Traces Of Water Research Articles

State of atmospheric pollution between vulnerabilities and criticalities from 2007 to 2022 and a projection in 2030 focused on the proliferation of gasoline sales in the city of N'Djamena

According to the World Health Organization (2008), 1.3 million annual deaths worldwide are attributable to air pollution, and that the latter is the cause of 16% of the total number of deaths. Among air pollutants, particles play an important role in worsening air quality in urban areas. The city of Ndjamena has recorded an increased proliferation of hydrocarbon stations since 2007 to the present day. The analysis of the vulnerability and criticality of pollutants from 2007 to 2022 and a projection to 2030 were made. For a response relating to the subject of our research, we chemically characterized two types of gasoline by following the recommended parameters. The result obtained following these analyses shows that street gasoline has a more or less negative result compared to gasoline produced, stored and sold in accordance with standards and regulations in Chad. We note that the analyzed contraband gasolines have negative results unlike other types of gasoline sold at the pump (some service stations) in terms of: - ASTM distillation, confirming the presence of significant heavy fractions, the Octane Index, presenting a minimum limit required by the standard for super 90 gasoline. Total sulfur, which reaches the maximum limit required and finally, Corrosion giving the maximum limit required by the standard in terms of corrosion. We also noted the presence of traces of water and unidentified solid debris at the bottom of most of our contraband samples.

Rising temperature impacts the trace metal uptake and toxicity in aquatic plants - A case study of Ni and Co in Elodea canadensis Michx.

The global warming and environmental pollution are two crucial contemporary concerns. As both are strongly connected with urbanisation and anthropogenic impact on the environment, they often affect the ecosystem simultaneously. Aquatic habitats are particularly susceptible to thermal and chemical pollution. Temperature influences nearly all physical and chemical features of water bodies and trace metals are known for their toxicity to aquatic organisms. However, effects of multiple stressors, cumulative effects as well as response and possible adaptations of organisms are still open questions. Thus, the aim of this study was to characterize the combined effect of temperature and two trace metals (Co and Ni) on the metal bioaccumulation and viability of a model aquatic macrophyte Elodea canadensis Michx. We exposed shoots of E. canadensis to three temperatures and four metal concentrations (together and separately) applied at environmentally relevant levels. Shoot growth and metal concentration in plants were measured after 120 h. Moreover, after 24, 72 and 120 h the changes in leaf cell morphology and viability were analysed. The results showed that metal accumulation was dose-dependent and was not affected by temperature. The growth of plants was not affected by temperature nor metals. On the other hand, the exposure to Co and Ni and the elevated temperature negatively affected cell viability of E. canadensis leaves which manifested by increased permeability of plasma membranes and visible necroses. The greatest damaged leaf areas were determined after 120 h in the highest concentration of both metals and the highest temperature which indicates synergistic impact of trace metals and temperature on performance of macrohydrophytes. The observed phenomena suggest that global warming and/or thermal pollution may have implications for the performance of aquatic macrophytes in chemically polluted waters, their ability to spread and colonize polluted habitats and their suitability in phytoremediation.

Application of Iodine-Amine Oxidation Approach in the Synthesis of Various N-Alkyl Phosphoramidate Oligonucleotide Derivatives

Introduction: Nowadays, use of phosphate modifications in oligonucleotide backbone has become a common approach for imbuing its structure with the desired beneficial properties. The recent advances in successful application of different classes of phosphate modifications in the design of therapeutic oligonucleotides have led to a renewed interest in the development of approaches for introducing diverse classes of phosphate modifications. Method: This study aims to investigate the efficiency and optimize protocols for the application of the iodine-amine oxidation reaction to produce various N-alkyl phosphoramidate oligonucleotide derivatives during the conventional solid-phase phosphoramidite synthesis method. Result: Various solvents and drying reagents were tested, and it was evaluated that even minor traces of water in a reaction mixture had a significant impact on yield. Using set of commercially available amines, it was shown that steric accessibility is a more critical parameter than nucleophilicity of the amino group in oxidative amination reaction. It was demonstrated that through use of amino alcohols and diamines during iodine-amine oxidation step various branched oligonucleotide structures can be synthesized. Conclusion: The obtained data indicates that the oxidative amination approach can be a promising tool for preparing various oligonucleotide derivatives during solid-phase synthesis without the use of specialized phosphoramidite monomers.

