Cadmium(Cd)and arsenic(As)co-contamination has threatened rice production and food safety.It is challenging to mitigate Cd and As contamination in rice simultaneously due to their opposite geochemical behaviors.Mg-loa...Cadmium(Cd)and arsenic(As)co-contamination has threatened rice production and food safety.It is challenging to mitigate Cd and As contamination in rice simultaneously due to their opposite geochemical behaviors.Mg-loaded biochar with outstanding adsorption capacity for As and Cd was used for the first time to remediate Cd/As contaminated paddy soils.In addition,the effect of zero-valent iron(ZVI)on grain As speciation accumulation in alkaline paddy soils was first investigated.The effect of rice straw biochar(SC),magnesiumloaded rice straw biochar(Mg/SC),and ZVI on concentrations of Cd and As speciation in soil porewater and their accumulation in rice tissueswas investigated in a pot experiment.Addition of SC,Mg/SC and ZVI to soil reduced Cd concentrations in rice grain by 46.1%,90.3%and 100%,and inorganic As(iAs)by 35.4%,33.1%and 29.1%,respectively,and reduced Cd concentrations in porewater by 74.3%,96.5%and 96.2%,respectively.Reductions of 51.6%and 87.7%in porewater iAs concentrationswere observed with Mg/SC and ZVI amendments,but notwith SC.Dimethylarsinic acid(DMA)concentrations in porewater and grain increased by a factor of 4.9 and 3.3,respectively,with ZVI amendment.The three amendments affected grain concentrations of iAs,DMA and Cd mainly by modulating their translocation within plant and the levels of As(Ⅲ),silicon,dissolved organic carbon,iron or Cd in porewater.All three amendments(SC,Mg/SC and ZVI)have the potential to simultaneously mitigate Cd and iAs accumulation in rice grain,although the pathways are different.展开更多
A successful extraction process relies heavily on an excellent extractant structure.The theory of extractant structure and extraction performance is still insufficient to guide the design of new extractants,despite ex...A successful extraction process relies heavily on an excellent extractant structure.The theory of extractant structure and extraction performance is still insufficient to guide the design of new extractants,despite extensive research into extractants.However,diglycolamide extractants have demonstrated certain advantages in nuclear fuel reprocessing and rare earth extraction and separation.This paper focuses on the synthesis of 13 structurally serially changed extractants.There is a good connection between the extraction performance and the energy consumption of the carbonyl conformation torsion of the extractant with symmetrical straight-chain alkyl substituents.The extraction capacity of extractant decreases with the increase of alkyl chain length.The methyl substituent extractant shows higher extractability than the other.The steric effect of the alkyl chain with more than two carbons is not significantly different.The relationship between the structure and performance of extractants was systematically studied by the combination of theoretical calculations and experimental data to investigate the effects of symmetric,asymmetric and branched N-substituents on extraction performance.展开更多
The development of new and efficient extractants plays a key role in the separation and recovery of rare earth elements.In this pape r,the extractant(N,N-methyl py ridineethyl-N',N'-dicyclohexyl-3-oxadiglycola...The development of new and efficient extractants plays a key role in the separation and recovery of rare earth elements.In this pape r,the extractant(N,N-methyl py ridineethyl-N',N'-dicyclohexyl-3-oxadiglycolamide,MPyEDChDGA) with a new structure was synthesized,and the pyridine group was successfully grafted onto the 3-oxadiglycolamide structure.Using MPyEDChDGA for efficient enrichment of rare earth ions,the self-assembled solids were recovered by simple filtration without further backextraction and final precipitation,achieving a one-step strategy for the recovery of rare earth ions.Several important parameters affecting the self-assembly extraction,including pH,diluent,temperature,and extractant concentration,were systematically evaluated using La(NO_(3))_(3),Tb(NO_(3))_(3),and Lu(NO_(3))_(3) as representatives.The self-assembled solids were investigated in detail by X-ray diffraction(XRD),scanning electron microscopy(SEM),1H nuclear magnetic resonance(1H NMR),Fourier transform infrared spectroscopy(FT-IR),Raman,and X-ray photoelectron spectroscopy(XPS) analyses.The stoichiometry of the extraction species was characterized using the Job's method and electrospray ionization mass spectrometry(ESI-MS).In addition,MPyEDChDGA was applied to the recovery of Sm in SmCoCu simulated liquid,and the results show that MPyEDChDGA has good selectivity of Sm from transition metals(Co,Cu).The separation factor of Sm/Co can reach 6281±117,which provides a new approach to recovering Sm from SmCoCu scrap magnets.This study presents an efficient and convenient new strategy for the recovery and separation of rare earth elements.展开更多
To improve the ability of diglycolamide extractants for the extraction of Sr(Ⅱ)from high-level waste liquid,N,N,N′,N′-tetracyclohexyldiglycolamide(TCHDGA)was proposed and studied to extract Sr(Ⅱ)from nitrate media...To improve the ability of diglycolamide extractants for the extraction of Sr(Ⅱ)from high-level waste liquid,N,N,N′,N′-tetracyclohexyldiglycolamide(TCHDGA)was proposed and studied to extract Sr(Ⅱ)from nitrate media.TCHDGA was prepared and characterized by 1H nuclear magnetic resonance spectroscopy(NMR),^(13)C NMR,and fourier transform infrared spectroscopy(FT-IR).Various factors affecting extraction were studied systematically.In just 20 s,the extraction rate can reach approximately 98.2%.The extraction capacity of cyclohexyl-substituted extractant TCHDGA is tens of times higher than that with linear or branched chain alkyl.The chemical structure of the complex has been demonstrated to be[Sr3TCHDGA]·(NO_(3))_(2),based on FT-IR,X-ray photoelectron spectroscopy(XPS),and crystal structure analysis.The crystal belongs to the monoclinic system,space group P21,and a strontium ion coordinates with nine oxygen atoms,all of which contribute from TCHDGA.The stripping rate can reach over 99%when using distilled water or 0.50 mol·L^(-1)oxalic acid as stripping agents.展开更多
