Salt Intrusion Research Articles

Study on the deterioration characteristics of aeolian sand concrete under the coupling effect of multiple factors in harsh environments.

This study takes the aeolian sand concrete as a research object, uses the relative dynamic elastic modulus to study its macro characteristics, and combines nuclear magnetic resonance、scanning electron microscope to study its pore characteristics and micro morphology under the action of prestress, freeze-thaw and salt intrusion. The results show that with the increase of the amount of aeolian sand, the dynamic elastic modulus of aeolian sand concrete shows a pattern of first decreasing, then increasing, and then decreasing; when no prestress is applied, the porosity of aeolian sand concrete first increases, then decreases, and then continues to increase. Among them, the porosity of aeolian sand concrete with a 40% content of aeolian sand decreases by 0.06% compared to that with a 0% content of aeolian sand, and decreases by 0.003% compared to that with a 60% content of aeolian sand; with the increase of prestress, the porosity of aeolian sand concrete with the same amount of aeolian sand increases gradually with the increase of damage degree. The porosity of concrete with 40% aeolian sand content increases by 0.33% when the damage degree is 0.0 compared to 0.3, with a 6.31% increase in the number of multi damage pores; under the coupling effect of multiple factors, when the amount of aeolian sand is 40%, the damage degree of the four groups of aeolian sand concrete before and after the coupling effect is 0.0, 0.1, 0.2, and 0.3, respectively, increases by 25.8%, 32.2%, 73.8%, and 85.8%, respectively; under the coupling effect of multiple factors, the content of aeolian sand is 60%, the damage degree is 0.2 and 0.3 groups, and the content of aeolian sand is 20%, the damage degree is 0.3 groups, which does not meet the standard requirements; under the coupling action of stress, freeze-thaw, salt intrusion and the amount of aeolian sand, the filling effect of aeolian sand on the internal pores of aeolian sand concrete decreases first, then increases, and then decreases with the increase of the amount of aeolian sand. The filling effect is further weakened after the action of stress. After the superposition of freeze-thaw and salt intrusion, the coupling effect of water and salt solution in frost heaving medium makes the variation law and range of physical and chemical characteristics of aeolian sand concrete show a great difference.

Study on the mechanical performance damage in laboratory-simulated periodic salt environment for asphalt concrete

The phenomenon of sustainable salt damage caused by soluble salt solutions in salt environments has raised concerns in asphalt pavement. However, the evaluation methods for salt erosion damage in asphalt concrete are limited, and there is a lack of comprehensive analysis of the composition of asphalt concrete. In this study, asphalt concrete specimens immersed in NaCl solution were subjected to dry-wet cycles and freeze-thaw cycles to analyze the erosion mechanisms of NaCl solution on their mechanical properties. The chemical stability and microstructure of asphalt after immersion in NaCl solution, as well as the microstructure and mechanical properties of aggregates after NaCl solution immersion and dry-wet cycles, were investigated. The results showed that NaCl solution has a softening effect on asphalt, promoting the intrusion of NaCl crystalline salt into the asphalt. The salt crystallization of NaCl solution altered the surface roughness of the aggregates, resulting in a decrease in skid resistance but an improvement in compressive strength. Specifically, limestone exhibited more stable mechanical properties than basalt. Meanwhile, the NaCl solution concentration has no significant impact on the mechanical performance of asphalt concrete initially, but its domination over mechanical performance gradually increases as the salt environment's cyclic effects intensify. The mechanisms of salt damage in asphalt concrete by NaCl solution mainly involve dry-wet cycles (crystal volume expansion), freeze-thaw cycles (ice volume expansion), and asphalt softening and viscosity reduction. The findings of this study provide a basis for the durability research of asphalt pavements in salt environments.

