Water Interactions Research Articles

Monitoring the coastal–offshore water interactions in the Levantine Sea using ocean color and deep supervised learning

Abstract. Understanding and tracking the surface circulation of the Levantine Sea present significant challenges, particularly close to the coast. This difficulty arises due to two main factors: the limited availability of in situ observations and the increasing inaccuracies in altimetry data close to the coastline. Here, we propose a new approach to monitor the interaction between offshore and coastal waters. In this approach, we develop a pattern detection model using deep learning by training the U-Net model on ocean color data to track the interactions between the coastal and offshore water in the Levantine Sea. The results showed the presence of notable variations in the behavior of coastal currents as they progress northward beyond 33.8° E. As these coastal currents become increasingly unstable, they exhibit continuous pinching-off events that are missed by conventional observational tools. These pinching-off events, especially observed along the Lebanese coast, manifest in various patterns that evolve simultaneously. Typically, these patterns have a relatively short lifespan of a few weeks, appearing and disappearing rapidly. However, these structures can evolve into larger eddies that endure for over 4 months in some years, especially in the northern part of the Lebanese coasts. Although these structures could be observed during all the seasons, spring consistently records the lowest activity of these structures. Overall, we showed that the pinching-off events were always observed in the eastern part of the Levantine Sea. On the contrary, in the southern part, along the Egyptian coasts, the coastal flow is more stable in the southern region, where these events are less frequently observed, with more than 63 % of the total observations not exhibiting any pinching-off events. Moreover, when these events occur in the south, their spatial extent is notably limited. This research not only sheds light on previously missed (or underestimated) coastal current dynamics in the Levantine Sea but also highlights the crucial need to increase in situ observations to advance our understanding of this region's complex oceanographic processes.

The influence of domestic politics on the transboundary water interactions in the Eastern Nile

The influence of domestic politics on the transboundary water interactions in the Eastern Nile

Incorporating incubation period distributions to precisely estimate the association between rainfall and Legionella infection.

Multiple studies have shown a positive relationship between weather events and, 1 to 2 weeks later, Legionnaires' disease (LD) cases. Narrowing this time window of association can help determine whether the mechanism linking rainfall and relative humidity to sporadic LD is direct or indirect. Due to the large number of daily water interactions and low incidence of LD, we propose a new Bayesian modeling approach to disentangle the potential for a direct vs. indirect exposure to precipitation. Incubation period distributions were used to redistribute LD cases to their estimated day of exposure. Then Bayesian distributed lag models were fit to estimate cases per day of exposure with predictor variables for rainfall and absolute humidity. Sensitivity analyses explored the impact of relatively humidity, rainfall post-estimated date of exposure and randomized rainfall to validate our results. One standard deviation increase in rainfall 2 and 3 days prior to the date of estimated exposure was associated with an approximately 15% increase in LD risk (per day). When heavy rainfall occurred 0 to 3 days prior to estimated exposure, risk increased by more than 40%, peaking at a 51% increased risk of LD 2 days after heavy rainfall. Our findings of a 2- and 3-day lag between rainfall and the date of estimated exposure is consistent with an indirect link with rainfall, rather than a same-day exposure. Potential pathways that can indirectly link rainfall to LD cases include rainfall-mediated declines in public water supplies but greater environmental sampling research is needed.

