Ratio Of Precipitation Research Articles

Interaction of Ca2+ and Fe3+ in co-precipitation process induced by Virgibacillus dokdonensis and its application

Biomineralization has garnered significant attention in the field of wastewater treatment due to its notable cost reduction compared to conventional methods. The reinjection water from oilfields containing an exceedingly high concentration of calcium and ferric ions will pose a major hazard in production. However, the utilization of biomineralization for precipitating these ions has been scarcely investigated due to limited tolerance among halophiles towards such extreme conditions. In this study, free and immobilized halophiles Virgibacillus dokdonensis were used to precipitate these ions and the effects were compared, at the same time, biomineralization mechanisms and mineral characteristics were further explored. The results show that bacterial concentration and carbonic anhydrase activity were higher when additionally adding ferric ion based on calcium ion; the content of protein, polysaccharides, deoxyribonucleic acid and humic substances in the extracellular polymers also increased compared to control. Calcium ions were biomineralized into calcite and vaterite with multiple morphology. Due to iron doping, the crystallinity and thermal stability of calcium carbonate decreased, the content of OC = O, NC = O and CO-PO3 increased, the stable carbon isotope values became much more negative, and β-sheet in minerals disappeared. Higher calcium concentrations facilitated ferric ion precipitation, while ferric ions hindered calcium precipitation. The immobilized bacteria performed better in ferric ion removal, with a precipitation ratio exceeding 90%. Free bacteria performed better in calcium removal, and the precipitation ratio reached a maximum of 56%. This research maybe provides some reference for the co-removal of calcium and ferric ions from the oilfield wastewater.

Geospatial dataset for hydrologic analyses in India (GHI): a quality-controlled dataset on river gauges, catchment boundaries and hydrometeorological time series

Abstract. Streamflow gauging stations not only track the pulse of rivers but also act as common reference points for hydrologic and other environmental analyses. As such, streamflow data and metadata on gauging stations – Geographic Information System (GIS) data on station locations, their upstream catchment boundaries and river flow networks – are critical for analyses. However, for India's river basins, the availability of such data is limited; when available, data are not in an analysis-ready format and can have substantial errors. Studies often use available information from India's water agencies as is, without checking its validity. This study addresses the above limitations by building a new dataset using existing metadata (from the Central Water Commission, CWC, and the Water Resources Information System, WRIS) and checking it against publicly available information from global data sources (e.g., World Wildlife Fund, Multi-Error-Removed Improved-Terrain Hydro and Copernicus) and online maps (e.g., Google Maps). The quality control process categorizes existing metadata based on their consistency with these sources; also, existing metadata are supplemented with additional information where needed. The new dataset developed here is called the “Geospatial dataset for Hydrologic analyses in India” (GHI) and uses Hydrological data and maps based on Shuttle Elevation Derivatives at multiple Scales (HydroSHEDS) data as the underlying template. GHI has both geospatial and time series information. In this initial version of GHI, the spatial domain includes only the river basins of Peninsular India where daily streamflow data are publicly available. Following the quality control process, the CWC's 645 stations in Peninsular India were categorized into three groups: Group 1 (reliable metadata and adequate daily streamflow data; 213 stations), Group 2 (reliable metadata and inadequate or no daily streamflow data; 259 stations) and Group 3 (missing or unreliable metadata; 173 stations). For each of the 472 stations falling into groups 1 and 2, catchment-specific annual and monthly time series spanning 71 water years (1950–2020) of the following were compiled: observed precipitation from the Indian Meteorological Department (IMD); observed streamflow from WRIS; estimated precipitation, evapotranspiration (ET) and streamflow from ERA5-Land; and ET from the Global Land Evaporation Amsterdam Model (GLEAM). A preliminary analysis of catchment-scale time series of data indicates that, while the compiled data appear reasonable over most of the study domain, spurious runoff–precipitation ratios were observed in the hilly coastal regions of Western India. This adds to yet another data-related obstacle faced by the hydrologic community. In order to quantify historical changes and reconcile them with anticipated future changes, the community needs robust and reliable hydrographic and hydrometeorological datasets as well as unrestricted access to such datasets. The goal of this study is to highlight the limitations of existing datasets and pave the way for a community-led effort towards building the needed datasets. GHI serves as a placeholder until such datasets become available. Potential improvements to GHI are discussed. GHI is publicly available at https://doi.org/10.5281/zenodo.7563599 (Goteti, 2023).

