Climate controls chemical weathering of silicate rocks on the transport of iron (Fe) and its isotopes from continent to the ocean, impacting the global Fe geochemical cycle. However, it's elusive if Fe isotope fractionation during silicate weathering reflects variations in climate factors. This study examines two granite derived regolith profiles; one in Beijing (BJ), representing a temperate climate, and the other in Guangdong (GD), representing a tropical climate, to investigate their mineralogy, Fe-bearing phases, element concentrations, and Fe isotope compositions. Our results show that, despite climate differences, the two granite weathering profiles have average delta Fe-56(bulk regolith) values within analytical uncertainty (0.09 +/- 0.02 parts per thousand vs. 0.12 +/- 0.04 parts per thousand, 2SD). The delta Fe-56(bulk) (regolith) values of temperate and tropical regolith are similar to or slightly higher than those of their respective bedrocks and remain steady along the entire weathering profile. The limited variation of Fe isotope composition in weakly weathered temperate regolith likely reflects the dissolution of primary minerals rather than the formation of secondary minerals. The Rayleigh fractionation calculations also show a Delta(56)Fepore (solution-regolith) value of similar to 0 parts per thousand between pore solution and regolith. In contrast, in the tropical profile, despite the abundance of secondary minerals and the differences in delta Fe-56 values among the extracted Fe-pools exceeding 0.68 parts per thousand, only limited Fe isotope fractionation is observed in the bulk regolith (0.01 parts per thousand to 0.24 parts per thousand). These variations are likely driven by the formation of Fe oxides, relying on the atomic distribution of Fe in hematite and goethite. The linear regression analysis estimates the apparent Fe isotope fractionation factor between hematite and goethite as 0.46 +/- 0.07 parts per thousand (Delta Fe-56(hematite-goethite), 1SE). These findings indicate that the sensitivity of Fe isotope fractionation in bulk regolith to variations in climate factors is relatively limited. However, combined with results from other weathering profiles in different climate zones, two models suggest that changes in delta Fe-56 values of easily leachable and silicate-bound Fe pools are likely influenced by climate factors such as temperature and precipitation. This work advances our understanding of the Fe isotope fractionation during silicate weathering and its potential climate connection on Earth's surface.

Zinc (Zn) is both an essential micronutrient and a common environmental contaminant. Addressing global Zn deficiency and pollution requires effective tools to track its biogeochemical pathways. Zn stable isotopes have become valuable tracers for identifying Zn sources, cycling processes, and anthropogenic impacts across different environmental systems. This review provides a comprehensive survey of Zn isotope signatures (S66Zn) across natural and anthropogenic sources and systematically evaluates the fractionation mechanisms operative during aqueous complexation, mineral sorption, biological uptake, and anthropogenic activities. It also covers advances in multi-collector inductively coupled plasma mass spectrometry and provides standardized protocols for sample preparation and isotope measurement. Key findings include bimodal S66Zn distributions in anthropogenic sources. Common sources (S66Zn = 0.23 f 0.27%o) are isotopically lighter than natural sources (S66Zn = 0.46 f 0.38%o), while smelting residues (S66Zn = 0.76 f 0.40%o) and coal fly ash (S66Zn = 1.14 f 0.69%o) are significantly heavier. In supergene environments, mass-dependent processes cause S66Zn variations of about 3%o. Zn isotopes have been applied in source apportionment, soil-plant system Zn translocation, and marine biogeochemical cycling studies. The review concludes that Zn isotopes are robust geochemical tracers for environmental systems, capable of resolving complex source inputs and pathways. To fully realize their potential, future work should focus on improving analytical methods for complex matrices, expanding applications in medical geology, and integrating digital technologies like artificial intelligence.

