, western Hubei, northeastern Guizhou-western Hunan, and the northeastern Guangxi-central Hunan areas.

Source of silica and its implications for organic matter enrichment in the Upper Ordovician-Lower Silurian black shale in western Hubei Province, China: Insights from geochemical and petrological analysis

To improve the understanding of the relationship between silica source and organic matter accumulation, the origin of silica and its implications for organic matter enrichment in the Upper Ordovician-Lower Silurian (O 3 w -S 1 l ) black shale in western Hubei Province in the middle Yangtze area, were investigated through geochemical and petrological analyses. The results show that the O 3 w -S 1 l black shale is mainly composed of five lithofacies with varying graptolite abundance, total organic carbon (TOC), and silica contents. Biogenic silica and terrigenous siliciclastic input constitute the main silica sources in O 3 w -S 1 l black shale and they exhibit an upward inverse variation trend interpreted to be related to sea-level changes. Moreover, with the increase in biogenic silica content or decrease in terrigenous siliciclastic input, TOC values in black shale initially rise and then fall, which is different from originally expected simple linear relationship. We infer that organic matter enrichment and the distribution of silica from different origins are controlled by sea-level changes and variations in terrigenous input in a continental shelf with little hydrothermal influence. An environment with appropriate sea level and terrigenous input should be most favorable for organic matter accumulation, rather than one with excessive high sea level and less terrigenous input.

Multiple controls on the organic matter accumulation in early Cambrian marine black shales, middle Yangtze Block, South China

This study aims to investigate paleoenvironments, hydrothermal activity, and seawater restriction of the lower Cambrian Shuijingtuo Formation in the Three Gorges area and clarify the dominating factors on organic matter (OM) accumulation. In the studied SL well in western Hubei Province, the Shuijingtuo Formation was divided into three intervals based on geological and geochemical characteristics. Total organic carbon (TOC) contents were variable, averaging 0.69% in Unit 1, 5.40% in Unit 2, and 1.12% in Unit 3. Enrichment factors (EF) of Cu and Ni indicated higher paleoproductivity in Unit 2. Unit 1 and the lower part of Unit 2 were affected by hydrothermal activity, whereas hydrothermal events receded in Unit 3. Hydrothermal activities could provide nutrients and may also facilitate the reducing water condition. Redox proxies (Corg/P, EF(Mo)-EF(U)) suggested that Unit 1, Unit 2, and Unit 3 were deposited in oxic-suboxic, euxinic, and suboxic environments, respectively. Upwelling/restriction proxies (EF(Co)*EF(Mn), Co (ppm)*Mn (%), Mo/TOC, and Cd/Mo) implied that Unit 1, Unit 2, and Unit 3 were deposited in upwelling, semi-restricted, strong restricted conditions, respectively. In summary, an anoxic environment, semi-restricted water conditions, and hydrothermal events are beneficial for OM enrichment during the early Cambrian.

Exploring the Effects of Land Use Changes on the Landscape Pattern and Soil Erosion of Western Hubei Province from 2000 to 2020.

Accelerated land use and land cover changes affect regional landscape patterns and change the ecological environment, including soil conservation capabilities. This is not conducive to the sustainable development of human society. In this research, we explored the land use change pattern and landscape change pattern in western Hubei from 2000 to 2020. Using the Chinese soil loss equation and stepwise regression, we measure how landscape patterns affect soil erosion under land use and cover changes in western Hubei Province. The results show that average soil erosion in the mountainous areas of western Hubei tended to increase from 2000 to 2010 and decrease from 2010 to 2020; soil erosion was higher in the western than in the eastern part of the study area. The land in areas with high-intensity and low-intensity soil erosion was mainly waterfront/grassland and cropland/forestland, respectively, and the area of moderate to severe soil erosion was greatest when the slope was 10–20°. When the slope exceeded 20°, the soil erosion area of each grade tended to decrease; thus, 20° is the critical slope for soil erosion in the study area. The landscape pattern in mountainous areas changed dramatically from 2000 to 2020. At the landscape level, landscape fragmentation increased and connectivity decreased, but the area of landscape diversity was stable. Soil erosion in western Hubei was positively correlated with the contiguity index, aggregation index and largest patch index but negatively correlated with the Shannon evenness index. The higher the landscape fragmentation and the greater the accumulation of single land-use types, the more severe the soil erosion is, while the higher the landscape connectivity and the richer the landscape diversity, the less severe the soil erosion is. The results can inform regional landscape management and soil conservation research.