The ratio of mesoscale convective system precipitation to total precipitation increases in future climate change scenarios

Mesoscale convective systems (MCSs) are a substantial source of precipitation in the eastern U.S. and may be sensitive to regional climatic change. We use a suite of convection-permitting climate simulations to examine possible changes in MCS precipitation. Specifically, annual and regional totals of MCS and non-MCS precipitation generated during a retrospective simulation are compared to end-of-21st-century simulations based on intermediate and extreme climate change scenarios. Both scenarios produce more MCS precipitation and less non-MCS precipitation, thus significantly increasing the proportion of precipitation associated with MCSs across the U.S.

Spatiotemporal Projections of Precipitation in the Lancang–Mekong River Basin Based on CMIP6 Models

The Lancang–Mekong River Basin (LMRB) is the largest international river in Southeast Asia, supporting a population of about 70 million people. Precipitation is the main source of water resources in the basin, with significant impacts on ecology, production, and livelihoods in the basin. In this study, future precipitation was projected using the Coupled Model Intercomparison Project Phase 6 (CMIP6) climate models. The initial bias of each model was corrected using the daily bias-correction (DBC) method, and then the models were ensembled using the Bayesian model-averaging (BMA) method. The evaluation, based on metrics such as climatology bias, root-mean-square error (RMSE), mean absolute error (MAE), and correlation coefficient (COR), showed that the ensemble precipitation performs better than the individual models. Precipitation under four future Shared Socioeconomic Pathway scenarios (SSP126, SSP245, SSP370, SSP585) displayed an increasing trend throughout the LMRB. The anomalies in annual precipitation in 2061–2090 under each scenario are 136 mm, 142 mm, 114 mm, and 227 mm, in that order. Precipitation in spring and winter shows a trend of increasing in the northern LMRB and decreasing in the southern LMRB, and precipitation in summer and autumn shows a significant trend of increasing in almost the whole basin (significance level 0.05). Spring precipitation in the Mekong Delta decreases in all scenarios. The ratio of wet-season precipitation to dry-season precipitation shows an increasing trend for all scenarios, indicating that the difference between wet-season precipitation and dry-season precipitation will increase in the future. For daily precipitation, the Lancang River Basin (LRB) is dominated by a 3–5% increase in the number of days with 5–10 mm/d of precipitation and the Mekong River Basin (MRB) by a 3–5% increase in the number of days with 10–20 mm/d of precipitation under four SSP scenarios in 2061–2090. There are important changes in the spatial distribution of future precipitation, with the 2500 mm isohyet expanding outwards in a circular pattern and the center of the 1500 mm isohyet moving westwards; i.e., areas with annual precipitation exceeding 2500 mm and 1500 mm will expand. For dry-season precipitation, the 500 mm isohyet shrinks, mainly in a circular pattern towards the center, while the 300 mm isohyet moves mainly towards the east, indicating that areas of dry-season precipitation below 500 mm and 300 mm will expand. In the future, the LMRB will generally become wetter in the wet season and drier in the dry season.