Earth's crustal materials are recycled into the mantle through subduction, but the depth and nature of recycled components remain debated. Here we report copper (Cu) isotope evidence for the involvement of recycled crustal materials in a deep-mantle plume source. Permian mantle plume-derived picrites and basalts from the Emeishan large igneous province (Southwest China), excluding three hydrothermally altered outliers, exhibit delta Cu-65 values up to 0.65 parts per thousand, obviously higher than typical mantle values (0.07 +/- 0.10 parts per thousand). The delta Cu-65 values show no correlation with loss-on-ignition (LOI), Mg#, epsilon(Nd(t)), Cu/Th, Cu/Pd, or redox state, ruling out magma differentiation or post-magmatic alteration. Instead, the elevated delta Cu-65 values most plausibly reflect recycled crustal sulfides with elevated delta Cu-65 value in the mantle source. These findings provide robust evidence for the recycling of Cu-rich sulfides into the deep mantle (potentially the lower mantle), elucidating the ultra-deep geochemical cycling of copper and sulfur within Earth's interior.

Heavy metals (HMs) are abundant in the karst soils of Southwest China, posing significant health risks to millions of people. Iron (Fe) (hyr)oxides serve as critical carriers of HMs in these soils; however, the processes governing Fe oxide formation and transformation associated with HM accumulation during carbonate weathering in karst region is less understood. In this study, we present Fe isotope compositions from a carbonate-derived profile to investigate the major factors controlling Fe migration. In the saprolite layer, strong correlations between delta 56Febulk and the proportions of extracted FeNH2OH.HCl or Feresidue fractions suggest that the formation of goethite and phyllosilicate may be responsible for variations in delta 56Febulk. The positive correlations between delta 56FeNH2OH. HCl values and HM concentrations in this layer suggest an enhanced capacity for HM fixation by goethite in these soils. In contrast, the fractionation of Fe isotopes in the soil layer appears to be influenced by vegetation, as indicated by the correlation between total organic carbon and delta 56Febulk. The negative correlations between

Gallium (Ga) has two naturally-occurring stable isotopes: Ga-69 (60.1%) and Ga-71 (39.9%). Their isotopic ratios were employed as a potential proxy to trace the geochemical behavior of Ga and its analogue Al. Ga is also an important component of many semiconductors. When exposed to aqueous solutions, it may be dissolved and then precipitate as Ga-bearing crystals (e.g., GaOOH). Thus, the exploration of Ga isotope fractionation during alpha-GaOOH precipitation could be helpful for understanding geochemical behaviors of Ga and other metals (including Al and Fe) during oxyhydroxide precipitation. In this study, three series of precipitation experiments with variable initial aqueous Ga concentrations (about 9.2, 2.0, and 1.8 ppm) were carried out to determine Ga isotope fractionation factor during alpha-GaOOH precipitation at similar to 20 degrees C and neutral pH as a function of time. The experimental results could be modeled using a Rayleigh precipitation process, in which fractionation factors between crystals and solution (Delta Ga-71(solid-solution)) are between -0.28 and - 0.37 parts per thousand, depending on the initial Ga concentration and type of matrix anion (Cl- vs. NO3-). This isotope fractionation is significantly smaller in magnitude than the values reported for Ga adsorption on goethite (-0.89 parts per thousand) and calcite (-1.27 parts per thousand). The isotope fractionation is mainly caused by the increase in GaO bond length from similar to 1.84 & Aring; in aqueous GaOH4- to similar to 1.991 & Aring; in alpha-GaOOH solid, with a simultaneous change of Ga coordination number from 4 to 6, although kinetic isotope fractionation may play an important role. Our study provides the first experimental evidence of significant Ga isotope fractionation during kinetic oxyhydroxide precipitation, and suggests that the measurable Ga isotope fractionation occurred at water-solid interface and during precipitations can be potentially used for tracing global geochemical cycling of Ga and its analogue Al and Fe.