Benzotriazole UV stabilizers (BT-UVs) have attracted concems due to their ubiquitous occurrence in the aquatic environment,and their bioaccumulative and toxic properties.However,little is known about their aquatic env...Benzotriazole UV stabilizers (BT-UVs) have attracted concems due to their ubiquitous occurrence in the aquatic environment,and their bioaccumulative and toxic properties.However,little is known about their aquatic environmental degradation behavior.In this study,photodegradation of a representative of BT-UVs,2-(2-hydroxy-5-methylphenyl) benzotriazole (UV-P),was investigated under simulated sunlight irradiation.Results show that UV-P photodegrades slower under neutral conditions (neutral form) than under acidic or alkaline conditions (cationic and anionic forms).Indirect photodegradation is a dominant elimination pathway of UV-P in coastal seawaters.Dissolved organic matter (DOM) from seawaters accelerate the photodegradation rates mainly through excited triplet DOM (3DOM*),and the roles of singlet oxygen and hydroxyl radical are negligible in the matrixes.DOM from seawaters impacted by mariculture exhibits higher steady-state concentration of 3DOM*([3DOM*]) relative to those from pristine seawaters,leading to higher photosensitizing effects on the photodegradation.Halide ions inhibit the DOM-sensitized photodegradation of UV-P by decreasing [3DOM*].Photodegradation half-lives of UV-P are estimated to range from 24.38 to 49.66 hr in field water bodies of the Yellow River estuary.These results are of importance for assessing environmental fate and risk UV-P in coastal water bodies.展开更多
A feasible guidance scheme with impact time constraint is proposed for attacking a stationary target by missiles with time-varying velocity.The main idea is to replace the constant velocity with the future mean veloci...A feasible guidance scheme with impact time constraint is proposed for attacking a stationary target by missiles with time-varying velocity.The main idea is to replace the constant velocity with the future mean velocity;therefore, the existing time-to-go estimation algorithm of the proportional navigation guidance law can be improved to adapt to varying conditions.In order to obtain the prediction of the velocity profile, the velocity differential equation to the downrange is derived, which can be numerically integrated between the current downrange and the target position by the on-board computer.Then, a third-order polynomial is introduced to fit the velocity profile in order to calculate the future mean velocity.At the beginning of each guidance loop, the future mean velocity is predicted and the time-to-go information is updated, based on which a novel biased proportional navigation guidance law is established to achieve the impact time constraint.Finally,numerical simulation results verified the effectiveness of the time-to-go estimation algorithm and the proposed law.展开更多
In Rhodopseudomonas palustris,an arsM gene,encoding bacterial and archaeal homologues of the mammalian Cyt19 As（III） S-adenosylmethionine methytransferase,was regulated by arsenicals.An expression of arsM was introd...In Rhodopseudomonas palustris,an arsM gene,encoding bacterial and archaeal homologues of the mammalian Cyt19 As（III） S-adenosylmethionine methytransferase,was regulated by arsenicals.An expression of arsM was introduced into strains for the methylation of arsenic.When arsM was expressed in Sphingomonas desiccabilis and Bacillus idriensis,it had 10 folds increase of methyled arsenic gas compared to wild type in aqueous system.In soil system,about 2.2%–4.5% of arsenic was removed by biovolatilization during 30 days.This study demonstrated that arsenic could be removed through volatilization from the contaminated soil by bacteria which have arsM gene expressed.These results showed that it is possible to use microorganisms expressing arsM as an inexpensive,efficient strategy for arsenic bioremediation from contaminated water and soil.展开更多
Arsenic （As） is a pervasive and ubiquitous environmental toxin that has created catastrophic human health problems world-wide. Chlamydomonas reinhardtii is a unicellular green alga, which exists ubiquitously in fres...Arsenic （As） is a pervasive and ubiquitous environmental toxin that has created catastrophic human health problems world-wide. Chlamydomonas reinhardtii is a unicellular green alga, which exists ubiquitously in freshwater aquatic systems. Arsenic metabolism processes of this alga through arsenate reduction and sequent store and efflux were investigated. When supplied with 10 μmol/L arsenate, arsenic speciation analysis showed that arsenite concentration increased from 5.7 to 15.7 mg/kg dry weight during a 7-day period, accounting for 18%–24% of the total As in alga. When treated with different levels of arsenate （10, 20, 30, 40, 50 μmol/L） for 7 days, the arsenite concentration increased with increasing external arsenate concentrations, the proportion of arsenite was up to 23%–28% of the total As in alga. In efflux experiments, both arsenate and arsenite could be found in the efflux solutions. Additionally, the efflux of arsenate was more than that of arsenite. Furthermore, two arsenate reductase genes of C. reinhardtii （CrACR2s） were cloned and expressed in Escherichia coli strain WC3110 （？arsC） for the first time. The abilities of both CrACR2s genes to complement the arsenate- sensitive strain were examined. CrACR2.1 restored arsenate resistance at 0.8 mmol/L. However, CrACR2.2 showed much less ability to complement. The gene products were demonstrated to reduce arsenate to arsenite in vivo. In agreement with the complementation results, CrACR2.1 showed higher reduction ability than CrACR2.2, when treated with 0.4 mmol/L arsenate for 16 hr incubation.展开更多
Recovery of scandium from titanium white waste acid is an essential source of scandium.Simple and economical production of high purity scandium remains a challenge.A new extractant,N,N,N’,N’-tetracyclohexyl-diglycol...Recovery of scandium from titanium white waste acid is an essential source of scandium.Simple and economical production of high purity scandium remains a challenge.A new extractant,N,N,N’,N’-tetracyclohexyl-diglycolamide(TCHDGA),was synthesized,and the separation performance of scandium from impurity metal ions(Ti,Mn,Ba,Fe,Al and Mg)was investigated,The effects of mixing time,acid concentration and temperature on the scandium extraction were considered.The extraction mechanism was studied by infrared spectroscopy and the Equimole Series Method.Under optimized conditions,the extractant shows a strong affinity to scandium in the nitric acid medium and high extraction separation factors between scandium and these impurity metal ions,A process for the purification of scandium was established.The crude product obtained from titanium white waste acid,95%purity scandium oxide,can be purified to 99.99%after only one step of extraction,scrubbing,and stripping:This technology is economical and straightforward and can realize the high-value recovery of scandium in the titanium white waste acid.展开更多
Arsenic （As） is ubiquitous in the environment in the carcinogenic inorganic forms, posing risks to human health in many parts of the world. Many microorganisms have evolved a series of mechanisms to cope with inorga...Arsenic （As） is ubiquitous in the environment in the carcinogenic inorganic forms, posing risks to human health in many parts of the world. Many microorganisms have evolved a series of mechanisms to cope with inorganic arsenic in their growth media such as transforming As compounds into volatile derivatives. Bio-volatilization of As has been suggested to play an important role in global As biogeochemical cycling, and can also be explored as a potential method for arsenic bioremediation. This review aims to provide an overview of the quality and quantity of As volatilization by fungi, bacteria, microalga and protozoans. Arsenic bio-volatilization is influenced by both biotic and abiotic factors that can be manipulated/elucidated for the purpose of As bioremediation. Since As bio- volatilization is a resurgent topic for both biogeochemistry and environmental health, our review serves as a concept paper for future research directions.展开更多
