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Intertidal groundwater springs provide thermally stable, nutrient‐rich freshwater that causes fine‐scale variability in water temperature and salinity and promotes biodiversity in coastal estuaries and lagoons. In this study, we combined three thermal sensing techniques to elucidate summer water temperature patterns at the mouths of intertidal groundwater springs and the ambient coastal lagoon in Prince Edward Island, Canada. Thermal infrared imagery captured the spatiotemporal variability in relative temperatures of the lagoon channel and cold‐water plumes from the springs. Thermal anomalies due to the springs were detected at the surface throughout a tidal cycle, suggesting that the thermal plumes were buoyant. Fiber‐optic distributed temperature sensing paired with temperature loggers near the spring outlets recorded groundwater temperatures at low tide (~ 7°C) but ambient lagoon temperatures (up to 26°C) at high tide due to the vertical thermal gradient in the stratified water column. Calculated estuarine Richardson numbers throughout the study confirm intertidal spring buoyancy due to salinity differences. The fiber‐optic distributed temperature sensing results revealed pronounced variations in temperature as evidenced by spatial (3.7°C) and temporal (5.5°C) standard deviations over the cable length during the study and lower mean lagoon bed water temperatures at high tide (22.5°C) than low tide (24.3°C) due to heat advection from tidal pumping. Lagoon temperatures fluctuate at diurnal (solar) and semi‐diurnal (tidal) frequencies. The findings emphasize the efficacy of a multi‐technology approach to reveal fine‐scale and dynamic thermal processes that drive temperature patterns and habitat distribution in coastal lagoon ecosystems and highlight the thermal influence of intertidal springs.

The distribution and state of subsea permafrost is largely unknown. Present maps, which rely heavily on model results, suggest that subsea permafrost is confined to the Beaufort, Siberian and Laptev seas. Here we show that discontinuous subsea permafrost exists along the Labrador coast (56 °N) under the influence of the Labrador Coastal Current. High-resolution bathymetric data reveal the presence of subsea thermokarst environments on the coastal seabed of Nain, Nunatsiavut, where an ice-rich sediment sample was recovered in July 2022 at a water depth of 27 m. Porewater analysis indicates that ground ice can persist in the sediments due to freshened submarine groundwater seepage that freezes at higher temperatures (0 °C) than seawater (−1.8 °C). The formation and preservation of subsea permafrost landforms is due to cold waters of the Labrador Coastal Current entering the coastal areas and remaining less than 0 °C for most of the year. Therefore, evidence of subsea permafrost landforms in coastal Labrador and the distribution of cold bottom water in the Northern Hemisphere suggests that subsea permafrost is likely to be preserved elsewhere in subarctic regions, especially where freshened submarine groundwater seepage elevates the freezing temperature. This highlights the potential underestimation of subsea permafrost in the world’s coastal oceans.

Aquifers contain the largest store of unfrozen freshwater, making groundwater critical for life on Earth. Surprisingly little is known about how groundwater responds to surface warming across spatial and temporal scales. Focusing on diffusive heat transport, we simulate current and projected groundwater temperatures at the global scale. We show that groundwater at the depth of the water table (excluding permafrost regions) is conservatively projected to warm on average by 2.1 °C between 2000 and 2100 under a medium emissions pathway. However, regional shallow groundwater warming patterns vary substantially due to spatial variability in climate change and water table depth. The lowest rates are projected in mountain regions such as the Andes or the Rocky Mountains. We illustrate that increasing groundwater temperatures influences stream thermal regimes, groundwater-dependent ecosystems, aquatic biogeochemical processes, groundwater quality and the geothermal potential. Results indicate that by 2100 following a medium emissions pathway, between 77 million and 188 million people are projected to live in areas where groundwater exceeds the highest threshold for drinking water temperatures set by any country.

Oceanic storms can strongly disturb the physical and biogeochemical conditions of transitional coastal waters. Impacts of extreme oceanic storms on coastal ecosystems have received limited attention worldwide, with no studies at higher latitudes (> 45°) where tropical cyclones have usually abated. This study investigates the combined impacts from marine and atmospheric forcing on a coastal lagoon in Prince Edward Island, Canada, during and after Extratropical Cyclone Fiona in September 2022. Physical (water levels and temperature) and biogeochemical (dissolved oxygen [DO], electrical conductivity, pH, nitrate–nitrogen concentrations, total suspended solids [TSS]) datasets from the lagoon and the watershed's tributaries, groundwater springs, and piezometers were used to assess ecosystem disturbance and recovery timelines following the storm. Fiona resulted in a 1.6 m storm surge into the lagoon that elevated water temperatures by up to 6°C, disturbed the density‐dependent stratification of salinity and temperature, and reduced the diel amplitude of DO, indicating a reduction in plant respiration due to ecosystem disturbance. The freshwater tributaries revealed sharp changes in flow (30‐fold increase), nitrate–nitrogen (NO3‐N) concentrations and loading (70‐fold increase), and TSS loading (40‐fold increase) to the lagoon during and immediately following the storm. The lagoon rapidly recovered (hours) from the hydraulic disturbance of the storm surge, but elevated nutrient levels persisted for months. The intensity and frequency of extratropical cyclones is projected to increase in the Northwest Atlantic, making field‐based studies of cyclone impacts on coastal waters critical for understanding future coastal ecosystem disturbance and recovery periods relative to the timing of future storms.