Influence of Iodine Chemistry in I2 Scrubbing Modeling

With the scrubbing of molecular iodine (I2) from gas streams in water pools at an accident site (boiling water reactor wetwell, filtered containment venting systems, etc.), some discernible impact on the aqueous radiochemistry of the I2 decontamination factor (DF) is expected, sometimes with hardly any effect on aerosol scrubbing. In the frame of the NUGENIA Integration of Pool Scrubbing Research to Enhance Source-Term Calculations (IPRESCA) project, the Central Research Institute of Electric Power Industry (CRIEPI) in Japan performed a series of tests to study the I2 scrubbing behavior at high pH values, with changing pH in the course of the tests. We used these data for our simulation analyses, and we obtained sensible estimates of the experimental DF values in many calculated cases. The employed tool for our simulations was a modified version of the SPARC code inside MELCOR. This program was used for the IPRESCA benchmark parametric calculations, where the pH-dependent effect of the iodine chemistry equilibria at the bubble-water interface was predicted to be significant. The same was true for our simulations in the CRIEPI experiments. We have now modeled not just the interface equilibria, but also some slower (kinetic-driven) chemical interactions in water, which would transform, at these high pH values, most of the I2 into nonvolatile aqueous iodine species. The overall chemistry effect is quite pronounced, like in the experiments, though the description of the bubble thermal hydraulics was at least of the same importance for modeling. Many open questions remain, one of the trickiest of which being the employment of radiochemistry models (relevant to real accident conditions) for explanations of experiments driven by the normal (thermal) chemistry of iodine.

Zn(II)-Responsive MRI Probe Based on an Fe(III) Macrocyclic Complex.

The development of responsive MRI contrast agents to detect fluctuations in Zn(II) is a growing area of research. Here we describe a high-spin Fe(III) coordination complex, Fe(ADAPT), as one of the first examples of an Fe(III) MRI probe that is responsive to Zn(II). The six-coordinate Fe(ADAPT) contains a phenolate-appended 1,4,7-triazacyclononane (TACN) ligand framework, with the phenolate groups linked to a Zn(II) binding moiety. Fe(ADAPT) lacks an exchangeable inner-sphere water and thus relies on second- and outer-sphere water interactions for proton relaxation. Fe(ADAPT) is highly kinetically inert under physiological conditions at pH 7.4 and 37 °C and to excess Zn(II) over 72 h. In the presence of 2 equiv of Zn(II) with a 200 μM Fe(III) probe, an increase in relaxivity of ∼80% is observed. A ternary complex among Fe(ADAPT), Zn(II), and human serum albumin leads to a nearly 200% increase in relaxivity.

Characterizing Soil and Bedrock Water Use of Native California Vegetation

The effective characterization of landscape water balance components—evapotranspiration, runoff, recharge, and soil storage—is critical for understanding the integrated effects of the water balance on vegetation dynamics, water availability, and associated environmental responses to climate change. An improved parameterization of these components can improve assessments of landscape stress and provide useful insights for predicting and managing vegetation responses to climate change. Hydrology models typically are not able to address water availability below the mapped soil profile, but we refined a landscape hydrology model, the Basin Characterization Model, by balancing measures of actual evapotranspiration (AET) with modeled subsurface soil water holding capacity, including bedrock storage. The purpose of this study was to characterize the effective rooting depth (the depth of soil and bedrock storage required to support AET) for 35 native vegetation types in California in order to quantify soil and bedrock water use, which ranged from 0 to 3.1 m for most vegetation types, exceeding mapped soil depths. This resulted in the quantification of bedrock water use, increasing available water 67% over that calculated by mapped soils alone. We found that mid-elevation vegetation types with lower water and energy limitations have the highest evapotranspiration rates and deepest effective rooting depth. We also evaluated the resilience to drought with this more spatially realistic characterization of water and vegetation interactions.

Groundwater quality assessment for drinking and irrigation: a case study in the Cauvery River Basin (CRB) of Tiruchirappalli District, Tamil Nadu, India

ABSTRACT The long-term impacts of human activities on groundwater quality in the Cauvery River Basin are not well understood, particularly the combined effects of urbanization, industrialization, and agriculture. Seasonal factors, such as precipitation and water-table fluctuations, also influence groundwater chemistry, affecting its suitability for drinking and irrigation. This research aims to assess the hydrochemical characteristics of groundwater and evaluate its long-term suitability for these purposes, considering both natural and anthropogenic factors. A total of 56 groundwater samples were collected and analyzed for various physicochemical and biochemical parameters. The results showed that the most prevalent ions are bicarbonate (27.3%), chloride (24.1%), and calcium (16.6%), followed by sulfate, magnesium, sodium, and others. The Piper and Gibbs plots indicated that most groundwater samples belong to the mixed calcium chloride facies, and rock–water interaction is the dominant natural mechanism, with some anthropogenic influences, respectively. The GIS-based drinking water quality index (DWQI) map showed that 66% of the samples were of excellent to good quality for drinking without treatment, while the remaining samples were of moderate quality and nearly unsuitable for drinking, requiring further treatment. However, most of the groundwater samples were suitable for irrigation based on irrigation water quality indices.