Garnet-group minerals, with their wide range of compositions, play a significant role in Earth's crust and upper mantle, participating in various petrological and geochemical processes. Oxygen isotope fractionation factors between garnets and other minerals hold crucial implications in these contexts. In this work, vibration frequencies were measured via Raman spectra on five garnet mineral samples in the pyrope-almandine-spessartine ternary system and four synthetic pyrope-grossular solid solutions at temperatures up to 1000 degrees C and pressures up to 17 GPa. Isobaric (gamma iP) and isothermal (gamma iT) mode Gr & uuml;neisen, as well as anharmonic (ai) parameters, were determined for the observed modes. Our study shows that the vibration bands tend to shift to lower frequencies with increasing temperature and to higher frequencies with increasing pressure. Moreover, the anharmonic correction has been found to contribute positively to equilibrium oxygen isotope fractionation beta factors in garnets, typically within 0.5 parts per thousand above 1000 K. The 103 center dot ln beta(T) factors calculated from vibration spectra (considering F points only) align closely with those from theoretical calculations (including all frequencies in the Brillouin zone). Contributions from phonon dispersion (including none-F points) are typically smaller than the uncertainties propagated from frequency measurements. Additionally, the pressure effect on the oxygen isotope fractionation in garnet, evaluated from the isothermal Gr & uuml;neisen parameters, is found to be insignificant under crustal and upper mantle conditions, consistent with thermodynamic expectations. Using published oxygen isotope fractionation beta factors for quartz and calcite, the equilibrium oxygen isotope fractionation factors (103 center dot ln alpha) are calculated between garnets of diverse compositions and any of these phases as functions of temperature, pressure and fraction of garnet endmembers. Considering composition effects helps to reduce the discrepancies among experimental and empirical calibrations of oxygen isotope fractionation factors between garnet and quartz. As an example application, oxygen isotope fractionation factors 103 center dot ln alpha(P, T ) between garnets and forsterite were calculated under upper mantle conditions. Our findings suggest that these fractionation factors are predominantly dependent on temperature and garnet compositions, with minor influence from pressure. Compared with our calculated fractionation factors between garnet and olivine, the oxygen isotope exchange equilibrium may have been reached in some in kimberlite and mantle xenolith samples between garnet and olivine. However, in other samples, the fractionation factors cannot be explained solely by the composition effect, likely due to metasomatism. Our results underscore the importance of considering garnet compositions when interpreting their oxygen isotope compositions.

Minerals in brucite-type structure, including brucite (Mg(OH)2) and portlandite (Ca(OH)2), have been studied as important analogs of hydrous silicate minerals for their thermodynamic properties, including equilibrium hydrogen and oxygen isotope fractionations between minerals and water at elevated temperatures and pressures. In this study, Raman and Fourier transform infrared (FTIR) spectra were collected at high-temperature (T) and high-pressure (P) conditions on synthetic hydrogenated and deuterated portlandite samples (i.e., Ca(OH)2 and Ca (OD)2), and their isobaric and isothermal mode Gruneisen parameters, as well as anharmonic parameters, were then evaluated. These high-precision vibrational spectra enable the evaluation of thermodynamic properties of portlandite (Delta U, CV, CP and Delta S) up to 427 degrees C, to which anharmonicity has positive contributions. More importantly, they help to determine the isobaric (at P =1 bar) beta factors of brucite and portlandite for equilibrium D/H fractionation considering anharmonic effects, and the D/H fractionation factor (103 center dot ln alpha) between brucite/ portlandite and water at high-P,T conditions. The calculated equilibrium fractionation factor (ln alpha brucite-water) agrees with experimental results in the temperature range from 300 to 647 K (-27 to-374 degrees C, the critical point of water) within analytical uncertainties estimated using Monte Carlo method. The Ab initio calculation using DFT theory and VASP program was also carried out to obtain phonon spectra for brucite and portlandite with three-split hydrogen sites and to evaluate the dispersion effect, which is found to be smaller than the statistical uncertainty at high temperatures. Our results show that the internal OH-stretching modes in brucite/portlandite play a dominant role in determining the beta values, and the anharmonic OH-stretching potential (xi parameter) contributes significantly to the D/H fractionation factor. Because previous studies show that OH-stretching frequencies generally decrease with increasing mass of cation in the metallic hydroxide having similar crystal structure, our results imply that the deuterium isotope may be preferentially enriched in the hydroxide phase with the light cation bonded to the hydroxyl group, which is also consistent with the observed D/H fractionations among hydrous silicates.