Effect of precipitate shape and distribution on mechanical behavior of shape memory metallic glass composites by molecular dynamics method

The deformation behaviors of metallic glass composites enhanced with brick and cylindrical shape B2-CuZr precipitates were investigated by molecular dynamics method. Both specimens experience a two-stage phase transformation and triple-yielding phenomenon. The brick-shaped precipitate enhanced bulk metallic glass composite (BMGC) exhibits significantly improved strength and mildly enhanced plasticity compared to cylindrical shape inclusion reinforced BMGC. The larger aspect ratio of brick-shaped precipitate enhanced BMGC strengthens the composite by improving elastic lattice deformation along loading direction, while the enhanced plasticity is ascribed to smaller free path for mature shear bands formation. The deformation mechanism for brick-shaped BMGCs is shear band cutting through precipitates, while that for cylindrical shape precipitate reinforced BMGCs is shear band wrapping around crystalline particles. Both specimens display high strain at crystalline/amorphous interface (CAI) region and might experience interfacial stability issue.

Response of Water Isotopes in Precipitation to a Collapse of the West Antarctic Ice Sheet in High-Resolution Simulations with the Weather Research and Forecasting Model

Abstract The West Antarctic Ice Sheet (WAIS) may have collapsed during the last interglacial period, between 132 000 and 116 000 years ago. The changes in topography resulting from WAIS collapse would be accompanied by significant changes in Antarctic surface climate, atmospheric circulation, and ocean conditions. Evidence of these changes may be recorded in water-isotope ratios in precipitation archived in the ice. We conduct high-resolution simulations with an isotope-enabled version of the Weather Research and Forecasting Model over Antarctica, with boundary conditions provided by climate model simulations with both present-day and lowered WAIS topography. The results show that while there is significant spatial variability, WAIS collapse would cause detectable isotopic changes at several locations where ice-core records have been obtained or could be obtained in the future. The most robust signals include elevated δ18O at SkyTrain Ice Rise in West Antarctica and elevated deuterium excess and δ18O at Hercules Dome in East Antarctica. A combination of records from multiple sites would provide constraints on the timing, rate, and magnitude of past WAIS collapse.

Belowground soil and vegetation components change across the aridity threshold in grasslands

Grassland ecosystem functions are affected by global climate change and increasing aridity. Belowground components of soil and vegetation, such as specific root length, belowground biomass and soil organic carbon are important for maintaining these functions. However, aridity affects these components in different ways. This research evaluates changes in soil properties and plant attributes with aridity along a 2600 km aridity gradient in the arid and semiarid grasslands of Inner Mongolia. The aridity index was used considering the ratio of precipitation to potential evapotranspiration, where a higher value indicates greater aridity. Results showed an overall aridity threshold for grassland ecosystems of 0.67, where abrupt changes in belowground components were observed. The effect of aridity on specific root length changed from negative (−0.18) below the threshold to positive (0.24) above the threshold, with the emergence of coordination between aboveground and belowground plant characteristics. Aridity exhibited a negative effect on belowground biomass, increasing from −0.24 below the threshold to −0.55 above the threshold as the positive effect of relative grass abundance disappeared. The total effect of aridity on soil organic carbon showed a subtle change, but the driving pathways through which aridity affects changed from soil loss to aridity itself and vegetation cover at plot scale. These findings highlight how aridity affects belowground components in grassland ecosystems above and below the aridity threshold. They provide a basis for better understanding aridity-driven interactions in grassland ecosystems, and can be used to inform actions to protect grasslands under future climate change.

Immobilizing arsenic-enriched wastewater from utilization of crude antimony oxides as scorodite using a novel multivalent iron source