Development of Low-Cost IoT System for Monitoring Piezometric Level and Temperature of Groundwater

Rural communities in Mexico and other countries with limited economic resources require a low-cost measurement system for the piezometric level and temperature of groundwater for their sustainable management, since anthropogenic action (pumping extractions), natural recharge and climate change phenomena affect the behavior of piezometric levels in the aquifer and its sustainability is at risk. Decrease in the piezometric level under a balanced level promotes salt intrusion from ocean water to the aquifer, salinizing and deteriorating the water quality for agriculture and other activities; and a decrease in water level under the pumps or well drilling depth could deprive communities of water. Water temperature monitoring is essential to determine electric conductivity and dissolved salt content in groundwater. Using IoT technology, a device was developed that monitors both variables inside the well, and the ambient temperature and atmospheric pressure outside the well. The measurements are made in real time, with sampling every second and sending data to a dedicated server every 15 min so that the visualization can be accessed through a device with Internet access. The time series of the variables measured inside and outside the well were obtained over a period of three months in the rural community of Agua Blanca, Guasave, Sinaloa, Mexico. Through these records, a progressive temporary drawdown of the piezometric level is observed, as well as the frequency of pumping. This low-cost IoT system shows potential use in hydrological processes of interest such as the separation of regional and local flow, drawdown rates and recognition of geohydrological parameters.

Salt intrusion length in well-mixed Moroccan estuaries during infrequent events: a simple empirical equation development

ABSTRACT Infrequent events, such as periodical total moon or sun eclipses can affect the water resources in the estuaries. The Super Blue Blood Moon on (31/01/2018) and Total Solar eclipse on (21/08/2017) were investigated. The Bouregreg and Sebou estuaries (Morocco) were selected as an example location due to the availability of field survey data during infrequent events; and during these events both estuaries are well-mixed. Results showed that during these phenomena, the gravitational pull on the ocean is strong, so the high water is at its highest point and the low water at its lowest point. Water level rise affects the hydrodynamic balance and can increase salt water intrusion into the river estuaries, causing many ecological problems. The paper also presents a straightforward empirical equation for estimating salt intrusion length during high water levels. This equation proves valuable in offering initial estimates of salt intrusion length (LHWS) in estuaries during infrequent events in Moroccan estuaries.

Sensitivity of salt intrusion to estuary-scale changes: A systematic modelling study towards nature-based mitigation measures

Estuaries are among the most densely populated and heavily utilised regions in the world, where crucial functions – e.g., freshwater availability and water safety – strongly relate to the natural dynamics of the system. When developing nature-based solutions to safeguard these essential functions, a thorough understanding of estuarine dynamics is required. This study describes an elaborate sensitivity analysis on the salt intrusion length using an idealised estuary, which is parametrically designed using key estuary-scale parameters – e.g., river discharge and tidal flats – to cover a wide range of estuary classes. We were able to systematically investigate such a wide range of estuary classes due to the combination of (1) state-of-the-art hydrodynamic modelling software, (2) high performance computing, and (3) reduction and analysis techniques using machine learning. The results show that the extent of the estuarine salt intrusion length is largely determined by four estuarine features: (1) river discharge; (2) cross-sectional area (especially water depth); (3) tidal damping/amplification; and (4) tidal asymmetry. In general, the salt intrusion length shows clear correlations with (a combination of) estuary-scale parameters, which all put an upper limit on the salt intrusion length. These relations provide crucial insights for successful development of nature-based solutions to mitigate salt intrusion in estuarine environments.

Hydrochemical characteristics and salt intrusion in groundwater of the lower Chao Phraya river basin: Insights from stable isotopes and hydrochemical analysis

Saltwater intrusion is a significant hydrogeological challenge in coastal regions. This study investigates salt intrusion and hydrogeological processes in the Lower Chao Phraya River basin using stable isotopes and hydrochemical analysis. One Hundred groundwater wells sampled from different aquifers were analyzed for major ions spanning from 2010 to 2021, as well as stable isotopes specifically for the samples in the year 2021. The results reveal four distinct groundwater types: Ca(HCO3)2, NaHCO3, NaCl, and CaSO4, based on their predominant cations and anions. Shallow groundwater, which represents the discharge zone affected by salt intrusion, halite dissolution, and cation exchange reactions, exhibits a significant concentration of NaCl. Water-rock interactions play a crucial role in shaping groundwater chemistry, with carbonate dissolution and precipitation dominating the Ca(HCO3)2 type and silicate weathering influencing the CaSO4 type. The NaHCO3 type is associated with ion exchange and seawater intrusion. Silicate and carbonate rock weathering are the dominant processes in the region. Stable isotope analysis indicates that groundwater recharge primarily comes from rainfall and surface water, with limited contributions from deep sources. Overall, this study provides valuable insights into the hydrochemical characteristics and complex water-rock interactions within the groundwater system of the Chao Phraya River basin. As a result, it holds significant potential for informing effective groundwater management practices and facilitating resource planning in the region. Furthermore, the findings and methodologies presented here offer valuable lessons for addressing saltwater intrusion and hydrogeological challenges in other coastal regions worldwide.