Unsymmetric Protonation Driven Highly Efficient H2O2 Photosynthesis in Supramolecular Photocatalysts via One‐Step Two‐Electron Oxygen Reduction

AbstractPhotocatalytic hydrogen peroxide (H2O2) production has emerged as an attractive alternative to the traditional anthraquinone process. However, its performance is often hindered by low selectivity and sluggish kinetics of oxygen reduction reaction (ORR). Herein, we report an anthrazoline‐based supramolecular photocatalyst, SA‐SADF‐H+, featuring an unsymmetric protonation structure for H2O2 photosynthesis from water and air. The introduction of unsymmetric protonation disrupts the initial mirror symmetry of SADF, significantly enhancing the molecular dipole and facilitating efficient charge separation and electron transfer. Additionally, this modification increases the hydrophilicity of SA‐SADF‐H+, enabling the interaction of water and dissolved oxygen with the catalytic sites. The altered electron density distribution creates numerous dual active sites for Yeager‐type O2 adsorption, facilitating an efficient ORR towards H2O2 via a direct one‐step two‐electron pathway. Notably, SA‐SADF‐H+ achieves an outstanding photocatalytic H2O2 production at a rate of 4666.7 μmol L−1 h−1, with a remarkable solar‐to‐chemical conversion (SCC) of 1.35 %, surpassing most organic photocatalytic systems. Furthermore, SA‐SADF‐H+ demonstrates remarkable photocatalytic antibacterial activity, achieving 100 % antibacterial efficiency against Staphylococcus aureus within 60 min.

Investigating Induced Infiltration by Municipal Production Wells Using Stable Isotopes of Water (δ18O and δ2H), Four Mile Creek, Ohio

Many municipalities around the world place their production wells in shallow alluvial aquifers that are adjacent to streams. Pumping these wells then induces the infiltration of surface water into the aquifer, allowing the greater extraction of water without significantly depleting the aquifer. However, induced infiltration poses a risk of introducing contamination from surface water into groundwater systems. The goal of this study was to quantify the amount of induced infiltration due to municipal pumping at the Four Mile Creek well field in Oxford, Ohio, using stable isotopes of water oxygen (δ18O) and deuterium (δ2H). In areas of municipal pumping, we sampled water from the production wells, Four Mile Creek, and from monitoring wells that we hypothesized to be both influenced and not influenced by induced infiltration. Samples were collected over 10 months in 2012 and over 12 months in 2021. In 2012, surface water δ18O values ranged from −3.89 to −8.04‰, and δ2H ranged from −26.55 to −55.65‰ at sampling sites. PW1 δ18O values ranged from −4.71 to −7.39‰ with a mean of −6.61 and −32.01 to −47.86‰ with a mean of −42.74‰ for δ2H. PW2 δ18O values ranged from −5.74 to −7.34‰, with a mean of −6.45‰, and δ2H ranged from −36.29 to −47.82‰ with a mean of −42.43‰. PW3 had lower values of both δ18O and δ2H, ranging from −6.36 to −8.02‰ and −47.7 to −40.35‰, and with means of −7.08 and −45.11, respectively. In 2021/2022, surface water δ18O values ranged from −5.32 to −7.93‰, and the δ2H ranged from −36.14 to −50.56‰. PW1 δ18O values ranged from −6.15 to −7.54‰ with a mean of −7.13‰, and δ2H ranged from −43.52 to −49.01‰ with a mean of −45.99‰. PW2 δ18O values ranged from −5.72 to −7.34‰, with a mean of −6.70‰, and δ2H ranged from −36.69 to −46.14‰, with a mean of −43.61‰. Using the time averaged values of δ18O of groundwater, production wells and surface water, the percentages of surface water resulting from induced infiltration in 2012 were 57%, 59% and 15% at the three wells, respectively, while in 2021, PW1 had 35% and PW2 91%. The amount of induced infiltration was apparently related to the pumping rates of the production wells, the length of time of pumping and the distance between Four Mile Creek and production wells. Our results indicate that stable isotopes of water provide a reliable method of quantifying groundwater/surface water interaction in alluvial aquifers.

