Vadose Research Articles

Scoured failure wedge model for analysis of scoured pile-soil interaction in sand

Comprehensive assessment of scour effects is an important consideration in the design of pile foundations in water bodies because they can have a significant impact on the performance and bearing capacity of piles and the integrity of the supported structure. This study presents a scoured failure wedge (SFW) model to simulate the interaction between the laterally loaded pile and sand with local scouring. The developed model is incorporated into an efficient theoretical method to analyze the nonlinear behavior of laterally loaded piles under scour conditions accounting for the scour-hole dimensions and soil stress history. The developed SFW model is validated by comparing its predictions with experimental observations from relevant literature. Subsequently, the validated solutions are utilized to investigate the lateral performance characteristics of the pile under scour conditions. The findings reveal several important insights: (1) the impact of scour on soil properties is primarily confined to the shallow zone, approximately four times the scour depth (4 Hs) below the mudline after scouring; (2) the scour hole dimension has a more pronounced influence on the behavior of laterally loaded piles compared to the soil stress history; and (3) the pile response under lateral loading is positively related to the depth and width of the scour hole and negatively related to the slope angle of the scour hole.

Seasonal Variability of Dissolved Methane in the Shallow Coastal Zone: The Case Study of the Golubaya Bay, Northeastern Part of the Black Sea

The variability of the dissolved methane content in coastal zones is an important component of the biogeochemical cycle in the marine ecosystem. The objective of this study is to investigate the seasonal variability of dissolved methane distribution in the aerobic shallow coastal zone through the example of the small bay in the northeastern Black Sea. This study is based on the direct observations carried out during a long-term monitoring program conducted in the bay from 1999 to 2016. The seasonal and inter-annual variability of the dissolved methane pattern is considered under the climatic conditions as well as under the influence of extreme flood. The seasonal range of the dissolved methane content variability in the shallow part of the northeastern Black Sea is 1–2 orders of magnitude higher compared with the areas remote from the coast. The dissolved methane content in Golubaya Bay in summer is an order of magnitude higher than the winter values. In particular, local methane maxima located near the river and stream mouths and in the central bottom part of the bay have a well-shown seasonal cycle. The extreme flood conditions observed in July 2012 resulted in high methane concentrations 2 months after the flood event, when the surface concentrations of the dissolved CH4 exceeded the equilibrium with the atmospheric values by a factor of 400. The obtained results provide a unique opportunity to estimate the scale of the biogeochemical processes in marine coastal environments under the influence of climatic and extreme conditions.

Preferential flow in the shallow vadose zone: Effect of rainfall intensity, soil moisture, connectivity, and agricultural management

AbstractPreferential flow is ubiquitous in soils, and it affects water infiltration, runoff, and contaminant transport. Undisturbed soil lysimeters (n = 10; 900 cm2) were collected from an agricultural field to quantify the effect of climate, soil moisture, connectivity, and agricultural practices on water transport through the shallow vadose zone. A series of 10 rainfall simulations was conducted on each lysimeter (n = 100 events) and data were analysed within a framework of five case studies where we assessed the impact of rainfall intensity (n = 30 events), soil moisture (n = 28), and tillage (n = 21). Three lysimeters that had near‐zero flow initially were modified to investigate dynamics of direct surface connectivity through an artificial macropore in which we assessed the impacts of soil moisture (n = 12) and subsequent disruption via tillage (n = 9). Stable water isotopes were used to separate leachate into event (Qe) and pre‐event water (Qpe). Results showed that event water transport in leachate was not affected by rainfall intensity (Qe/Q = 49% ± 21% to 50% ± 24%); however, event water decreased from 65% ± 5% to 23% ± 28% with increasing soil moisture. Lysimeters with artificial macropores resulted in leachate that was nearly all event water (85% ± 12% to 92% ± 4%) irrespective of soil moisture. Tillage decreased event water transport for both lysimeters with and without an artificial macropore by ~30%. Findings show how varying initial and boundary conditions produce a continuum of preferential flow. Water and tracer flux data collected in the current study are therefore essential for predicting conditions with high relevance of preferential flow and contaminant transport when assessing or modelling long‐term hydrographs where these conditions are only met during a small proportion of the flow time.

