Heterogeneous Water Research Articles

Comparative study of the structure and dynamics of water confined between nickel nanosheets and bulk water, a study using reactive force fields

In this study, the structure and dynamics of water molecules confined between nickel surfaces and its comparison with water in bulk are investigated. To this end, molecular dynamics approach accompanied by reactive force field is used to study the characteristics of the confined water. The results showed that water molecules near the enclosing surfaces change in terms of structure and dynamics. The water molecules form a two-layer structure close to the nickel surface, and the results of the partial charge distribution give an electric double layer at the interface, with a positive partial charge of nickel atoms at surface against the negative partial charge of the first layer of water molecules. In addition, intense stratification effects near the nickel surfaces are visible. The radial distribution functions showed that, on average, the hydrogen atoms of the water molecules in the near-surface layers are closer to the nickel than the oxygen atoms, and also because of the repulsive effects induced by the interaction with the surfaces, water molecules would be found at distances further than 2 Å. Different orientations of the water molecules relative to the nickel surface were calculated using orientational ordering. This calculation shows the character of heterogeneous water molecules in confined state.

Data Mining to Uncover Heterogeneous Water Use Behaviors From Smart Meter Data

AbstractKnowledge on the determinants and patterns of water demand for different consumers supports the design of customized demand management strategies. Smart meters coupled with big data analytics tools create a unique opportunity to support such strategies. Yet, at present, the information content of smart meter data is not fully mined and usually needs to be complemented with water fixture inventory and survey data to achieve detailed customer segmentation based on end use water usage. In this paper, we developed a data‐driven approach that extracts information on heterogeneous water end use routines, main end use components, and temporal characteristics, only via data mining existing smart meter readings at the scale of individual households. We tested our approach on data from 327 households in Australia, each monitored with smart meters logging water use readings every 5 s. As part of the approach, we first disaggregated the household‐level water use time series into different end uses via Autoflow. We then adapted a customer segmentation based on eigenbehavior analysis to discriminate among heterogeneous water end use routines and identify clusters of consumers presenting similar routines. Results revealed three main water end use profile clusters, each characterized by a primary end use: shower, clothes washing, and irrigation. Time‐of‐use and intensity‐of‐use differences exist within each class, as well as different characteristics of regularity and periodicity over time. Our customer segmentation analysis approach provides utilities with a concise snapshot of recurrent water use routines from smart meter data and can be used to support customized demand management strategies.

Use of a Food Web Bioaccumulation Model to Uncover Spatially Integrated Polychlorinated Biphenyl Exposures in Detroit River Sport Fish.

We applied and tested a bioenergetic-based, steady-state food web bioaccumulation model to predict polychlorinated biphenyl (PCB) exposures in sport fish of the Detroit River (USA-Canada), which is a Great Lakes area of concern. The PCB concentrations in the sediment and water of the river were found to exhibit high spatial variation. The previously contained areas of high contamination may have spread to adjacent food webs as a result of fish movements. This process may cause biased predictions in single-compartment bioaccumulation models. We performed multiple simulations and contrasted model predictions against a database of 1152 fish sample records comprising 19 sport fish species. The simulations evaluated 4 spatial scales (river-wide, 2-nation, 4-zone, and 6-zone models) to reveal how the spatial heterogeneity of contamination and species-specific movements contribute to variation in fish PCB exposures. The model testing demonstrated that the 2-nation model provided the most accurate global prediction of fish contamination. However, these improvements were not equally observed across all species. The model was subsequently calibrated for poorly performing species, by allowing cross-zone exposures, demonstrating the importance of accounting for specific ecological factors, such as fish movement, to improve PCB bioaccumulation prediction, especially in highly heterogeneous water systems. Environ Toxicol Chem 2019;38:2771-2784. © 2019 SETAC.

Interfacial Charge Transport in 1D TiO2 Based Photoelectrodes for Photoelectrochemical Water Splitting.

