Evaporation Period Research Articles

Analysis of Flash Drought and Its Impact on Forest Normalized Difference Vegetation Index (NDVI) in Northeast China from 2000 to 2020

Flash drought is characterized by rapid onset and short-duration drought conditions caused by a combination of factors, including high evaporation, high temperature, and prolonged periods of little to no precipitation, leading to a sudden and severe decrease in soil moisture levels. In comparison to conventional drought, it is more susceptible to the effects of global warming and has the potential to become a common drought phenomenon in the coming years, necessitating further research. In this paper, we focused on flash drought events, specifically in forest parts of northeastern China that are included within the Greater Khingan Mountains (GKM), Lesser Khingan Mountains (LKM), and Changbai Mountains (CM), using daily soil moisture data as well as SPOT- VEGETATION NDVI satellite data from 2000 to 2020 and determined their impact on the forest NDVI. Our major findings are as follows. (1) The forest within GKM had the maximum area being affected by flash drought events. (2) The frequency ranged from 1 to 2 times, whereas the total duration varied between 20 and 55 days over the study area in a 21-year period. (3) Flash drought was most common in the plant-growing seasons. (4) The flash drought events had a negative influence on the forest NDVI. Our study contributes to a deeper understanding of the flash drought dynamics in forest areas of northeast China for flash drought monitoring, prediction, and management strategies in this region.

Untangling the implications of climate-forcing and human-induced drivers in streamflow variability: the Magdalena River, Colombia

ABSTRACT A comprehensive study was conducted to analyse the impact of different drivers on streamflow downstream of the Magdalena River (MR), Colombia, between 1971 and 2020. The study considered El Niño Southern Oscillation (ENSO) events as a climate-forcing driver and evaporation from the reservoir network as a human-induced driver. Streamflow data was linked to previously categorized ENSO events, then standardized and classified based on date and year to evaluate inter- and intra-annual changes in streamflow. Daily evaporation losses were calculated using meteorological records and the aerodynamic method. The study also grouped 10-year periods of evaporation and streamflow to assess their ranges, rates, and water volumes. The results showed a decrease in means, volume, and maximum streamflow, while evaporation and minimum streamflow increased, especially during positive ENSOs. These changes in streamflow could have a significant impact on river-dominated dependent ecosystems, such as the MR downstream wetland complex, putting these ecosystems at risk.

Evaporation Mechanisms and Heat Transfer in Porous Media of Mixed Wettabilities with a Simulated Solar Flux and Forced Convection Through the Media

Abstract An experimental apparatus was designed to study the impacts of wettability on evaporation of water for: 1) a 5.7-cm-thick layer of hydrophilic Ottawa sand; 2) a 5.7-cm-thick layer with 12% hydrophobic content, consisting of a 0.7-cm-layer of n-Octyltriethoxysilane-coated hydrophobic sand buried 1.8 cm below the surface of hydrophilic sand; and 3) a 5.7-cm-thick layer with mixed wettabilities, consisting of 12% n-Octyltriethoxysilane-coated hydrophobic sand mixed into hydrophilic sand. The sand-water mixtures experienced forced convection above and through the sand layer, while a simulated solar flux (i.e., 112 ± 20 W/m2) was applied. Evaporation from homogeneous porous media is classified into the constant-rate, falling-rate, and slow-rate periods. Wettability affected the observed evaporation mechanisms, including the transition from constant-rate to falling-rate periods. Evaporation entered the falling-rate period at 12%, 20%, and 24% saturations for the all hydrophilic sand, hydrophobic layer, and hydrophobic mixture, respectively. Wettability affected the duration of the experiments, as the all hydrophilic sand, hydrophobic layer, and hydrophobic mixture lasted 17, 20, and 26 trials, respectively. Both experiments with hydrophobic particles lasted longer than the all hydrophilic experiment and had shorter constant-rate evaporation periods, suggesting hydrophobic material interrupts capillary action of water to the soil surface and reduces evaporation. Evaporation fluxes were up to 12× higher than the vapor diffusion flux due to enhanced vapor diffusion and forced convection.