Influence of vegetation‐induced water table seasonality on groundwater chloride concentration dynamics in a riparian fen peatland

AbstractPeatlands are environments that rely mainly on high water levels to accumulate organic matter. Depending on the chemical species observed, the lowering of the water table can change biogeochemical equilibriums, with various impacts. This paper aims to understand the effect of shallow groundwater seasonality on chloride concentrations in a French riparian peatland by combining water table monitoring, geochemical and stable water isotopes analysis. Water table levels and groundwater samples were recorded and collected for 3 years, every 2 months, in nine observation wells and the nearby river. Chloride concentrations were highly variable in space and time, ranging from 10 to 100 mg L−1. They are shown to be related to the water table dynamics, which are closely linked to the life cycle of the local vegetation. These dynamics were characterized by a significant drawdown between June and October due to plant transpiration and a fast recovering period just after its senescence. Results show that the chloride accumulates within the unsaturated zone during the drying phase and is solubilized back into the groundwater during the rewetting phase, increasing its concentration. Moreover, the water table rises in autumn with various dynamics according to the location in the peatland, which induces some special differences in hydraulic gradients. Such gradients allow lateral transfers from zones of fast recovery to zones of slow recovery, where year‐to‐year chloride accumulation was observed. These complex 3D processes preclude the use of chloride to constrain how the peatland hydrogeological system functions. Conversely, the use of stable water isotopes in this work emphasizes the importance of the river's role during the summer as a water supplier to counterbalance vegetation transpiration.

Processes Controlling Formation of Salt Efflorescence in Coastal Salt Flats

AbstractSalt flats are bare soil surfaces with elevated salinity levels which inhibit vegetation. They are commonly found in areas of coastal wetlands where salt in surface soil accumulates due to evaporation from the shallow saline water table. The expansion of these vegetation‐free zones may severely affect the bio‐ecological function of these coastal wetland systems. In this study, sand flume experiments and numerical modeling were carried out to investigate the mechanisms underpinning the development of salt flats in the elevated areas of coastal wetlands. We found that salt precipitation occurred on the soil surface where water content is low, but the hydraulic connection to the saline groundwater table is maintained. This connection is required for evaporation to promote upward porewater flow and bring salt to the surface. However, the surface salinity level decreases with increasing surface saturation due to the density‐driven removal of salt. As a result, salt efflorescence is absent on the surface with higher water saturations, despite strong evaporation. Density‐driven flows can be triggered by the evaporation‐induced upward salinity gradient and transfer salt from the surface back to the water table. Numerical simulations confirmed this salt removal process and suggested the intensity of the density‐driven flow is mainly dictated by the soil permeability in the unsaturated zone. The findings from this study increase understanding of the processes involved in the formation and evolution of salt flats.

The Outstanding Geology And Geoheritage Of The Niah Caves And Karst Area

This paper provides an overview of current information (including research results since 2011) on outstanding geological features of Niah karst region and caves, to support nomination of the property for World Heritage status. The geomorphology visible today is due to geological processes affecting the predominantly Miocene Subis Limestone since uplift: dissolution in vadose and phreatic zones, sediment deposition and removal, mechanical breakdown, speleothem formation and surface weathering. The caves developed at several levels in tropical tower karst (fenglin), with vertical cliffs, swamp notches and a semi-flooded epiphreatic cave network, evidence of ongoing karstification. The walls of relict Traders’ Cave have anastomosing ceiling grooves associated with wall notches indicating that it was partially filled with sediment and flow from large streams several times during its formation, prior to more recent mechanical breakdown. The numerous large and complex caves have high aesthetic value, with ceiling skylights and impressive entrances connecting to the surrounding forest. They contain speleothems (stalagmites and stalactites) of types rarely found elsewhere in the world. The Painted Cave holds one of the world’s largest cluster of unique crayback-like stalagmites, which are influenced by constructive activity of calcifying cyanobacteria and only form under limited environmental conditions of specific light levels and wind. Microbial activity can also be erosive and is likely responsible for pancake pinnacles and rare photokarren, reported here in Niah for the first time. In addition to their undisputed archaeological, cultural, ecosystems and conservation values, the Niah caves and karst region also have many interesting geological and geomorphological features, some of which are rare and hence have geoheritage value.