Tracing Groundwater‐Surface Water Interactions in a Volcanic Maar Lake Using Stable Isotopes and 222Rn

AbstractIsotope hydrological studies to understand groundwater‐surface water interactions in tropical, high‐elevation catchments are limited. These interactions are important in controlling lake water residence time, aqueous biogeochemistry, and water availability for downstream communities and ecosystems. To better comprehend the complexity of spatio‐temporal variations in the aquifer‐lake domain in tropical volcanic regions, a multi‐tracer approach including water and inorganic carbon stable isotopes (δ2H, δ18O, δ13CDIC), hydrochemistry, and 222Rn was applied in Lake Hule, northern Costa Rica. Seasonal isotope mass balance calculations using lake, stream, precipitation, and groundwater compositions were supplemented with local hydrometeorological information. Evaporation to inflow ratios (E/I) revealed a small variability between the dry (December–April) and wet seasons (May–November), with relatively low evaporation losses, 2.9 ± 1.0 % and 3.2 ± 1.8 %, respectively. Bayesian end‐member analysis indicated that annual inputs from groundwater, precipitation, and runoff represented 61.3 ± 8.1%, 24.4 ± 8.4, and 14.3 ± 5.9% of total lake inflow, respectively. Temporal variations of δ13CDIC confirmed the key role volcanic carbonate buffering plays in this lake and indicated greater CO2 degassing from groundwater sources in the wet season. This tracer‐aided assessment in a volcanic lake maar of northern Costa Rica provides evidence of previously unknown groundwater‐surface water interactions and illustrates the application of isotopic tools for estimating water balances and seasonal variability of groundwater discharge into natural lakes across the volcanic front of Central America.

Patterns of nitrate load variability under surface water-groundwater interactions in agriculturally intensive valley watersheds

Nitrate pollution is a significant environmental issue closely related to human activities, complicated hydrological interactions and nitrate fate in the valley watershed strongly affects nitrate load in hydrological systems. In this study, a nitrate reactive transport model by coupling SWAT-MODFLOW-RT3D between surface water and groundwater interactions at the watershed scale was developed, which was used to reproduce the interaction between surface water and groundwater in the basin from 2016 to 2019 and to reveal the nitrogen transformation process and the evolving trend of nitrate load within the hydrological system of the valley watershed. The results showed that the basin exhibited groundwater recharge to surface water in 2016-2019, particularly in the northwestern and northeastern mountainous regions of the valley watershed and the southern Beishan Reservoir vicinity. Groundwater recharge to surface water declined by 20.17% from 2016 to 2019 due to precipitation. Nitrate loads in the hydrologic system of the watershed are primarily derived from human activities (including fertilizer application from agricultural activities and residential wastewater discharges) and the nitrogen cycle. Nitrate loads in surface water declined 16.05% from 2016 to 2019. Nitrate levels are higher in agricultural farming and residential areas on the eastern and northern sides of the watershed. Additionally, hydrological interactions are usually accompanied by material accumulation and environmental changes. Nitrate levels tend to rise with converging water flows, a process that becomes more pronounced during precipitation events and cropping seasons in agriculturally intensive valley watersheds. However, environmental changes alter nitrogen transformation processes. Nitrogen fixation, nitrification, and ammonification intensify nitrogen inputs during river pooling, enhancing nitrogen cycling fluxes and elevating nitrate loads. These processes are further enhanced during groundwater recharge to surface water, leading to evaluated nitrate load. Enhanced denitrification, dissimilatory nitrate reduction to ammonium (DNRA), anaerobic ammonia oxidation, and assimilation promote the nitrogen export from the system and reduce the nitrate load during surface water recharge to groundwater.