Arsenic–enriched wastewater (A–EW) is a hypertoxic sewage from the utilization of crude antimony oxides in lead anode slime metallurgy. In traditional methods, the H+ accumulation inhibits the arsenic immobilization during scorodite synthesis. In this study, a novel multivalent iron source comprised of Fe(OH)3 and FeSO4·7H2O was proposed to resolve the adverse effects of pH fluctuation during immobilizing A–EW as scorodite. Various approaches, such as scanning electron microscopy and X–ray photoelectron spectroscopy, were applied to characterize the synthesized scorodite. This work was divided into two parts. In thermodynamics, HnAsO4(3−n)- (n = 1, 2, 3) and Fe(OH)n(3−n)+ (n = 0, 1, 2, 3) can feasibly coprecipitate as scorodite according to their △rGm,Tθ ranged from −111.10 kJ mol−1 to −33.53 kJ mol−1. In experimental research, A–EW was immobilized as scorodite by optimizing conditions as initial pH = 2.0, molar ratio of Fe to As = 1.2, molar ratio of Fe(II) to Fe(III) = 4:6, arsenic concentration = 40 g/L, and temperature = 95 °C. The arsenic precipitation ratio is 99.60%, and the micromorphology of synthesized scorodite presents a regular octahedron having size of 5–10 μm. The low leachability of As (0.41 mg/L) in toxicity characteristic leaching procedure (TCLP) confirmed that the prepared scorodite is nonhazardous. The solution pH is stable at 2.0 as the H+ depletion (0.5660 mol) by Fe(OH)3 dissolution and Fe2+ oxidization balanced with that (0.5657 mol) generated from As(V)–Fe(III) coprecipitation. In general, the A–EW was effectively immobilized by proposed multivalent iron source, and can be potentially applied to safely dispose other industrial effluents, such as high arsenic leachates and arsenic–bearing waste acid from nonferrous metallurgy.

A speleothem record of seasonality and moisture transport around the 8.2 ka event in Central Europe (Vacska Cave, Hungary)

AbstractA stalagmite was collected in northern Hungary from the Vacska Cave, where monitoring and ventilation-based site selection had been conducted. The stalagmite covers the 10–8 ka (relative to AD 1950) period, including the so-called 8.2 ka event, and showed preceding signs of climate change that were evaluated by petrographic observations, 14C activities, Sr concentrations, and stable isotope compositions of calcite and inclusion-hosted water. Comparisons of speleothem records show that isotope peaks at ca. 8.5 ka are related to a regional climate anomaly, rather than to a continental-scale event. In accordance with regional proxy records, the 8.2 ka event was associated with a series of temperature and precipitation amount changes, starting with cooling and a reduction in the winter-to-summer precipitation ratio, and then becoming a humid and warm phase at 8.15 ka. X-ray diffraction-based crystallinity parameter (FWHM) values provided evidence for diagenetic alteration of the stable oxygen isotope compositions of inclusion waters. Nevertheless, the stable hydrogen isotope compositions of inclusion waters and the oxygen isotope values of the host calcite revealed elevated d-excess values, and therefore increased Mediterranean moisture contribution during the 8.2 ka event, which indirectly indicate the southward displacement of moisture transport from the Atlantic Ocean.

A new daily gridded precipitation dataset for the Chinese mainland based on gauge observations

Abstract. High-quality, freely accessible, long-term precipitation estimates with fine spatiotemporal resolution play essential roles in hydrologic, climatic, and numerical modeling applications. However, the existing daily gridded precipitation datasets over China are either constructed with insufficient gauge observations or neglect topographic effects and boundary effects on interpolation. Using daily observations from 2839 gauges located across China and nearby regions from 1961 to the present, this study compared eight different interpolation schemes that adjusted the climatology based on a monthly precipitation constraint and topographic characteristic correction, using an algorithm that combined the daily climatology field with a precipitation ratio field. Results from these eight interpolation schemes were validated using 45 992 high-density daily gauge observations from 2015 to 2019 across China. Of these eight schemes, the one with the best performance merges the Parameter-elevation Regression on Independent Slopes Model (PRISM) in the daily climatology field and interpolates station observations into the ratio field using an inverse-distance weighting method. This scheme had median values of 0.78 for the correlation coefficient, 8.8 mm d−1 for the root-mean-square deviation, and 0.69 for the Kling–Gupta efficiency for comparisons between the 45 992 high-density gauge observations and the best interpolation scheme for the 0.1∘ latitude × longitude grid cells from 2015 to 2019. This scheme had the best overall performance, as it fully considers topographic effects in the daily climatology field and it balances local data fidelity and global fitting smoothness in the interpolation of the precipitation ratio field. Therefore, this scheme was used to construct a new long-term, gauge-based gridded precipitation dataset for the Chinese mainland (called CHM_PRE, as a member of the China Hydro-Meteorology dataset) with spatial resolutions of 0.5, 0.25, and 0.1∘ from 1961 to the present. This precipitation dataset is expected to facilitate the advancement of drought monitoring, flood forecasting, and hydrological modeling. Free access to the dataset can be found at https://doi.org/10.6084/m9.figshare.21432123.v4 (Han and Miao, 2022).