Quantifying free tropospheric moisture sources over the western tropical Atlantic with numerical water tracers and isotopes

AbstractTropical free‐tropospheric humidity plays a crucial role for the Earth's radiative balance and climate sensitivity. In addition to atmospheric humidity, stable water isotopes can provide important information about the hydrological cycle. We use the isotope‐ and water tagging‐enabled version of the COSMOiso model to determine isotopic fingerprints of diagnosed moisture pathways over the western tropical Atlantic (WTA). A convection‐permitting, high‐resolution (5 km) nudged simulation is performed for January–February 2020. During this period, the target region is characterized by alternating large‐scale circulation regimes with different humidity and isotope signatures. Moist conditions in the middle troposphere (300–650 hPa) are associated with moisture transport from the south, east, southeast, as well as evaporation from the North Atlantic, while dry conditions correspond to extratropical transport from the north and west. To predict the contribution of different moisture sources, we used a statistical model based on the local specific humidity and temperature as predictors and obtained an R‐squared (R2) of 0.52. Adding water isotopes improved the prediction (R2 = 0.73), showing that isotopes provide unique information on moisture sources and transport patterns beyond conventional local observations.

On the Functionalization of C60 with Vinylallenes Generated in situ by Rhodium Catalysis

The functionalization of fullerenes is important for several reasons, primarily related to enhancing their chemical reactivity, solubility, and potential of applications in optoelectronics and biomedicine. In this study, we present a novel approach to functionalize C60 through a cascade process encompassing an unprecedented Rh‐catalyzed cycloisomerization of 1,6‐allenynes to in situ generate a vinylallene that is followed by a Diels‐Alder reaction with pristine fullerene, resulting in the formation of 6,6‐fused bicyclic fullerene derivatives. The mechanism governing this process was elucidated by DFT calculations and confirmed by deuterium labelling and control experiments, demonstrating the critical role of traces of water in the reaction medium to mediate the observed reactivity.

A highly sensitive fluorescent sensor for reversible visual detection of fluoride ion and trace water in food products

A simple diphenylimidazole-based fluorescent sensor (DIP) had been designed for reversible fluorescence sensing of F− and trace water. The sensor showed superior selectivity for F− compared to other anions with fluorescence “turn on” mode. After adding F− to CH3CN solution of DIP, the emission color of DIP changed markedly from weak blue to strong cyan, which could be facilely discerned by the naked eye. The various technical analysis, including spectroscopies, 1H NMR titration and DFT calculation, indicated that the deprotonation of imidazole –NH and –OH occurred in the presence of F−. The detection limit of DIP toward F− could reach as low as 72.3 nM. Moreover, F−-induced deprotonation of DIP-F− system exhibited high sensitivity for water with the detection limit of 0.0015 vol%. The reversible switching characteristic of DIP prompted it suitable for the construction of molecular logic gate. In addition, DIP and DIP-F− were successfully applied to the determination of F− content in toothpaste and water content in table salt, sugar and tea, respectively. Moreover, DIP and DIP-F−-coated filter paper strips could be used as fluorescent display materials for inkless writing with repeatability.