Evaporation of a heated saline marble: Interplay of interfacial and thermal effects

A multistage evaporation of continuously heated liquid marbles, coated with polytetrafluoroethylene colloidal particles was investigated experimentally and theoretically. Liquid marbles initially contained an almost saturated aqueous NaCl solution. Numerical heat transfer calculations and analytical evaluations of initial evaporation showed that the equilibrium marble temperature and saturated salt concentration are reached relatively rapidly compared to the “long” marble evaporation time. This means that a typical long period of marble evaporation is determined by the low permeability of the salt crust formed beneath the marble colloidal shell. A theoretical estimation of the total evaporation time of marble water based on Darcy's law for the porous crust and the marble shell is suggested. A comparison with experimental data allowed obtaining an approximate value of the very low permeability of this bilayer barrier to marble evaporation. The proposed phenomenological model of the saline marble evaporation provides insight into why marble evaporation is so slow.

Interfacial Effects of Nanostructured Doubly Reentrant Surfaces on the Evolution of Local Concentration and Fluid Flow in an Evaporating Droplet.

Surface modification, such as bioinspired nanostructured doubly reentrant surfaces that have presented superhydrophobic wettability even under low-surface-tension liquid, is a very promising technology for controlling droplet dynamics, heat transfer, and evaporation. In this article, we investigate the interfacial effects of nanostructured doubly reentrant surfaces on the flow behaviors and local concentration evolution during the evaporation of an ethanol/water multicomponent droplet. Using particle image velocimetry (PIV) and novel aggregate-induced emission-based (AIE) techniques, the flow patterns and local concentration distributions on both hydrophobic and nanostructured doubly reentrant surfaces were probed and compared. It is found that in addition to the established Marangoni flow-dominated stage, transition stage, and buoyancy-induced flow-dominated stage, a new transition stage and a rolling stage for the nanostructured doubly reentrant surface are detected in the late evaporation period. Differences in the local concentration distribution evolution occur depending on the hydrophobicity of the surface on which the droplet is placed. For the hydrophobic surface, a nonuniform local concentration distribution exists consistently, with a high water fraction in a shell-shaped region near the liquid-air interface and a secondary concentration gradient within this shell-shaped region. The concentration distribution on the nanostructured doubly reentrant surface evolves in a more complex manner, with a strip-shaped region of high water fraction forming in the intermediate stage and then reorganized by rolling flow in the late stage. Finally, theoretical analysis combining PIV and AIE visualization results reveals that the variations in droplet concentration distributions on surfaces with different hydrophobicities exert a significant impact on evaporative behaviors. These behaviors, in turn, affect the evolution of the local concentration distribution.

Loading atoms from a large magnetic trap to a small intra-cavity optical lattice

We show that an optimized loading of a cold ensemble of rubidium-87 atoms from a magnetic trap into an optical lattice sustained by a single, far-red-detuned mode of a high-Q optical cavity can be efficient despite the large volume mismatch of the traps. The magnetically trapped atoms are magnetically transported to the vicinity of the cavity mode and released from the magnetic trap in a controlled way meanwhile undergoing an evaporation period. Large number of atoms get trapped in the dipole potential of the cavity mode for several hundreds of milliseconds. We monitor the number of atoms in the mode volume by a second tone of the cavity close to the atomic resonance. While this probe tone can pump atoms to another ground state uncoupled to the probe, we demonstrate state-independent trapping by applying a repumper laser.

Taking Titan’s Boreal Pole Temperature: Evidence for Evaporative Cooling in Ligeia Mare

From 2004 to 2017, the Cassini RADAR recorded the 2.2 cm thermal emission from Titan’s surface in its passive (radiometry) mode of operation. We use this data set to investigate the seasonal evolution of the effective temperature sensed by the microwave radiometer in two regions in the northern pole of the satellite: the sea Ligeia Mare, and its nearby solid terrains. We find that despite the arrival of summer at the end of the mission, the effective temperature of Ligeia Mare decreased by almost 1 K, while that of the solid region slowly increased until 2017 by 1.4 ± 0.3 K. These observations, as well as the lag in summer warming observed by Cassini’s Composite Infrared Spectrometer, can be explained by evaporative cooling in both the solid and liquid surfaces after the vernal equinox. It therefore supports the idea that the northern polar terrains are wet. Using an ocean circulation model, we show that the cooling of the sea surface should initiate convection in the sea’s interior, ultimately cooling the whole liquid column sensed by the Cassini radiometer and thus decreasing the temperature at depths even long after the evaporation period has ceased. Overall, this work highlights the key role of methane hydrology in controlling the surface and submarine temperatures in the boreal polar regions of Titan.