Quantification of Precipitation and Latent Heating Associated with Northern Hemisphere Winter Extratropical Cyclones Using the GPM KuPR

Abstract The four-dimensional characteristics of precipitation and latent heating associated with Northern Hemisphere winter extratropical cyclones (ETCs) are quantitatively analyzed using over 1000 ETCs observed by the Ku-band radar on board the Global Precipitation Measurement (GPM) Core Observatory. We find that the maximum precipitation amount is observed before the minimum central pressure of ETCs (developing stage), independent of the deepening ratio. A key finding is that a cyclone in the developing stage has two large precipitation areas with contrasting precipitation characteristics. One is observed on the forward-left side of ETCs, collocating with warm fronts (Area X). The other is identified on the right-hand side of the ETC center in association with the warm sector and cold fronts (Area Y). These areas become unclear in the mature stage and disappear in the decaying stage. Many stratiform precipitation pixels weaker than 5 mm h−1 compose the large precipitation amount in Area X, with a stratiform-to-total precipitation ratio of more than 90%. In contrast, intense convective precipitation pixels of over 20 mm h−1 are observed about 3 times more in Area Y than in Area X, resulting in a stratiform-to-total precipitation ratio of 65%–80%. The most intense precipitation around ETCs is observed in this area. A larger latent heating maximum at 3.5-km altitude and a higher near-surface cooling rate in Area X result in a higher vertical heating gradient compared to Area Y. The contrasting characteristics between the two areas are more pronounced in the rapidly developing ETCs. Significance Statement Statistical analyses are conducted to elucidate the four-dimensional structures of precipitation and latent heating associated with more than 1000 Northern Hemisphere winter extratropical cyclones using data observed by the Ku-band radar on board the Global Precipitation Measurement (GPM) Core Observatory. The horizontal precipitation composite at the developing stage of the cyclones shows two areas with large precipitation amounts. One is characterized by a large amount of weak stratiform precipitation, and a higher vertical heating gradient, collocating with warm fronts. The other is characterized by intense convective precipitation in association with the warm sector and cold fronts. The quantitative information on precipitation and latent heating obtained from the observation of many cyclones is valuable for the validation of numerical simulation results.

An assessment of CMIP6 climate signals and biases in temperature, precipitation and soil moisture over Europe

AbstractThe CMIP6 projections constitute the basis of our latest understanding of the climate response to anthropogenic forcing. However, there is still considerable uncertainty in the projections, especially at the regional scale. One way to constrain the uncertainty is by comparing the models historical climate change signals against observations and investigate the physical reasons for divergences. Here, we assess the signal‐to‐noise ratio (S/N) of surface air temperature (SAT), precipitation (PREC) and soil moisture (SM) over Europe for a set of CMIP6 historical simulations and compare them against the E‐OBS observational product and the ERA5 reanalysis. We found considerable divergences between the CMIP6 ensemble mean S/N and that of E‐OBS and ERA5, as well as between ERA5 and E‐OBS. The latter indicates that the S/N is affected by data coverage. We show that the differences among model signals are associated with different atmospheric circulation responses. We also investigate the potential relationships between the models' signals and climatological biases, and we found evidence that the models with a warm climatological bias in southern Europe tend to have smaller SAT signals (warm less). Finally, we found no apparent relationship between SM biases and the warming signal, suggesting that the mechanism by which SM–atmosphere interactions affect climate variability does not explain the mean changes. However, there is a tendency for models with higher SM to dry faster than models with lower SM.