Comprehensive approach to sustainable groundwater management in semi-arid Ninh Thuan plain, Vietnam

Vietnam is a country with a long coastline and a high population density residing in the coastal plains. The largest dry area in Vietnam, the coastal plain of Ninh Thuan province, always lacks water in the first dry months of the year (Jan., Feb., Mar., and Apr.). Groundwater is an extremely valuable resource for supplies at this time. Therefore, the objective of this study is to establish a comprehensive approach to sustainable groundwater management in this semi-arid region. This approach is not only mitigating the negative impacts of factors such as climate change, sea level rise, and socio-economic development but also suggesting measures for management of aquifer recharge. A groundwater model for a 3-layer system with variable density flow SEAWAT is built to predict the impacts of climate change and sea level rise without a change in groundwater abstraction. This model helps to understand the trend of salt intrusion and lowering groundwater level in the study area. Afterwards, scenarios with different ground water abstraction and groundwater development such as ground dam, infiltration basin have been set up to meet the demands of socio-economic development in the future. Predicted results will show the impacts of the groundwater systems in the area such as groundwater level change, and saltwater intrusion. Controlled groundwater abstraction and some measures of groundwater development such as infiltration basin, underground dam would allow for an increase of up to 50000m3/day in the year 2050 without negative impacts on the aquifer system.

Forecasting estuarine salt intrusion in the Rhine–Meuse delta using an LSTM model

Abstract. Estuarine salt intrusion causes problems with freshwater availability in many deltas. Water managers require timely and accurate forecasts to be able to mitigate and adapt to salt intrusion. Data-driven models derived with machine learning are ideally suited for this, as they can mimic complex non-linear systems and are computationally efficient. We set up a long short-term memory (LSTM) model to forecast salt intrusion in the Rhine–Meuse delta, the Netherlands. Inputs for this model are chloride concentrations, water levels, discharges and wind speed, measured at nine locations. It forecasts daily minimum, mean and maximum chloride concentrations up to 7 d ahead at Krimpen aan den IJssel, an important location for freshwater provision. The model forecasts baseline concentrations and peak timing well but peak height is underestimated, a problem that becomes worse with increasing lead time. Between lead times of 1 and 7 d, forecast precision declines from 0.9 to 0.7 and forecast recall declines from 0.7 to 0.5 on average. Given these results, we aim to extend the model to other locations in the delta. We expect that a similar setup can work in other deltas, especially those with a similar or simpler channel network.

The hyperturbid mesotidal Guadalquivir estuary during an extreme turbidity event: Identifying potential management strategies

The Guadalquivir estuary (SW Iberian Peninsula) is a mesotidal system within a Mediterranean climatic region. It experiences severe and persistent hyperturbid conditions during the wet and cold season, significantly impacting both the ecosystem and various economic activities.During an investigation of an extreme turbidity event, suspended particulate matter (SPM) concentrations exceeding 30 g/L were found near the salt intrusion limit, with a 45 km stretch showing a depth-averaged SPM concentration greater than 10 g/L. Throughout this event, the estuary can accumulate more than 900,000 tonnes of SPM, leading to severe surface light blockage, with the euphotic layer remaining shallower than 10 cm in most areas. Additionally, hypoxia develops in the zone of maximum turbidity, near the bottom.These extreme turbidity events are linked to short-duration freshets that discharge a large amount of sediment from a highly erodible catchment area, followed by a significant reduction in river flow, primarily due to strong water regulation. However, hyperturbid conditions never extend into the summer in this estuary, indicating a non-negligible capacity to clear the SPM.Considering these findings, several recommendations are proposed. First, establishing a monitoring programme for extreme turbidity processes can aid in implementing necessary management actions. Second, it is crucial to develop an optimal protocol for water discharges from the network of dams to maximise sediment export to the sea, minimise plankton washout, and prevent excessive freshwater loss.