Travertine samples deposited in Earth's surface environments can be used as an effective archive for paleo-climatic reconstruction. As a common element in carbonates, magnesium (Mg) and its isotopic composition in travertine could provide useful information for evaluating paleo-environment changes. In this study, we investigate the Mg isotope systematics in both endogenic travertines (mainly calcite) and spring/stream waters at Baishuitai, Yunnan, SW China. Our results show a systematic increase in δ26Mg value from −1.37 to −1.26‰ for water samples downstream, but varied δ26Mg values between −4.12 and −3.95‰ (average −4.02‰) for solid carbonates, thus a corresponding fractionation Δ26Mgcalcite-water between −2.76 to −2.59‰ (mean value of −2.69‰). Therefore, the solid carbonates preferentially incorporate light Mg isotopes during travertine formation. More interestingly, the Mg distribution coefficient (KMg/Ca) between travertine and water exhibits two variation trends with the calcite deposition rate (Rp) along the canal, which can be explained by the change of calcite formation mechanism from direct nucleation to precipitation via amorphous calcium carbonate (ACC) intermediate. In the upper-stream, the direct nucleation of calcite results in the rapid incorporation of Mg ions into crystal lattice, while a relatively slow precipitation of calcite downstream would incorporate Mg via ACC formation pathway in a quasi-equilibrium pattern. This is consistent with the grain size distribution and crystal morphology observed under SEM. Our results show the important control of water Mg/Ca ratios on the calcite precipitation during travertine formation, and imply the potential and complexity of using Mg isotopes of travertine deposits to reconstruct paleo-environments.

Magnesium (Mg) isotopes have been utilized to constrain continental weathering; however, to date, little is known about the climate effects on Mg isotope fractionation during weathering. In this study, we measured δ 26 Mg values of bulk regolith and exchangeable fraction in two granite regolith profiles developed under temperate, semiarid and tropical, humid climate conditions, respectively. Combined with mineralogy and element composition, we aimed to investigate how climate influences fractionation patterns of Mg isotopes during chemical weathering. At the temperate site, δ 26 Mg values of regolith are slightly higher than that of the bedrock and negatively correlated with τ Mg,Th . Correspondingly, the exchangeable Mg is characterized by low δ 26 Mg values. These results can be explained by the formation of small number of clay minerals. For the tropical regolith profile, δ 26 Mg values decrease toward the surface, and the regolith has either lower δ 26 Mg values above −250 cm or higher δ 26 Mg values below −250 cm relative to the bedrock. The δ 26 Mg value of exchangeable Mg is markedly lower than that of the regolith and varies significantly. These results can be explained by the mixing of Mg from solid weathering products and atmospheric deposition. The Mg from rainwater and/or marine aerosol deposit on the regolith and some may enter the crystal structure of the illite. The deposited Mg can overprint the granitic Mg, and the δ 26 Mg value of shallow regolith samples will reflect mixing between granitic and atmospheric sources. The compilation of our and previously published Mg isotopic data reveals the potential control of climate on Mg isotope fractionation during continental weathering.