Model based impact assessment on groundwater vulnerability during aggregate quarry operation

A general methodological approach is proposed for the preliminary assessment of the potential impact on groundwater during the operation of quarries for aggregates. The practical application and effectiveness of this approach are by using a numerical model to predict groundwater and soil contamination during the implementation of a project in the region of Breznik, Western Bulgaria. The spread of highly mobile pollutants in both the unsaturated and saturated zones of the rock complex is simulated after emergency spills and prolonged discharges of contaminated water in the quarry area. The forecast is made for a period of 100 years. The numerical model was compiled using the VS2DI program.

Estimating annual CO2 emissions and building a leakage scenario in a tectonically quiescent area

Soil CO2 flux (FCO2) was intensively measured in a natural CO2 emission site located in a tectonically quiescent area, with topographic and geophysical investigation, to estimate annual emissions and causes of focused leaks. FCO2 varied between 6.5 and 2155.4 g/m2/d (median 76.1 g/m2/d; n = 67) within a 612 m2 area situated close to a CO2-rich groundwater well. The threshold value for geogenic FCO2 was determined to be 23 g/m2/d using a Q-Q plot. A FCO2 hotspot was delineated where FCO2 exceeded the threshold. Based on linear regression using air pressure and temperature, the annual CO2 emissions from the hotspot in 2019 were approximately 19 tons/y. According to the 2D electrical resistivity distribution, the subsurface around the well was highly weathered, showing low electrical resistivity (<2000 Ω-m) down to a depth of 50 m, whereas the top layer around the hotspot showed a relatively high electrical resistivity (> 500 Ω-m), implying a resistant unsaturated zone. High signal attenuation and discontinuous and dipping reflectors of ground-penetrating radar signals suggested gaseous CO2 transport through preferential pathways in the resistant near-surface. Based on these and previous hydrochemical results, the extremely high FCO2 in the narrow extent can be explained by a leakage scenario in which the frequent usage of CO2-rich water through the well enhances CO2 degassing, while defects in the well casing accelerate the upward movement of CO2 gas, which flows out through a preferential pathway in the resistant unsaturated zone. This study provides insights into focused leakages through faulty wells and near-surface preferential pathways. In addition, the quantification of annual CO2 emissions through point sources is applicable for assessing natural gas emissions produced by hotspots. The non-negligible emission rate in the hotspot (about 92 g/m2/d) emphasizes the need to quantify natural CO2 emissions in tectonically quiescent areas for risk assessments and carbon budgets.

Assessment of the influence of abiotic environmental factors on the distribution of bream and carp in the Northern Caspian

Changing habitat conditions is an important driving force affecting the distribution of fish in the range. A quantitative assessment was made of the influence of environmental factors on the distribution of bream Abramis brama Linnaeus, 1758 and carp Cyprinus carpio Linnaeus, 1758 in the waters of the eastern part of the Northern Caspian. The number was estimated based on the results of research net catches. The preferred temperatures and habitat depths of bream and carp in the shallow zone of the Northern Caspian are shown. The colleof field material was carried out during complex expedition observations in 2014 and 2020. The installation of nets with a mesh of 30–200 mm was carried out in the shallow-water zone of the eastern part of the Northern Caspian. Bream and carp in the Northern Caspian Sea form concentrations in areas with depths up to 6–8 m. In the time interval from the end of April to October, bream was observed in the temperature range from 7.0 to 28.5 °C, carp — from 5.5 to 28.0 °C. A mathematical assessment of the influence of depth, temperature and water transparency on the number of these fish species was carried out. The obtained regression models took into account from 44.9 to 80.1% of the factors determining the number of fish in the studied water area. Carp are more sensitive to the effects of temperature, depth and transparency compared to bream. The obtained results provide a theoretical basis for predicting changes in the habitat of fish due to abiotic environmental factors, which is relevant in connection with pronounced climatic changes

A multi-disciplinary approach for trap identification in the Southern Meleiha Area, North Western Desert, Egypt: integrating seismic, well log, and fault seal analysis