Respiration in intertidal salt marshes generates dissolved inorganic carbon (DIC) that is exported to the coastal ocean by tidal exchange with the marsh platform. Understanding the link between physical drivers of water exchange and chemical flux is a key to constraining coastal wetland contributions to regional carbon budgets. The spatial and temporal (seasonal, annual) variability of marsh pore water exchange and DIC export was assessed from a microtidal salt marsh (Sage Lot Pond, Massachusetts). Spatial variability was constrained from 224Ra : 228Th disequilibria across two hydrologic units within the marsh sediments. Disequilibrium between the more soluble 224Ra and its sediment‐bound parent 228Th reveals significant pore water exchange in the upper 5 cm of the marsh surface (0–36 L m−2d−1) that is most intense in low marsh elevation zones, driven by tidal overtopping. Surficial sediment DIC transport ranges from 0.0 to 0.7 g C m−2d−1. The sub‐surface sediment horizon intersected by mean low tide was disproportionately impacted by tidal pumping (20–80 L m−2d−1) and supplied a seasonal DIC flux of 1.7–5.4 g C m−2d−1. Export exceeded 10 g C m−2d−1for another marsh unit, demonstrating that fluxes can vary substantially across salt marshes under similar conditions within the same estuary. Seasonal and annual variability in marsh pore water exchange, constrained from tidal time‐series of radium isotopes, was driven in part by variability in mean sea level. Rising sea levels will further inundate high marsh elevation zones, which may lead to greater DIC export.

Depuis le milieu des années 2010, les approches bayésiennes sont parfois utilisées pour l'analyse des essais contrôlés randomisés (ECR) évaluant l'efficacité des médicaments. Bien que ces approches permettent une interprétation directe (en donnant la probabilité de supériorité par rapport au contrôle), l'introduction : d'information a priori peut modifier l'estimation de l'effet du traitement. En outre, alors que les seuils standards pour le risque de faux positifs dans l'inférence fréquentiste sont depuis longtemps acceptés par les agences d'enregistrement et d'accès au marché, l'expérience reste encore limitée avec les méthodes bayésiennes. L'objectif principal de cette étude est de décrire les priorset les seuils de décision utilisés dans les essais contrôlés randomisés de phase 2 et 3 évaluant l'efficacité des médicaments.

Coastal flooding transforms barrier island morphology and rapidly salinizes freshwater lenses that support island populations and ecosystems. Climate change is expected to increase coastal flood risks, and understanding future island vulnerability requires understanding erosion and salinization processes and their feedbacks. This study investigates how island morphology and groundwater salinity distributions on Hog Island, Prince Edward Island, Canada, responded to high water levels during post‐tropical storm Fiona (24 September 2022), the costliest hurricane to make landfall in Canadian history. Island morphology was monitored with drone‐based LiDAR, and beach groundwater dynamics were investigated with frequency‐domain electromagnetic geophysics surveys and monitoring wells. Comparing pre‐storm and post‐disturbance data revealed high dune scarping that thinned the ocean‐side foredune by 12.3 m on average and reduced the total island volume by 12%. Beach groundwater levels and electrical conductivity increased by up to 2 m and 19 mS cm−1, respectively, and the freshwater lens was lost under the eroded foredune. Measurements 9 months after the storm revealed early‐stage recovery of the foredune; however, high dune scarping prolonged recovery, and the island volume only increased by 1%. Without a stable ocean‐side foredune, the landward extent of recurring coastal flooding increased and limited freshwater flushing and aquifer recovery. Results indicate that rapid erosion from extreme coastal storms shifts coastal boundaries, salinizes formerly freshwater resources, and limits freshwater recovery. These findings emphasize the importance of understanding the often‐overlooked interconnections between coastal flooding, erosion, and groundwater salinization to effectively manage coastal resources in an age of environmental change. Rising sea levels and more frequent storm surges will increase coastal flooding events that erode barrier island coastlines and salinize fresh groundwater. This poses a risk to economic assets, ecosystems, and potable water resources along island coasts. This study monitored changes in shoreline position and groundwater salinity following a tropical cyclone that impacted a barrier island in Prince Edward Island, Canada. Results show that high water levels and associated beach flooding drive rapid erosion and groundwater salinization. After the storm, seawater flooding increases along the eroded coastline, limiting recovery of the high‐elevation dunes and groundwater freshening. Collected data show that the state of coastal dunes controls the distribution of fresh groundwater on barrier islands, and rapid erosion can have prolonged but often overlooked impacts on available freshwater. These findings have important implications for understanding and managing coastal flood risks and water security on barrier islands in a changing climate. Morphologic and hydrogeologic monitoring captured related coastal flooding, erosion, and beach aquifer salinization following a hurricaneHigh water levels drove extensive foredune scarping, which reduced island width and increased flooding and rapid seawater intrusionSlow recovery from dune scarping increases the landward extent of flood inundation during moderate water levels and prolongs aquifer recovery Morphologic and hydrogeologic monitoring captured related coastal flooding, erosion, and beach aquifer salinization following a hurricane High water levels drove extensive foredune scarping, which reduced island width and increased flooding and rapid seawater intrusion Slow recovery from dune scarping increases the landward extent of flood inundation during moderate water levels and prolongs aquifer recovery