1D nanostructured photoelectrodes are promising for application as photoelectrochemical (PEC) devices for solar energy conversion into hydrogen (H2 ) owing to the optical, structural, and electronic advantages. Titanium dioxide (TiO2 ) is the most investigated candidate as a photoelectrode due to its good photostability, low production cost, and eco-friendliness. The obstacle for TiO2 's practical application is the inherent wide bandgap (UV-lights response), poor conductivity, and limited hole diffusion length. Here, a comprehensive review of the current research efforts toward the development of 1D TiO2 based photoelectrodes for heterogeneous PEC water splitting is provided along with a discussion of nanoarchitectures and energy band engineering influences on interfacial charge transfer and separation of 1D TiO2 composited with different dimensional photoactive materials. The key focus of this review is to understand the charge transfer processes at interfaces and the relationship between photogenerated charge separation and photoelectrochemical performance. It is anticipated that this review will afford enriched information on the rational designs of nanoarchitectures, doping, and heterojunction interfaces for 1D TiO2 based photoelectrodes to achieve highly efficient solar energy conversion.

Multihole water oxidation catalysis on haematite photoanodes revealed by operando spectroelectrochemistry and DFT.

Water oxidation is the key kinetic bottleneck of photoelectrochemical devices for fuel synthesis. Despite advances in the identification of intermediates, elucidating the catalytic mechanism of this multi-redox reaction on metal-oxide photoanodes remains a significant experimental and theoretical challenge. Here, we report an experimental analysis of water oxidation kinetics on four widely studied metal oxides, focusing particularly on haematite. We observe that haematite is able to access a reaction mechanism that is third order in surface-hole density, which is assigned to equilibration between three surface holes and M(OH)-O-M(OH) sites. This reaction exhibits low activation energy (Ea ≈ 60 meV). Density functional theory is used to determine the energetics of charge accumulation and O-O bond formation on a model haematite (110) surface. The proposed mechanism shows parallels with the function of the oxygen evolving complex of photosystem II, and provides new insights into the mechanism of heterogeneous water oxidation on a metal oxide surface.

Metallic iron limits silicate hydration in Earth’s transition zone

The Earth's mantle transition zone (MTZ) is often considered an internal reservoir for water because its major minerals wadsleyite and ringwoodite can store several oceans of structural water. Whether it is a hydrous layer or an empty reservoir is still under debate. Previous studies suggested the MTZ may be saturated with iron metal. Here we show that metallic iron reacts with hydrous wadsleyite under the pressure and temperature conditions of the MTZ to form iron hydride or molecular hydrogen and silicate with less than tens of parts per million (ppm) water, implying that water enrichment is incompatible with iron saturation in the MTZ. With the current estimate of water flux to the MTZ, the iron metal preserved from early Earth could transform a significant fraction of subducted water into reduced hydrogen species, thus limiting the hydration of silicates in the bulk MTZ. Meanwhile, the MTZ would become gradually oxidized and metal depleted. As a result, water-rich region can still exist near modern active slabs where iron metal was consumed by reaction with subducted water. Heterogeneous water distribution resolves the apparent contradiction between the extreme water enrichment indicated by the occurrence of hydrous ringwoodite and ice VII in superdeep diamonds and the relatively low water content in bulk MTZ silicates inferred from electrical conductivity studies.

A cooperative target search method based on intelligent water drops algorithm

This study investigates the problem of cooperative search path planning for multiple unmanned aerial vehicles. Firstly, we present a search probability map based environmental model, and formulate a multi-UAV cooperative search path optimization problem. Then, we propose a solution strategy based on an improved intelligent water drops (IWD) optimization algorithm. Compared with the traditional IWD algorithm, the proposed algorithm can simultaneously model the cooperation and competition among UAVs by introducing several heterogeneous water drop populations and a co-evolutionary mechanism. Water drops in the same population cooperate with each other, whereas water drops among different populations compete with each other to obtain the optimal path and reduce meaningless search effort. Meanwhile, the proposed algorithm can improve its search capability using a new soil update mechanism. Simulation results demonstrate the advantages of the proposed method over other baselines.