Dual-emission spiropyran-functionalized covalent organic framework–based nanofiber mat microsensors for fluorescence colorimetric sensing of trace water

A dual-emission spiropyran-functionalized covalent organic framework (MCH@COF) was synthesized using acyl chlorination for the first time in this study. The excited state of MCH@COF had a strong intramolecular charge transfer property, and its solvent-solvent interaction with polar solvents caused MCH@COF to exhibit solvatochromic behavior. Furthermore, the face-to-face stacking of the H-aggregating form of MCH@COF was found to be disrupted in the presence of water. Consequently, MCH@COF demonstrated exceptional sensitivity (detection limit = 0.02 %, v/v) and a wide linear range (0 %–50 %, v/v) as a ratiometric fluorescence probe for water. To expand its applications, MCH@COF was doped with a nanofiber mat comprising polylactic acid/polyvinylpyrrolidone, resulting in the development of a microsensor. By combining the microsensing device with a heating volatilization extraction method, the visual fluorescence colorimetric detection of water in solid samples was realized. The method showed the advantages of small-sample requirement (20 mg), low matrix interference (achieved through the separation of matrix and water via heating volatilization), high sensitivity (maximum color difference (ΔC) of 166.14), and suitability for rapid field detection (sensing time of 4 min, with color change observed using the naked eye under visible light).

Miocene Climatic Optimum and Middle Miocene Climate Transition: a foraminiferal record from the central Ross Sea, Antarctica

Abstract. The Ross Sea record of the Miocene Climatic Optimum (MCO; ∼ 16.9–14.7 Ma) and the Middle Miocene Climate Transition (MMCT; ∼ 14.7–13.8 Ma) provides critical insights into Antarctic ocean–cryosphere interactions during a time of extreme warmth and subsequent cooling. Here we report on Lower to Middle Miocene foraminiferal assemblages from the International Ocean Discovery Program (IODP) Site U1521 on the outer shelf of the central Ross Sea to identify regional shifts in environmental and water mass conditions and trace continental shelf evolution. We identified seven benthic biofacies clusters, dominated by abundant Globocassidulina subglobosa (a proposed indicator of proto-Circumpolar Deep Water, pCDW), Uvigerina cf. U. fueguina (high productivity and enhanced bottom-water currents), Nonionella spp. (high productivity), or Melonis spp. (high productivity) using a Q-mode cluster analysis to develop preliminary regional paleoenvironmental interpretations. Four unique assemblages, including Globobulimina cf. G. auriculata (high productivity and low oxygen), are also identified. Unit IV (representing the early MCO event) is a short-lived (∼ 80 ka), progradational, clast-poor sandy diamictite, likely deposited during deglaciation; the upper part of Unit IV is transitional with overlying Unit III. Unit IV sediments contain the most persistently abundant and diverse foraminiferal assemblages recovered at U1521 because they are mud-rich and diatom-poor, despite very high sedimentation rates. The benthic assemblages shift between Globocassidulina and Uvigerina dominance, suggesting changes in the pCDW influence relative to productivity and/or current activity. We suggest the abundance of Uvigerina (a shelf-edge proxy) in Unit IV records the northward progradation of the Ross continental shelf at this location during the late Early to Middle Miocene. Unit III (MCO) was deposited in an open-marine setting, evident by the ice-rafted detritus or debris (IRD) clast-free, diatom-rich/diatom-bearing muds. The sporadic nature of foraminiferal abundances in Unit III is likely due to intervals of terrigenous mud alternating with more diatom-rich/diatom-bearing muds. As in Unit IV, the muddier lithologies (higher natural gamma ray (NGR) values) are more likely to preserve calcareous foraminifera, whereas the most diatom-rich sediments (lower NGR values) are more corrosive to carbonate. We interpret the muddier intervals as interglacials with incursions of pCDW, as indicated by increased Globocassidulina subglobosa, and sporadic occurrences of rare warmer-water planktic foraminifera. Collectively, these multiple incursions of warmer-water planktic foraminifera provide evidence for polar amplification in the Ross Sea during the MCO and MMCT. The diatom-rich muds are interpreted as glacials during the MCO with open-marine conditions and higher productivity. The dominance of Globobulimina in the upper part of Unit III corresponds with the carbon maximum of Carbon Maxima 2 (CM2) and low-oxygen conditions in the sediments at ∼ 16.1 Ma. Subsequent glaciation (including Mi2, Miocene Isotope event 2), marine-based ice sheet grounding, and erosion on the shallow shelf are recorded by the widespread Ross Sea Unconformity 4 (RSU4; ∼ 15.95–14.2 Ma) at Site U1521. Unit II (MMCT) likely represents sedimentation in the interval between the RSU4 and the Mi3 (Miocene Isotope event 3) glaciation at ∼ 13.9–13.8 Ma. The benthic biofacies composition of Unit II shows a further increase in neritic taxa, including Elphidium magellanicum and Epistominella vitrea, suggesting continued shoaling of the continental shelf, which facilitated the growth of marine-based ice sheets during the Middle Miocene. Our initial correlation between Site U1521 and the ANtarctic geological DRILLing Project (ANDRILL) site, AND-2A, yields similar environmental interpretations, including peak warm events 3 and 4 during the MCO, supported by the foraminifera and unit lithologies. Suspected glacial intervals during the MCO, including Mi2 at the top of Unit III, correlate well with the reconstructed deep-sea estimates of ice volume changes (seawater δ18Osw record) from the Ocean Drilling Program (ODP) Site 1171 on the South Tasman Rise.