Oscillatory pumping tests presents a potential advancement in aquifer testing as they minimize hydraulic perturbations and result in no net water abstraction or injection. However, aquifer property estimates can be less accurate if they are compromised by well head losses during the pumping test. Currently, oscillatory pumping test models ignore these losses. The objective of this study is to develop and evaluate an analytical solution that can interpret oscillatory pumping test data affected by rate‐dependent skin losses. Accordingly, the sensitivity of the drawdown response to small variations in aquifer and well parameters was analyzed. In addition, a previous field aquifer test was analyzed to evaluate the feasibility of the solution for aquifer parameter estimation. The results indicate that neglecting the rate‐dependent skin effect can lead to substantial errors in the determination of aquifer parameters such as transmissivity and storativity. Additionally, the proposed solution effectively reproduces the sharp groundwater level peaks observed in field data, whereas the solution that does not consider the rate‐dependent skin effect greatly underestimates the peak values. This study looks at a new method called the oscillatory pump test for measuring aquifer properties. There can be problems with obtaining accurate results when testing aquifer properties, because there can be a loss of water at the top of the well. This study aims to solve this problem by creating a new solution that can account for this loss of water and still yield accurate results. The study found that ignoring this loss of water can lead to significant errors in the estimation of the aquifer properties. The study shows that when the value of the loss of water is over 10,000 min/m3, it can have a substantial effect on the accuracy of the results. Overall, this study improves our ability to estimate aquifer properties using the oscillatory pumping test method. An analytical solution is developed for oscillatory pumping tests with rate‐dependent skinThe effects of rate‐dependent skin on the head response are evident in field dataNeglecting rate‐dependent skin can lead to biased estimates of aquifer parameters An analytical solution is developed for oscillatory pumping tests with rate‐dependent skin The effects of rate‐dependent skin on the head response are evident in field data Neglecting rate‐dependent skin can lead to biased estimates of aquifer parameters

