Coupled multiphysical model for investigation of influence factors in the application of microbially induced calcite precipitation

The study presents a comprehensive coupled thermo-bio-chemo-hydraulic(T-BCH)modeling framework for stabilizing soils using microbially induced calcite precipitation(MICP).The numerical model considers relevant multiphysics involved in MICP,such as bacterial ureolytic activities,biochemical reactions,multiphase and multicomponent transport,and alteration of the porosity and permeability.The model incorporates multiphysical coupling effects through well-established constitutive relations that connect parameters and variables from different physical fields.It was implemented in the open-source finite element code OpenGeoSys(OGS),and a semi-staggered solution strategy was designed to solve the couplings,allowing for flexible model settings.Therefore,the developed model can be easily adapted to simulate MICP applications in different scenarios.The numerical model was employed to analyze the effect of various factors,including temperature,injection strategies,and application scales.Besides,a TBCH modeling study was conducted on the laboratory-scale domain to analyze the effects of temperature on urease activity and precipitated calcium carbonate.To understand the scale dependency of MICP treatment,a large-scale heterogeneous domain was subjected to variable biochemical injection strategies.The simulations conducted at the field-scale guided the selection of an injection strategy to achieve the desired type and amount of precipitation.Additionally,the study emphasized the potential of numerical models as reliable tools for optimizing future developments in field-scale MICP treatment.The present study demonstrates the potential of this numerical framework for designing and optimizing the MICP applications in laboratory-,prototype-,and field-scale scenarios.

Statistical landslide susceptibility assessment in a dynamic environment:A case study for Lanzhou City,Gansu Province,NW China

This study presents a statistical landslide susceptibility assessment(LSA) in a dynamic environment. The study area is located in the eastern part of Lanzhou, NW China. The Lanzhou area has exhibited rapid urbanization rates over the past decade associated with greening, continuous land use change, and geomorphic reshaping activities. To consider the dynamics of the environment in the LSA, multitemporal data for landslide inventories and the corresponding causal factors were collected. The weights of evidence(Wof E) method was used to perform the LSA. Three time stamps, i.e., 2000, 2012, and 2016, were selected to assess the state of landslide susceptibility over time. The results show a clear evolution of the landslide susceptibility patterns that was mainly governed by anthropogenic activities directed toward generating safer building grounds for civil infrastructure. The low and very low susceptibility areas increased by approximately 10% between 2000 and 2016. At the same time, areas of medium, high and very high susceptibility zones decreased proportionally. Based on the results, an approach to design the statistical LSA under dynamic conditions is proposed, the issues and limitations of this approach are also discussed. The study shows that under dynamic conditions, the requirements for data quantity and quality increase significantly. A dynamic environment requires greater effort to estimate the causal relations between the landslides and controlling factors as well as for model validation.

Assessing Possibilities and Limitations for Biomarker Analyses on Outcrop Samples:A Case Study on Carbonates of the Shibantan Member (Ediacaran Period, Dengying Formation, South China)

The Shibantan Member（Dengying Formation, South China） represents one of only two carbonate settings with Ediacara-type organisms and offers a rare opportunity to study the biogeochemistry of these ecosystems. To evaluate possibilities and limitations for future biomarker studies on fossil-bearing outcrop samples of the Shibantan Member, we analysed the spatial distribution of hydrocarbons in extractable organic matter（i.e. bitumen） on a millimetre scale. Our study demonstrates that the sample and most likely also other rocks from the same setting are contaminated with petroleum-derived compounds that bear the potential for erroneous interpretations in palaeo-reconstructions. The contamination was revealed by distribution patterns and amounts of extractable n-alkanes and acyclic isoprenoids. The contamination is linked to the external weathering surfaces but also to cracks within the rock, and the extent most likely depends on concentration gradients between these contamination sources. Here we show that contamination can successfully be distinguished from syngenetic signals obtained from non-extractable organic matter（i.e. kerogen） using catalytic hydropyrolysis（Hy Py）. However, we observed that decalcification is necessary to achieve sufficient yields of kerogen-bound hydrocarbons and to avoid artificial alteration of the biomarker signals due to matrix effects.

Geology, Mineralogy and Geochemistry of the Oligocene Oolitic Iron Ore of the Continental Terminal Formation, Kandi Basin, North-East Benin

The Oligocene Continental Terminal Formation of the Kandi Basin contains high grades of iron mineralization (~56.72% Total Fe). The microscopic study under the polarized and reflected light showed that the iron ore consists of silicate minerals (quartz 50% and zircon 1%) and non-silicate minerals (goethite 30%, hematite 7%, magnetite 3%, pyrite 1%, chalcopyrite 1%, blende 3%, galena 3%, scheelite 1% and gold 2%). The X-rays fluorescence shows that the iron ore is characterized by various elements, such as Fe2O3 (57.91% to 91.33%), SiO2 (3.07% to 33.19%), aluminum (2.94% to 7.74%), vanadium (0.04% to 0.11%), phosphorus (0.79% to 2.29%) and sulfur (<0.3%). The deleterious elements grade is above the permissible limit in metallurgy (0.05% - 0.07% for phosphorus and 0.1% for sulfur). Their high grades indicate that the Kandi Basin iron ore characteristics are not favorable for steel manufacturing despite its good vanadium contents (0.04% to 0.11%). However, it could be used for the cast iron manufacture. Spectrometric analysis by atomic absorption confirms the presence of low-grade gold associated to the iron ore (from 0.006 to 0.015 ppm). The comparative study of discontinuous stratiform iron ore of the Kandi Basin with other oolitic iron ores in exploitation from other countries such as Brazil, Australia, China, Russia, Uganda and the United States shows that iron ore of the Kandi Basin can be mined despite its high silica content.