Diglycolamides(DGAs) show excellent application prospects for the extraction and separation of rare earth metals from highly radioactive liquid wastes and rare earth ores.The extraction ability of DGAs for rare earth ...Diglycolamides(DGAs) show excellent application prospects for the extraction and separation of rare earth metals from highly radioactive liquid wastes and rare earth ores.The extraction ability of DGAs for rare earth ions in nitrate or chloride media increases with increasing atomic number of the rare earth metal.To understand the origin of this phenomenon,three binuclear crystals [Ln(TEDGA)_(3)][Ln(NO_(3))_(6)] of N,N,N’,N’-tetraethyldiglycolamide(TEDGA) with rare earth ions La(Ⅲ),Pr(Ⅲ) and Eu(III) were prepared and characterized crystallographically.The three complexes belong to the triclinic crystal system,P-1 space group.The bond lengths of Ln-O_(amide) are significantly shorter than those of Ln-O_(ether) in the same crystal.The Ln-O_(amide) and Ln-O_(enher) bond lengths gradually decrease with increasing atomic number of the rare earth ion.The dihedral angle formed by TEDGA and metal ions through the tridentate coordination gradually increases with increasing metal ion atomic number,tending toward the formation of sizeable planar coordination structures for the most massive rare earth ions.The structures of the compounds formed by the extractant and metal ion were optimized by means of DFT simulations.We find that the interaction between TEDGA and the rare earth ion is dominated by electrostatic interaction by analyzing binding energy,WBIs,Mulliken charge,natural electron configurations,and molecular orbital interaction.The covalent component of the Ln-O bonds of the complexes increases with increasing metal atomic number.The observed increase in extraction and separation capacity of diglycolamides for rare earth ions with increasing atomic number might be due to the formation of two fivemember rings by one tridentate ligand.The rare earth ions with large atomic numbers tend to form planar structures with large dihedral angles with DGA ligands.展开更多
Objective To investigate the differences in intestinal flora of patients with primary liver cancer and ofhealthy individuals and to investigate the effect of the differential flora on the development of liver cancer.M...Objective To investigate the differences in intestinal flora of patients with primary liver cancer and ofhealthy individuals and to investigate the effect of the differential flora on the development of liver cancer.Methods Overall, 67 patients with primary liver cancer who received systematic and complete treatmentbetween January 2019 and December 2020 at the Sixth People’s Hospital of Qingdao and had completeclinical data were enrolled in this study, and 26 individuals who were healthy on physical examination inthe same period were used as healthy controls. Macro genome and 16s ribosome Deoxyribo Nucleic Acid(rDNA) high-throughput sequencing were performed on the stool flora of the enrolled patients and controls,and the differences in the intestinal flora were analyzed using the LEfSe bioinformatics software.Results Compared with the control samples, all the tested patient samples showed statistically significantdifferences in the number of colonies of 5 bacterial phyla, 5 orders, 8 families, 11 genera, and 14 species(P < 0.05).Conclusion Compared with healthy people, patients with primary liver cancer have significant differencesin the intestinal flora composition. The alteration of the intestinal flora may be correlated with the occurrenceof primary liver cancer, and the intestinal flora may become a novel target for the prevention and treatmentof primary liver cancer.展开更多
Rational design of extractant structure to improve the extraction and separation capacity of rare earth elements(REEs)is a long-standing challenge.Herein,a new strategy was proposed to improve the stability of the che...Rational design of extractant structure to improve the extraction and separation capacity of rare earth elements(REEs)is a long-standing challenge.Herein,a new strategy was proposed to improve the stability of the chelating structure formed by malonamide and REEs.The stability of the chelating structure is greatly improved by using a double-ring framework structure which makes the two carbonyl groups of malonamide unable to rotate freely and both of them point to the metal ion position.Three benzyl groups were used to construct the hydrophobicity of the extractant and the organic shell of the extracted species.Tribenzylhexahydro-pyrrolo-pyridine-dione(THPPD)was designed and synthesized.The structure reduces the energy consumed by rotating carbonyl group in the coordination with metal ions and then improves the extraction ability of extractant.The crystal structure was preorganized as expected,with the two carbonyls pointing in a favorable coordination direction to the structural complement of the metal ion.The extraction behaviors of REEs with THPPD in a nitric acid medium were studied.Compared with N,N’-dibenzyl-N,N’-dimethylmalonamide(DBDM-MA)with a chain structure,the extraction capacity of THPPD is 360 times higher than that of DBDM-MA at 5.0 mol/L sodium nitrate.Furthermore,the binding energy and Gibbs free energy were investigated by density functional theory(DFT)in conjunction with the B3LYP.The theoretical results show that THPPD has more effective interaction with Pr(NO_(3))3 than DBDM-MA.The construction of chelating groups conformation is a worthy direction to improve the coordination ability and even selectivity of extractant.展开更多