Key point of desert riparian forest development in the arid area: The response of phreatic water table depth to ecological water supply

Desert riparian forest vegetation maintains the fragile balance of ecosystems in extreme arid areas. Raising the phreatic water table through efficient ecological water supply is the key to the desert riparian forests in extreme arid areas. The main objective of this study is to explore an innovative framework in which the response of phreatic water table depth (PWTD) to ecological water supply flow (EWSF) can be effectively reflected. The framework is based on the computationally efficient integrated surface water - groundwater model (ISGWM), through which surface water processes, groundwater recharge and discharge processes, and PWTD changes under different EWSF can be accurately simulated. A large number of simulations were conducted to reflect the response of PWTD to EWSF, and to explore the suitable EWSF and its intra-annual process considering the efficiency of PWTD reduction. The applicability and advantages of ISGWM were evaluated for the Tarim River Basin (TRB), a typical inland river basin, northwest China. The response of PWTD to EWSF was studied in 55 gate control areas in the mainstream of TRB. The formulas of suitable EWSF of 55 gates with different initial PWTDs were fitted. It is more beneficial to concentrate the ecological water supply in flood season (Jun.-Oct.). Overall, the ISGWM can accurately describe the multi-process of surface water and groundwater interactions. This study can provide scientific support for water resources management and allocation in the TRB and other similar inland river basins.

Exploring Optimal Complexity for Water Stress Representation in Terrestrial Carbon Models: A Hybrid‐Machine Learning Model Approach

AbstractTerrestrial biosphere models offer a comprehensive view of the global carbon cycle by integrating ecological processes across scales, yet they introduce significant uncertainties in climate and biogeochemical projections due to diverse process representations and parameter variations. For instance, different soil water limitation functions lead to wide productivity ranges across models. To address this, we propose the Differentiable Land Model (DifferLand), a novel hybrid machine learning approach replacing unknown water limitation functions in models with neural networks (NNs) to learn from data. Using automatic differentiation, we calibrated the embedded NN and the physical model parameters against daily observations of evapotranspiration, gross primary productivity, ecosystem respiration, and leaf area index across 16 FLUXNET sites. We evaluated six model configurations where NNs simulate increasingly complex soil water and photosynthesis interactions against test data sets to find the optimal structure‐performance tradeoff. Our findings show that a simple hybrid model with a univariate NN effectively captures site‐level water and carbon fluxes on a monthly timescale. Across a global aridity gradient, the magnitude of water stress limitation varies, but its functional form consistently converges to a piecewise linear relationship with saturation at high water levels. While models incorporating more interactions between soil water and meteorological drivers better fit observations at finer time scales, they risk overfitting and equifinality issues. Our study demonstrates that hybrid models have great potential in learning unknown parameterizations and testing ecological hypotheses. Nevertheless, careful structure‐performance tradeoffs are warranted in light of observational constraints to translate the retrieved relationships into robust process understanding.

Analysis of Groundwater Quality in A Coastal Area: Case Study of Durung Village, Aceh Besar Regency

Groundwater quality in coastal areas is responsive due to the interaction of fresh water with seawater. Groundwater quality monitoring studies in coastal area needs to be done regularly to prevent natural disasters and clean water crises in the future. In this study, measurements of groundwater physics parameter were carried out, i.e. electrical conductivity to analyze groundwater quality. The interpolation method based on Geographic Information Systems (GIS) was used to obtain values ​​between each sample point to produce a spatial distribution map of groundwater quality over the research location. The results of the study showed that groundwater quality in the coastal area of ​ Durung Village was generally still quite good with conductivity values ​​between 689 - 3,391 µS/cm. However, for the locations which is nearby the coast such as in the location of Malahayati Merchant Marine Polytechnic, it was indicated that it had been contaminated by seawater with the highest conductivity values between 5,763 – 6.270 µS/cm.