Technical note: Isotopic fractionation of evaporating waters: effect of sub-daily atmospheric variations and eventual depletion of heavy isotopes

Abstract. Isotopic fractionation of evaporating waters has been studied constantly in recent decades, particularly because it enables calculation of both the volume of water evaporated from a water body and the isotopic composition of its source water. We studied the stable water isotopic composition of an artificial pan filled with water and subject to total evaporation in a sub-humid environment, in order to put into practice an operational method for estimating the time since disconnection of riverine pools when these are sampled for the quality of aquatic life. Results indicate that (i) when about 70 % of pan water had evaporated and its isotopic composition had become enriched in heavy isotopes, some subsequent periods of depletion instead of enrichment happened; and (ii) the customary application of isotopic fractionation equations to determine the isotopic composition of the water in the pan using weekly averaged atmospheric conditions (temperature and relative humidity) strongly underestimated the changes observed but predicted an early depletion of heavy isotopes. The first result, rarely reported in the literature, was found to be fully consistent with the early studies of the isotopic composition of evaporating waters. The second one could be attributed to the fact that weekly averages of temperature and relative humidity strongly overestimated air relative humidity during daylight periods of active evaporation. However, when the fractionation equations were parameterized using temperature and relative humidity weighted by potential evapotranspiration at sub-hourly time steps, they adequately reproduced the observed isotopic composition of the water in the pan, including the late periods of heavy isotope depletion. We demonstrate how weekly increases in air relative humidity when the pan water was already enriched in heavy isotopes led to their depletion. We also analyse the errors that can be incurred if time averages are used instead of flux-weighted meteorological data for model parameterization and if unidentified periods of heavy isotope depletion occur. Our results should be taken into account when applying fractionation equations, particularly in conditions or areas with high air relative humidity.

Developing a highly efficient, environmentally friendly and cost-effective copper sulfide semiconductor sponge for nuclear wastewater treatment under one sun

Solar-driven interfacial evaporation technology, as a green and low-energy water treatment method, finds widespread applications in desalination, power generation, and wastewater treatment systems. In this study, a three-dimensional sponge solar evaporator was prepared using hydrophilic compounds (konjac glucomannan, KGM) and a solar absorber (copper sulfide, CuS). In a single instance of solar irradiation, the sponge demonstrated swift evaporation rates at 1.58 kg m−2 h−1, coupled with an impressive interfacial water evaporation efficiency of 94.30%. Due to the characteristics of CuS and KGM, the sponge demonstrated photothermal properties, insulation, and rapid water transport. Even under radiation (1 kW/m2) and a wide range of pH conditions (pH∼2–12), the concentration of elements in radioactive wastewater could be reduced by a million times (from 1 g/L to 0.253 μg/L). Notably, during 20 cycles of testing, the sponge's evaporation efficiency only decreased by 1.13%. Furthermore, over an extended 5-hour evaporation period, it consistently sustained a steady evaporation rate of 1.577 kg m−2 h−1, showcasing its exceptional reproducibility and enduring resilience. Therefore, solar-driven interfacial evaporation technology exhibits significant potential for efficient treatment of radioactive wastewater.