Objective To analyze the characteristics of the intestinal microflora in patients with breast fibroadenoma using 16S ribosomal RNA(rRNA)high-throughput sequencing.Methods Fecal samples from 20 patients with breast fib...Objective To analyze the characteristics of the intestinal microflora in patients with breast fibroadenoma using 16S ribosomal RNA(rRNA)high-throughput sequencing.Methods Fecal samples from 20 patients with breast fibroadenoma and 36 healthy subjects were randomly collected and analyzed using high-throughput sequencing technology for 16S rRNA V4 region sequencing,and the alpha diversity(Chao index,Shannon index)was calculated using Mothur(v.1.39.5)software.Beta diversity was analyzed using QIIME(v1.80).SPSS software(version 23.0)and the t-test of two independent samples were used to analyze differences in the abundance of bacteria between the two groups.Results Compared with that in the healthy control group,theαdiversity of the intestinal microflora in breast fibroadenoma patients increased,but the difference was not statistically significant(P>0.05).At the phylum level,significant differences were observed between the two groups.The abundance of Firmicutes was higher in the breast fibroadenoma group(P<0.05),whereas the abundance of Synergistetes was higher in the healthy control group(P<0.005).A total of five bacterial genera showed significant differences between the two groups:the breast fibroadenoma group showed higher levels of Bautia(P<0.005),Coprococcus(P<0.005),Roseburia(P<0.05),and Ruminococcus(P<0.005),whereas Sutterella was more abundant in the healthy control group than in the breast fibroadenoma group(P<0.05).Conclusion The diversity and abundance of the intestinal flora in patients with breast fibroadenoma are significantly different from those in healthy subjects,suggesting that an imbalance in the intestinal flora is correlated with the occurrence of breast fibroadenoma.展开更多
[Objectives]To observe the clinical effect of acupuncture on blepharospasm.[Methods]72 patients were randomly divided into treatment group and control group with 36 cases in each group.In the treatment group,Shenmai,Z...[Objectives]To observe the clinical effect of acupuncture on blepharospasm.[Methods]72 patients were randomly divided into treatment group and control group with 36 cases in each group.In the treatment group,Shenmai,Zhaohai,Fengchi,Taichong,Fuyang,Jiaoxin and Jingming were selected as the main acupoints,while in the control group,routine acupoints were selected.With 4 weeks as a course of treatment,the two groups were compared after a course of treatment.The clinical effect of primary blepharospasm,blepharospasm intensity and scores of Hamilton Depression Scale were compared between the two groups before and after treatment.[Results]After treatment,the clinical efficacy of the two groups were significantly improved compared with that before treatment,the effective rate of the control group was 75.00%,the effective rate of the treatment group was 88.89%,indicating that the effective rate of control group was lower than that of the treatment group(P<0.05);after treatment,the degree of blepharospasm in both groups was significantly lower than that before treatment(P<0.05),and the treatment group had better effect in improving primary blepharospasm;the score of Hamilton depression scale in control group was lower than that in observation group(P<0.05).[Conclusions]The clinical curative effect of acupuncture at Yinqiao and Yangqiao meridians was better than that of conventional acupoints selected in relieving mild and moderate blepharospasm;it could definitely reduce the intensity of blepharospasm and relieve anxiety and depression of patients,so it is worthy of clinical promotion.展开更多
Despite extensive research,fungal diversity along elevation gradients remains difficult to generalize.In this study we examined soil fungal diversity and network stability on two snow mountains in the Hengduan Mountai...Despite extensive research,fungal diversity along elevation gradients remains difficult to generalize.In this study we examined soil fungal diversity and network stability on two snow mountains in the Hengduan Mountain Range of China and identified distinct biodiversity patterns.On Meili Snow Mountain,fungal ASV richness declined significantly with altitude,with MAT identified as the primary driver.On Baima Snow Mountain,richness exhibited a hump-shaped pattern,with TN as the key influencing factor.Regression analysis and structural equation modelling revealed that elevation indirectly influenced fungal richness by affecting climate,vegetation,and soil properties.Despite similar climatic conditions,elevational patterns of fungal communities on the two mountains are driven by distinct local factors:Fungal communities on Meili Snow Mountain are mainly driven by NDVI,whereas those on Baima Snow Mountain are mainly shaped by soil fertility.Co-occurrence network analysis further indicates that fungal network complexity on Meili Snow Mountain increases with altitude,while fungal network stability follows a U-shaped distribution driven by species interactions and environmental filtering.In contrast,on Baima Snow Mountain,fungal network complexity peaks at mid-altitudes and stability shows no significant correlation with altitude,suggesting strong niche adaptability.These findings highlight the complex effects of elevation on fungal diversity and networks,providing new insights into biodiversity in mountain ecosystem and guidance for ecosystem management under climate change.展开更多
Accurate prediction of the heat load is the basic premise of intelligent regulation of the heating system,which helps to realize effective management of heating,ventilation,air conditioning system.For the problem that...Accurate prediction of the heat load is the basic premise of intelligent regulation of the heating system,which helps to realize effective management of heating,ventilation,air conditioning system.For the problem that the weight of each influencing factor is not taken into account in the current heat load prediction and is not highly targeted,this article deeply explores the influence of different factors on the room heat load,and we propose a method to calculate room heat load prediction based on the combination of analytic hierarchy process(AHP)and back-propagation(BP)neural network.Firstly,eight environmental factors affecting the heat load are selected as prediction inputs through parametric analysis,and then the weights of each input are determined by AHP and normalize the prediction data by combining expert opinions,and finally do one-to-one training the quantified score and the room heat load to predict the future heat load by BP neural network.The simulation tests show that the mean absolute relative error(MARE)of the proposed prediction method is 5.40%.This article also verifies the influence of different expert opinions on the stability of the model.The results show that the proposed method can guarantee higher prediction accuracy and stability.展开更多
The combination of two bacteria （Bacillus sp. PY1 and Sphingomonas sp. PY2） and a fungus （Fusarium sp. PY3）, isolated from contaminated soils near a coking plant, were investigated with respect to their capability...The combination of two bacteria （Bacillus sp. PY1 and Sphingomonas sp. PY2） and a fungus （Fusarium sp. PY3）, isolated from contaminated soils near a coking plant, were investigated with respect to their capability to degrade pyrene and volatilize arsenic. The results showed that all strains could use pyrene and arsenic as carbon and energy sources in a basal salts medium （BSM）, with the combined potential to degrade pyrene and volatilize arsenic. Bacillus sp. PY1, Sphingomonas sp. PY2 and Fusarium sp. PY3 were isolated from the consortium and were shown to degrade pyrene and volatilize arsenic independently and in combination. Fungal-bacterial cocul- ture has shown that the most effective removal of pyrene was 96.0% and volatilized arsenic was 84.1% after incubation in liquid medium after 9 days culture, while bioremediation ability was 87.2% in contaminated soil with 100 mg-kg-1 pyrene. The highest level of arsenic volatilization amounted to 13.9% of the initial As concentration in contaminated soil after 63 days. There- fore, a synergistic degradation system is the most effective approach to degrade pyrene and remove arsenic in contaminated soil. These findings highlight the role of these strains in the bioremediation of environments contaminated with pyrene and arsenic.展开更多