Soil is one of the largest reservoirs and re-emission sources of mercury (Hg) on Earth's surface. The accumulation and remobilization of Hg during pedogenesis affect how Hg is transported from terrestrial to aquatic environment and biota, but these processes are poorly understood. Here we present Hg concentration and isotope ratios of soil and bedrock samples from a latosol profile formed through intense weathering of Cenozoic basalts in Zhanjiang, Guangdong Province, China, to trace the sources, transport and transformation processes of Hg during pedogenesis, and to gain insights on the potential impact of tropical soils on global Hg cycling. The entire soil profile shows negative delta Hg-202 (-2.97 parts per thousand +/- 0.08 parts per thousand to -2.54 parts per thousand +/- 0.08 parts per thousand) and negative Delta Hg-199 (-0.68 parts per thousand +/- 0.04 parts per thousand to -0.43 parts per thousand +/- 0.04 parts per thousand), with a gradual downward positive shift of Delta Hg-199 below 35 cm. An isotopic mixing model based on Delta Hg-199 suggests a dominant Hg input from atmospheric Hg (Hg-Atm) and limited contribution (<36%) of geogenic Hg (Hg-Geo) from the bedrock. The strongly negative Delta Hg-199 throughout the latosol profile suggests that Hg-Atm was likely subject to substantial photoreduction on soil surface and migrated downward after incorporation into soils. Moreover, there is a distinct positive shift of delta Hg-202 alongside a rapid decrease of Hg-Geo from the bedrock to the weakly weathered basalt, indicating a substantial loss of Hg-Geo with the preferential release of lighter isotopes during the initial weathering, likely due to the dissolution of primary minerals. In addition, the delta Hg-202 shows a negative correlation with soil pH at some horizons, attributable to the isotopic fractionation during Hg(II) speciation change in soil solution and the selective complexation/adsorption of different Hg(II) species onto mineral surfaces, which are affected by surface charge properties and thus soil pH. Overall, our results provide direct evidence for the accumulation and downward migration of Hg-Atm in tropical soils during pedogenesis, as well as the loss of Hg-Geo during the weathering of bedrock, which may serve as an underappreciated source of Hg in tropical regions and have a potential impact on the Hg isotope signatures in aquatic environments.

Cd-rich wastes from open-pit mining can be transported into rivers, which are often followed by deposition in river sediments and/or further transfer into agricultural soils. The lithology of bedrock exerts a huge effect on physicochemical properties (e.g., buffering capacities, metal species, mineral phases, etc.) of the river system, thereby potentially impacting the Cd mobility in watersheds. However, to date, little is known about the microscopic processes (e.g., dissolution, adsorption, and precipitation) controlling the migration of Cd from mines to varied watersheds. This study, therefore, aims to determine the controlling factors on Cd mobilization in two mining-impacted watersheds with contrasting bedrock lithology using both Cd and Pb isotopes. The Pb isotope ratios of sediments and soils in both watersheds fall into a binary mixing model with two isotopically distinct sources, i.e., mining wastes and bedrock. These results indicate that mining activities are the main sources of Cd in sediments and soils. However, the Cd isotope ratios reveal different Cd migration processes between the two watersheds. In the siliceous watershed, the δ114/110Cd values of sediments decrease from -0.116‰ in the upper reach to -0.712‰ in the lower reach, with a concomitant increase in Cd concentration, which may result from Cd adsorption by goethite due to the increased pH. In contrast, in the calcareous watershed, the Cd isotope compositions of sediments (-0.345 to -0.276‰) and the pH of river water are nearly invariable, suggesting that the adsorption and release of Cd in sediments are limited. This may result from the strong pH buffering effect due to the presence of carbonate rocks. This study highlights the different fates of Cd in siliceous and calcareous watersheds and suggests that the development of Cd pollution control policies must consider regional lithology.

Laterites are important iron (Fe) reservoirs impacting the biogeochemical cycle of Fe at Earth's surface, and Fe oxides are critical Fe-host minerals in laterites that affect the geochemical behavior of Fe. Whether and how the differentiation of Fe minerals controls Fe isotope fractionation during laterization, however, remains unclear. In this study, the mineralogy, element concentrations, and Fe isotope compositions are reported for a basalt-derived lateritic profile on Hainan Island, China, to investigate the role of Fe solid-phase differentiation in controlling Fe isotope fractionation during lateritic weathering. 57Fe Mo spacing diaeresis ssbauer spectroscopy at 13 K is conducted to quanti-tatively identify the solid-phase Fe, including FeIII-(oxy)hydroxides, FeIII-oxides, and organic/silicate-bound FeIII. The results from soil samples in the lower section show that RMZr,Fe values are positive and that delta 56Fe values (-0.01%0 to 0.07%0; 0.05 +/- 0.05%0 on average) are identical to those in parent basalt (0.03 +/- 0.04%0). The limited variation in delta 56Fe values is likely caused by the compaction effect and/or the downward transport of Fe from the upper soils. In contrast, RMZr,Fe values in soils from the upper section are generally negative, and their delta 56Fe values (0.01%0 to 0.29%0) display zigzag variations and are linearly correlated with the amount of Fe present in hematite and goethite. The variation in delta 56Fe value is likely caused by the atomic distribution of Fe in hematite and goethite, with heavy Fe preferentially incorporated into hematite rather than goethite. Based on the linear regression analysis, we calculated the apparent Fe isotope fractionation factor between hematite and goethite as 0.99 +/- 0.18%0 (SD). A comparison of published Fe isotope data shows that the variation in delta 56Fe value of silicate-derived soils and rivers may have a potential link with climatic factor (mostly temperature). Our study highlights the importance of Fe-mineral differentiation in controlling Fe isotope fractionation in laterite systems.