DICTUM

Lawns make up the largest irrigated crop by surface area in North America and carry with it a demand for over 7B gallons of freshwater each day. Despite recent developments in irrigation control and sprinkler technology, state-of-the-art irrigation systems do nothing to compensate for areas of turf with heterogeneous water needs. In this work, we overcome the physical limitations of the traditional irrigation system with the development of a sprinkler node that can sense the local soil moisture, communicate wirelessly, and actuate its own sprinkler based on a centrally computed schedule. A model is then developed to compute moisture movement from runoff, absorption, and diffusion. Integrated with an optimization framework, optimal valve scheduling can be found for each sprinkler node in the space. In a turf area covering over 10,000ft 2 , two separate deployments with four weeks of fine-grained data collection show that DICTUM can reduce water consumption by 23.4% over traditional campus scheduling, and by 12.3% over state-of-the-art evapotranspiration systems while substantially improving conditions for plant health. In addition to environmental, social, and health benefits, DICTUM is shown to return its investment in 16 to 18 months based on water consumption alone.

Understanding the structure and dynamical properties of stretched water by molecular dynamics simulation

Stretched water can sustain a large extent of stretching owing to the strong cohesion force prior to cavitation. However, the impacts of the stretching extent on the structure and dynamic properties of water is rarely investigated. In this work, molecular dynamics (MD) simulation was performed to explore the structure and dynamical properties of stretched water under varying stretching extents (i.e. evaporation coefficient). It was revealed that stretched water was more ordered under stretching and the ordering was enhanced with the increase of stretching extent. Moreover, the hydrogen bond was prolonged under stretching, accompanied with the decreased diffusion coefficients. However, the suddenly decreased structure ordering and the increased diffusion from = 0.106 to = 0.121 prior to cavitation was observed, which could be ascribed to the small cavity size of heterogeneous water phase that cannot satisfy the requirement for cavitation. This work may provide helpful insights into the molecular behaviours of water under stretching.

Water Brokers: Exploring Urban Water Governance through the Practices of Tanker Water Supply in Accra

Accra, the capital city of Ghana, is characterized by limited networked supply, heterogeneous water providers, and various forms of provision. In this paper, we explore how the people delivering water through water tankers shape the distribution of water across the city. Drawing on empirical descriptions of water sourcing and distribution by truck drivers, we show that who gets what water at what price is shaped by the ability of tanker drivers to act as brokers, piecing together various social and material arrangements and resorting to different rationalities and expertise. We analyze how state actors deal with tanker supply seeking to reconcile their mandates with the realities of water supply. Analyzing urban water supply through the practices of water distribution, we show the messy and open-ended character of water governance processes. A practice-based approach makes the complex interrelations between different water providers across the city visible, and underscores the role of individual and collective identities, emotions, moral norms, and unequal interdependencies between actors in shaping urban water distributions.

Effect of microstructure on hydric strain in clay rock: A quantitative comparison

This paper presents a new method able to compare quantitatively strains and microstructure of a clay material. This method was applied to a Tournemire clay rock sample subjected to cyclic hydric loading in laboratory conditions. Local strains of a centimeter-size Tournemire clay rock sample were quantified by digital image correlation (DIC) on a field of view of 5.5 × 4.1 mm2 at the resolution of 2 μm.pixel−1, at a temperature of 22 °C and between 98 and 33% of relative humidity. At the end of the hydric loading, at dry state, the microstructure of the same field of view was mapped by an extended mosaic of scanning electron microscopy images at the resolution of 0.625 μm.pixel−1 and superimposed to the reference images used for DIC. Two microstructural parameters: the mean area and the area fraction of rigid clasts and clay matrix, were quantified by image analysis to be directly superimposed to local strain values. Speckle artefacts partly due to polished surfaces of clasts were filtered in the comparison between strains and microstructure. Strains concentrated in parts of the clay matrix, and at the interface between matrix and several quartz clasts which showed a slight detachment from the matrix. Constant clay and clast area fractions and sizes corresponded to very variable strain values at the microstructure scale. The relationship between strain values, mineral size and area fractions was not linear. Micro-mechanisms of deformation were therefore very complex at the scale of the experiment. On a very large field of view, very different microstructure behaviors were averaged which avoided any simple relationship between microstructure and strains. Heterogeneous water distribution and non-local microstructural control factors were suspected.