Alpine forest soil in the southeastern Qinghai–Xizang Plateau plays a crucial role in regional and global climate and biogeochemical cycles,yet the elevational distribution of soil nitrogen(N)availability and losing ...Alpine forest soil in the southeastern Qinghai–Xizang Plateau plays a crucial role in regional and global climate and biogeochemical cycles,yet the elevational distribution of soil nitrogen(N)availability and losing risk is unresolved.In this study,we characterized soil N composition and key N transformation processes across different elevations in 3 typical mounts of the Qinghai–Xizang Plateau.In contrast to previous suggestions,soil total N and ammonium are found to accumulate in high elevation zones.This accumulation of N at higher altitudes is due to a consistent soil net N mineralization rate coupled with an extremely low net nitrification rate,which is suppressed by low p H and high soil moisture in high elevation zones.Moreover,the elevated rates of biological N fixation along the elevation further contribute to N accumulation in high elevation regions in which the acid-tolerant Bradyrhizobium,plant-associated Herbaspirillum,and Klebsiella are identified as the key diazotrophic microbial taxa responsible for active N fixation.Collectively,our results suggest that total N and NH_(4)^(+)-N accumulation in higher altitude zone is a ubiquitous phenomenon in the southeast Qinghai–Xizang Plateau,with lower nitrification rates and higher biological nitrogen fixation being key processes enabling this occurrence.展开更多
基金supported by the National Key Research and Development Program of China(No.2021YFC1809205)the Beijing Natural Science Foundation(No.8232029)the National Natural Science Foundation of China(No.41501336).
文摘Cadmium(Cd)and arsenic(As)co-contamination has threatened rice production and food safety.It is challenging to mitigate Cd and As contamination in rice simultaneously due to their opposite geochemical behaviors.Mg-loaded biochar with outstanding adsorption capacity for As and Cd was used for the first time to remediate Cd/As contaminated paddy soils.In addition,the effect of zero-valent iron(ZVI)on grain As speciation accumulation in alkaline paddy soils was first investigated.The effect of rice straw biochar(SC),magnesiumloaded rice straw biochar(Mg/SC),and ZVI on concentrations of Cd and As speciation in soil porewater and their accumulation in rice tissueswas investigated in a pot experiment.Addition of SC,Mg/SC and ZVI to soil reduced Cd concentrations in rice grain by 46.1%,90.3%and 100%,and inorganic As(iAs)by 35.4%,33.1%and 29.1%,respectively,and reduced Cd concentrations in porewater by 74.3%,96.5%and 96.2%,respectively.Reductions of 51.6%and 87.7%in porewater iAs concentrationswere observed with Mg/SC and ZVI amendments,but notwith SC.Dimethylarsinic acid(DMA)concentrations in porewater and grain increased by a factor of 4.9 and 3.3,respectively,with ZVI amendment.The three amendments affected grain concentrations of iAs,DMA and Cd mainly by modulating their translocation within plant and the levels of As(Ⅲ),silicon,dissolved organic carbon,iron or Cd in porewater.All three amendments(SC,Mg/SC and ZVI)have the potential to simultaneously mitigate Cd and iAs accumulation in rice grain,although the pathways are different.
基金supported by the Natural Science Foundation of Shandong Province (ZR2022QB067)。
文摘A successful extraction process relies heavily on an excellent extractant structure.The theory of extractant structure and extraction performance is still insufficient to guide the design of new extractants,despite extensive research into extractants.However,diglycolamide extractants have demonstrated certain advantages in nuclear fuel reprocessing and rare earth extraction and separation.This paper focuses on the synthesis of 13 structurally serially changed extractants.There is a good connection between the extraction performance and the energy consumption of the carbonyl conformation torsion of the extractant with symmetrical straight-chain alkyl substituents.The extraction capacity of extractant decreases with the increase of alkyl chain length.The methyl substituent extractant shows higher extractability than the other.The steric effect of the alkyl chain with more than two carbons is not significantly different.The relationship between the structure and performance of extractants was systematically studied by the combination of theoretical calculations and experimental data to investigate the effects of symmetric,asymmetric and branched N-substituents on extraction performance.
基金Project supported by the Natural Science Foundation of Shandong Province (ZR2022QB067)。
文摘The development of new and efficient extractants plays a key role in the separation and recovery of rare earth elements.In this pape r,the extractant(N,N-methyl py ridineethyl-N',N'-dicyclohexyl-3-oxadiglycolamide,MPyEDChDGA) with a new structure was synthesized,and the pyridine group was successfully grafted onto the 3-oxadiglycolamide structure.Using MPyEDChDGA for efficient enrichment of rare earth ions,the self-assembled solids were recovered by simple filtration without further backextraction and final precipitation,achieving a one-step strategy for the recovery of rare earth ions.Several important parameters affecting the self-assembly extraction,including pH,diluent,temperature,and extractant concentration,were systematically evaluated using La(NO_(3))_(3),Tb(NO_(3))_(3),and Lu(NO_(3))_(3) as representatives.The self-assembled solids were investigated in detail by X-ray diffraction(XRD),scanning electron microscopy(SEM),1H nuclear magnetic resonance(1H NMR),Fourier transform infrared spectroscopy(FT-IR),Raman,and X-ray photoelectron spectroscopy(XPS) analyses.The stoichiometry of the extraction species was characterized using the Job's method and electrospray ionization mass spectrometry(ESI-MS).In addition,MPyEDChDGA was applied to the recovery of Sm in SmCoCu simulated liquid,and the results show that MPyEDChDGA has good selectivity of Sm from transition metals(Co,Cu).The separation factor of Sm/Co can reach 6281±117,which provides a new approach to recovering Sm from SmCoCu scrap magnets.This study presents an efficient and convenient new strategy for the recovery and separation of rare earth elements.
基金supported by the Natural Science Foundation of Shandong Province(ZR2022QB067).