Self-floating Janus hydrovoltaics for sustainable electricity generation

Water is widely available in nature that attracts increasing interesting in simulating transpiration effect to induce the electricity. However, it faces great challenges in establishing continues moisture gradient rather than periodic wetting behaviors. Here, we propose a self-floating Janus generator containing the hydrophilic and hydrophobic regions to induce the continues electricity. The self-floating and hydrophilic behavior ensures a continuous water supply. The asymmetric Janus structure forms a distinct wet/dry interface to create a significant water gradient with evaporation equilibrium state. At wetting region, the electric double layer (EDL) is formed due to the interaction of water and carbon black particles. Attributed to the large water gradient and fast contact line evaporation, proton accumulates across the capillary front that induces a potential difference. As a result, the Janus generator achieves 0.46 V open circuit voltage lasting for 40 h. It also demonstrates the potential applications of Janus generator in power supply, moisture detection and sweat monitoring et al. The proposed Janus generators show great potential in ocean energy development and be of great significance to the sensing of rescue signals in the sea.

A Fluorescent Perspective on Water Structuring: ACDAN in Salt Solutions and Hydrogels

The interactions and structural organization of water molecules play a crucial role in a wide range of physical, chemical, and biological processes. The ability of water to form hydrogen bonds (H-bonds) underpins its unique properties and enables it to respond dynamically to various environmental factors. These interactions at the molecular level may affect vital processes like protein folding, enzyme activity, and cellular organization. The presence of solutes and spatial constraints can alter the H-bonding network of water, and these effects are ubiquitous in the biological environment. In this study, we analyzed the fluorescence of 2-acetyl-6-(dimethylamino)naphthalene (ACDAN) fluorescence emission in water solutions containing kosmotropic and chaotropic salts and in agar hydrogels. Recently, this dye has proven invaluable in studying water network structure and dynamics, as its fluorescence signal changes based on the local dielectric environment, revealing variations in the dipolar relaxation of water. Our results show that ACDAN spectral response correlates with the degree of water ordering, providing important insights into solute–water interactions and water dynamics in free and confined environments.

Atmospheric air pollution from the Ermakovskoe fluorite-beryllium deposit development waste

Relevance. Negative impact of waste from mining enterprises on the ecological state of the surrounding areas. Aim. To determine the migration ability of toxic chemical elements from waste storage sites of the Ermakovskoe beryllium deposit in the air. Object. Ermakovskoe fluorite-bertrandite-phenacite deposit and the surrounding area. Methods. Inductively coupled plasma mass spectrometry, laser diffraction, inductively coupled plasma atomic emission spectrometry. Results and conclusions. The paper introduces the experimental studies of surface atmospheric pollution by mining waste from the Ermakovskoe fluorite-bertrandite-phenakite deposit are presented using an installation for collecting aerosols above the sand surface. It was established that toxic components formed during the decomposition of residual sulfide mineralization and products of the interaction of acidic waters with rocks move from the sand thickness to the surface along with water vapor. The moisture condensed over the sand contains high contents of aluminum, iron, manganese, zinc, and phosphorus. These elements form a halo of air pollution over mining waste and are then dispersed by air currents into the surrounding area. In winter, due to wind dispersion of aerosols, the snow cover becomes contaminated over a vast area. Among the toxic elements found were beryllium, lead, cadmium, and molybdenum, which belong to the second hazard class. The solid residue of the snow cover contains a fine fraction of dust, the size of which is less than 10 microns. The halo of snow contamination with toxic chemical elements and dust extends several kilometers away from the disturbed lands.

Unsymmetric Protonation Driven Highly Efficient H2O2 Photosynthesis in Supramolecular Photocatalysts via One-Step Two-Electron Oxygen Reduction.