A coupled equilibrium boundary layer model with stable water isotopes and its application to local water recycling

The contribution of evapotranspiration (ET) to regional precipitation, known as “local water recycling”, is a key process in the water cycle that can affect water management. However, the amount of planetary boundary layer (PBL) moisture that arises from ET is highly uncertain due to complex atmosphere and land surface conditions. In this study, an idealized two-layer equilibrium boundary layer model was coupled with a stable water isotope module including HDO and H218O to constrain PBL growing season water transport processes. The model was validated using turbulent heat fluxes and isotope ratios of water vapor (δm) and precipitation (δP) measured at a cropland site and a nearby tall tower in the Upper Midwest, United States. The results show that the PBL equilibrium features of δm and δP are well-constrained by thermal and moisture equilibrium in the PBL. For this study region, the summer values of rain evaporation fraction (f) and local water recycling ratio (LRR) are estimated to be 0.09 and 0.29 ± 0.12, respectively. The summer LRR values for the years 2006–2010 were 0.35, 0.36, 0.17, 0.29, and 0.29, respectively. The small value of LRR in 2008 corresponded to a drought condition with the lowest precipitation and second lowest ET among the five years. The summer magnitude of the amount effect is −2.8‰ (mm day−1)−1 and −0.8‰ (mm day−1)−1 for HDO and H218O, respectively. The local water recycling is identified as a significant factor influencing the continental isotope effect. Cropland has likely changed the regional LRR by −7.6 to 19.5% under different pre-agriculture land use scenarios. The feedback processes revealed here indicate that local water recycling is expected to be weakened under drought conditions, but it will be enhanced if irrigation is applied more intensely with more frequent drought events as the climate continues to warm.

An innovative scheme for the separation of potassium from lithium-bearing solution: A jarosite precipitation method

As an indispensable raw material for green energy, securing an adequate supply of lithium has become a worldwide policy. However, the difficult separation of the homologous elements lithium and potassium severely hinders the efficient extraction of lithium from lithium minerals. Current research provides an industrialization promising technology, the highly selective precipitation of potassium through the jarosite process, for the separation of potassium from lithium-bearing solution. The conditions for precipitating potassium in the jarosite process without or with seed were optimized. Results showed the precipitation ratios of potassium and lithium at optimized conditions are 99.17 % and 0.43 %, respectively, corresponding to a selectivity coefficient (SKLi) as high as 28.00×103. The effectiveness of the jarosite process in selective precipitating potassium is barely influenced by the initial concentrations of lithium and potassium. Adding seed enables the separation of lithium and potassium at lower temperatures with a faster speed in a broader pH range. Compared to some other separation technologies, both the jarosite process without or with seed can achieve significantly higher SKLi in a shorter time. Overall, the jarosite process is an effective and commercially promising technology for separating potassium from lithium-bearing solution, favoring the sustainability of the lithium industry.

Efficient extraction and recovery of lithium from waste aluminum cryolite electrolyte

The accumulation of alkali metals in cryolite electrolyte has negative impacts on the operation of aluminum electrolysis, and part of electrolytes need to be periodically replaced and discharged. A cleaner and efficient process was proposed to recover LiF and Al2(SO4)3 from the waste cryolite electrolyte. Under the optimum sulfated roasting conditions, 87.55% of Li and 30.30% of Al were leached. The obtained cryolite residue with a low molecular ratio could be returned to the aluminum electrolysis system. The addition of sodium benzoate achieved the efficient separation of Al3+ from Li-containing leachate, and the Al precipitation ratio was 99.78%. Acid leaching of the aluminum precipitate regenerated benzoic acid and recovered 99.62% of Al2(SO4)3. Finally high-purity cubic LiF was prepared from Li2SO4 solution, and the recovery of LiF was 98.78%.