Recent and Predicted Changes in Habitat of the Eurasian Skylark Alauda arvensis Based on the Link between the Land Cover and the Field Survey Based Abundance Data

The European avifauna on agricultural land has been permanently diminished over the past few decades. This phenomenon is clearly connected with agricultural intensification and the recent land cover changes. The main aims of this study were to identify the land cover preferences of a farmland bird species, the Eurasian Skylark Alauda arvensis in Hungary and investigate the link between the recent trend of the abundance of this species and the land-cover change. We employed GIS and statistical methods to assess the link between the abundance of this species based on the Hungarian common bird monitoring database (MMM) and the spatial proportion of the Corine Land Cover (CLC) categories in different buffer zones with 300, 600 and 1200 m from the observation points. Based on the significant statistical connections, we could identify and select land cover categories that serve as habitats and land cover categories that this bird species does not inhabit. The land cover preference of the Eurasian Skylark, in case of some land cover category, is depending on the grain scale (circle radius distance from the observation points). In analyses arable lands has been omitted because this land cover type is the well-known habitat of the species. According to our results, the Eurasian Skylark prefers permanent crops (vineyards, fruit trees and berry plantations) inside 600m and 1200m buffer zones, and pastures inside 1200m buffer zones, while it does not prefer urban fabric areas and heterogeneous agricultural, forests, and wetlands or water bodies inside 300m and 600m, scrub and/or herbaceous vegetation associations (transitional woodland-shrub and natural grassland areas) inside the 600m and 1200m radius buffer areas. The identification of these regional (European level) land-cover categories allowed us to analyse the recent (1990–2012) and the predicted (2006–2050) characteristics of habitat changes of this bird species, associated with land cover change. Based on our results, we could estimate that the Skylark habitat will decrease by 188 560 ha between 2006–2050 in Hungary.

Geminate Recombination versus Cage Escape in the Reductive Quenching of a Re(I) Carbonyl Complex on Mesoporous ZrO2

In the wider context of artificial photosynthesis, this work aims to explore the functionality and characteristics of rhenium tricarbonyl complexes as photosensitizers in heterogeneous water reduct...

Importance of Entropic Contribution to Electrochemical Water Oxidation Catalysis

Electrochemical water oxidation is considered as one of the most important reactions for a sustainable future. However, in heterogeneous water oxidation, atomistic understanding of this four-electron reaction is still elusive. In particular, the mechanism of O–O bond formation, the coupled transfer of proton and electron, and the hopping of high-valent metal-oxo intermediates are challenging issues. To date, binding energy related descriptors have been used successfully to predict the catalytic activities by matching the experimental data and quantitatively comparing the performances. In this Perspective, we attempt to emphasize the significance of entropic contribution, like enthalpy, by highlighting recent literature and calculating the entropy from the available data. We envision that this Perspective can suggest a new research direction toward the catalyst design to control the entropy during water oxidation and be technologically useful for characterizing the temperature effects.

Spatially Heterogeneous Water Properties at Disordered Surfaces Decrease the Hydrophobicity of Nonpolar Self-Assembled Monolayers.

Understanding the relationship between hydrophobicity and the properties of functionalized surfaces is vital to the design of materials that interact in aqueous environments. In this Letter, we use atomistic molecular dynamics simulations to investigate the effects of surface order on the hydrophobicity of self-assembled monolayers (SAMs) containing nonpolar ligands. We find that the interfacial hydrophobicity is highly correlated with SAM order and, strikingly, poorly correlated with the solvent-accessible surface area, which typically has been related to interfacial hydrophobicity. Analysis of spatial variations in both SAM and water properties reveals that the SAM-water interface is pinned near regions of disordered SAM surfaces with increased free volume, decreasing the overall interfacial hydrophobicity. Spatial variations in ligand end group positions at disordered SAM surfaces thus translate to spatial variations in hydrophobicity, yielding heterogeneous surface properties. These findings provide new insights into how surface order can alter the hydrophobicity of chemically uniform surfaces.