Shale Heterogeneity in Western Hunan and Hubei: A Case Study from the Lower Silurian Longmaxi Formation in Well Laidi 1 in the Laifeng-Xianfeng Block, Hubei Province

Shale heterogeneity directly determines the alteration ability and gas content of shale reservoirs, and its study is a core research topic in shale gas exploitation and development. In this study, the shale from the Longmaxi Formation from well Ld1 located in western Hunan and Hubei is investigated. The shale’s heterogeneity is analyzed based on shale mineral rocks, microslices, geochemistry, and low-temperature N2 adsorption-desorption. It is found that the shales of the Longmaxi Formation from well Ld1 are mainly composed of siliceous shale, mixed shale, and clayey shale. The three types of shale facies exhibit strong heterogeneity in terms of the occurrence state of organic matter, organic content, mineral composition, microstructure and structure, brittleness, and micropore type. Sedimentation, late diagenesis, and terrigenous input are the main factors influencing the shale’s heterogeneity. With a total organic carbon (TOC) of 0.41%-4.18% and an organic matter maturity ( R o ) of 3.09%-3.42%, the shales of the Longmaxi Formation from well Ld1 are in an overmature stage, and their mineral composition is mainly quartz (5%-66%) and clay minerals (17.8%-73.8%). The main pore types are intergranular pores, intragranular pores, microfractures, and organic pores. The results of the low-temperature N2 adsorption-desorption experiment show that the shale pores are mainly composed of micropores and mesopores with narrow throats and complex structures, and their main morphology is of a thin-necked and wide-body ink-bottle pore. Based on the Frenkel-Halsey-Hill (FHH) model, the pore fractal dimension is studied to obtain the fractal dimension D 1 (2.73-2.76, mean 2.74) under low relative pressure ( P / P 0 ≤ 0.5 ) and D 2 (2.80-2.89, mean 2.85) under high relative pressure ( P / P 0 > 0.5 ). The shales of the Longmaxi Formation in the study area have a strong adsorption and gas storage capacity; however, the pore structure is complex and the connectivity is poor, which, in turn, imposes high requirements on reservoir reformation measures during exploitation. Moreover, the fractal dimension has a positive correlation with organic matter abundance, TOC, clay mineral content, and pyrite content and a negative correlation with quartz content. Since the organic matter contained in the shales of the Longmaxi Formation in the study area is in the overmature stage, the adsorption capacity of the shales is reduced, and the controlling effect of organic matter abundance on the same is not apparent.

Analysis of the Influence of the Distribution and Development of Soil Caves on the Stability of High‐Voltage Transmission Tower Foundations

As a kind of concealed flawed geology, karst geology easily forms soil caves, which may have a negative effect on adjacent transmission tower foundations. Since soil caves are continuously developed when surface water flows through soil, or groundwater levels fluctuate, the effect of soil caves on transmission lines in power transmission engineering needs to be investigated. In this paper, combined with an engineering case in western Hubei, first, FLAC3D finite element software is used to analyze the influence of a single underground soil cave during continuous development and expansion on 500 kV transmission towers. Considering the maximum allowable tilt value of the tower foundation, the stress state and deformation of the soil around the foundation are monitored during the calculation and analysis, and the maximum allowable radius of the soil cave in different positions is obtained. For example, the development radii of soil holes are 1.5 m, 2 m, and 2.5 m for burial depths of 7 m and 8 m, 9 m, and 10 m and 11 m, respectively, and the development radius of soil holes with a burial depth of 12 m and below can reach the maximum value of 3 m under actual working conditions. Then, the results of two simplified models of columnar and spherical development of the soil cave are compared, and it is found that columnar development is more in line with the actual situation. Finally, under the condition of a close‐range double soil cave distribution, the influence of the size, depth, and gap between the two caves on the tower foundation is simulated. This study can provide references for the safe operation of transmission towers and the assessment of possible disasters in karst areas.