Small‐island populations disproportionately rely on fresh groundwater resources, which are increasingly threatened by salinization from changing ocean and climate conditions. This study investigates island groundwater dynamics and salinization over multiple timescales in response to marine, atmospheric, and morphologic drivers. New geophysical and hydrological data sets were collected on a remote sand island in the Northwest Atlantic Ocean between 2020 and 2022 and compared to historical baseline data from the 1970s. Data reveal saltwater intrusion due to multi‐decadal erosion, seasonal climate patterns, tidal forcing, and episodic flooding from Atlantic hurricanes. Long‐term dune erosion has caused the freshwater lens to thin and become asymmetrical; however, a lagged groundwater response causes the freshwater lens to be in disequilibrium with present island morphology. The maximum vertical lens thickness is seasonally constant, but the lateral transition zone along the coast thickens and moves seaward in spring when the water table is high from precipitation and frequent beach flooding. Groundwater level and electrical conductivity along low‐lying beaches significantly increase following Atlantic hurricanes due to seawater flooding, and reach a maximum of 1.93 m above sea level and 38 mS/cm, respectively. While groundwater levels recover quickly, conductivity (salinity) remains elevated due to the short intervals between winter flood events that outpace freshening from meteoric recharge. Results emphasize the importance of multi‐temporal groundwater dynamics and feedbacks between coastal flooding, erosion, and salinization. Field‐based studies considering multiple drivers and timescales of saltwater intrusion are critical for understanding and managing coastal freshwater resources in an age of rapid environmental change. Small island communities rely on groundwater for freshwater supply that is increasingly threatened by salinization. Along the coast, erosion, seasonal changes in atmospheric conditions, and sea levels control groundwater salinity changes over multiple timescales. We collected groundwater data and compared the present distribution and salinity of groundwater to results from monitoring conducted in the 1970s. In this work we show that decades of erosion, seasonal wave and precipitation patterns, tides, and intermittent seawater flooding drive freshwater decline on Sable Island, Nova Scotia, Canada. Long‐term erosion and dune loss along the south coastline has caused widespread salinization. Seawater flooding rapidly salinizes groundwater, and repeat flood events prevent groundwater recovery. These processes are connected as storm surges can erode coastal dunes and increase the future extent of flooding and salinization. These findings have important implications for understanding and managing coastal fresh groundwater resources over short and long timescales. Geophysical and in‐situ monitoring reveals island groundwater salinization from different drivers operating at different time scalesCoastal flooding drives episodic, vertical saltwater intrusion, and aquifer recovery is prolonged by frequent stormsContinuous morphologic change drives saltwater intrusion and causes fresh groundwater to be in disequilibrium with island morphology Geophysical and in‐situ monitoring reveals island groundwater salinization from different drivers operating at different time scales Coastal flooding drives episodic, vertical saltwater intrusion, and aquifer recovery is prolonged by frequent storms Continuous morphologic change drives saltwater intrusion and causes fresh groundwater to be in disequilibrium with island morphology

Temperature can be used to trace groundwater flows due to thermal disturbances of subsurface advection. Prior hydrogeological studies that have used temperature‐depth profiles to estimate vertical groundwater fluxes have either ignored the influence of climate change by employing steady‐state analytical solutions or applied transient techniques to study temperature‐depth profiles recorded at only a single point in time. Transient analyses of a single profile are predicated on the accurate determination of an unknown profile at some time in the past to form the initial condition. In this study, we use both analytical solutions and a numerical model to demonstrate that boreholes with temperature‐depth profiles recorded at multiple times can be analyzed to either overcome the uncertainty associated with estimating unknown initial conditions or to form an additional check for the profile fitting. We further illustrate that the common approach of assuming a linear initial temperature‐depth profile can result in significant errors for groundwater flux estimates. Profiles obtained from a borehole in the Veluwe area, Netherlands in both 1978 and 2016 are analyzed for an illustrative example. Since many temperature‐depth profiles were collected in the late 1970s and 1980s, these previously profiled boreholes represent a significant and underexploited opportunity to obtain repeat measurements that can be used for similar analyses at other sites around the world. Repeated temperature‐depth profiles provide an excellent opportunity to study the transience of subsurface heat flow processesThe classic approach to infer ground water flow from temperature‐depth profiles disturbed by surface warming has serious shortcomingsNovel analytical approaches provide good estimates of groundwater flow when used on repeated temperature‐depth profiles

Alpine watersheds source major rivers throughout the world and supply essential water for irrigation, human consumption, and hydroelectricity. Coarse depositional units in alpine watersheds can store and transmit significant volumes of groundwater and thus augment stream discharge during the dry season. These environments are typically data scarce, which has limited the application of physically based models to investigate hydrologic sensitivity to environmental change. This study focuses on a coarse alpine talus unit within the Lake O'Hara watershed in the Canadian Rockies. We investigate processes controlling the hydrologic functioning of the talus unit using field observations and a numerical groundwater flow model driven with a distributed snowmelt model. The model hydraulic parameters are adjusted to investigate how these properties influence the propagation of snowmelt‐induced diurnal signals. The model results expectedly demonstrate that diurnal signals at the talus outlet are progressively damped and lagged with lower hydraulic conductivity and higher specific yield. The simulations further indicate that the lag can be primarily controlled by a higher hydraulic conductivity upper layer, whereas the damping can be strongly influenced by a lower hydraulic conductivity layer along the base of the talus. The simulations specifically suggest that the talus slope can be represented as a two layer system with a high conductivity zone (0.02 m s−1) overlying a 10 cm thick lower conductivity zone (0.002 m s−1). This study demonstrates that diurnal signals can be used to elucidate the hydrologic functioning and hydraulic properties of shallow aquifers and thus aid in the parameterization of hydrological models. Many alpine aquifers and streams are characterized by diurnal flow signals caused by snow or glacier meltSmall shallow aquifers retain diurnal signals at their outlet but the signals are damped and laggedResults from a numerical groundwater model demonstrate that these signals can help characterize aquifer storage and hydraulic properties