The southern Meleiha concession, situated within the development encouragement areas of the Agiba Petroleum Company between Matrouh Basin and Shushan basin, spans approximately 700 km2. This study examined late Cretaceous strata to improve trap identification in the Bahariya, Alamein Dolomite, and Alam El Bueib Members. This required a thorough study of 33 seismic lines and five well log records. Our investigations revealed the presence of hydrocarbons in the deep, mid, and shallow target zones, underscoring the significant potential of the Khatatba-Ras Qattara and Bahariya layers. The net pay thicknesses observed ranged from 12 to 43 feet, while effective porosity values fluctuated between 10 and 18%. Water saturation varied from 10 to 98%, while hydrocarbon saturation varied from 48 to 90%. Seismic interpretation revealed abundant normal faults in the study area, and our maps showed structural closures, including three-way and four-way dip closures, influenced by these faults. The shallowness of the Bahariya layer, coupled with Shally Sand facies intercalations in the upper target, makes it particularly susceptible to fault leakage, necessitating careful consideration when selecting drilling locations. Notably, the western half of our investigation area exhibited more Alam El Bueib Member net pay zones compared to the eastern and south-eastern regions. The geological structure of the deep-target Khatatba-Ras Qattara is of particular interest, revealing a total of 37 potential leads across all levels. These leads encompass destinations like Bahariya, Alam El-Bueib, and Khatatba formations, some of which may have dual targets, while others may focus on a single objective.

Is crystalline chromium phosphate environmentally stable? A study on the formation, dissolution and oxidation risk of CrPO4·6H2O

Hexavalent chromium (Cr(VI)) contamination in soil and groundwater is usually remediated via reduction techniques. The formation of crystalline chromium phosphate (CrPO4·6 H2O) occurs as a byproduct during Cr(VI) remediation processes in the presence of phosphate, yet its stability in the environment has received limited attention. In this study, the formation conditions, structure, properties, and risks associated with the dissolution and oxidation of CrPO4·6 H2O were comprehensively assessed. Results showed that crystalline CrPO4·6 H2O was formed under pH 5 – 7 at room temperature. CrPO4·6 H2O exhibits higher dissolution risk compared to Cr(OH)3·3 H2O due to a long Cr-P bond (4.2 Å). H+ and OH– increased the risk of dissolution at pH 5 and 11, respectively, owing to the formation of CrH2PO42+ and Cr(OH)4–. In addition, under faintly acidic conditions, the high solubility of CrPO4·6 H2O increases the risk of oxidation; under neutral and weakly alkaline conditions, the presence of positively charged Cr(H2O)63+ structures on the surface elevates its susceptibility to contact and oxidation by δ-MnO2 compared to Cr(OH)3·3 H2O. Specifically, at pH 11, the conversion of CrPO4·6 H2O to Cr(OH)3·3 H2O results in similar oxidation risks for both Cr(III) precipitates.

Enhanced Groundwater Protection and Management Using Gravity and Geoelectrical Data (Valls Basin, Spain)

The basis for the protection and prevention of groundwater pollution lies in the accurate assessment of vulnerability in terms of the exposure of groundwater bodies to contaminants before they are potentially discharged into the environment. The vulnerability assessment consists of calculating the ease with which pollutants can reach the aquifer from the surface through the vadose zone, which effectively reduces the pollutant load when the transit time is long. Index methods are mostly used, as they are based on input data that are readily available, easy to implement and interpret, and which are simple and practical. However, there are also limitations, as some methods are somewhat subjective and provide only a qualitative approximation. This case study aims to develop a methodology that can quantitively estimate the hydrogeological parameters of the aquifer formations of the Valls basin using geophysical methods and the Dar Zarrouk parameters. The specific treatment carried out on data from gravity stations and vertical electric soundings, supported by the available well data, allows for the delineation of the most favourable areas for the exploitation of groundwater resources (higher hydraulic transmissivity) and the areas most susceptible to pollution (with a shorter transit time) on a regional scale. Geophysical methods have proved useful, sustainably providing valuable information without the need to drill new boreholes that could act as preferential pathways for pollutants into the aquifer.