The Theoretical Connotation and Realistic Path of the Development of County Finance Media Center—The Research Report of Finance Media in Western Hubei ii

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Spatial Potential of Recreational Services in Western Hubei Region in Light of the “All-for-One Tourism” Development—A Machine Learning Approach Based on Ensemble Model

Under the call for “all-for-one tourism” development, the focus of regional-scale recreational services is shifting from the construction of individual scenic spots and tourist areas towards the comprehensive planning of tourist destinations, so as to propel China’s rural revitalization and regional coordinated development. In research and practice, however, it is still challenging to identity and evaluate spatial locations for developing tourism according their cultural and environmental resource and characteristics and prioritizing the high-potential ones. Employing the whole western Hubei region as a case study, this paper proposes a method of assessing recreation potential within the research framework on cultural ecosystem services, and uses multi-sourced social-ecological data to develop an SDM model via ensemble machine learning. Through analyses of the environmental features of 336 recreational hotspots in the study area, the model predicts the areas with high recreation potential in continuous areas. This study intends to establish a technique path to examine the regional-scale pattern of recreational spaces via numerical analysis of environmental features, and to provide a reference for relevant spatial development strategies of all-for-one tourism and rural revitalization.

Distribution and Potential Sources of OCPs and PAHs in Waters from the Danshui River Basin in Yichang, China.

To investigate the concentrations, spatial distribution, potential sources and mass fluxes of organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) in waters from the Danshui River Basin, a total of 20 water samples were collected and analyzed from a karstic river in Western Hubei of Central China. The average concentrations of total OCPs and PAHs in the river water were 4719 pg·L−1 and 26.2 ng·L−1, respectively. The characteristic ratios of different isomers and the composition analysis of individual OCPs and PAHs revealed that HCHs originated from a mixed input of technical HCHs and Lindane, DDTs were mainly from technical DDTs, and PAHs mainly originated from biomass and coal combustion. The mass flux analysis showed that PAHs had a higher emission and heavier burden than OCPs in the Danshui River Basin. OCPs and PAHs emitted from agricultural or other human activities could enter the groundwater and then be transported to the surface/river water in the karst area. The adsorption of OCPs and PAHs by particles and the sedimentation of particles could be the primary processes to intercept these pollutants in the water of the karstic river system.

Shale types and sedimentary environments of the Upper Ordovician Wufeng Formation-Member 1 of the Lower Silurian Longmaxi Formation in western Hubei Province, China

Abstract By performing scanning electron microscopy, microscopic observations, whole-rock X-ray diffraction analysis, organic geochemistry analysis, and elemental analysis on drill core specimens and thin sections, in this study, we classified the shale types of the Wufeng Formation-Member 1 of the Longmaxi Formation in western Hubei, southern China, and explored the development characteristics and formation environments of the different shale types. The results show that (1) the shales of the Wufeng Formation-Member 1 of the Longmaxi Formation are composed of three types of shale: siliceous shale, mixed clay-siliceous shale, and clay shale. The siliceous shale is a type of shale unique to deep-water environments; clay shale is the main type of shale formed in shallow-water environments; and mixed clay-siliceous shale falls between the two. (2) The changes in shale type are characterized by multiple depositional cycles in the vertical direction with strong heterogeneity and an obvious tripartite character, and the siliceous shales gradually thicken as they laterally extend northwestward, with their last depositional cycle gradually ending at a later time. (3) The Late Ordovician-Early Silurian paleoenvironment can be divided into six evolutionary stages (A, B, C, D, E, and F) from early to late. In particular, the sea level was relatively lower in stages A and F when the bottom water was mainly oxygen rich with higher terrigenous inputs and a lower paleoproductivity, which led to the formation of clay shales poor in organic matter but rich in terrigenous quartz clasts. The sea level was higher in stages B, C, and D when the bottom water was anoxic with lower terrigenous inputs and a higher paleoproductivity, which led to the formation of siliceous shales rich in organic matter and biogenic silica. The total organic carbon (TOC) contents of siliceous shales decrease in the order of stage C > stage D > stage B, which is mainly attributed to the different degrees of water restriction in the three stages and the consequently different paleoproductivities. Stage E corresponds to the mixed clay-siliceous shales, the depositional environment of which is between those of the siliceous shales and the clay shales, thereby resulting in the mineral composition and TOC content of the mixed clay-siliceous shales being between those of the other two shale types.