Simulation of dilatancy-controlled gas migration processes in saturated bentonite using a coupled multiphase flow and elastoplastic H2 M model

Dilatancy-controlled gas flow in preferential pathways plays a key role in the safety analysis of radioactive waste repositories.This is particularly the case for bentonite,an often-preferred barrier material.Gas flow in preferential pathways is characterized by localization and spontaneous behavior,which is challenging to simulate in numerical models due to strong hydro-mechanical coupling.To analyze a laboratory experiment in the framework of the DECOVALEX-2023 project,this study introduced a new approach of combining continuous modelling methods with spatial material properties derived from material heterogeneities and experimental observations.The proposed model utilized hydro-mechanical spatial distributions,namely Young’s modulus and gas entry pressure,and elastoplasticity combined with a linear swelling model.A conceptual strain-dependent permeability approach simulated dilatancycontrolled gas flow based on hydro-mechanical coupling.To test the effectiveness of the presented approach,a gas injection test in a compacted,saturated bentonite sample was simulated using the opensource code OpenGeoSys 5.8 and compared with experimental observations.The presented methodology is capable of simulating localized gas flow in preferential pathways.The spatial distributions of Young’s modulus and gas entry pressure affect the swelling pressure,relative permeability and,in combination with the strain-dependent permeability model,also the intrinsic permeability.

Mechanical behavior of sandy facies of Opalinus Clay under different loadconditions

The mechanical behavior of sandy facies of Opalinus Clay at the Mont Terri underground rock laboratory(URL)in Switzerland was investigated with drained and undrained triaxial compression and extension,cyclic compression,and creep tests.Samples were taken from boreholes drilled parallel to bedding.Most of the samples were reconditioned to minimize sampling effects of desaturation and micro-cracking.The compression was accomplished by increasing axial stress at constant radial stress.The extension was carried out by increasing radial stress at constant axial stress.Moreover,extension was also achieved by simultaneously increasing radial stress and decreasing axial stress under constant mean stress.The test results showed elastoplastic stress-strain behavior with volumetric compaction until onset of dilatancy at high deviatoric stresses above 80%-90%of the peak failure strength.The strength is dependent upon load path and mean stress.The strength under triaxial compression is higher than that under extension.The respective strength increases with increasing mean stress.Desaturation enhances the stiffness and strength of the claystone.The deformation and strength of the elaystone are time-dependent.Under constant deviatoric stress,the claystone crept continuously with time,which can be characterized by a transient phase and a following stationary phase,and even a tertiary phase at high deviatoric stresses to rupture.

Groundwater Vulnerability and Hazard Mapping in an Arid Region: Case Study, Amman-Zarqa Basin (AZB)-Jordan

The importance of groundwater portability and the possible sources of anthropogenic contamination have led to the development of intrinsic groundwater vulnerability mapping. In this study, groundwater vulnerability map for Amman Zarqa Basin (AZB) has been generated based on information derived and calculated from processed remote sensing information and laboratory analysis. The database was prepared from soil hydro geological and hydrological data, Digital Elevation Model (DEM), and geological maps. For assessment of groundwater vulnerability, the method proposed by the state geological surveys of Germany (GLA-method) has been adapted and applied. The vulnerability map shows about 77% which is about 2919 Km2 of the AZB is classified as very low to low which could be corresponding to the pollution sources due to the absence of potential hazards and also due to low vulnerabilities. These areas could consequently be interesting for future development as they set preferable in view of ground water protection. In addition, about 14% (530 km2) is classified within the moderate vulnerability zone. About 5% (around 19 km2) of the study area lies under the area of high vulnerability zone. Only 4% can be classified as very high risk areas. Groundwater quality results revealed that water leach ate from point source is the main cause for groundwater contaminations in highly vulnerable karstic limestone aquifer (Amman Wadi Es Sir Aquifer-B2/A7). On the other hand, the Kurnub Sandstone aquifer (K) is generally well protected in the central and eastern part of the AZB due to its thick cover of partly marly sequences. However, the Kurnub aquifer might have a potential risk from the recharged infiltrating surface water from the Zarqa River, which is highly polluted due to industrial activities located along the river.