Forecast of changes in the beach condition of the Yuzhne city under the influence natural factors

The study of the factors of degradation and the forecast of the state of recreational areas of the coast to prevent their negative changes is relevant. Purpose. Forecast of changes in the condition of the Yuzhne beach, provision of general proposals for its protection from degradation. Methods. Mathematical statistics, linear analysis and mathematical modeling, comparative analysis, cartographic and grapho-analytical studies. Results. The beach of Yuzhne is located on the coast of the Black Sea. Its length is approximately 700 m. The southern direction in the sector 180±22.5⁰ is dangerous for waves. The distance from the beach to the opposite shore (wave acceleration) is 540-610 km. The boundary between the shallow and deep water zones is at a distance of approximately 200 km with a depth of 75 m. With southerly winds, recurring once every 25 years, on the approach to the shallow water zone with a depth of 50-75 m, a developed disturbance with extreme wave parameters is formed, which, transforming in the shallow water zone, significantly affects the coast. A profile of relative dynamic equilibrium with a length of 1,200 m and a depth at this distance of 11.2 m is formed during the calculated disturbance. From the water cut, the boundary between the near-cut and surf zones is located at a distance of 220 m with a depth of 3.6 m. Regardless of the standing water level, the calculated storm destroys the original shore at the extreme parts of the beach. When the sea level is high, the disturbance moves the destroyed material with the beach material into the cut-off zone, while the water cut at the 0.0 m BS mark does not change its planned location. The amount of beach material on the upper part of the coastal slope may decrease significantly. At an average level of the sea, the washing away of destroyed and beach material is accompanied by the advance of the water cut toward the sea for a distance of up to 20 m, but at the same time, a decrease in beach material on the above-water part of the coastal slope is also observed. Conclusion. Without taking special protection measures, the beach of the Yuzhne city will degrade in the future. In areas of the beach, in order to prevent its erosion, it is necessary to erect a retaining wall with a backfilling layer. An option for an active method of protection can be the construction of permeable bunkers on the beach or an intermittent breakwater at a distance from the shore. Such protection will not impede the alongshore transport of sand. Dunes or waves will contribute to the accumulation of sand on the beach. At the same time, after strong storms from the southern direction, with high sea level, episodic additions of sand to the beach are necessary

Moisture Migration and Recharge Pattern of Low-Permeability Thick Cohesive Soil in Northern Margin of the Jianghan Plain

An extremely low hydraulic conductivity of cohesive soil causes a low transport rate of water and solute, with a time-consuming result, as we all know. Stable isotopes (δD and δ18O) and in situ monitoring systems of the data about soil water, rainfall, and groundwater were used to analyze the soil moisture migration pattern, using a conceptual model in the field test site, simulated by Hydrus 1D. The results show that multiple rainfalls’ accumulations can cause the water to recharge from soil moisture to micro-confined groundwater, gradually. The soil moisture dynamic change is composed of a dehydration period and absorption period; the cohesive soil water content below 5.0 m was affected by the micro-confined groundwater level and dehydrated in advance due to the level decline. The thick cohesive soil profile can be divided into a shallow mixing zone (0–2 m), steady zone (2–5 m), and deep mixing zone (5–15 m). The effective precipitation recharge was 234 mm and the average infiltration recharge coefficient (Rc) was 0.1389, but the water exchange between the cohesive soil moisture and groundwater was 349 mm in two hydrological years. This paper reveals the moisture migration and recharge pattern of low-permeability thick cohesive soil in a humid area with a micro-confined groundwater aquifer; this is of great significance for groundwater resources evaluation and environmental protection in humid climate plain areas.

Effects of groundwater evaporation on the natural recharge to groundwater lenses residing in coastal dunes in Southern Central Vietnam

Groundwater lenses in the coastal dunes along the South Central coast of Vietnam are often of shallow table. The lithologic composition of the vadose zone in these areas is mainly fine to medium-grained sand, characterised by high porosity. The vegetation is sparse, the annual time of sunrise is long, the air temperature and surface evaporation are high. The above-mentioned conditions are favourable for the evaporation of the groundwater. This study utilised direct evaporation measurement by Lysimeter (LS) according to the principle of water balance. The LS measurement is designed to simulate the groundwater level at a depth of 0.9 m to monitor groundwater loss due to evaporation corresponding to the conditions of natural climate and the vadose zones. Monitoring results showed that the total amount of groundwater evaporation in 2022 at three stations Da Nang, Phu Yen and Binh Thuan is 259.9, 335.6, and 377.0 mm, respectively. With the assumed groundwater level at a depth of 0.9 m, the annual amount of groundwater evaporation has caused the reduction in the groundwater level in the aquifer in Da Nang, Phu Yen and Binh Thuan by 0.64, 0.78, and 0.92 m, respectively.