Gallium (Ga) isotopes are potentially advantageous for characterizing the surficial biogeochemical cycles of Ga and tracking the geochemical behavior of the monoisotope element aluminum (Al) during chemical weathering. To test the potential of Ga and its isotopes to trace continental weathering, we studied Ga isotope compositions of a strongly-weathered latosol profile developed from basalt on the Leizhou Peninsula, Guangdong Province, South China. In the profile, d71GaSRM-994 values of latosol samples decrease from -0.69%0 in unweathered basalts at the bottom to -0.51%0 in shallow sections, while the Ga concentration increases from -19.9 mg/g in the bedrock to -42.7 mg/g in soil, indicating significant enrichment of Ga and its isotope fractionation triggered by weathering processes. Bulk samples analysis and sequential leaching of selected weathering products suggest that the majority of Ga in these samples occurs in the crystal lattice of Al-rich and Fe-rich minerals, with the light Ga isotope (69Ga) enriched in latosol samples relative to the coexisting solution. Interestingly, our results show d71Ga values of latosols display a bigger variation (about 3-4 times of its analytical uncertainty) than their Ga/Al ratios (about 1.5 times of its analytical uncertainty) throughout the profile, indicating d71Ga values may be a more sensitive proxy to track the loss of Al3+ and involvement of Fe3+ during weathering process. Based on a simple Rayleigh model, the upper limit of Ga isotope fractionation between solution and weathered basalt (D71Gasolution-weathered rocks) is estimated to be -1.50%0, implying that heavy Ga isotopes may be enriched in surface river systems. This study highlights the potential of Ga elemental and isotope geochemistry to trace continental weathering and global Ga cycling. (c) 2022 Elsevier Ltd. All rights reserved.

The extremely thick sedimentary sequence in the Qaidam Basin, northeastern Tibetan Plateau (TP) is closely related to the uplift of the TP. Due to the scarcity of minerals that can be dated continuously, little is known about the isotopic responses of the minerals in this area to the changes in the weathering and sources over a long time period. A 938.5-m long core (magnetostratigraphic age of ~ 2.8-0.1 Ma) was drilled in the western Qaidam Basin in 2008. The mineralogy and isotopic compositions of gypsum in this core were investigated. The gypsum recorded the primary information about the brine that formed during ~ 2.8-0.1 Ma. The variations in the Sr isotopes (0.709817-0.714473, average of 0.711249) and Nd (0.512114-0.512614, average of 0.512184) of the gypsum samples suggest that the weathering products of the rocks in the Kunlun and Altyn mountains (Mts) likely exerted a strong control on the Sr-Nd isotopes of the lakes. The climate and the Sr content/isotopic compositions of the gypsum samples were affected by the regional tectonic activities throughout the evolution of the paleolake since 2.8 Ma. The results of this study demonstrate that Sr-Nd isotopes are useful tools for investigating the origins of evaporite deposits and the interactions between tectonic activities and climate change.