Groundwater chemistry and entropy weighted water quality index of tsunami affected and ecologically sensitive coastal region of India

Quality groundwater is the most essential prerequisite for the better livelihood of the coastal villages and a vital resource for a safe living. Seawater interaction and coastal inundation modify hydro geochemical cycles leading to gross utility as a challenge. Poor quality water intake causes diseases and seriously affects human health. In this study, the suitability of shallow drinking water sources (10–15 m) has been studied with a focus on coastal village in south west of India (Alappad coast, Kollam, Kerala) which is a host of huge placer mineral reserve of the country. This coastal stretch has good deposition of Late Quaternary sediments of heavy mineral placers subjected to severe seawater interactions. Mineralogically, garnet and heavy minerals comprises the beaches and most coastal plains of the Alappad. A concerted geological process where moving water and waves causes erosion, leads to lowering of the earth's surface -is prominent in this fragmented land. This study critically evaluates the temporal-spatial impact of these interactions in an age of varying climatic conditions and hence for reference beyond. Water quality index analysis has been attempted using the entropy weighted water quality index (EWQI) method for a total of 45 samples (15 samples season-wise). It aims to ascertain better choices of groundwater sources for domestic uses for isolated settlers endowed with estuaries, and old coastal plains with barrier beaches. Irrigation suitability was evaluated using sodium adsorption ratio (SAR) and Na%. Observed EWQ Indices (38.2 ± 14.5) for post-monsoon (80% samples), (66.1 ± 77.7) for monsoon (66% samples), and (71.4 ± 71.3) for pre-monsoon (53% samples) fall in excellent category. Post-monsoon is most favoured for a better quality groundwater as evidenced by WQI of 80% among the samples tested. Ca–HCO3 is the dominant hydrochemical type observed. The mean value of iron (0.9 ± 1.3 mg/L) exceeded the permissible limit of 0.3 mg/L during monsoon season due to mineral-water interactions. In pre-monsoon season the parameters Na+ (95.9 ± 200.7 mg/L), Cl− (173.4 ± 510.2 mg/L), EC (1559.3 ± 2510.6 μS/cm), and TDS (492.5 ± 629.7 mg/L) were observed in higher ranges. Significant correlation (p < 0.05) prevailed between EWQI, and parameters-conductivity (0.75), TDS (0.75), Iron (0.59), Ca2+ (0.66), and Mg2+ (0.74). Principal component analysis (PCA) on chemical parameters accounted for the total variance of 84.2% in pre-monsoon, 89.9% in monsoon and 82.9% in post-monsoon. Groundwater quality is influenced by geochemical processes, salt intrusion, and human activities like fertiliser application and domestic sewage discharge. Hierarchical cluster analysis (HCA) grouped the samples into three clusters. Cluster 3 represents poor quality water (13%) in pre-monsoon (EWQI ranged 32.2–192.7), and monsoon (EWQI ranged 171.8–309.7). Cluster 3 in post-monsoon (20%) indicating good water quality (EWQI ranged 51.4–72.6). Ultimate finding is that post-monsoon groundwater is more suitable for drinking and domestic purposes for the selected coastal area.

The effect B impurity and Xe intrusion in the graphite moderator on void reactivity feedback of thermal MSR

Thermal Molten Salt Reactor (MSR) massively utilizes graphite as both moderator and reflector. The molten fuel circulates around the primary loop and directly contacts with the graphite. Gaseous fission products, such as neutron poison Xe-135, are normally separated out from the core. However, deposition of Xe-135 in graphite could take place through direct Xe-135 intrusion into graphite pores, or salt intrusion that eventually undergoes fission in the graphite and leaves the Xe-135 inside. Another possible way of strong neutron absorber deposition in the graphite is boron impurity. Beside reducing the core excess reactivity, the existence of strong neutron absorbers in graphite could alter the core reactivity feedbacks. Thus, this study is meant to analyse the effects of Xe-135 and natural boron deposition in the graphite to the core reactivity feedbacks. The evaluations were done by monte Carlo calculations on their effects on void coefficient, fuel, and moderator temperature reactivity feedbacks. The introduction of void into under-moderated thermal MSR core generally produces positive void reactivity feedback. The deposition of strong neutron absorbers in the graphite decreases the void reactivity coefficient, yet still positive. Despite of core excess reactivity loss, the existence of strong neutron absorber in the graphite is favourable in safety point of view.