Photocatalytic hydrogen peroxide (H2O2) production has emerged as an attractive alternative to the traditional anthraquinone process. However, its performance is often hindered by low selectivity and sluggish kinetics of oxygen reduction reaction (ORR). Herein, we report an anthrazoline-based supramolecular photocatalyst, SA-SADF-H+, featuring an unsymmetric protonation structure for H2O2 photosynthesis from water and air.The introduction of unsymmetric protonation disrupts the initial mirror symmetry of SADF, significantly enhancing the molecular dipole and facilitating efficient charge separation and electron transfer. Additionally, this modification increases the hydrophilicity of SA-SADF-H+, enabling the interaction of water and dissolved oxygen with the catalytic sites. The altered electron density distribution creates numerous dual active sites for Yeager-type O2 adsorption, facilitating an efficient ORR towards H2O2 via a direct one-step two-electron pathway. Notably, SA-SADF-H+ achieves an outstanding photocatalytic H2O2 production at a rate of 4667 μmol L-1 h-1, with a remarkable solar-to-chemical conversion (SCC) of 1.35%, surpassing most organic photocatalytic systems. Furthermore, SA-SADF-H+ demonstrates remarkable photocatalytic antibacterial activity, achieving 100% antibacterial efficiency against Staphylococcus aureus within 60 min.

Hydrochemical and Isotopic Characterization of Groundwater in the Nakivale Sub-Catchment of the Transboundary Lake Victoria Basin, Uganda

This study characterized groundwater resources for the Nakivale sub-catchment of the transboundary Victoria Basin in Uganda using classical hydrochemical and stable isotopic approaches. Groundwater in the study area is essential for domestic, agricultural, and industrial uses. As a sub-domain of the larger Victoria Basin, it also plays a crucial role in shaping the hydrological characteristics of this vital transboundary basin, both in terms of quality and quantity fronts. This makes its sustainable management and development vital. The predominant groundwater type is Ca-SO4, with other types including Ca-HCO3, Na-Cl, Na-HCO3, and Ca-Mg-SO4-Cl. Hydrochemical facies analysis highlights the importance of rock–water interactions in controlling groundwater chemistry, mainly through incongruent chemical weathering of Ca-rich plagioclase feldspars and the oxidation of sulfide minerals, such as pyrite, which are prevalent in the study area. Groundwater recharge is primarily influenced by the area’s topography, with recharge zones characterized by lineament networks, located in elevated areas. Stable isotope analyses indicate that groundwater mainly originates from local precipitation, while tritium data suggest the presence of both recent and older groundwater (likely over 20 years old). The study’s comprehensive approach and findings contribute significantly to the understanding of groundwater systems in the region, thus providing valuable insights for policymakers and stakeholders involved in water resource management and development strategies.

Hydrolysis of poly(ester urethane): In-depth mechanistic pathways through FTIR 2D-COS spectroscopy

The hydrolysis of thermoplastic poly(ester urethane) (PEU) is convoluted by its block copolymer phase structure and competing hydrolytic sensitivities of multiple functional groups. The exact pathways for water ingress, water interaction with the material and ultimately the kinetics and order of functional group hydrolysis remain to be refined. Additional diagnostics are needed to enable deeper insight and deconvolution of material changes. In combination with GPC results, a promising analytical technique – two-dimensional correlation spectroscopy (2D-COS) – has been reviewed and applied to analyze FTIR spectra of hydrolyzed PEUs aged under various conditions, such as exposure time, temperature, and relative humidity. 2D-COS allows the complex role of water with distinct intermediate steps to be established, plus it emphasizes the initial stages of PEU hydrolysis at more susceptible functional groups. As a complication for the raw material, ATR IR detected some talc on the surface of commercial PEU beads and pressed sheets thereof, which can interfere with water ingress and thereby retards PEU hydrolysis, particularly in its natural form or moderate aging at lower temperatures (e.g., below the melting point of PEU). As aging temperature increases above the melting temperature, even traces of water trapped inside the PEU are sufficient to initiate the hydrolysis, which then progresses strongly with increasing temperatures. Feedback from 2D-COS analysis confirms that PEU hydrolysis starts at esters in the soft-segments before those in the urethane linkage become susceptible. Only when the molecular weight of PEU is below a critical molar mass (Mc) will the hydrolysis occur in parallel in the hard-segments since protective morphological phase structures are then absent. The current observations demonstrate unexpected behavior that may result from 'unknown' additives in polymer degradation, the temporal and group-specific hydrolysis of PEU as a function of locally available water molecules, the order of reactivity of susceptible functional groups, and the importance of changes in molecular weight coupled with the phase structure of the polymer.