Rare earth elements and yttrium (REY) distribution pattern of lower Cambrian organic-rich shale in Yichang area, Western Hubei Province, South China, and source of carbonate minerals

Critical breakthroughs of Cambrian shale-gas exploration have been achieved in the lower Cambrian organic-rich Shuijingtuo shale in the Yichang area, Western Hubei Province, South China. High carbonate content (at times >50 wt%) of the lower Shuijingtuo Formation could have facilitated shale-gas retention, but its source remains uncertain. In this study, a 100-m-long, continuous core interval from well EYY1 (2970 to 3070 m) covering the lower Cambrian Yanjiahe and Shuijingtuo Formations in the Yichang area was characterized using whole-rock rare earth elements and yttrium (REY), total organic and inorganic carbon (TOC and TIC), and major and trace-element analyses, and cathodoluminescence (CL) imaging. Shales and carbonates in Yanjiahe and the organic-rich lower Shuijingtuo Formations at Yichang area were imprinted with REY signatures derived from oxic-seawater or basinal hot brine, in which the enrichment factor of total REY contents (ΣREYEF = (ΣREY/Al) sample/(ΣREY/Al) PAAS) correlated positively to TIC contents and negatively to aluminum contents, indicating that carbonates serve as both carriers of hydrogenous REY and diluent of terrigenous REY signatures. Two kinds of carbonate minerals were distinguished under CL. Dolomite with bright-red-orange CL luminescence in upper Yanjiahe Formation was responsible for whole-rock HREE-depletion, and its association with abundant barite and silt-sized terrigenous silicate minerals likely indicate alteration of basinal hot brine in low-sea-level conditions and provide evidence supporting a depositional hiatus after deposition of the Yanjiahe Formation in the Yichang area (∼526–521 Ma). Calcite particles with dark-orange CL luminescence were the carrier of oxic-seawater-like REY features in the organic-rich shale deposited under anoxic conditions (indicated by high ratios of (U/Th) wt and (Corg/P) mol) in the lower Shuijingtuo Formation. These calcite particles could be allochthonous and perhaps formed in an oxic environment on the carbonate platform and transported to the adjacent anoxic, deepwater basinal environment. The enrichment of calcite leads to an elevation in rock brittleness, which is favorable to shale-gas exploration in the lower Shuijingtuo Formation in the Yichang area.

Effects of three fertilizer application patterns on wheat sowed by machinery in slope cropland of Western Hubei, China.

Unscientific fertilization, unstable grain quality, and low profit are the key problems on wheat production in slope cropland of Western Hubei. To solve these problems, three optimized planting patterns (high nitrogen and potassium reduction, HNPR; medium nitrogen and potassium reductionm, MNPR; low nitrogen and potassium reduction, LNPR) were conducted during two consecutive years to assess their effects on wheat yield, quality, profit, and fertilizer use efficiency in Danjiangkou Reservoir area, a typical slope cropland region with wheat-maize rotation. The results showed that the application of chemical fertilizer significantly increased grain yield (GY) and wet gluten content (WGC) of wheat. Compared with the conventional planting pattern (CK), the partial factor productivity (PFPK) and agricultural fertilizer use efficiency (AFUEK) of potassium were significantly improved in the three optimized planting patterns. The dry matter amount (DMA), GY, and crude protein content (CPC) were the highest under HNPR, which increased by 9.4%, 19.4%, and 7.8% than CK, respectively. Such a result indicated that HNPR benefited wheat to exploit high yield potential. WGC and falling number (FN) were the highest under MNPR, and increased by 3.9%, and 9.3% than CK, respectively, which was suitable for high-efficiency production of medium-gluten wheat. PFPN, AFUEN, PFPK, AFUEK, and net profit were the highest under LNPR, which increased by 15.7%, 134.1%, 131.3%, 368.2%, and 37.3% than CK, respectively, while the CPC and WGC were decreased by 2.1% and 2.6% than CK, respectively, suggesting it was suitable for environment-friendly and simplified production of weak-gluten wheat production. Our results could provide a reference for wheat production in the slope cropland.