Ammonia release characteristics during desulfurization wastewater evaporation: Mechanisms and implications

This study investigated the mechanisms of ammonia release during desulfurization wastewater evaporation and its potential environmental impacts. A single droplet evaporation device (SDD) assessed the wastewater evaporation and ammonia release characteristics. Approximately 8.5 % of ammonia was released during the free water evaporation period (0–35 s). As the droplet underwent shell inflation-deflation and core-shell drying, the remaining ammonia was mainly released due to increased vapor pressure and poor thermal stability of ammonium salts. The wastewater properties, especially pH value, greatly influenced the release of ammonia. Alkaline wastewater exhibited a significantly higher ammonia release rate. Ammonia migration and transformation were studied in a 600 MW power plant. Approximately 9.2–11.7 % of ammonia was released, while the rest was retained in solid form within the evaporation product. Characterization techniques and DFT simulations showed that the released NH3 probably combines with fly ash due to the water vapor, HCl, SO3, and other acidic gases in the flue gas. Risk analysis suggested that ammonia release during evaporation would not significantly increase ammonia concentration in flue gas or hinder fly ash comprehensive utilization. However, when handling desulfurization wastewater with high-concentration ammonia, it was essential to consider the potential corrosion of downstream equipment caused by released ammonia.

Factors and processes controlling hydrochemistry and evaporitic deposits in hypersaline wetland‐shallow lake systems

AbstractThree wetland‐shallow lakes were studied with the aim of analysing the processes and factors that control hydrochemistry and evaporite deposits in them in basins of the Pampean Plain, Argentina. In this sense, water balances and analysis of the water content of the lakes with normalized water difference index were made, and geologic‐geomorphological characteristics and groundwater flows were defined. Groundwater, surface water and evaporite samples were taken, along with sediment samples from wetland‐shallow lakes and surroundings. In situ pH, electrical conductivity and temperature, and laboratory chemical determinations of major ions of the water were measured. x‐ray diffraction (XRD) and scanning electron microscope (SEM)‐energy dispersive spectroscopy (EDS) analyses of evaporite and sediment samples were carried out. The results obtained allow the identification of two different systems. One of them is represented by Leubucó wetland‐lake basin, which is topographically higher and smaller than the other system, with Na‐HCO3 and Na‐Cl/SO4 groundwater inflows, with high concentrations of Ca2+ and Mg2+. In periods of high evaporation, the regional water table drops, and due to its topographic position, the lake dries. These determine the formation of thick layers of halite associated with magnesium salts on surface, and gypsum layers interbedded with clastic sediments. The other system involves de la Sal and Chasilauquen wetland‐lake basins, which have larger extensions. They receive Na‐HCO3 and Na‐Cl/SO4 groundwater inflow, but with low Mg2+ and Ca2+. Their lower topographic position determines that even during deficit periods, the water table intercepts the lakes surface and therefore, lakes have a shallow surface water level almost all the year, which is hypersaline, Na‐Cl type. These systems only have thin evaporite crusts, composed of halite and thenardite at the edges of the lakes, and the formation of Ca‐Mg sulfates is not observed. It is concluded that topographic position, basins size, geology, groundwater inflow and evaporation are the main processes and factors controlling hydrochemistry and evaporitic deposits.

Simulation study on the single droplet evaporation of N-tetradecane with CeO2 nanoparticles

To investigate the influence of CeO2 nanoparticles on the evaporation characteristics of fuel droplets, numerical simulation for single nano-fuel droplet evaporation was conducted based on ANSYS FLUENT software according to the single droplet evaporation visualization experiment. And the effects of nanoparticles’ concentration and size on the temperature and fuel-vapor concentration during the evaporation of were emphatically discussed. The simulation results showed that the temperature field and concentration field were distributed in a gradient. Nano-fuel droplets absorbed heat from the external environment, and the temperature of the nano-fuel droplets kept rising until reaching the evaporation equilibrium temperature. The evaporation equilibrium temperature of nano-fuels droplets was higher than that of N-tetradecane (C14) at the temperature of 573 K. In addition, it increased with the increment of nanoparticle concentration and reduction of the nanoparticle size. In the beginning of the evaporation, the vapor volume fraction of nano-fuel was relatively low and it increased slowly with time. As the evaporation process continued, the evaporation rate of nano-fuel droplets increased. The liquid nano-fuel was constantly evaporating to the fuel vapor, and the vapor volume fraction was increased. The vapor volume fraction was increased during the same evaporation period when elevated nanoparticles concentration and minished nanoparticles size.