With the ongoing climate warming, changes in drought and the adverse effects on water resources, food production and ecosystem functioning have been key research topics of ever-increasing interest. The Palmer Drought Severity Index (PDSI) is among the most widely used indicators for drought monitoring and research. However, the two-layer bucket water balance model embedded in the original PDSI model has been criticized for being over-simplified to accurately quantify the surface water balance and therefore raising uncertainties in the subsequent PDSI estimates (PDSIoriginal). Here we improve the water balance calculations in the PDSI model by using direct hydrological outputs from physically-based, more sophisticated global hydrological models (GHMs) participated in the Inter-Sectoral Impact Model Inter-Comparison Project (ISIMIP). Validation results show that the estimated runoff (Q) and evapotranspiration (ET) from ISIMIP GHMs perform much better than those from the original PDSI two-layer bucket model in capturing the long-term trend and monthly variabilities of Q and ET, especially in cold regions and relatively dry areas, using observed Q (at 2191 catchments) and an independent satellite-based ET product (the Global Land Evaporation Amsterdam Model, GLEAM; over the entire terrestrial environment) as the reference. In addition, the new PDSI estimates with improved hydrological modeling (PDSIISIMIP) exhibit a significantly stronger correlation with observed Q than PDSI(original )in nearly all studied catchments, suggesting that PDSIISIMIP is superior to PDSI(original )in capturing hydrological droughts. We further compare the long-term PDSI trends and changes in drought using PDSI(original )and PDSIISIMIP under both historical climate (1900-2005) and future climate change scenarios (2006-2099). We find that PDSI(original )and the PDSIoriginal -identified land areas under drought generally show a larger trend than those based on PDSIISIMIP. For future climate change scenarios, the PDSIoriginal -projected increasing trend of land proportion under drought is about two times larger than that assessed with PDSIISIMIP, implying that PDSI(original )may largely overestimate future drought increases, as commonly done in existing studies. In this light, our approach of directly using hydrological outputs from physically-based, more sophisticated GHMs provide an effective, yet relatively simple approach to reduce uncertainties in PDSI estimates thereby achieving a better prediction of drought changes under warming.

Iron (Fe) is an essential nutrient for living organisms and Fe deficiency is a worldwide problem for the health of both rice and humans. Zinc (Zn) contamination in agricultural soils is frequently observed. Here, we studied Fe isotope compositions and transcript levels of Fe transporter genes in rice growing in nutrient solutions having a range of Zn concentrations. Our results show Zn stress reduces Fe uptake by rice and drives its δ56Fe value to that of the nutrient solution. These observations can be explained by the weakened Fe(II) uptake through Strategy I but enhanced Fe(III) uptake through Strategy II due to the competition between Zn and Fe(II) combining with OsIRT1 (Fe(II) transporter) in root, which is supported by the downregulated expression of OsIRT1 and upregulated expression of OsYSL15 (Fe(III) transporter). Using a mass balance box model, we also show excess Zn reduces Fe(II) translocation in phloem and its remobilization from senescent leaf, indicating a competition of binding sites on nicotianamine between Zn and Fe(II). This study provides direct evidence that how Zn regulates Fe uptake and translocation in rice and is of practical significance to design strategies to treat Fe deficiency in rice grown in Zn-contaminated soils.

The Payenia region of Argentina (34.5–38°S) is a large Pliocene‐Quaternary volcanic province of basaltic compositions in the Andean Cordillera foothills representing the northernmost extent of back‐arc volcanism in the Andean Southern Volcanic Zone (SVZ). Although the chemical diversity of the Payenia basalts has been characterized previously, the processes and sources responsible for such variation remain controversial. Here, we report new whole‐rock major and trace element concentrations, Sr‐, Nd‐, Hf‐, and Pb‐isotope ratios and high‐precision olivine oxygen‐isotope ratios in a suite of 35 alkaline basalts from Payenia. These lavas have major and trace elements that define a compositional range from arc‐influenced to intraplate signature. Variable crustal contamination and/or recent slab‐derived inputs inadequately account for elemental and isotopic systematics and spatial compositional variations of Payenia lavas. We present a simple forward model indicating that early metasomatism and subsequent melting of the metasomatized subcontinental lithospheric mantle (SCLM) has significantly contributed to the Payenia lava compositional range. Isotopic ingrowth calculations of radiogenic Sr, Nd, Hf, and Pb suggest that the SCLM metasomatism occurred at 50–150 Ma, consistent with the timing of the breakup of Gondwana and the development of the proto‐Pacific Andean arc. Variations in δ 18 O olivine values from modeled melts indicate that the metasomatism and melting within the SCLM can fractionate oxygen isotopes even when the metasomatizing melt has MORB‐like δ 18 O values, providing a different explanation for the low‐δ 18 O signatures observed in continental arc settings.