Using MCFC for capturing CO2 from flue gases and delivering to Sabatier reactor for SNG synthesis

In contemporary power generation, enhancing efficiency and mitigating environmental contamination are of paramount importance. The imperative to curtail greenhouse gas emissions stands as a preeminent challenge within this sector. Concurrently, there is a marked surge in the exploitation of renewable energy sources, which, due to their intermittent nature, precipitates the imperative for advanced energy storage solutions. This paper introduces an integrated system designed to address both the reduction of CO2 emissions and the storage of energy. The advocated system integrates a Molten Carbonate Fuel Cell (MCFC), Solid Oxide Electrolysis Cell (SOEC), and a Sabatier reactor. The MCFC is employed for its proficient CO2 capture capabilities at the cathode, exhibiting remarkable efficiency, operational flexibility, and a high CO2 separation quotient. The SOEC is recognized for its effective hydrogen production, leveraging high operational temperatures to augment hydrogen output while diminishing electrical energy consumption through thermal energy substitution. The Sabatier reactor is utilized for catalytic methanation, transforming CO2 into Substitute Natural Gas—a compound predominantly comprising methane and hydrogen with minimal CO2 and water traces. This system facilitates the capture and utilization of over 80% of CO2 from exhaust fumes, achieving an overall energy efficiency of 71%. The system's design and off-design operational parameters were meticulously modeled and analyzed.

Trace element partitioning controls on cave drip water compositions through prior calcite and aragonite precipitation

Speleothem trace element records can provide seasonal resolution climate reconstructions, but the interpretation can be challenging. Aragonite samples are understudied compared to calcite samples, despite that aragonite has 10x higher uranium concentrations and thus provide excellent dating precision. Here we present a high-resolution dataset of drip water trace elements (calcium, magnesium, strontium, barium, uranium) that are commonly affected by prior carbonate (calcite / aragonite) precipitation, a process often driven by effective rainfall. Our data suggest that prior calcite and aragonite precipitation can occur at the same drip site complicating the interpretation of strontium and uranium concentrations in aragonite speleothems. However, both processes can be distinguished with the “Sinclair test” through the trendline analysis of logarithmic relationships. Furthermore, our data show that aragonite speleothems slowly growing under relatively constant conditions are ideal to record variations in prior carbonate precipitation with its barium concentrations, independent from the prior carbonate precipitation mode.