文摘To improve the ability of diglycolamide extractants for the extraction of Sr(Ⅱ)from high-level waste liquid,N,N,N′,N′-tetracyclohexyldiglycolamide(TCHDGA)was proposed and studied to extract Sr(Ⅱ)from nitrate media.TCHDGA was prepared and characterized by 1H nuclear magnetic resonance spectroscopy(NMR),^(13)C NMR,and fourier transform infrared spectroscopy(FT-IR).Various factors affecting extraction were studied systematically.In just 20 s,the extraction rate can reach approximately 98.2%.The extraction capacity of cyclohexyl-substituted extractant TCHDGA is tens of times higher than that with linear or branched chain alkyl.The chemical structure of the complex has been demonstrated to be[Sr3TCHDGA]·(NO_(3))_(2),based on FT-IR,X-ray photoelectron spectroscopy(XPS),and crystal structure analysis.The crystal belongs to the monoclinic system,space group P21,and a strontium ion coordinates with nine oxygen atoms,all of which contribute from TCHDGA.The stripping rate can reach over 99%when using distilled water or 0.50 mol·L^(-1)oxalic acid as stripping agents.
基金supported by the National Key R&D Program of China(No.2018YFC1801604)the National Natural Science Foundation of China(No.21661142001)
文摘Benzotriazole UV stabilizers (BT-UVs) have attracted concems due to their ubiquitous occurrence in the aquatic environment,and their bioaccumulative and toxic properties.However,little is known about their aquatic environmental degradation behavior.In this study,photodegradation of a representative of BT-UVs,2-(2-hydroxy-5-methylphenyl) benzotriazole (UV-P),was investigated under simulated sunlight irradiation.Results show that UV-P photodegrades slower under neutral conditions (neutral form) than under acidic or alkaline conditions (cationic and anionic forms).Indirect photodegradation is a dominant elimination pathway of UV-P in coastal seawaters.Dissolved organic matter (DOM) from seawaters accelerate the photodegradation rates mainly through excited triplet DOM (3DOM*),and the roles of singlet oxygen and hydroxyl radical are negligible in the matrixes.DOM from seawaters impacted by mariculture exhibits higher steady-state concentration of 3DOM*([3DOM*]) relative to those from pristine seawaters,leading to higher photosensitizing effects on the photodegradation.Halide ions inhibit the DOM-sensitized photodegradation of UV-P by decreasing [3DOM*].Photodegradation half-lives of UV-P are estimated to range from 24.38 to 49.66 hr in field water bodies of the Yellow River estuary.These results are of importance for assessing environmental fate and risk UV-P in coastal water bodies.
文摘A feasible guidance scheme with impact time constraint is proposed for attacking a stationary target by missiles with time-varying velocity.The main idea is to replace the constant velocity with the future mean velocity;therefore, the existing time-to-go estimation algorithm of the proportional navigation guidance law can be improved to adapt to varying conditions.In order to obtain the prediction of the velocity profile, the velocity differential equation to the downrange is derived, which can be numerically integrated between the current downrange and the target position by the on-board computer.Then, a third-order polynomial is introduced to fit the velocity profile in order to calculate the future mean velocity.At the beginning of each guidance loop, the future mean velocity is predicted and the time-to-go information is updated, based on which a novel biased proportional navigation guidance law is established to achieve the impact time constraint.Finally,numerical simulation results verified the effectiveness of the time-to-go estimation algorithm and the proposed law.
基金supported by the National Natural Science Foundation of China (No.40973058)the Ministry of Science and Technology (No.2007CB407304)
文摘In Rhodopseudomonas palustris,an arsM gene,encoding bacterial and archaeal homologues of the mammalian Cyt19 As（III） S-adenosylmethionine methytransferase,was regulated by arsenicals.An expression of arsM was introduced into strains for the methylation of arsenic.When arsM was expressed in Sphingomonas desiccabilis and Bacillus idriensis,it had 10 folds increase of methyled arsenic gas compared to wild type in aqueous system.In soil system,about 2.2%–4.5% of arsenic was removed by biovolatilization during 30 days.This study demonstrated that arsenic could be removed through volatilization from the contaminated soil by bacteria which have arsM gene expressed.These results showed that it is possible to use microorganisms expressing arsM as an inexpensive,efficient strategy for arsenic bioremediation from contaminated water and soil.
基金supported by the National Natural Sci- ence Foundation of China (No. 40973058, 21077100)the Doctor Foundation of Shandong Province (No. BS2009HZ024)
文摘Arsenic （As） is a pervasive and ubiquitous environmental toxin that has created catastrophic human health problems world-wide. Chlamydomonas reinhardtii is a unicellular green alga, which exists ubiquitously in freshwater aquatic systems. Arsenic metabolism processes of this alga through arsenate reduction and sequent store and efflux were investigated. When supplied with 10 μmol/L arsenate, arsenic speciation analysis showed that arsenite concentration increased from 5.7 to 15.7 mg/kg dry weight during a 7-day period, accounting for 18%–24% of the total As in alga. When treated with different levels of arsenate （10, 20, 30, 40, 50 μmol/L） for 7 days, the arsenite concentration increased with increasing external arsenate concentrations, the proportion of arsenite was up to 23%–28% of the total As in alga. In efflux experiments, both arsenate and arsenite could be found in the efflux solutions. Additionally, the efflux of arsenate was more than that of arsenite. Furthermore, two arsenate reductase genes of C. reinhardtii （CrACR2s） were cloned and expressed in Escherichia coli strain WC3110 （？arsC） for the first time. The abilities of both CrACR2s genes to complement the arsenate- sensitive strain were examined. CrACR2.1 restored arsenate resistance at 0.8 mmol/L. However, CrACR2.2 showed much less ability to complement. The gene products were demonstrated to reduce arsenate to arsenite in vivo. In agreement with the complementation results, CrACR2.1 showed higher reduction ability than CrACR2.2, when treated with 0.4 mmol/L arsenate for 16 hr incubation.