Groundwater is critical for maintaining stream baseflow and thermal stability; however, the influence of groundwater on streamflow has been difficult to evaluate at broad spatial scales. Techniques such as baseflow separation necessitate streamflow records and do not directly indicate whether groundwater inflow may be sourced from more dynamic shallow flowpaths. We present a web tool application PASTA(Paired Air and Stream Temperature Analysis; https://cuahsi.shinyapps.io/pasta/) that capitalizes on increased public stream temperature data availability and large‐scale, gridded climate observations to provide new and efficient insights regarding relative groundwater influence on streams. PASTAanalyzes paired air and stream water temperature signals to evaluate spatiotemporal patterns in stream thermal sensitivity and relative groundwater influence, including inference regarding the dominant source groundwater depth (shallow or deep (i.e., approximately >6 m depth)). The tool is linked to publicly available stream temperature datasets and accepts user‐uploaded datasets. As local air temperature is not often monitored, PASTA pulls daily air temperature data from the comprehensive Daymet products when directly measured data are unavailable, allowing the repurposing of existing stream temperature data. After data are selected or uploaded, the tool (a) fits sinusoidal curves of daily stream and air temperatures by year (water or calendar) to indicate groundwater influence characteristics and (b) performs linear regressions for stream versus air temperatures to indicate stream thermal sensitivity. Results are exported in ASCII file format, creating an efficient and approachable analysis tool for the adoption of newly developed heat tracing analysis from stream reach to landscape scales. Comparing stream temperature to air temperature records can identify streamflow sources, or examine stream vulnerability to land use (e.g., impervious cover), climate change, or river use practices (e.g., dams). We have created a website that allows users to conduct two methods of stream and air temperature comparison using their stream temperature data or use publicly available stream temperature resources in a consistent and accessible format. These analyses generate metrics that indicate similarities and differences in air and stream temperature records over time that can provide insight into hydrologic connectivity for a single site or can be compared across time or space to inform changes in stream process within an area or period of interest. PASTA is a web application for analyzing paired stream water and air temperature from public and user‐owned datasets, even without air dataThe output metrics can evaluate stream thermal sensitivity, relative groundwater contributions, and effective source depthApplication design allows method consistency and accessibility for various flowing water communties PASTA is a web application for analyzing paired stream water and air temperature from public and user‐owned datasets, even without air data The output metrics can evaluate stream thermal sensitivity, relative groundwater contributions, and effective source depth Application design allows method consistency and accessibility for various flowing water communties

Low‐elevation coastal areas are increasingly vulnerable to seawater flooding as sea levels rise and the frequency and intensity of large storms increase with climate change. Seawater flooding can lead to the salinization of fresh coastal aquifers by vertical saltwater intrusion (SWI). Vertical SWI is often overlooked in coastal zone threat assessments despite the risk it poses to critical freshwater resources and salt‐intolerant ecosystems that sustain coastal populations. This review synthesizes field and modeling approaches for investigating vertical SWI and the practical and theoretical understanding of salinization and flushing processes obtained from prior studies. The synthesis explores complex vertical SWI dynamics that are influenced by density‐dependent flow and oceanic, hydrologic, geologic, climatic, and anthropogenic forcings acting on coastal aquifers across spatial and temporal scales. Key knowledge gaps, management challenges, and research opportunities are identified to help advance our understanding of the vulnerability of fresh coastal groundwater. Past modeling studies often focus on idealized aquifer systems, and thus future work could consider more diverse geologic, climatic, and topographic environments. Concurrent field and modeling programs should be sustained over time to capture interactions between physical processes, repeated salinization and flushing events, and delayed aquifer responses. Finally, this review highlights the need for improved coordination and knowledge translation across disciplines (e.g., coastal engineering, hydrogeology, oceanography, social science) to gain a more holistic understanding of vertical SWI. There also needs to be more education of communities, policy makers, and managers to motivate societal action to address coastal groundwater vulnerability in a changing climate. Along the world's coastlines, seawater flooding on the land surface by storms and high tide events can drive the downward infiltration of seawater into coastal aquifers that are an important source of fresh groundwater. Rising sea levels and the intensification of coastal storms are expected to exacerbate seawater flooding events globally. The salinization of fresh groundwater along the coast following floods is often “out of sight, out of mind,” but this process threatens freshwater resources that sustain dense coastal human populations and valuable, sensitive ecosystems. This paper reviews prior studies that have applied monitoring and/or computer modeling methods to better understand processes and controls on vertical saltwater intrusion. Our review details how surface flood dynamics, groundwater processes, environmental characteristics, and human activities combine to create complex patterns of salinization and flushing over space and time. From our synthesis we identify future research needs, including long‐term, globally dispersed monitoring and collaboration across scientific disciplines. We further emphasize the need for communication with local stakeholders about this topic to motivate informed management and research initiatives to understand and reduce the vulnerability of coastal fresh groundwater resources in a changing climate. Vertical saltwater intrusion following coastal floods threatens fresh groundwater in an age of rising seas and intensifying stormsWe review salinization and flushing processes identified with field and modeling methods and identify future research opportunitiesKnowledge gaps can be addressed through multidisciplinary studies to advance science and inform water resources management and policy Vertical saltwater intrusion following coastal floods threatens fresh groundwater in an age of rising seas and intensifying storms We review salinization and flushing processes identified with field and modeling methods and identify future research opportunities Knowledge gaps can be addressed through multidisciplinary studies to advance science and inform water resources management and policy