Structural and spectroscopic characterization of N1,N2-diphenylacenapthylene-1,2-diimines and the influence of substituents on the viscosity of alkyl magnesium solutions

Butyl octyl magnesium solutions are important raw materials in various chemical processes but suffer from their high reactivity with even traces of water, protic solvents or oxygen and an increased viscosity in hydrocarbon solution due to the formation of polymeric structures. N1,N2-diphenylacenaphthylene-1,2-diimines (BIANs) have already been identified as potential candidates to reduce the viscosity of alkyl magnesium solutions and this study provides a systematic insight into the dependence of this ability on the position and structures of substituents on the BIAN. Besides the various BIANs, ZnCl2 complexes and hydrogenated derivatives were characterized and tested for their ability to reduce the viscosity. HPLC-high resolution mass spectrometry, MALDI-ToF mass spectrometry, but most important FTIR and NMR experiments under inert conditions have been used to shine light on the interaction of the different BIAN derivatives with alkyl magnesium solutions. Hydrogenated BIANs, especially those with bulky alkyl groups in the ortho position(s) have been identified as the most promising candidates. An additional benefit of the hydrogenated species is that in contrast to BIANs and BIAN-Zn complexes they do not undergo permanent chemical modification and can be reused after extraction.

Understanding the Source and Evolution of Precipitation Stable Isotope Composition across O‘ahu, Hawai‘i

Abstract Pacific Islands present unique challenges for water resource management due to their environmental vulnerability, dynamic climates, and heavy reliance on groundwater. Quantifying connections between meteoric, ground, and surface waters is critical for effective water resource management. Analyses of the stable isotopes of oxygen and hydrogen in the hydrosphere can help illuminate such connections. This study investigates the stable isotope composition of rainfall on O‘ahu in the Hawaiian Islands, with a particular focus on how altitude impacts stable isotope composition. Rainfall was sampled at 20 locations from March 2018 to August 2021. The new precipitation stable isotope data were integrated with previously published data to create the most spatially and topographically diverse precipitation collector network on O‘ahu to date. Results show that δ18O and δ2H values in precipitation displayed distinct isotopic signatures influenced by geographical location, season, and precipitation source. Altitude and isotopic compositions were strongly correlated along certain elevation transects, but these relationships could not be extrapolated to larger regions due to microclimate influences. Altitude and deuterium excess were strongly correlated across the study region, suggesting that deuterium excess may be a reliable proxy for precipitation elevation in local water tracer studies. Analysis of spring, rainfall, and fog stable isotope composition from Mount Ka‘ala suggests that fog may contribute up to 45% of total groundwater recharge at the summit. These findings highlight the strong influence of microclimates on the stable isotope composition of rainfall, underscore the need for further investigation into fog’s role in the water budget, and demonstrate the importance of stable isotope analysis for comprehending hydrologic dynamics in environmentally sensitive regions.

Feasibility Research on Surface Water Reinjection into the Sandstone Geothermal Reservoir of the Guantao Formation in Tianjin Based on Laboratory Experiments

Tianjin possesses abundant geothermal resources, and geothermal reinjection is an effective strategy for maintaining the sustainable development and utilization of these resources. However, several issues have arisen in the reinjection of sandstone geothermal reservoirs in the Tianjin area, including a mismatch between the reinjection capacity and effluent capacity, as well as challenges related to continuous reinjection. Therefore, it is crucial to investigate the reinjection of exogenous water into sandstone pore-type geothermal reservoirs. This study focuses on the geothermal reservoir of the Guantao Formation in the Binhai New Area. The surface water treatment process for reinjection into sandstone geothermal reservoirs was determined through water treatment simulation experiments. Additionally, experiments examining the interaction between the reinjected water and reservoir rock were conducted to assess the feasibility of using treated surface water for reinjection into sandstone geothermal reservoirs. The hydrogeochemical response mechanisms and the impact on the reservoir under reinjection conditions were also investigated. The results indicate that a nanofiltration module and tubular microfiltration membrane are essential to ensure the stability of the system. The pH and TDS of water samples decreased after reinjecting mixed water (HHS) into the sandstone reservoir. The hydrochemical type consistently remained Cl-Na. The conventional water chemistry components and trace elements were influenced by the corresponding water–rock reactions. The reservoir minerals exhibited minimal precipitation, primarily consisting of K-feldspar and Fe-dolomite. The minerals produced during the experiment accounted for only 0.08% of the total cuttings’ mass, indicating a negligible impact on the reservoir structure. PHREEQC was employed to simulate the changes in mineral saturation index before and after the reinjection of mixed water and geothermal water, respectively. Notably, similar hydrogeochemical changes were observed in the geothermal fluids. Thus, this study demonstrates the feasibility of reinjecting treated surface water into sandstone geothermal reservoirs from a hydrogeochemical perspective. This research provides valuable insights for the development of external water reinjection projects in hot spring health care units, contributing effectively to the achievement of carbon peaking and carbon neutrality goals.