塔里木盆地库车坳陷烃源灶特征和天然气成藏过程

根据模拟实验数据,建立了库车坳陷典型源岩天然气产率和碳同位素的化学动力学参数。基于探井和人工井(13条地震剖面共230个人工井点)地质数据和今、古地温数据,采用BasinMod软件,分析了各井点成熟度和天然气产率随时间的变化规律,查明了三叠、侏罗系源岩的生烃历史和烃源灶的演化特征,指出,库车坳陷中生界源岩自新近纪以来快速埋藏和成熟,特别是5×106a以来,上新统库车组快速沉积,引起成熟度急剧增高,进入干气阶段,表现为5×106a以来气源灶极高的生气速率,这是库车坳陷形成高效天然气藏的重要原因。库车坳陷的前缘隆起带和克依构造带捕获了同一腐殖型气源灶(T-J)不同阶段生成的天然气;前缘隆起带的牙哈凝析气田主要捕获了生油窗阶段近源生成的天然气,表现为天然气甲烷碳同位素相对较轻;克拉2气藏主要是晚期(5×106a以来)捕获了镜质体反射率在1.0%～2.5%阶段生成的天然气,表现为天然气甲烷碳同位素相对较重。

煤系有机质多阶段成气的分子碳同位素表征及其对高过成熟干酪根生气潜力评价的启示

采用开放体系在线程序升温裂解-色谱-碳同位素比值质谱技术(PY/GC-IRMS)考察了煤系有机质热演化过程中甲烷瞬时生成速率与碳同位素组成特征,提出煤系有机质不同热演化进程甲烷生成的四个阶段:生油窗阶段、主生气阶段、晚期生气阶段(芳环侧链断裂)、开环-缩聚作用阶段。以一级反应动力学为基础,采用高斯分布算法,计算了各阶段甲烷产出的动力学参数。研究结果对煤成气资源量的正确评价,特别是近年来有机质高演化阶段成气潜力的评价具有重要指示意义。

The Muruntau gold deposit(Uzbekistan)--A unique ancient hydrothermal system in the southern Tien Shan

The Muruntau gold deposit in the Central Kyzylkum,Uzbekistan is one of the largest single gold deposits worldwide.Data available from the literature are reviewed with the aim to（1） integrate the present knowledge on this unique deposit from Russian and English literature;（2） show the considerable progress made in the understanding of the genesis of the Muruntau deposit during the last decades;and（3） point to problems still open for future research.Deposit formation occurred through a multi-stage process involving sedimentation,regional metamorphism including thrusting,magmatism with formation of hornfels aureoles and several stages of hydrothermal activity.According to recent knowledge,synsedimentary or pure metamorphic formation of gold mineralization seems unlikely.The role of granite magmatism occurring roughly within the same time interval as the main hydrothermal gold precipitation remains uncertain.There are no signs of interaction of matter between the magma（s） and the hydrothermal system（s）.On the other hand,there was an intense,high-temperature（above 400 ℃）fluid- wall rock interaction resulting in the formation of gold-bearing,cone-like stockworks with veins,veinlets and gold-bearing metasomatites.Several chemical and isotope indicators hint at an involvement of lower-crustal or mantle-related sources as well as of surface waters in ore formation.Deposit formation through brecciation involving explosion,hydrothermal or tectonic breccias might explain these data.Further investigations on breccia formation as well as on the exact timing of relevant sedimentary,metamorphic,magmatic and hydrothermal events are recommended.

Numerical analysis of thermal process in the near field around vertical disposal of high-level radioactive waste

For deep geological disposal of high-level radioactive waste(HLW)in granite,the temperature on the HLW canisters is commonly designed to be lower than100fiC.This criterion dictates the dimension of the repository.Based on the concept of HLW disposal in vertical boreholes,thermal process in the nearfield(host rock and buffer)surrounding HLW canisters has been simulated by using different methods.The results are drawn as follows:(a)the initial heat power of HLW canisters is the most important and sensitive parameter for evolution of temperaturefield;(b)the thermal properties and variations of the host rock,the engineered buffer,and possible gaps between canister and buffer and host rock are the additional key factors governing the heat transformation;(c)the gaps width and thefilling by water or air determine the temperature offsets between them.

Identification and temporally-spatial quantification of geomorphic relevant changes by construction projects in loess landscapes:case study Lanzhou City,NW China

Sustainable development of urban areas demands,among others,a holistic approach for identification and monitoring of environmental changes caused by human activities.In this study,the human-made impact on the geo-environment is studied through the application of the change detection study based on Principal Component Analysis on Landsat imageries and comparison of the digital elevation models taken at different times.The analysis is set up to identify and quantify the anthropogenic geomorphological changes in the loess landscape in Lanzhou city,Northwest China.Since 2002 Lanzhou has been undergoing a rapid economic development associated with construction boom.Due to limited flat building ground in the narrowed Yellow River Valley and subsequent expansion into the surrounding loess mountains,massive earthworks are conducted for reclamation of the suitable building ground.The results of the change detection analysis show that approximately 10%of the semi-natural study area corresponding to 35 km2 has been reshaped by leveling and terracing since 1994.In particular,the geomorphology was significantly changed in these and adjacent areas.For the single developing area Taipingyang,a moving volume of up to 57 million m3 was roughly estimated.