Ethanol consumption has long been associated with brain damage. However, the mechanism underlying this deleterious effect remains unclear. Among different hypotheses, acetaldehyde is regarded by certain authors as playing a major role in the expression of ethanol toxicity, but there are still some uncertainties about the exact nature of its implication. We therefore tried to characterize the profile of the alterations of neuronal viability and DNA integrity obtained after either a direct exposure to ethanol or to acetaldehyde. Ethanol at concentrations within the range of blood alcohol levels in intoxicated humans (≤100 mmol/L) induced DNA alterations without any apparent effect on cell viability. Acetaldehyde (≤ 1000 μmol/L) can also induce DNA alterations but with a different profile of the DNA cellular alterations. The comparison between the distributions of the comet tail DNA indicated that ethanol induced strong breaks (tail DNA ≥60 a.u.) generation whereas acetaldehyde rather induced lower breaks (20≤tail DNA ≤50 a.u.) formation but affecting a greater number of neurones. Acetaldehyde had thus a different genotoxic potential which may suggest a different mode of action or a different cellular target. Furthermore, when a single 100 mmol/L ethanol exposure did not lead to any loss of cell viability, the addition of an inhibitor of aldehyde dehydrogenase was followed by a significant loss in viability. In contrast, the inhibition of catalase, which suppresses acetaldehyde synthesis, led to no reduced viability in the same exposure conditions. ROS also reduced viability, but this was observed only after both cytochrome P450 stimulation and catalase inhibition. These combined results could suggest that acetaldehyde may play a significant role in the expression of ethanol toxicity in brain.

Abstract: The central nervous system is vulnerable to oxidative stress, especially when a toxicant can modify the physiological balance between anti‐ and pro‐oxidant mechanisms. Among brain cells, astrocytes seem less vulnerable than neurons, but their impairment can dramatically affect neurons because of their protective role toward neurons. Ethanol is able to stimulate the formation of reactive oxygen species and modify the activity of most of the antioxidant agents. However, ethanol can react with the OH· radical to form the α‐hydroxyethyl radical, which is considered to be less toxic. Ethanol also can stimulate H2O2degradation through catalase activation.This study, therefore, sought to determine whether ethanol affected the sensitivity of astrocytes exposed to various free radical‐generating systems. The cellular impact of such exposure was assessed by assays exploring cytotoxicity (i.e., NR (neutral red) and MMT (3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetiazolium bromide) reduction assays) and genotoxicity (comet assay) induced by these treatments. DNA alterations were evaluated by single‐cell gel electrophoresis (comet assay), considered a precocious biomarker of intracellular alterations.After concomitant exposure to H2O2and ethanol, the viability of astrocytes decreased significantly whereas the mean percentage of DNA in the tail increased, reflecting DNA damage (H2O2was either directly added to the culture medium or endogenously produced from menadione). Ethanol also reduced the loss of viability and DNA alterations after exposure to OH· radicals produced by a Fenton system. The exposure to a xanthine/xanthine oxidase system had the same effect.

A 49-year-old male chemical industry worker was admitted to intensive care with a 24-hour history of respiratory failure, vomiting, headache, stupor, arterial hypotension, and cyanosed face and limbs. He had acute haemolysis (3.9 g/L plasma haemoglobin concentration) and 30% methaemoglobinaemia. Whereas the search for alcohol, barbiturates and opiates was negative, benzodiazepines and tricyclic antidepressants were present. The patient was in fact being treated with fluvoxamine, amitryptiline, and alprazolam. As the clinical and biological signs suggested chlorate poisoning, chlorate was looked for by using an aniline color reaction. It was found in gastric content and urine. Treatment consisted in mechanical ventilation, vasoactive amines, methylene blue, plasma exchange, exchange transfusion, and haemodialysis. Despite this, the patient had several cardiac arrests and refractory metabolic acidosis. He died 12 h after his admission. Specific ion chromatography was used afterhand to assay the chlorate in various body fluids. The technique was based on a separation on an ion exchange Dionex® AS 12A column coupled with conductivity detection. A quantitative estimation was carried out by using external calibration with a four-point calibration curve which was linear between 1 and 15 mg/L. The measured plasma levels of chlorate were 78 and 29 mg/L respectively before and after exchange transfusion. Gastric-lavage liquid contained 1300 mg/L of chlorate and urine 4300 mg/L. Ion chromatography, which is routinely used in environmental studies helped to confirm a massive oral intake of chlorate by measuring the corresponding blood and urine chlorate concentrations, data which had only rarely been reported previously.