Theoretical analysis of the initial nucleation characteristics of trace water vapor frosting on a cryogenic surface

In certain extreme conditions characterized by ultra-low water vapor content and ultra-low temperatures (e.g. cryogenic wind tunnel), trace water vapor frosting can also pose significant hazards. Considering the crucial role of initial nucleation on subsequent frosting processes, this study firstly investigated and compared the nucleation characteristics of frosting at different water vapor contents (0.1−1000 ppmv) from humid air to trace water vapor based on classical nucleation theory. The preferred nucleation phase diagrams and critical nucleation conditions were analyzed. Sensitivity of the nucleation mass transfer rate, as well as the frosting pathways were further identified. Results show that the nucleation characteristics of trace water vapor frosting (<100 ppmv) is significantly different from that of humid air frosting (>1000 ppmv). Trace water vapor frosting is more inclined towards desublimation nucleation due to its lower nucleation temperature and larger critical contact angle. The critical contact angles for 1000 ppmv, 100 ppmv and 0.1 ppmv are 49°, 75° and 120°, respectively. Furthermore, trace water vapor nucleation requires a greater subcooling degree, has a smaller critical nucleation radius, and is highly sensitive to surface contact angle and further-subcooling degree. At a surface contact angle of 120°, the nucleation subcooling degree of 0.1 ppmv is 2.9 K greater than that of 1000 ppmv. This study helps understanding the nucleation characteristics under different water vapor content conditions, which indicates that reducing subcooling degree and increasing contact angle are more effective anti-frosting methods than reducing water vapor content for trace water vapor frosting.

Occurrence, persistence, and removal of contaminants of emerging concern through drinking water treatment processes – A case study in South Africa

The presence of contaminants of emerging concern (CECs) in drinking water is a global issue of concern. Evidence galore of the potential impacts of CECs on human health, yet there are no concrete guidelines or regulatory oversight to effectively tackle CECs exposure from drinking water. As a result, CECs concentrations can be well-above the suggested thresholds, particularly in low and middle-income countries (LMICs) due to undeveloped or underdeveloped (waste)water treatment infrastructure and/or substandard treatment practices. Yet, CECs occurrence and particularly their persistence during drinking water treatment is not well-documented in such settings. For this reason, here, the occurrence of 19 CECs was monitored across the different treatment steps (coagulation, sedimentation, sand filtration, and chlorination) of a typical water treatment plant in South Africa using UPLC-MS/MS. The most dominant CEC was, by and large, efavirenz (1103.9 ± 743.1 ng/L in raw water) tracing back to antiretroviral treatment for the human immunodeficiency virus (HIV) and revealing unpleasant realities about the HIV epidemic crisis in Sub-Sahara Africa (Global South) and possible drug abuse for illicit drug (whoonga/nyaope) manufacturing. For the other examined CECs, their concentrations in drinking water were, from higher to lower score: 1,7 dimethylxanthine (403.3 ± 244.2 ng/L) ≥ emtricitabine (358.4 ± 250.8 ng/L) ≥ atrazine (227.0 ± 61.0 ng/L) ≥ caffeine (194.1 ± 216.5 ng/L) ≥ tramadol (189.5 ± 112.4 ng/L) ≥ carbamazepine (122.9 ± 24.5 ng/L) ≥ sulfamethoxazole (107.8 ± 55.1 ng/L) ≥ methaqualone (72.2 ± 20.5 ng/L) ≥ benzotriazole (61.2 ± 18.8 ng/L) ≥ trimethoprim (59.1 ± 30.4 ng/L) ≥ cetirizine (33.7 ± 19.6 ng/L) ≥ codeine (26.7 ± 57.2 ng/L) ≥ naproxen (25.7 ± 11.3 ng/L) ≥ venlafaxine (21.6 ± 16.3 ng/L) ≥ acetaminophen (17.7 ± 25.8 ng/L) ≥ benzoylecgonine (9.6 ± 5.1 ng/L) ≥ methamphetamine (8.6 ± 6.4 ng/L) ≥ diclofenac (5.2 ± 7.9 ng/L). The large standard deviations indicate the high temporal variations in CECs releases in freshwater. The silver lining is that in the final drinking water, CECs concentrations are greatly reduced, with percentage removals in the range of 9 % (diclofenac) to 75 % (efavirenz). Nonetheless, in LMICs tangible limits and regulatory frameworks for the effective removal of CECs from drinking water, along with more robust polishing techniques such as activated carbon treatment, are missing and should be introduced to avoid the worst effects of CECs exposure.