Constraints on the Ratio between Tropical Land and Ocean Precipitation Derived from a Conceptual Water Balance Model

Abstract Which processes control the mean amounts of precipitation received by tropical land and ocean? Do large-scale constraints exist on the ratio between the two? We address these questions using a conceptual box model based on water balance equations. With empirical but physically motivated parameterizations of the water balance components, we construct a set of coupled differential equations that describe the dynamical behavior of the water vapor content over land and ocean as well as the land’s soil moisture content. For a closed model configuration with one ocean and one land box, we compute equilibrium solutions across the parameter space and analyze their sensitivity to parameter choices. The precipitation ratio χ, defined as the ratio between mean land and ocean precipitation rates, quantifies the land–sea precipitation contrast. We find that χ is bounded between zero and one as long as the presence of land does not affect the relationship between water vapor path and precipitation. However, for the tested parameter values, 95% of the obtained χ values are even larger than 0.75. The sensitivity analysis reveals that χ is primarily controlled by the efficiency of atmospheric moisture transport rather than by land surface parameters. We further investigate under which conditions precipitation enhancement over land (χ > 1) would be possible. An open model configuration with an island between two ocean boxes and nonzero external advection into the domain can yield χ values larger than one, but only for a small subset of parameter choices, characterized by small land fractions and a sufficiently large moisture influx through the windward boundary.

Reactive crystallization of ammonium polyvanadate from vanadium-bearing solution assisted by efficient ultrasound irradiation: Crystallization characteristics and growth process

Ultrasound crystallization (UC) technique was previously proposed to solve the issues caused by the acidic ammonium salts crystallization of vanadium. In this work, the influence of various parameters on vanadium crystallization characteristics were detailedly investigated. Results showed that high vanadium precipitation ratio (99.67%) and V2O5 purity (99.50%) of the final products can be obtained under the conditions of ultrasonic power of 600 W, initial pH value of 2.0, reaction temperature of 95 °C, ammonium salt addition coefficient of 0.5, reaction duration of 5 min and vanadium concentration of 20 g/L. Moreover, the NH4+ content in the supernatant liquid was notably reduced to 1.08 g/L. Crystallization kinetic analysis manifests that the crystallization rate constant augments with the increasing temperature, and the activation energy and pre-exponential factor is 71.87 kJ/mol and 7.44 × 109, respectively. Ultrasound enhances the collision frequency between NH4+ and vanadium ions, further improving the crystallization rate of the (NH4)2V6O16 crystals. Meanwhile, ultrasound induces a secondary nucleation, which would promote the intercalation among small flakes and further improves the nucleation and growth of the (NH4)2V6O16 crystals. Scanning electron microscopy analysis demonstrates that the flaky crystals are firstly formed, then a part of flakes gradually intercalate with each other, and finally most of the lamellar crystals complete the intercalation process. Meanwhile, selected area electron diffraction verifies the single crystalline characteristic of the micron-flakes, which grows along the (010) crystal plane. This work will lay theoretical and technical basis for UC technique appliance and promote the progress of the vanadium extraction industry.

An innovative index for separating the effects of temperature and precipitation on global vegetation change

Temperature and precipitation changes are among the vital climatic driving forces of global vegetation change. However, the strategy to separate the relative contributions of these two critical climatic factors is still lacking. Here, we propose an index CRTP (contribution ratio of temperature and precipitation) to quantify their impacts on vegetation and then construct the CRTP classification prediction models based on climatic, geographic, and environmental factors using the Random Forest classifier. We find that precipitation predominates more than 70% of the significant vegetation change, mainly located in the low and middle latitudes during 2000-2021. Precipitation will remain the dominant climatic factor affecting global vegetation change in the coming six decades, whereas areas with temperature-dominated vegetation change will expand under higher radiative forcings. Hopefully, the promising index CRTP will be applied in the research about climatic attribution for regional vegetation degradation, monitoring drought-type conversion, and alarming the potential ecological risk.