Experimental investigation on evaporation characteristics of RP-3 aviation kerosene droplet above the critical temperature under various pressure conditions

The evaporation of aviation kerosene droplets in the aeroengine combustion chamber is one of the basic processes during liquid fuel combustion, which directly affects fuel atomization, air-fuel mixture formation and the combustion quality. However, the data are rarely reported due to the difficulty of conducting experiments in high temperature and pressure conditions. In this study, a series of experiments were carried out to investigate the evaporation characteristics of RP-3 aviation kerosene droplet. The environmental pressure and temperature of droplet evaporation ranged from 1 and 20 bar and 400 and 600°C respectively. An individual RP-3 kerosene droplet with initial diameter between 0.9 and 1.1 mm was suspended at a thermocouple bead with 50 μm diameter to measure droplet temperature. Droplet diameter during the whole evaporation process was recorded simultaneously by a high-speed camera. Experimental results indicated that at lower evaporation rate, RP-3 kerosene droplet evaporation experienced two processes: transient heating and equilibrium evaporation periods. While under high evaporation rates, the droplet only underwent equilibrium evaporation period without droplet expansion. At all the studied temperatures, droplet temperature kept increasing during the entire evaporation process without reaching a stable temperature. In most cases, the transient evaporation rate (K) of RP-3 kerosene droplet first increased rapidly until reaching the peak, and then followed by a monotonous decrease. However, at 20 bar above 500°C conditions, the temporal K curve exhibited a double-peak feature. Above the critical temperature of the fuel, increasing ambient pressure and temperature both can promote the heating and evaporation. However, the promotion of increasing ambient temperature to droplet evaporation was weakened at high ambient pressure. The quantitative correlations of droplet lifetime and evaporation rate constant with pressure were proposed under different ambient temperatures.

Distribution of trace substances in the coolant of a BWR fuel element

A transport model was developed and numerically solved for trace substances dissolved in the coolant flowing through a complete BWR fuel element. The integration of the trace substance transport equations is carried out on the same computational grid used by a two-phase three-field subchannel code, the output of which provides the necessary coolant mass flow data, including field exchange terms. The results consist of complete, field specific trace substance distributions within the domain of the simulation and with the same spatial resolution as used by the subchannel code. Downstream the onset of annular flow, it was observed that the trace substance concentrations in liquid films on heated rods are significantly higher than the concentrations in droplets and in films on unheated surfaces. A mechanistic model for disturbance waves was further introduced to assess the additional trace substance concentration increase in the time period of base film evaporation between two successive disturbance waves. The highest trace substance concentrations were found next to part-length rods in the corner of the considered fuel assembly just upstream of the two uppermost spacer grids, which approximately corresponds to the location of trace substance deposition observed during fuel inspections at a Swiss nuclear power plant.

Geological and Geochemical Constraints on the Origin of the Sr Mineralization in Huayingshan Ore District, Chongqing, South China

There are many celestine deposits and mineralization points in the Huayingshan ore district which form the largest strontium resource base in China. Among these celestine deposits, the Yuxia and Xinglong are two of the larger deposits. Previous studies have displayed different views on the genesis of the celestine deposit in the Huayingshan ore district. In this study, we conducted field obversions, geochemistry, and fluid inclusion studies to investigate the sources of ore-forming matters and the metallogenic mechanism of the celestine deposit. Four types of fluid inclusion (FI), namely PL (pure liquid FI), PV (pure vapor FI), L-V (liquid-vapor two-phase FI), and L-V-S (liquid-vapor-solid three-phase FI) have been identified in celestine from different types of ore in the Xishan anticline. The ore-forming fluids belong to the NaCl-H2 O system with moderate to low temperature (190–220 °C) and moderate salinity (5–9 wt%, NaCl equiv.). Different types of ores were formed by the same period of hydrothermal activity, which is supported by the results of the microthermometer study. Geological, thermometric data, and published hydrogen and oxygen isotope results indicate that the hot brines associated with mineralization mainly originated from meteoric water and some of diagenetic fluid. The Sr (87Sr/86Sr = 0.7076–0.7078) and S (δ34S = 36.4–39.0) isotope values of celestine are consistent with those of the Jialingjiang Formation, indicating that ore metals in hot brines were predominantly derived from that formation. In situ analysis of celestine shows that there is a strong negative correlation between Sr and CaO (R2 = 0.95) and combined with mineralogical and isotope geochemical evidence, we concluded that the precipitation mechanism of celestine is the replacement of gypsum with Sr-rich hot brines. Based on the above research and the classification of celestine deposit type, we classified the celestine deposits in Huayingshan as being of hydrothermal type. The formation of celestine deposits can be divided into three periods: (1) evaporation period, forming the source bed; (2) hydrothermal activity period, forming celestine by replacement of gypsum with Sr-rich hot brines; (3) supergene period, where meteoric water dissolves orebodies and strontianization occurs.