All roads lead to Rome: Trace water-dominated the formation of nanosheet-assembled hollow metal-organic frameworks for high performance supercapacitors

Controlling the structure of metal-organic frameworks (MOFs) is a crucial strategy to enhance electrochemical performance. In this work, nanosheet-assembled hollow Ni-MOF spheres are synthesized by controlling the transition states through a facile trace water-assisted solvothermal method. During the research, it is found that water in the system, whether from the precursor Ni(NO3)2·6H2O or from an additional source, is a key influencing factor that can regulate the reaction process to control structural changes. Theoretical calculations prove that the water present in the reaction system can affect the distribution of terephthalic acid (TPA) and Ni2+, indicating that trace water can provide an accelerating effect. The nanosheet-assembled sphere shells can expose more active surface area, and the hollow structure can prevent the restacking of nanosheets and shorten the charge transport path. Based on these structural advantages, the prepared Ni-TPA MOF electrode achieves a high specific capacitance of 1010 F g−1 at 1 A g−1 and a 61 % rate capability at 20 A g−1. This work offers a feasible and highly effective strategy to design nanosheet-assembled hollow MOF spheres for high-performance supercapacitors and helps to understand the key factors influencing the formation of hollow MOF spheres.

Cryogenic vacuum distillation vs Cavitron methods in ecohydrology: Extraction protocol effects on plant water isotopic values

Stable isotope ratios of hydrogen and oxygen in plant water are widely used for water tracing in ecohydrology studies. In this approach, plant water is extracted for isotopic analysis of δ2H and δ18O. Among the extraction methods, cryogenic vacuum distillation (CVD) has been the most popular, but its impact on the isotopic composition of plant water is currently under debate. Newer Cavitron method have been proposed to replace CVD method for xylem water extraction. These recommendations have been largely based on comparisons between Cavitron-xylem water with low temperatures CVD-xylem water. However, the CVD protocol (extraction temperature and time) varies widely across laboratories, and no direct, systematic comparison has yet been made between extraction temperature and time protocols vs. the Cavitron approach. Here we compared the isotopic values of xylem water from the same tree obtained through CVD extraction at 60 °C (60, 120, 240, 360 min), 100 °C (30, 60, 120, 240 min), 140 °C (15, 30, 60, 120, 240 min), and 200 °C (15, 30 min). Subsequently, we compared the results of CVD-xylem water with Cavitron-xylem water. Our data show that isotopic values for CVD-xylem water became more positive with increasing extraction time under the same extraction temperature. Such extractions also became more isotopically positive with increasing extraction temperature for the same extraction time. When total extraction efficiency exceeded 98 %, there was no δ18O difference in CVD-xylem water among any of the different protocols (p > 0.05). However, lower extraction temperatures resulted in more negative δ2H when compared to higher temperature extraction (p < 0.05). Cavitron-xylem water was close to CVD-xylem water (average difference of 3 ‰ for δ2H and 0.5 ‰ for δ18O, n = 79) when total extraction efficiency for CVD was below 98 %. But for extraction efficiencies beyond 98 %, the Cavitron-xylem water was more negative in δ2H (17.3 ‰, n = 70) and δ18O (1.7 ‰, n = 70) than CVD-xylem water. Compared to Cavitron-xylem water, CVD-xylem water at 200 °C with extraction efficiency > 98 % was closer to the soil water. Further study is necessary to conduct a complete cross-comparison between Cavitron and CVD at different temperatures with different species at various water and salt stress conditions. But our results suggest that abandoning CVD for plant water maybe premature until such complete comparison work is done.