Surface effects of sea‐level rise (SLR) in permafrost regions are obvious where increasingly iceless seas erode and inundate coastlines. SLR also drives saltwater intrusion, but subsurface impacts on permafrost‐bound coastlines are unseen and unclear due to limited field data and the absence of models that include salinity‐dependent groundwater flow with solute exclusion and freeze‐thaw dynamics. Here, we develop a numerical model with the aforementioned processes to investigate climate change impacts on coastal permafrost. We find that SLR drives lateral permafrost thaw due to depressed freezing temperatures from saltwater intrusion, whereas warming drives top‐down thaw. Under high SLR and low warming scenarios, thaw driven by SLR exceeds warming‐driven thaw when normalized to the influenced surface area. Results highlight an overlooked feedback mechanism between SLR and permafrost thaw with potential implications for coastal infrastructure, ocean‐aquifer interactions, and carbon mobilization. Along coastlines globally, sea‐level rise is causing saltwater to intrude into terrestrial environments and freshwater reservoirs (i.e., saltwater intrusion). The impact of saltwater intrusion on temperate and tropical environments has been extensively studied, but assessment of saltwater intrusion impacts on high‐latitude permafrost environments is lacking due to limited field data and appropriate models. This knowledge gap limits projections of climate change impacts to coastal Arctic ecosystems and communities. In this study, we develop and use a mathematical model that incorporates multiple, interrelated processes, including how salt content affects the freezing temperature of water, to evaluate the impacts of sea‐level rise and associated saltwater intrusion on coastal permafrost. Results show that sea‐level rise causes saltwater to intrude into the unfrozen pore space of permafrost. With a lower freezing temperature than freshwater, saltwater intrusion triggers permafrost thaw and lateral retreat. The combination of atmospheric and oceanic warming and sea‐level rise has the potential to drive extensive permafrost loss along Arctic coastlines. Newly developed cryohydrogeological model incorporates salinity‐dependent freeze‐thaw processes and solute exclusionSubsurface saltwater intrusion drives lateral thaw of coastal ice‐saturated permafrostCombination of sea‐level rise and land surface warming results in extensive ice‐saturated permafrost loss Newly developed cryohydrogeological model incorporates salinity‐dependent freeze‐thaw processes and solute exclusion Subsurface saltwater intrusion drives lateral thaw of coastal ice‐saturated permafrost Combination of sea‐level rise and land surface warming results in extensive ice‐saturated permafrost loss

The nervous system is one of the main targets of ethanol toxicity. Astrocytes might play an important role in ethanol‐induced brain toxicity, because their integrity is essential for the normal growth and functioning of neurons. On the other hand, acetaldehyde has been implicated as a mediator in some of the biochemical, pharmacological, and behavioral effects of ethanol. The present study aimed at demonstrating the ability of astrocytes in culture to produce acetaldehyde from ethanol. Significant metabolization of ethanol with production of acetaldehyde was demonstrated in the primary culture of astrocytes. This production was quite low, compared with that usually observed in hepatocytes, but was in the same range as that measured in whole brain homogenates and corresponded to biologically active levels. Such a demonstration could bring new elements for understanding of ethanol neurotoxicity.

Formation of the α-hydroxyethyl radical (CH3°CHOH) has already been extensively demonstrated after ethanol metabolism in the liver. Despite favourable conditions, this formation in the brain has remained speculative since there is no direct experimental evidence in intact brain cells. In this preliminary study, the formation of such a radical was observed after exposure of astrocytes and astrocytic C6 glioma cells to ethanol. These cells were studied because astrocyte integrity is essential for normal growth and functioning of neurons. The free radicals were detected by EPR spectroscopy using the spin trapping technique. Astrocytes appeared to be more sensitive than the C6 cells to free radical formation as the intensity of the signal was higher after exposure of the astrocytes and increased with time, a fact not observed after exposure of the C6 cells.