Diversity and chemical fingerprinting of endo-metabolomes from endophytes associated with Ampelopsis grossedentata (Hand.-Mazz.) W. T. Wang possessing antibacterial activity against multidrug resistant bacterial pathogens

BackgroundSerious infections caused by bacteria and their resistance to antibiotics are one of the biggest healthcare threats to mankind. Therefore, the present study aimed to isolate endophytes from medicinal plant Ampelopsis grossedentata, an endemic species of Western Hubei, China and to investigate its antibacterial efficacy and chemical diversity of the secondary metabolites. MethodsThe antibacterial potential of the endophytes was evaluated by disc diffusion method against a panel of eleven type strains and some multidrug resistant pathogenic bacteria. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were estimated by broth microdilution using iodonitrotetrazolium chloride assay. Further, the chemical diversity of the metabolites was estimated using LC-Q-TOF-MS/MS and GC–MS fingerprinting. ResultsFour endophytic fungi were isolated from the tender shoot of A. grossedentata; they were identified as Fusarium graminearum TC-1, Phomopsis mali TC-3, Pestalotiopsis maculans TC-5 and Alternaria alternata TC-11. Among the endophytes screened, A. alternata TC-11 exhibited significant antibacterial activity with the zones of inhibition ranging from 13.72 ± 0.30 to 21.76 ± 0.53 mm against all the tested type strains and multidrug resistant bacterial pathogens. Further, it showed significant antibacterial activity with MIC values ranging from 0.37 to 3.00 μg/mL. The combined LC-Q-TOF-MS/MS and GC–MS analyses of active extract revealed that alternarian acid, altertenuol, dimethyl sulfone, docosane, dodecane, duclauxin, ergosta-4,6,8(14),22-tetraen-3-one, ethyl 6-cyano-5-oxo-1-phenyl-7-thiophen-2-yl-[1,2,4]triazolo[4,3-a]pyrimidine-3-carboxylate, heptacosane, linoleic acid, neodecanoic acid, oxiranylmethyl ester, pentadecane, verrulactone E, 2,6,11-Trimethyldodecane and 4-[(E,4R,6R)-11-(furan-3-yl)-6-hydroxy-4,8-dimethylundec-8-enyl]-2-hydroxy-2H-furan-5-one were the most abundant compounds present which were responsible for the significant antibacterial activity. ConclusionsTo our knowledge, this is the first report of fungal endophytes isolated from the tender shoot of A. grossedentata with bacteriostatic and bactericidal activities. Our finding provides a new insight into the antibacterial potential of endophytes and envisages the possibility of using them for drug discovery.

Risk Assessment of Pipeline Engineering Geological Disaster Based on GIS and WOE-GA-BP Models

Oil and gas pipelines are part of long-distance transportation projects which pass through areas with complex geological conditions and which are prone to geological disasters. Geological disasters significantly affect the safety of pipeline operations. Therefore, it is essential to conduct geological disaster risk assessments in areas along pipelines to ensure efficient pipeline operation, and to provide theoretical support for early warning and forecasting of geological disasters. In this study, the pipeline routes of the Sichuan-Chongqing and Western Hubei management offices of the Sichuan-East Gas Transmission Project were studied. Seven topographic factors—surface elevation, topographic slope, topographic aspect, plane curvature, stratum lithology, rainfall, and vegetation coverage index—were superimposed using the laying method with a total of eight evaluation indicators. The quantitative relationships between the factors and geological disasters were obtained using the geographic information system (GIS) and weight of evidence (WOE). The backpropagation neural network (BP) was optimised using a genetic algorithm (GA) to obtain the weight of each evaluation index. The quantified index was then utilized to identify the geological hazard risk zone along the pipeline. The results showed that the laying method, stratum lithology, and normalised difference vegetation index were the factors influencing hazards.

The Link between Landscape Characteristics and Soil Losses Rates over a Range of Spatiotemporal Scales: Hubei Province, China.