Triggering dual-mode dynamic optical responses by anchoring carbon dots on MnO2 hollow spheres

Multi-mode responsive optical materials with versatile application prospects for optical sensing, optoelectrical devices, and information encryption are highly desired. Here we integrate fluorescent carbon dots onto the hollow MnO2 spheres, and modulate the interaction between them to achieve a water-stimulated responsive system with dual-mode dynamic signals in both fluorescence and structural color. The composite film shows a structural color shifting from blue to green as well as displays a fluorescence “on” in the presence of trace water, with both changes capable of being reversibly switched up to 10 times. The amide bond between the two components enables the controllable dispersion and aggregation of the carbon dots which is essential to the reversibility. Fabrication of several security labels with separate information in structural color and fluorescence channels demonstrates the application potential of the composite. This work provides a concise route to develop new multi-mode responsive optical materials for applications in anti-counterfeiting, sensing, and coding.

Zoning and regulation of compound flooding in coastal cities coupled with tracer method

Urban inland rivers play a significant role in mitigating flooding. However, the influence of their discharge on urban flooding affected by different flood drivers remains to be fully explored. Taking a catchment area in Haikou City, Hainan Province, China as an example, in light of the urban flooding model coupled with the water tracer method, this study investigates the degree of inundation in each flood zone under different inland river flows. The flood zones are determined by the flooding simulation results of three cases, and then are verified by the zonation based on the tide tracer approach. Finally, the tracer method is used to study the impact of urban inland rivers on flooding and the connection of hydraulic and water volume between rivers and pipelines. The results indicate that the inundation area decreased by 3.71 % as the river flow increased from 15 to 25 m3/s. In the process of river flow rising from 5 to 45 m3/s, The average flooding depth in the rainfall-affected area climbs slowly from 0.53 m to 0.62 m; In the tidal-affected area, the average flooding depth drops from 0.52 m to 0.12 m when the inland river flow increases from 5 to 25 m3/s, and rises from 0.12 m to 0.54 m when the inland river flow continues from 25 to 45 m3/s; The percentage of pipelines grows from 18.5 % to 28.0 %. This study provides valuable scientific insights and support for flood prevention planning and flood control strategies in coastal cities.

Best of Both Worlds: Adsorptive Ultrafiltration Nanocellulose‐Hypercrosslinked Polymer Hybrid Membranes for Metal Ion Removal

Efficient water treatment ideally combines ion exchange for the removal of hardness elements and toxic trace metals as well as ultrafiltration for the removal of particulate matter. Although promising for adsorption, many high‐surface‐area polymer materials cannot be easily processed into freestanding membranes or packed bed columns, due to poor solution processability and high back pressures, respectively. The preparation of hybrid membranes comprising sulfonated hypercrosslinked polymers entrapped in nanocellulose papers is described. The hybrid membranes are effective for simultaneous ultrafiltration and ion exchange. Increasing the polymer loading of the hybrid membrane produces synergy by increasing the permeance of the membranes while enhancing the ion adsorption capacity to values exceeding those of bulk hypercrosslinked polymers. The maximum ion adsorption capacity for copper is determined to be ≈100 mg g−1 outperforming that of pure polymer (71 mg g−1) and commercially available ion exchange resins. Competitive adsorption is tested in samples containing water hardness elements and trace toxic metal ions showing high ion‐exchange capacities. Even when fully loaded with water hardness elements, Ba2+ and Sr2+ are still removed from solution.