Influence of Ion Beam-Assisted Deposition on the Wetting Properties of Al-1.0 at.% Cr Alloy Films

The surface microstructure and wettability of Al-1.0 at.% Cr alloy films obtained by ion-beam-assisted deposition on glass substrates have been investigated using atomic force microscopy, scanning electron microscopy and the sessile drop method. In the passive deposition regime, the surface roughness of the films increased from 8.9[Formula: see text]nm to 21.6[Formula: see text]nm with an increase in coating time from 3[Formula: see text]h to 9[Formula: see text]h. A quantitative analysis of the morphology evolution of the films during their growth was performed. The results revealed that Al-1.0 at.% Cr alloy films are hydrophilic. The mechanism of heterogeneous water wetting of Al-1.0 at.% Cr alloy films was considered, when the increasing surface roughness accounts for a decrease of hydrophilicity.

Degradation of tris-(2-chloroisopropyl) phosphate via UV/TiO2 photocatalysis: kinetic, pathway, and security risk assessment of degradation intermediates using proteomic analyses

As a class of emerging organic contaminants (EOCs), organophosphate flame retardants (OPFRs) have been raising concern due to their persistence, bioaccumulation and toxicity. Therefore, it is urgent need to develop environmental-friendly and high-efficient techniques to remove OPFRs. The degradation kinetics and mechanism of tris-(2-chloroisopropyl) phosphate (TCPP), a representative OPFRs, by UV/TiO2 photocatalytic degradation were explored in current research. It was found that degradation reaction was well documented by first-order kinetics with a kobs of 0.3146 min−1, and hydroxyl radical was identified as a dominating contributor for the TCPP elimination. Simultaneously, six steady intermediate products were generated with the release of Cl− and PO43− as photocatalytic reaction further proceeded. The degradation efficiency can be interfered by natural organic matters, anions and pH value, implying that an incomplete mineralization of TCPP could be ubiquitous in heterogeneous water matrix. Combining the proteomics analysis with KEGG metabolism networks analysis, the process of transmembrane transport and energy generation in Escherichia coli altered by intermediates has proved that the intermediates could be transported and utilized through cellular metabolism. Moreover, the diminution of stress resistance suggested that the toxicity of degradation products through UV/TiO2 photocatalytic degradation was lower than that of intact TCPP. To sum up, environmental safety of degrading intermediate products and the satisfactory detoxification effect of TCPP were identified under appropriate mineralization, indicating that UV/TiO2 photocatalysis technique was safe and high-efficient for TCPP control.

A spatiotemporal interpolation method for the assessment of pollutant concentrations in the Yangtze River estuary and adjacent areas from 2004 to 2013

Nitrogen is one of the most significant pollutants in the Yangtze River estuary (YRE), China. Reliable estimation of nitrogen concentration in the water is crucial for assessment of the water quality of the estuary. Because ocean fronts exist in the YRE, which divide water masses into different regions, it is necessary to account for the heterogeneity of the water surface when predicting nitrogen concentrations. A new geostatistical method, called spatiotemporal point mean of surface with non-homogeneity (ST-PMSN), is proposed to model the non-stationary spatiotemporal random process of nitrogen concentrations between 2004 and 2013 in the YRE. The method considers the spatiotemporal correlation of surface water nitrogen and uses information from both sides of a boundary for heterogeneous water masses. Comparing with several other interpolating methods, including spatial ordinary kriging (OK), stratified ordinary kriging (SOK), point mean of surface with non-homogeneity (P-MSN), spatiotemporal ordinary kriging (STK), and stratified spatiotemporal ordinary kriging (SSTK), the cross-validation results show that ST-PMSN has the highest accuracy, followed by SSTK, STK, P-MSN, SOK, and OK in descending order. ST-PMSN is therefore demonstrated to be effective in estimating the nitrogen pollutant concentrations in a stratified estuary. According to interpolated nitrogen concentrations in the YRE, water quality has generally deteriorated—with fluctuations—from 2004 to 2013. The average annual reduction in area of water quality of Grades I and II from 2004 to 2013 was 1.10%. At the same time, the average annual increase in area of water quality of Grades III and IV was 0.89% and that of Grade V was 0.21%. The results of this study provide a new and more accurate interpolating method for assessing the pollutant concentration in the marine and offers guidance for more precise classification of water quality in the YRE.