Controlling soil erosion is beneficial to the conservation of soil resources and ecological restoration. Understanding the spatial distribution characteristics of soil erosion helps find the key areas for soil control projects and optimal scale for investing in a soil and water conservation project at the lowest cost. This study aims to answer the question of how the spatial distribution of soil erosion in Hubei Province changed between 2000 and 2020. Moreover, how do the effects of natural factors and human activities on soil erosion vary over the years? What are the differences in landscape pattern characteristics and the spatial cluster of soil erosion at multiple administrative scales? We simulated the spatial distribution of soil erosion in Hubei province from 2000 to 2020 by the Chinese Soil Loss Equation model at three administrative scales. We investigated the relationship between soil erosion and driving factors by Geodector. We explored the landscape pattern and hotspots of land at different levels of soil erosion by Fragstat and hotspot analysis. The results show that: (1) The average soil erosion rate decreased from 2000 to 2020. Soil erosion is severe in the mountainous areas of western Hubei province, while it is less severe in the central plains. (2) Land-cover type, precipitation, and normalized difference vegetation index are the most influencing factors of soil erosion in 2000–2010, 2015, and 2020, respectively. (3) The aggregation index values at the town scale are higher than those at the city and county scales, while the fractal dimension index values at the town scale are lower, which indicates that soil erosion projects are most efficient when the project unit is ‘town’. (4) At the town scale, if the hotspot area (6.84% of the total area) is treated as the protection target, it can reduce 50.42% of the total soil erosion of Hubei province. Hotspots of soil erosion overlap with high erosion zones, mainly in the northwestern, northeastern, and southwestern parts of Hubei province in 2000, while the hotspots in northwestern Hubei disappear in 2020. In conclusion, land managers in Hubei should optimize the land-use structure, soil and water conservation in slope land, and eco-engineering controls at the town scale.

Numerical analysis of groundwater flow behaviour at a dam site in Karst area during its reservoir impoundment

The Jiangpinghe concrete-faced rockfill dam, with a maximum height of 219 m, is located in the karst area in western Hubei Province, China. The bedrocks at the dam site are highly dissolved, in which karst conduits, faults, fractures and weak interlayers are developed. Given the complex geological conditions, a large-scale grouting curtain covering an area of 376,000 m2 was built to control the seepage in the dam foundation. However, the piezometers in the middle section of the lowest grouting tunnel at the right bank manifest an abnormal rise of hydraulic head after reservoir impounding. The hydraulic head varies with a good correlation with the reservoir water level. This abnormal rise of hydraulic head can be attributed to higher permeability of strata where small-scale karst pipes and conduits are developed. In this study, an inverse modelling procedure combined orthogonal design, finite element forward modelling of transient groundwater flow, artificial neural network, and genetic algorithm was adopted to evaluate the permeability of the strata. The inverse results show that the permeability of shallow-buried rocks is one order of magnitude larger than that of deep-buried rocks in the right bank. The numerical simulations show good agreement with field measurements. Based on the inversed results, the groundwater flow behaviour at the dam site was analysed and the performance of the seepage control system was evaluated. It is demonstrated that the abnormal rise of hydraulic head is induced by the permeable structures developed along karst strata, and the seepage control system performs well in lowering the hydraulic head and limiting the amount of leakage through the dam foundation.

Spatial and seasonal variations of PAHs in soil, air, and atmospheric bulk deposition along the plain to mountain transect in Hubei province, central China: Air-soil exchange and long-range atmospheric transport

Polycyclic aromatic hydrocarbons (PAHs) are a long-term environmental problem faced by human society. The sources of involuntary PAHs are complex, moreover, secondary emissions of fixed PAHs in the environment occur due to global change and disturbance of human activities. Samples of three environmental media including soil, air, and atmospheric bulk deposition were collected to observe the spatial distribution and seasonal variation, to discuss the source or sink of PAHs and their association with the air mass transport along the plain (Jianghan Plain, JHP) to mountain transect, and explore the geographic scope of the atmospheric transport influence. The results obtained showed that 16 individual PAHs generally existed in all environmental multimedia being studied, and the PAHs concentration in air, soil and deposition flux of atmospheric bulk was higher in JPH than in “Western Hubei Mountains” (WHMs). Considerably high PAHs concentrations were obtained from the soil, air and atmospheric bulk deposition in winter, summer, and both summer and winter, respectively. The air-soil fugacity fraction of PAHs indicated that the soil of Dajiuhu (DJH) is likely to be a sink. Backward air trajectory simulation confirmed that most of the air mass passes over the JHP before reaching DJH, combined with the (transport and persistence level III) TaPL3 model results JHP are acting as sources. However, seasonal changes lead to a shift in the roles of soil sources and sinks. The TaPL3 model calculated that PAHs are transported through water for a wider range of effects and a longer persistence, even up to 10 years.