Stratigraphy of the Alveolina elliptica group from the Middle Eocene of Iran: Calibration with calcareous nannofossils biozones and description of Alveolina ozcani n. sp.

Precise taxonomy and the chronostratigraphic calibration of the Middle Eocene Alveolina from Central Iran is here undertaken from the Chah-Talkh section of the southern Sabzevar region (Central Iran). We have identified Alveolina kieli, Alveolina stercusmuris and Alveolina nuttalli along with the new species Alveolina ozcani n. sp. that we include into the Alveolina elliptica group. We have also found Nummulites uroniensis, Nummulites obesus and Nummulites cf. verneuili and associated calcareous nannofossils that look reliable to make thoughtful correlations with the Shallow Benthic Zones (SBZ). The foraminiferal biostratigraphy suggests an assignment to the upper part of the lower Lutetian–lower part of the middle Lutetian, SBZ13 (Middle Eocene), further strengthened through the identification of the calcareous nannofossil NP14b–NP15b or CNE8–CNE10 biozones, providing a solid correlation with the global stratigraphic standards.

Combined application of microbial inoculant and kelp-soaking wastewater promotes wheat seedlings growth and improves structural diversity of rhizosphere microbial community

Industrial processing of kelp generates large amounts of kelp-soaking wastewater (KSW), which contains a large amount of nutrient-containing substances. The plant growth-promoting effect might be further improved by combined application of growth-promoting bacteria and the nutrient-containing KSW. Here, a greenhouse experiment was conducted to determine the effect of the mixture of KSW and Bacillus methylotrophicus M4-1 (MS) vs. KSW alone (SE) on wheat seedlings, soil properties and the microbial community structure in wheat rhizosphere soil. The available potassium, available nitrogen, organic matter content and urease activity of MS soil as well as the available potassium of the SE soil were significantly different (p < 0.05) from those of the CK with water only added, increased by 39.51%, 36.25%, 41.61%, 80.56% and 32.99%, respectively. The dry and fresh weight of wheat seedlings from MS plants increased by 166.17% and 50.62%, respectively, while plant height increased by 16.99%, compared with CK. Moreover, the abundance and diversity of fungi in the wheat rhizosphere soil were significantly increased (p < 0.05), the relative abundance of Ascomycetes and Fusarium spp. decreased, while the relative abundance of Bacillus and Mortierella increased. Collectively, the combination of KSW and the plant growth-promoting strain M4-1 can promote wheat seedlings growth and improve the microecology of rhizosphere microorganisms, thereby solving the problems of resource waste and environmental pollution, ultimately turning waste into economic gain.

A parsimonious approach to predict regions affected by sewer-borne contaminants in urban aquifers

Leaky urban drainage networks (UDNs) exfiltrating wastewater can contaminate aquifers. Detailed knowledge on spatiotemporal distributions of water-dissolved, sewer-borne contaminants in groundwater is essential to protect urban aquifers and to optimize monitoring systems. We evaluated the effect of UDN layouts on the spreading of sewer-borne contaminants in groundwater using a parsimonious approach. Due to the UDN’s long-term leakage behavior and the existence of non-degradable sewer-borne contaminants (equivalent to a conservative and constant contaminant source), we employed a concept of horizontal line sources to mimic the UDN layout. This does not require the consideration of bio-degradation processes or temporal delay and effectively bypasses the vadose zone, thus reducing computational requirements associated with a full simulation of leakages. We used a set of synthetic leakage scenarios which were generated using fractals and are based on a real-world UDN layout. We investigated the effects of typical leakage rates, varying groundwater flow directions, and UDN’s layouts on the shape of the contaminant plume, disregarding the resulted concentration. Leakage rates showed minimal effects on the total covered plume area, whereas 89% of the variance of the plume’s geometry is explained by both the UDN’s layout (e.g., length and level of complexity) and groundwater flow direction. We demonstrated the potential of applying this approach to identify possible locations of groundwater observation wells using a real UDN layout. This straightforward and parsimonious method can serve as an initial step to strategically identify optimal monitoring systems locations within urban aquifers, and to improve sewer asset management at city scale.