ESTUARINE SENSITIVITY TO NATURE-BASED SALT INTRUSION MITIGATION MEASURES

All around the world, deltas are among the most densely populated and heavily utilised regions, where crucial functions, such as freshwater availability and safety against flooding, strongly relate to the natural dynamics of the system. Therefore, a thorough understanding of the estuarine system is crucial, especially when developing nature-based solutions for safeguarding these essential functions for today’s society as well as future generations. To better understand the effect of different estuarine parameters on salt intrusion, an extensive sensitivity analysis has been executed based on an idealised estuary layout. The idealised estuary is parametrically designed using thirteen parameters that represent both boundary conditions and geometric features, such as river discharge and water depth. Subsequently, the Delft3D Flexible Mesh (DFM) model has been used to determine the salt intrusion, allowing the exploration of a wide range of estuary layouts.

Seal failure and fluid flow in salt-bearing sedimentary basins: A critical example from the Espírito Santo basin, SE Brazil

Salt giants are viewed as competent seals for sub-salt fluids. Yet, salt can reveal large inter-crystalline and polyhedral permeability when deeply buried and a certain fluid pressure threshold is reached. This work uses high-resolution three-dimensional (3D) seismic data to explain the processes favouring fluid flow in areas affected by salt tectonics, with emphasis on deformed salt structures offshore Espírito Santo (SE Brazil). Documented fluid flow features include pockmarks, dissolution related pockmarks on the crest of salt structures, gas chimneys, bright spots, polygonal fault systems, and pushed-down reflections within salt structures. Offshore Espírito Santo, fluid was sourced: a) from sub-salt compartments, b) through hydrite dewatering processes, c) through slabs in salt-withdraw basins, d) from deformed strata within salt structures, and e) from supra-salt fluids that migrated through the flanks of salt structures. Focused fluid flow on the crests of salt giants may evolve to active salt intrusion when overburden rocks are <1200 m thick, depending on the intensity of regional halokinesis. The crests of salt structures are also important fluid flow paths, particularly when developing closely-spaced fault families. As a corollary, the interpreted data show that salt dissolution and intra-salt deformation are important processes accompanying the migration of fluid into faulted supra-salt strata or evolving into active diapirism. Our study has important implications to understand salt seal breaching mechanisms around the globe.

The Influence of Metakaolin and Polypropylene Fiber Concrete on Mechanics Properties and Microstructure Combined Action under Multi-Salt Soaking and Freeze-Thaw.

The wide distribution of alpine saline areas in China is faced with two major problems, which are salt intrusion and freeze-thaw. In total, 216 specimens were prepared with 6 kinds of concrete mix proportions in this paper. The effects of the single and compound incorporation of metakaolin (MK) and polypropylene fiber (PPF) of different amounts on the mechanical properties and microstructure properties of concrete were investigated under the dual action of multi-salt (NaCl, MgCl2, Na2SO4, and NaHCO3) soaking and freeze-thaw. Potable water and freeze-thaw concrete were adopted as the control group. Changes in the appearance morphology, mass loss, relative dynamic elastic modulus, and compressive strength of the concrete were tested, and the microstructure of the concrete was analyzed by scanning electron microscopy (SEM). The results showed that an admixture of both MK and PPF in the potable water and freeze-thaw cycle test can improve the mechanical properties and frost resistance of concrete. The admixture of PPF can effectively improve the mechanical properties and frost resistance of concrete. However, the admixture of MK failed to improve the mechanical properties and frost resistance of concrete during multi-salt soaking and freeze-thaw. The frost resistance of concrete under multi-salt soaking and freeze-thaw was optimally improved with 10% MK and 0.6 kg/m3 PPF. Its microstructure shows that PPF can effectively inhibit crack propagation and reduce the deterioration of concrete under multi-salt soaking and freeze-thaw.