Sedimentary tectonic pattern of Wufeng and Longmaxi Formations in the northern margin of Sichuan Basin, South China

ABSTRACT Organic-rich black shales in the Sichuan Basin from the Upper Ordovician and Lower Silurian are considered excellent source rocks and unconventional reservoirs of hydrocarbons in South China. The Wufeng and Longmaxi Formations in the Micangshan – Dabashan areas of the northern margin of Sichuan Basin were taken as the research objects. The purpose of this study is to reconstruct the sedimentary tectonic pattern of the Wufeng and Longmaxi Formations in the study area. First, the stratigraphic framework correlation and sedimentary facies analysis of Wufeng and Longmaxi Formations in the study area were carried out. Then, Mo/TOC and Al-Co[EF]×Mn[EF] geochemical indicators were used to identify the degree of water restricted during the deposition period. It was found that the thickness of black shale was relatively small near the uplift area. However, far away from the uplift area, from west to east, the black shale thickened and the TOC content increased gradually, which were controlled by the upwelling of continental margin and intracontinental depression. The results show that: (1) At the front edge of Micangshan, during the deposition period of Wufeng Formation, Fucheng and Qiaoting profiles were located in the intersection area of upwelling formed by two kinds of monsoon, which led to the long-term influence of upwelling in this area. The sedimentation period of Longmaxi Formation was mainly affected by ‘Xixiang Rise’, which led to the uplift of Wangcang and Nanjiang areas into islands. (2) At the front edge of Dabashan and Western Hubei – Eastern Chongqing areas, the Wufeng Formation presented a tectonic pattern of alternating uplift and depression. Due to the continuous compression of the Cathaysian Block from southeast to northwest, the Shizhu – Wuxi areas continued to subside during the deposition period of Longmaxi Formation, and the black shale was quite thick.

Response of Carnian Pluvial Episode evidenced by organic carbon isotopic excursions from western Hubei, South China

We here report a high-resolution organic C-isotope record from terrestrial–marine transitional sediments of the Badong Formation in the Luojiagou section, Zigui Basin of Hubei Province, South China. Our organic carbon isotope (δ13Corg) profile, ranging from -21.2‰ to -26.2‰, shows four negative carbon-isotope shifts. We suggest that the sharpest negative carbon isotope excursion in the upper portion of the Badong Formation marks the main phase of the Carnian Pluvial Episode (CPE) in the basin, likely correlated with those in other depositional records of this time. The occurrence of the CPE in the Badong Formation would imply that the stratigraphic coverage of the Badong Formation might be prolonged to incorporate (at least part of) the Late Triassic Carnian stage. This result provides a potential case for understanding the CPE in continental–marine environments in the eastern Tethys realm, and is significant for exploring the palaeoclimate variation across the Late Triassic.

Effects of land use transition on ecological vulnerability in poverty-stricken mountainous areas of China: A complex network approach

Poverty-stricken mountainous areas are often subject to ecological vulnerability, and land use transition is a major factor affecting that vulnerability. Land use transition forms a complex network comprised of different land use types which interact with each other and respond to external environment processes, resulting in dynamics. This study develops complex network approach with cascade failure model to quantitatively explore the effects of land use transition on ecological vulnerability from the holistic and dynamic perspective. The study analyzes the characteristics of land use transition, identifying key transition types and simulating their impact on ecological vulnerability in 16 poverty-stricken mountainous counties in western Hubei Province, China, with the following findings. (1) The heterogeneity of change in agricultural land and construction land is significant; from 1990 to 2015, a short-term increase in the amount of agricultural land is followed by a gradual reduction, while the amount of construction land increased continuously. (2) Agricultural land is the dominant output land type, exported mainly to construction land and water area, and construction land is the dominant input land type, imported mainly from agricultural land. Sparse woods, woods, and dryland are the key land use types in the study area. (3) the critical points for maintaining resilience of ecosystem are 80% or higher for cultivated land and 80% or higher for woodland. (4) For the tolerance parameter α, 20% increase in cultivated land and a 10% increase in woodland would enhance ecosystem resilience and reduce its damage degree to corresponding land use transition. These findings are important points of reference for the sustainable management of poverty-stricken mountainous counties in western Hubei Province and in China more generally. They also have policy implications for land resources, especially in terms of the alleviation of poverty and the coordination between ecological protection and economic development.