Low variation in microbial carbon sequestration between farmland and apple orchards in typical loess-covered regions

The cultivation of deep-rooted vegetation greatly alters the tradeoffs between water and carbon dynamics, yet their impact on microbial carbon sequestration (MCS) remains inadequately documented, particularly in thick vadose zones. This information is crucial for global climate mitigation and ecosystem service enhancement. As such, we collected triplicate samples for each land use type, exploring the abundance and structure of cbbL-harboring microbial communities within 10-m deep profiles under cultivated farmland and two apple orchards of varying ages (n = 72). Our findings indicated a shift from water-dominated (improved water retention at the expense of reduced carbon sequestration) to carbon-dominated benefits (enhanced carbon sequestration at the expense of decreased water retention) in deep soil layers (2–10 m) after the transformation from farmland to apple orchards. Despite the lack of significant differences among the three land use types, the gene abundances and microbial diversity indices reduced with soil depths because of variations in substrates, resources, and microenvironments. The cbbL-harboring microorganisms consisted of 5 phyla, 7 classes, 19 orders, 30 families, and 55 genera, with Proteobacteria as the predominant bacterial phylum. The relative contributions of different genera varied with soil depths, reflecting their distinct survival strategies. The microbial network was positively connected in various soil layers under farmland and apple orchards. Furthermore, the results of correlation, redundancy analysis, and structural equation modeling jointly indicated that plant roots and soil properties, including total nitrogen and organic carbon, governed MCS processes in deep unsaturated zones. Specifically, the low microbial variation between farmland and apple orchards can be attributed to the predominant effects of climatic and pedogenic factors on soil properties, the restricted contribution of plant roots to soil nutrient levels per unit depth, and the adverse effects of plant-induced ecohydrological consequences on root systems and microbial populations. This study offers new insights within thick vadose zones containing deep-rooted plants, thereby contributing to a better understanding of global terrestrial carbon cycle processes.

Wedge plasticity and a minimalist dynamic rupture model for the 2011 MW 9.1 Tohoku-Oki earthquake and tsunami

One crucial yet unanswered question about the 2011 MW 9.1 Tohoku-Oki earthquake and tsunami is what generated the largest tsunami (up to 40 m) along the Sanriku coast north of 39°N without large slip near the trench. A minimalist dynamic rupture model with wedge plasticity is presented to address this issue. The model incorporates the important variation of sediment thickness along the Japan Trench into the Japan Integrated Velocity Structure Model (JIVSM). By revising a heterogeneous stress drop model, the dynamic rupture model with a standard rate-and-state friction law can explain the GPS, tsunami, and differential bathymetry data (within data uncertainties) with minimum tuning. The rupture is driven by a large patch of stress drop up to ∼10 MPa near the hypocenter with significantly smaller stress drop (< 3 MPa) in the upper ∼10 km. The largest shallow slip reaches 75.67 m close to the trench north of hypocenter, which is caused by the large fault width, free surface, shallowly dipping fault geometry, and northwardly increasing sediment thickness, dominated by elastic off-fault response. North of large shallow slip zone, however, inelastic deformation of thick wedge sediments significantly controls the rupture propagation along trench, giving rise to slow rupture velocity (∼850 m/s), diminishing shallow slip, and efficient seafloor uplift. The short-wavelength inelastic uplift produces impulsive tsunami consistent with the observations off the Sanriku coast in terms of timing, amplitude, and pulse width. Wedge plasticity and variation of sediment thickness along the Japan Trench thus provides a self-consistent interpretation to the along-strike variation of near-trench slip and anomalous tsunami generation in the northern Japan Trench in this earthquake.