基金supported by the National Natural Science Foundation of China(21876062)。
文摘Recovery of scandium from titanium white waste acid is an essential source of scandium.Simple and economical production of high purity scandium remains a challenge.A new extractant,N,N,N’,N’-tetracyclohexyl-diglycolamide(TCHDGA),was synthesized,and the separation performance of scandium from impurity metal ions(Ti,Mn,Ba,Fe,Al and Mg)was investigated,The effects of mixing time,acid concentration and temperature on the scandium extraction were considered.The extraction mechanism was studied by infrared spectroscopy and the Equimole Series Method.Under optimized conditions,the extractant shows a strong affinity to scandium in the nitric acid medium and high extraction separation factors between scandium and these impurity metal ions,A process for the purification of scandium was established.The crude product obtained from titanium white waste acid,95%purity scandium oxide,can be purified to 99.99%after only one step of extraction,scrubbing,and stripping:This technology is economical and straightforward and can realize the high-value recovery of scandium in the titanium white waste acid.
基金supported by the National Natural Science Foundation of China (No. 21077100, 41090284)
文摘Arsenic （As） is ubiquitous in the environment in the carcinogenic inorganic forms, posing risks to human health in many parts of the world. Many microorganisms have evolved a series of mechanisms to cope with inorganic arsenic in their growth media such as transforming As compounds into volatile derivatives. Bio-volatilization of As has been suggested to play an important role in global As biogeochemical cycling, and can also be explored as a potential method for arsenic bioremediation. This review aims to provide an overview of the quality and quantity of As volatilization by fungi, bacteria, microalga and protozoans. Arsenic bio-volatilization is influenced by both biotic and abiotic factors that can be manipulated/elucidated for the purpose of As bioremediation. Since As bio- volatilization is a resurgent topic for both biogeochemistry and environmental health, our review serves as a concept paper for future research directions.
基金Project supported by the National Natural Science Foundation of China(21876062)。
文摘Diglycolamides(DGAs) show excellent application prospects for the extraction and separation of rare earth metals from highly radioactive liquid wastes and rare earth ores.The extraction ability of DGAs for rare earth ions in nitrate or chloride media increases with increasing atomic number of the rare earth metal.To understand the origin of this phenomenon,three binuclear crystals [Ln(TEDGA)_(3)][Ln(NO_(3))_(6)] of N,N,N’,N’-tetraethyldiglycolamide(TEDGA) with rare earth ions La(Ⅲ),Pr(Ⅲ) and Eu(III) were prepared and characterized crystallographically.The three complexes belong to the triclinic crystal system,P-1 space group.The bond lengths of Ln-O_(amide) are significantly shorter than those of Ln-O_(ether) in the same crystal.The Ln-O_(amide) and Ln-O_(enher) bond lengths gradually decrease with increasing atomic number of the rare earth ion.The dihedral angle formed by TEDGA and metal ions through the tridentate coordination gradually increases with increasing metal ion atomic number,tending toward the formation of sizeable planar coordination structures for the most massive rare earth ions.The structures of the compounds formed by the extractant and metal ion were optimized by means of DFT simulations.We find that the interaction between TEDGA and the rare earth ion is dominated by electrostatic interaction by analyzing binding energy,WBIs,Mulliken charge,natural electron configurations,and molecular orbital interaction.The covalent component of the Ln-O bonds of the complexes increases with increasing metal atomic number.The observed increase in extraction and separation capacity of diglycolamides for rare earth ions with increasing atomic number might be due to the formation of two fivemember rings by one tridentate ligand.The rare earth ions with large atomic numbers tend to form planar structures with large dihedral angles with DGA ligands.
基金Supported by a grant from the Qingdao Science and Technology Bureau of China(No.19-6-1-9-nsh).
文摘Objective To investigate the differences in intestinal flora of patients with primary liver cancer and ofhealthy individuals and to investigate the effect of the differential flora on the development of liver cancer.Methods Overall, 67 patients with primary liver cancer who received systematic and complete treatmentbetween January 2019 and December 2020 at the Sixth People’s Hospital of Qingdao and had completeclinical data were enrolled in this study, and 26 individuals who were healthy on physical examination inthe same period were used as healthy controls. Macro genome and 16s ribosome Deoxyribo Nucleic Acid(rDNA) high-throughput sequencing were performed on the stool flora of the enrolled patients and controls,and the differences in the intestinal flora were analyzed using the LEfSe bioinformatics software.Results Compared with the control samples, all the tested patient samples showed statistically significantdifferences in the number of colonies of 5 bacterial phyla, 5 orders, 8 families, 11 genera, and 14 species(P < 0.05).Conclusion Compared with healthy people, patients with primary liver cancer have significant differencesin the intestinal flora composition. The alteration of the intestinal flora may be correlated with the occurrenceof primary liver cancer, and the intestinal flora may become a novel target for the prevention and treatmentof primary liver cancer.
基金Project supported by the National Natural Science Foundation of China(21876062)Shandong Provincial Natural Science Foundation(ZR2022QB067)。
文摘Rational design of extractant structure to improve the extraction and separation capacity of rare earth elements(REEs)is a long-standing challenge.Herein,a new strategy was proposed to improve the stability of the chelating structure formed by malonamide and REEs.The stability of the chelating structure is greatly improved by using a double-ring framework structure which makes the two carbonyl groups of malonamide unable to rotate freely and both of them point to the metal ion position.Three benzyl groups were used to construct the hydrophobicity of the extractant and the organic shell of the extracted species.Tribenzylhexahydro-pyrrolo-pyridine-dione(THPPD)was designed and synthesized.The structure reduces the energy consumed by rotating carbonyl group in the coordination with metal ions and then improves the extraction ability of extractant.The crystal structure was preorganized as expected,with the two carbonyls pointing in a favorable coordination direction to the structural complement of the metal ion.The extraction behaviors of REEs with THPPD in a nitric acid medium were studied.Compared with N,N’-dibenzyl-N,N’-dimethylmalonamide(DBDM-MA)with a chain structure,the extraction capacity of THPPD is 360 times higher than that of DBDM-MA at 5.0 mol/L sodium nitrate.Furthermore,the binding energy and Gibbs free energy were investigated by density functional theory(DFT)in conjunction with the B3LYP.The theoretical results show that THPPD has more effective interaction with Pr(NO_(3))3 than DBDM-MA.The construction of chelating groups conformation is a worthy direction to improve the coordination ability and even selectivity of extractant.