Sepiolite- rosemary oil combination as an environmentally oriented insecticide

Pest management is essential for cost-effective agriculture, however, due to the pests' ability to develop resistance to pesticides and the environmental and health considerations, there is a need for new and less hazardous alternatives. Certain essential oils that are regularly consumed by humans, are known to be lethal to specific pests and may serve as an alternative to traditional pesticides, even though their rapid volatility and potential phytotoxicity limit their direct use. Clays and organoclays were suggested as matrices for controlled-or slow-release of organic compounds, and thus might increase the pesticide efficiency and reduce the phytotoxicity of essential oils, by influencing their release. This study combined in vitro studies evaluating the rate of evaporation of rosemary (Rosmarinus officinalis) or lemongrass (Cymbopogon citratus) essential oils (ROEO and CCEO, respectively) from clay-based formulations, with in vivo experiments of essential oil-sepiolite insecticides on onion thrips (Thrips tabaci) while avoiding phytotoxicity damage to chives' (Allium schoenoprasum) crops. Fourier transform infrared spectroscopy (FTIR) and gravimetric kinetic measurements of the evaporation led to the conclusion that sepiolite increased the half-life evaporation period when compared to the raw essential oils or oils pre-adsorbed to other clays or even organoclays. Gas chromatography measurements showed that the interaction with the clay yielded differences in evaporation for the different components in the ROEO oil. Lethality tests of canola:essential oil combinations indicated that ROEO is effective at very low ratios, whereas CCEO activity required higher ratios. Plant tests showed that while the efficiency of CCEO formulation was not very significant, binding ROEO to sepiolite reduced its phytotoxicity yielding efficient pesticidal activity on thrips with less damage to chives' plants even one month after application.

Release and migration of Hg during desulfurization wastewater evaporation process: Whole process evaluation by experimental and theoretical study.

Hot flue gas evaporation technology is an effective strategy for zero liquid discharge of desulfurization wastewater. However, there is a potential risk that heavy metals such as Hg may be released from the wastewater during evaporation, disrupting the original balance of the power plant or even exceeding the Hg emission standard. Wastewater evaporation and Hg release behavior were obtained using a single droplet drying system. At an evaporation temperature of 300°C, approximately 18.5% of Hg was released in the constant wet-bulb temperature period, and the remaining was released in the following evaporation periods. Furthermore, a fixed-bed experiment, in combination with density functional theory calculations, was used to investigate the possible migration mechanisms of released Hg. The results revealed that high HCl concentration, introduced fly ash, and precipitated evaporation products play a crucial role in the fate of Hg, and 85.3% of Hg finally turned into less harmful particulate-bound Hg. This study provides a new and effective strategy for evaluating the migration process of pollutants in wastewater treatment. Moreover, it will serve as an essential reference for advanced wastewater treatment and heavy metals control technologies in the future.