Results of a study of trigeminal nerve impairment resulting from trichloroethylene intoxication by the somatosensory-evoked potential method reveal three kinds of abnormalities: increased stimulation voltage, excessive latency delay with morphological abnormalities, and excessive graph amplitude. These abnormalities confirm clinical disturbance (hypesthesia of the trigeminal nerve area) and open debate about the real mechanism of trichloroethylene neurotoxicity.

Carbon monoxide (CO) is a common source of poisoning, yet the diagnosis is often overlooked. A study was undertaken to establish the true incidence of missed diagnosis and to assess retrospectively the effects of a campaign of public medical information on this subject. The wrong diagnoses reflected all the unusual clinical presentations that CO could produce. The high initial rate of wrong diagnoses (30% in 1975-1977) was reduced following the campaign (12% in 1978 and 5% in 1980) despite a considerable increase in the rate of admission to hospital of confirmed CO poisoning cases.

Summary One hundred and eighty-eight workers occupationally exposed to trichloroethylene (TRI) were studied by physical examination, exposure parameters (measure of atmospheric TRI and urinary trichloroacetic acid (CA) and evaluation of personal factors (age, alcoholic and tobacco consumption). A statistical comparison (?2 test) of the frequency of the symptoms observed in the high- and low-exposure populations with an analysis of non-professional factors allowed us to distinguish different classes of symptoms. Those more likely linked with TRI exposure are trigeminal and optic nerve impairment, asthenia, headache and dizziness. An interaction between TRI exposure and alcohol intake on the occurrence of clinical liver impairment and degreaser flush is suggested.

Observations reveal recent Arctic warming, but future societal impacts are poorly understood. Now research identifies potential abrupt thaw-driven soil moisture shifts, with consequences for northern development including more intense wildfires and rainfall.

Understanding the interactions between ground freeze‐thaw, groundwater flow, and solute transport is imperative for evaluating the fate of contaminants in permafrost regions. However, predicting solute migration in permafrost‐affected groundwater systems is challenging due to the inherent interactions and coupling between subsurface mass and energy transport processes. To this end, we developed a numerical model that considers coupled groundwater flow, subsurface heat transfer, and solute transport, including water‐ice phase change, solute‐dependent porewater freezing, and temperature‐dependent solute reaction rates. As an illustrative example, we present simulations to investigate the potential for contamination from a municipal wastewater lagoon in the Canadian sub‐arctic. Two‐dimensional groundwater models assuming varying permafrost conditions were developed to evaluate possible contaminant migration scenarios associated with groundwater flow from the lagoon to a river, including the transport of conservative, degradable, and sorbing solutes. Model results reveal important transport mechanisms controlling the behavior of aqueous contaminants in permafrost landscapes as well as the hydrogeologic factors affecting reactive transport in cold regions. Seasonal freeze‐thaw episodically restricts connectivity of transport pathways, which attenuates both transport and reaction rates. However, elevated solute concentrations can depress the freezing temperature of porewater and produce thaw‐induced solute transport. Both thermally driven and solute‐enhanced thaw can decrease ice content in permafrost, which can have significant implications for solute migration. Therefore, thermo‐hydrogeologic process controlling reactive transport in cold‐region groundwater systems must be considered when quantitatively assessing the impact of changing environmental conditions on contaminant hydrogeology. Groundwater contamination associated with increased human and industrial activity is a growing risk in northern regions. However, current groundwater flow models generally do not simulate both permafrost dynamics and reactive solute transport. In this study we develop a hydrological model to simulate groundwater flow and dissolved contaminant transport for permafrost environments. The new model was applied at a site in the Canadian sub‐arctic to investigate the possibility of groundwater contamination associated with a wastewater lagoon. Results identified important mechanisms controlling the migration of contaminants in permafrost landscapes, including the effects of seasonal ground freezing and groundwater flow. Results show that the physical relationships describing the effects of contaminant levels on ground freezing characteristics and the influence of temperature on contaminant degradation properties strongly affect contamination movement. The new model will be useful for understanding how climate change and permafrost thaw will impact groundwater flow and associated subsurface migration of dissolved chemicals in cold regions. Subsurface aqueous contaminant transport in permafrost regions is controlled by coupled water, energy, and reactive solute transportWe developed a groundwater model to simulate reactive solute transport in permafrost landscapesConstitutive relationships describing solute‐dependent freezing and temperature‐dependent reaction rates strongly influence contaminant migration Subsurface aqueous contaminant transport in permafrost regions is controlled by coupled water, energy, and reactive solute transport We developed a groundwater model to simulate reactive solute transport in permafrost landscapes Constitutive relationships describing solute‐dependent freezing and temperature‐dependent reaction rates strongly influence contaminant migration