Road salt intrusion dynamics in an ex-urban native wetland complex

Inland freshwater wetlands throughout the northern U.S. and Canada are experiencing an increase in salinity due to road salt runoff during winter months. Salinization affects soil texture, contaminant transport, microbial activity, and plant growth in wetlands. Therefore, there is a pressing need to understand the dynamics of road salt intrusion in urbanized freshwater ecosystems. We used distributed high-resolution sensors to evaluate the dynamics of road salt intrusion into a wetland complex, Gensburg Markham Prairie (GMP), located in the ex-urban area outside Chicago, Illinois (USA). The in situ sensors measure electrical conductivity (EC), surface and groundwater level, precipitation, water temperature, and air temperature at 30-minute intervals. Water samples were collected monthly from 13 shallow groundwater wells and eight surface water locations and analyzed for Cl-, Mg2+, Na+, Ca2+, and K+. Two-years of continuous data show periodic spikes in EC during winter months, generally by an order-of-magnitude, due to intrusion of road salt applied on nearby roads. However, this behavior was not evident from monthly water samples, indicating that traditional water quality sampling methods likely miss such abrupt salt intrusion dynamics caused by rapid snowmelt runoff events. Higher levels of EC and Cl- occurred at the periphery of GMP near roadways, as well as in a preferential flow path to the interior of the wetland. Spectral analysis of EC time-series in ditches suggests that there is no correlation between salinity dynamics at super-annual timescales. This indicates that the salinity dynamics at GMP are event-driven, and the introduced solutes are rapidly exported from the site. This research supports development of improved de-icing strategies by local agencies and informs site-specific management of wetland ecosystems under anthropogenic stressors.

Identification of quantitative trait loci controlling nitrogen use efficiency-related traits in rice at the seedling stage under salt condition by genome-wide association study.

Rice cultivation is facing both salt intrusion and overuse of nitrogen fertilizers. Hence, breeding new varieties aiming to improve nitrogen use efficiency (NUE), especially under salt conditions, is indispensable. We selected 2,391 rice accessions from the 3K Rice Genomes Project to evaluate the dry weight under two N concentrations [2.86 mM - standard N (SN), and 0.36 mM - low N (LN)] crossed with two NaCl concentrations [0 (0Na) and 60 mM (60Na)] at the seedling stage. Genome-wide association studies for shoot, root, and plant dry weight (DW) were carried out. A total of 55 QTLs - 32, 16, and 7 in the whole, indica, and japonica panel - associated with one of the tested traits were identified. Among these, 27 QTLs co-localized with previously identified QTLs for DW-related traits while the other 28 were newly detected; 24, 8, 11, and 4 QTLs were detected in SN-0Na, LN-0Na, SN-60Na, and LN-60Na, respectively, and the remaining 8 QTLs were for the relative plant DW between treatments. Three of the 11 QTLs in SN-60Na were close to the regions containing three QTLs detected in SN-0Na. Eleven candidate genes for eight important QTLs were identified. Only one of them was detected in both SN-0Na and SN-60Na, while 5, 0, 3, and 2 candidate genes were identified only once under SN-0Na, LN-0Na, SN-60Na, and LN-60Na, respectively. The identified QTLs and genes provide useful materials and genetic information for future functional characterization and genetic improvement of NUE in rice, especially under salt conditions.

Salinity Modeling Using Deep Learning with Data Augmentation and Transfer Learning

Salinity management in estuarine systems is crucial for developing effective water-management strategies to maintain compliance and understand the impact of salt intrusion on water quality and availability. Understanding the temporal and spatial variations of salinity is a keystone of salinity-management practices. Process-based numerical models have been traditionally used to estimate the variations in salinity in estuarine environments. Advances in data-driven models (e.g., deep learning models) make them effective and efficient alternatives to process-based models. However, a discernible research gap exists in applying these advanced techniques to salinity modeling. The current study seeks to address this gap by exploring the innovative use of deep learning with data augmentation and transfer learning in salinity modeling, exemplified at 23 key salinity locations in the Sacramento–San Joaquin Delta which is the hub of the water-supply system of California. Historical, simulated (via a hydrodynamics and water quality model), and perturbed (to create a range of hydroclimatic and operational scenarios for data-augmentation purposes) flow, and salinity data are used to train a baseline multi-layer perceptron (MLP) and a deep learning Residual Long-Short-Term Memory (Res-LSTM) network. Four other deep learning models including LSTM, Residual Network (ResNet), Gated Recurrent Unit (GRU), and Residual GRU (Res-GRU) are also examined. Results indicate that models pre-trained using augmented data demonstrate improved performance over models trained from scratch using only historical data (e.g., median Nash–Sutcliffe efficiency increased from around 0.5 to above 0.9). Moreover, the five deep learning models further boost the salinity estimation performance in comparison with the baseline MLP model, though the performance of the latter is acceptable. The models trained using augmented data are then (a) used to develop a web-based Salinity Dashboard (Dashboard) tool that allows the users (including those with no machine learning background) to quickly screen multiple management scenarios by altering inputs and visualizing the resulting salinity simulations interactively, and (b) transferred and adapted to estimate observed salinity. The study shows that transfer learning results more accurately replicate the observations compared to their counterparts from models trained from scratch without knowledge learned and transferred from augmented data (e.g., median Nash–Sutcliffe efficiency increased from around 0.4 to above 0.9). Overall, the study illustrates that deep learning models, particularly when pre-trained using augmented data, are promising supplements to existing process-based models in estuarine salinity modeling, while the Dashboard enables user engagement with those pre-trained models to inform decision-making efficiently and effectively.