Sedimentary processes and paleoenvironment reconstruction of the Barra Velha formation, Santos Basin, Brazilian pre-salt

The Barra Velha carbonates are widely known for their complexity regarding facies, diagenetic features, and depositional history. The absence of recent analogues representing the depositional setting of these rock formations leaves many uncertainties concerning the sedimentary process that generated them. The present work aims to propose a model for the depositional environment of the Barra Velha Formation based on sedimentary features identified through facies description and interpretation. The employed data consists of 645 m of core descriptions, 2300photomicrographs, 1201 plug samples, and 44 thin sectionsdistributed throughout 34 wells in two Santos Basin oil fields. Fourteen facies were identified and classified into four categories: in situ, microbial, reworked, and altered. The in situ facies are composed of spherulites, shrubs, and mud. Sedimentological evidence points out that spherulites and shrubs precipitated within layers of mud, as a post depositional process. Microbial facies have several characteristics that refer to stromatolites and occur laterally and vertically associated with in situ facies. The spatial association between them indicates that in situ and microbial facies formed in the lower energy portions of the lake. Reworked facies were formed by grain fragmentation and transportation, indicating an energetic lake-littoral zone, where grainstones and packstones formed in the shallowest portions, and wackestones formed in the less energetic portion of the littoral zone. The altered category comprises the weathering profiles. These profiles resemble soils and developed in response to periods of strong evaporation, when lake brines would become dense enough to infiltrate into the groundwaters, leading to the precipitation of the dolocretes in the mixing zone. The spatial distribution of the facies corroborates the sedimentological interpretations. In situ and microbial facies are frequently found in the structurally lower regions of the study area. In contrast, reworked facies and weathering profiles are more common on structural highs.

Investigation of supercritical transition and evaporation process of a hydrocarbon droplet under diesel engine-relevant conditions

Fuel spray supercritical transition in the diesel engine has been concerned widely, especially supercharged ones, however, whether the transition can significantly affect the fuel–air mixing under diesel engine-relevant conditions is an issue that still needs evaluating carefully. Thus, the transition and evaporation of individual n-heptane droplets in a nitrogen environment under various ambient conditions were investigated through a high-pressure evaporation model. The influence of ambient pressures on droplet lifetime (τlife) and evaporation rate constant (K) varies with ambient temperature. When Tr < 0.98, with increasing pressure, τlife first increases and then decreases, and K decreases. When 0.98 < Tr < 1.28, as pressure increases, τlife would increase even if K increases, because the increment of initial heat-up periods exceeds the decrease in quasi-steady evaporation periods. When Tr > 1.28, with increasing pressure, τlife decreases, and K increases. As the droplet heats up, the droplet interface is where the binary mixture would reach the critical mixing state if ambient conditions are high enough. Increasing ambient density decreases the minimum ambient temperature (Tm) required for the transition to occur. Above the Tm, transitions occur earlier with the increasing energy density of ambient gas. Increasing ambient density decreases the minimum ambient temperature required for diffusive fuel-gas mixing modes to dominate the mixing process. For droplets large enough to ignore gas–liquid interfacial thickness, the Tm required for the attainment of critical mixing states is almost independent of droplet diameter.

A Biogeochemical Alkalinity Sink in a Shallow, Semiarid Estuary of the Northwestern Gulf of Mexico

Estuarine total alkalinity (TA), which buffers against acidification, is temporally and spatially variable and regulated by complex, interacting hydrologic and biogeochemical processes. During periods of net evaporation (drought), the Mission-Aransas Estuary (MAE) of the northwestern Gulf of Mexico experienced TA losses beyond what can be attributed to calcification. The contribution of sedimentary oxidation of reduced sulfur to the TA loss was examined in this study. Water column samples were collected from five stations within MAE and analyzed for salinity, TA, and calcium ion concentrations. Sediment samples from four of these monitoring stations and one additional station within MAE were collected and incubated between 2018 and 2021. TA, calcium, magnesium, and sulfate ion concentrations were analyzed for these incubations. Production of sulfate along with TA consumption (or production) beyond what can be attributed to calcification (or carbonate dissolution) was observed. These results suggest that oxidation of reduced sulfur consumed TA in MAE during droughts. We estimate that the upper limit of TA consumption due to reduced sulfur oxidation can be as much as 4.60 × 108 mol day−1 in MAE. This biogeochemical TA sink may be present in other similar subtropical, freshwater-starved estuaries around the world.