Whether river flows remain stationary is of great concern to hydrologists, water engineers, and society in general, yet is subject to substantial debate. Here we provide the first comprehensive assessment of the long-term stationarity of annual streamflow for 11 069 catchments globally. Our observation-based evidence shows that the long-term annual streamflow remains stationary in 79% of catchments with minimal human disturbance, indicating that historical climate change alone has not led to non-stationarity in annual streamflow series in most catchments. In direct contrast, we found streamflow has remained stationary in only 38% of those catchments where substantial human interventions have occurred. These results demonstrate the scale of the human impact on the freshwater system, and highlight the ongoing need for dealing with the impacts of direct human interventions to ensure successful water management into the future.

OBJECTIVE: To evaluate the diagnostic value of real-time shear wave elastography (SWE) in children with chronic kidney disease (CKD). METHODS: Children with CKD diagnosed by the ultrasound-guided biopsy between January 2018 and May 2019 were enrolled as the case group. Age- and sex- matched healthy children were selected as the control group. The Young’s Modulus (YM) of the renal cortex was measured by SWE after the traditional ultrasound examination. Variance analysis was performed to compare the values of YM between the two groups. Receiver operating characteristic curve (ROC) analysis was used to compare the values of YM, and explore the cut-offs of the YM. RESULTS: In the case group (n = 60, 45% male, mean age of 9.2 years), the kidney YM modulus on the left side (16.8±4.8 kPa vs. 8.3±2.1 kPa) and the right side (16.0±4.7 kPa vs. 8.3±2.4 kPa) were both higher than the control group (all P values < 0.001). With the progress of CKD, the YM value of the left and right kidneys gradually increased. ROC analysis showed that when the left and right kidney YM value was 11.7 kPa and 11.0 kPa, the diagnostic sensitivity and specificity were the highest (left: respectively 93.3% and 95.0%; right: respectively 93.3 % and 91.7%). CONCLUSION: The increase of YM in CKD is related to the progression of renal dysfunction which may provide a new method for early diagnosis of CKD, dynamic monitoring of disease progression, and evaluation of curative effect and prognosis.

[目的]研究干扰雄性小鼠睾丸Cloc k基因后,对小鼠胚胎着床及后期胎鼠发育的影响,并从甲基化的角度探讨引起胎鼠发育异常的原因.[方法]将成年雄性小鼠分为干扰组和对照组,分别于睾丸中注射干扰质粒和阴性质粒,与经过促排处理的雌鼠合笼,研究比较两组胚胎着床情况,观察两组胎鼠的外形及体重等指标的差异;观察胎鼠组织结构,比较两组是否存在差异;分析胎鼠总甲基化水平,同时测定甲基转移酶(DNMTs)水平,比较两组是否存在差异.[结果]:①与对照组比较,干扰组胚胎着床数下降(14.5 vs.20.33),胎儿体重减轻,死胎和异常胎数增多(P<0.05).②干扰组胎鼠的心脏和脊柱发育分节出现异常.③11.5～16.5 dpc阶段胎鼠总甲基化水平,干扰组较对照组显著降低(8.59 vs.18.25);干扰组甲基转移酶DNMT3B-4的相对IOD值低于对照组(0.124 vs.0.141),有统计学意义.[结论]干扰雄性小鼠睾丸Clock基因,可导致胚胎着床数下降,胎鼠发育异常增多,体重减轻.甲基转移酶DNMT3B-4水平下调及总甲基化水平下降,可能是影响胎鼠发育异常的原因.本研究表明Clock基因与胎鼠发育密切相关,初步探讨引起不育的机制,为揭示该类疾病发病机制提供依据.