Numerical investigation of coupled density-driven flow and hydrochemical processes in coastal aquifers influenced by storm surges

Storm surges can result in significant damage to coastal aquifers. Studies have investigated groundwater salinization caused by storm surge inundation. However, the phenomenon of evaporation-driven mineral precipitation in saltwater lakes has not received much attention in the literature. To address this gap, this study simulated the impact of saltwater lakes formed after a storm surge on coastal aquifers by coupling the PHREEQC and SEAWAT models. Six scenarios were considered, with varying lake depth, area, evaporation rate and vertical hydraulic conductivity of lakebed. The results indicate that the total dissolved solids (TDS) and water level of saltwater lake are subject to constant changes due to evaporation. Scenario 2, with the smallest lake area exhibited the least susceptibility to evaporation, with a maximum TDS concentration in the lake of ∼86 g/L, and only dolomite and calcite reached saturation. However, infiltration of saline water into the aquifer was higher than for the other scenarios. A comparing of scenarios with different vertical hydraulic conductivities of lakebed (scenarios 5 and 6 have conductivities that are 0.1 × and 0.01 × that of scenario 1, respectively) shows that a smaller vertical hydraulic conductivity leads to less saline infiltration into the aquifer, but a greater amount of salt precipitates (precipitation ratios of 1.03%, 1.92%, and 5.73% for scenario 1, 5 and 6, respectively). The results of scenario 4, which has double the evaporation rate of the other scenarios, indicate that evaporation leads to significantly greater salt precipitation and a corresponding decrease in the amount of salt that enters the aquifer. The results of secondary salinization indicate that salt precipitated on the surface may infiltrate the aquifer through rainfall dissolution, causing groundwater to become saline again. These findings emphasize the importance of accounting for the impact of evaporation on saltwater lake dynamics and coastal groundwater salinization in future studies.

Exploring the Signal Filtering Properties of Idealized Watersheds Using Spectral Analysis

Watersheds act as low-pass filters, damping and attenuating climatic signals as water moves through the surface and subsurface. This is a well observed phenomenon; however, the ways in which watershed properties control the nature of this filtering are less well documented, especially with respect to groundwater surface water interactions. Here, we use a physically based groundwater surface water model to simulate idealized hillslope ensembles with varying watershed properties (hillslope slope, hydraulic conductivity, and precipitation magnitude) to quantitively explore the impact of watershed configuration on temporal filtering in both the surface and subsurface. To limit the complexities of this system an idealized titled-v domain is used. Multi-decadal simulations (95 years) are run, and then power spectral densities and transfer functions are used to quantify the temporal dynamics and damping of each simulation. Overall, we show that the degree of filtering and the degree of signal transformation is controlled by the total time spent in the subsurface and the degree of groundwater surface water exchanges. The ratio of precipitation to hydraulic conductivity controls the partitioning between infiltration and runoff. Greater infiltration results in less filtering in the subsurface and more filtering in streamflow. For a given precipitation conductivity ratio, deeper water table depths lead to greater streamflow filtering for periods less than 5 years. For time periods greater than 5 years the streamflow filtering is most strongly related to hydraulic conductivity which controls the baseflow dynamics. The majority of the input signal is filtered in the subsurface for short periods less than one year. For longer time scales, hydraulic conductivity is found to be the primary control of filtering and power shift taking place in the subsurface with larger conductivities correlated to less filtering and less of a signal transformation. Deeper water table depths lead to more signal transformation in saturated storage but are not correlated to filtering in unsaturated storage. This is likely due to counteracting effects of higher conductivity (which decreases filtering) and deeper water table depths (which increase filtering).