Explaining the Statistical Properties of Salt Intrusion in Estuaries Using a Stochastic Dynamical Modeling Approach

AbstractDetermining the statistical properties of salt intrusion in estuaries on sub‐tidal time scales is a substantial challenge in environmental modeling. To study these properties, we here extend an idealized deterministic salt intrusion model to a stochastic one by including a stochastic model of the river discharge. In the river discharge model, two types of stochastic forcing are used: one independent (additive noise) and one dependent (multiplicative noise) on the river discharge state. Each type of forcing results in a non‐Gaussian response in the salt intrusion length, which we consider here as the distance of the 2 psu isohaline contour to the estuary mouth. The salt intrusion model including both types of stochastic forcing in the river discharge provides a satisfactory explanation of the multi‐year statistics of observed salt intrusion lengths in the San Francisco Bay estuary, in particular for the skewness of its probability density function.

A neutron tomography study to visualize fluoride salt (FLiNaK) intrusion in nuclear-grade graphite

Manufactured graphite is a preferred material for in-core components of molten salt reactors and fluoride salt-cooled high-temperature reactors, which are in permanent contact with liquid salts. However, owing to the porous nature of nuclear graphite, under certain conditions, molten salts may intrude graphite's pores and affect graphite's properties and functionality. Therefore, a better understanding of molten salt intrusion (distribution across sample cross section and penetration depth) is needed to assess its effects. In this work, we have demonstrated the use of neutron imaging (computed tomography) in the evaluation of salt penetration and distribution of a wide range of graphite grades with diverse microstructures that have been subjected to FLiNaK (LiF–NaF–KF) intrusion at 750 °C and 5 bar pressure for 12 h. Because of the great neutron attenuation contrast from scattering and adsorption between Li (from FLiNaK) and the graphite matrix, we have obtained direct visualization of FLiNaK salt distribution in the salt-impregnated graphites for the first time. Three-dimensional reconstructed images and cross-sectional concentration profiles demonstrate that salt penetration and density distribution are greatly dependent on the microstructural properties of the graphite grade.

Vulnerability and Resilience to Drought and Saltwater Intrusion of Rice Farming Households in the Mekong Delta, Vietnam

Adverse impacts of climate and environmental hazards are unevenly distributed between socioeconomic groups due to differences in exposure, vulnerability and resilience. This study examines the distribution of vulnerability and resilience to drought and salt intrusion impacts among rice farmers in the rural Mekong Delta in Vietnam. By defining both aspects independently, we can study potential differences in the socio-economic factors that steer them and analyse how these two aspects of adaptive capacity are related. Using fixed-effect regressions, we find that poorer communes are more vulnerable to direct environmental impacts (loss in rice yield). Several household characteristics that reflect a low socioeconomic status, such as low asset values, small plots, and limited education level, are linked with higher vulnerability to direct drought impacts. High vulnerability does, however, not necessarily translate to low resilience, which we proxy by measuring indirect impacts (loss in household income). Several household activities and characteristics help mitigate indirect impacts. Our results suggest that the least resilient household group consists of smallholder, asset-low households that are unable to diversify to non-crop agriculture or off-farm employment. Supportive policies targeting this particular socioeconomic group to enable transition to non-crop or off-farm labour would substantially improve their resilience to future environmental events. Distinguishing between resilience and vulnerability enables a broader understanding of the mechanisms influencing the distribution of direct and indirect adverse impacts, which enables drafting targeted policy measures for specific socioeconomic groups.