Poly(diallyldimethylammonium-MoS4) based amorphous molybdenum sulphide composite for selectively mercury uptake from wastewater across a large pH region

Amorphous molybdenum sulphide materials are attracting more attention in heterogeneous catalysis, gas adsorption and water remediation fields. Herein, a new type of amorphous molybdenum sulphide composite (poly(diallyldimethylammonium-MoS4), shorten as PDADMA-MoS4) was synthesized via a facile precipitation reaction. Metal adsorption tests of prepared PDADMA-MoS4 composite shows that Hg2+ and Pb2+ concentrations in solution can decrease from 10 ppm to <0.5 ppb level much lower than the drinking water requirement (<2 ppb) in 10 min. The metal adsorption isotherms suggest that maximum metal-uptake capacities are 1460.0 mg/g for Hg (pH = 5) and 433.7 mg/g for Hg (pH = 1), indicating that this sorbent works over a wide pH range (1.0–7.0) to effectively remove Hg from aqueous solution. More importantly, at very low pH = 1, this sorbent material exhibits extraordinarily high selectivity of Hg over Pb and Cu (separation factors βHg/Cu=4.5×104 and βHg/Pb=3.6×104). The excellent Hg capacity and selectivity at low pH region (pH < 2) has shed light on the new generation of adsorbent materials for acidic wastewater treatment.

Crossing the bridge from molecular catalysis to a heterogenous electrode in electrocatalytic water oxidation

Significant progress has been made in designing single-site molecular Ru(II)-polypyridyl-aqua catalysts for homogenous catalytic water oxidation. Surface binding and transfer of the catalytic reactivity onto conductive substrates provides a basis for heterogeneous applications in electrolytic cells and dye-sensitized photoelectrosynthesis cells (DSPECs). Earlier efforts have focused on phosphonic acid (-PO3H2) or carboxylic acid (-CO2H) bindings on oxide surfaces. However, issues remain with limited surface stabilities, especially in aqueous solutions at higher pH under conditions that favor water oxidation by reducing the thermodynamic barrier and accelerating the catalytic rate using atom-proton transfer (APT) pathways. Here, we address the problem by combining silane surface functionalization and surface reductive electropolymerization on mesoporous, nanofilms of indium tin oxide (ITO) on fluorine-doped tin oxide (FTO) substrates (FTO|nanoITO). FTO|nanoITO electrodes were functionalized with vinyltrimethoxysilane (VTMS) to introduce vinyl groups on the electrode surfaces by silane attachment, followed by surface electropolymerization of the vinyl-derivatized complex, [RuII(Mebimpy)(dvbpy)(OH2)]2+ (12+; Mebimpy: 2,6-bis(1-methyl-1H-benzo[d]imidazol-2-yl)pyridine; dvbpy: 5,5'-divinyl-2,2'-bipyridine), in a mechanism dominated by a grafting-through method. The surface coverage of catalyst 12+ was controlled by the number of electropolymerization cycles. The combined silane attachment/cross-linked polymer network stabilized 12+ on the electrode surface under a variety of conditions especially at pH > ∼6. Surface-grafted poly12+ was stable toward redox cycling at pH ∼ 7.5 over an ∼4-h period. Sustained heterogeneous electrocatalytic water oxidation by the electrode gave steady-state currents for at least ∼6 h with a Faradaic efficiency of ∼68% for O2 production.