基金Supported by a grant from the Qingdao Pharmaceutical Research Guidance Plan 2019(No.2019-WJZD140).
文摘Objective To analyze the characteristics of the intestinal microflora in patients with breast fibroadenoma using 16S ribosomal RNA(rRNA)high-throughput sequencing.Methods Fecal samples from 20 patients with breast fibroadenoma and 36 healthy subjects were randomly collected and analyzed using high-throughput sequencing technology for 16S rRNA V4 region sequencing,and the alpha diversity(Chao index,Shannon index)was calculated using Mothur(v.1.39.5)software.Beta diversity was analyzed using QIIME(v1.80).SPSS software(version 23.0)and the t-test of two independent samples were used to analyze differences in the abundance of bacteria between the two groups.Results Compared with that in the healthy control group,theαdiversity of the intestinal microflora in breast fibroadenoma patients increased,but the difference was not statistically significant(P>0.05).At the phylum level,significant differences were observed between the two groups.The abundance of Firmicutes was higher in the breast fibroadenoma group(P<0.05),whereas the abundance of Synergistetes was higher in the healthy control group(P<0.005).A total of five bacterial genera showed significant differences between the two groups:the breast fibroadenoma group showed higher levels of Bautia(P<0.005),Coprococcus(P<0.005),Roseburia(P<0.05),and Ruminococcus(P<0.005),whereas Sutterella was more abundant in the healthy control group than in the breast fibroadenoma group(P<0.05).Conclusion The diversity and abundance of the intestinal flora in patients with breast fibroadenoma are significantly different from those in healthy subjects,suggesting that an imbalance in the intestinal flora is correlated with the occurrence of breast fibroadenoma.
文摘[Objectives]To observe the clinical effect of acupuncture on blepharospasm.[Methods]72 patients were randomly divided into treatment group and control group with 36 cases in each group.In the treatment group,Shenmai,Zhaohai,Fengchi,Taichong,Fuyang,Jiaoxin and Jingming were selected as the main acupoints,while in the control group,routine acupoints were selected.With 4 weeks as a course of treatment,the two groups were compared after a course of treatment.The clinical effect of primary blepharospasm,blepharospasm intensity and scores of Hamilton Depression Scale were compared between the two groups before and after treatment.[Results]After treatment,the clinical efficacy of the two groups were significantly improved compared with that before treatment,the effective rate of the control group was 75.00%,the effective rate of the treatment group was 88.89%,indicating that the effective rate of control group was lower than that of the treatment group(P<0.05);after treatment,the degree of blepharospasm in both groups was significantly lower than that before treatment(P<0.05),and the treatment group had better effect in improving primary blepharospasm;the score of Hamilton depression scale in control group was lower than that in observation group(P<0.05).[Conclusions]The clinical curative effect of acupuncture at Yinqiao and Yangqiao meridians was better than that of conventional acupoints selected in relieving mild and moderate blepharospasm;it could definitely reduce the intensity of blepharospasm and relieve anxiety and depression of patients,so it is worthy of clinical promotion.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program(Grant No.2019QZKK0306)the National Natural Science Foundation of China(Grant No.42101058).
文摘Despite extensive research,fungal diversity along elevation gradients remains difficult to generalize.In this study we examined soil fungal diversity and network stability on two snow mountains in the Hengduan Mountain Range of China and identified distinct biodiversity patterns.On Meili Snow Mountain,fungal ASV richness declined significantly with altitude,with MAT identified as the primary driver.On Baima Snow Mountain,richness exhibited a hump-shaped pattern,with TN as the key influencing factor.Regression analysis and structural equation modelling revealed that elevation indirectly influenced fungal richness by affecting climate,vegetation,and soil properties.Despite similar climatic conditions,elevational patterns of fungal communities on the two mountains are driven by distinct local factors:Fungal communities on Meili Snow Mountain are mainly driven by NDVI,whereas those on Baima Snow Mountain are mainly shaped by soil fertility.Co-occurrence network analysis further indicates that fungal network complexity on Meili Snow Mountain increases with altitude,while fungal network stability follows a U-shaped distribution driven by species interactions and environmental filtering.In contrast,on Baima Snow Mountain,fungal network complexity peaks at mid-altitudes and stability shows no significant correlation with altitude,suggesting strong niche adaptability.These findings highlight the complex effects of elevation on fungal diversity and networks,providing new insights into biodiversity in mountain ecosystem and guidance for ecosystem management under climate change.
基金supported by the Natural Science Foundation of China(No.61765012)the Natural Science Foundation of Inner Mongolia Autonomous Region(No.2021LHBS05005)+4 种基金the Science and Technology Research Project of Inner Mongolia Autonomous Region Higher Education(No.2021SHZR0620)the Inner Mongolia Autonomous Region 2017 Science and Technology Innovation Guidance Award Funding Projects(No.2017CXYD-2)the Natural Science Foundation of Inner Mongolia Autonomous Region(No.2019MS05008).The funders had no role in the design of the studyin the collection,analyses,or interpretation of datain the writing of the manuscript,or in the decision to publish the results.
文摘Accurate prediction of the heat load is the basic premise of intelligent regulation of the heating system,which helps to realize effective management of heating,ventilation,air conditioning system.For the problem that the weight of each influencing factor is not taken into account in the current heat load prediction and is not highly targeted,this article deeply explores the influence of different factors on the room heat load,and we propose a method to calculate room heat load prediction based on the combination of analytic hierarchy process(AHP)and back-propagation(BP)neural network.Firstly,eight environmental factors affecting the heat load are selected as prediction inputs through parametric analysis,and then the weights of each input are determined by AHP and normalize the prediction data by combining expert opinions,and finally do one-to-one training the quantified score and the room heat load to predict the future heat load by BP neural network.The simulation tests show that the mean absolute relative error(MARE)of the proposed prediction method is 5.40%.This article also verifies the influence of different expert opinions on the stability of the model.The results show that the proposed method can guarantee higher prediction accuracy and stability.
文摘The combination of two bacteria （Bacillus sp. PY1 and Sphingomonas sp. PY2） and a fungus （Fusarium sp. PY3）, isolated from contaminated soils near a coking plant, were investigated with respect to their capability to degrade pyrene and volatilize arsenic. The results showed that all strains could use pyrene and arsenic as carbon and energy sources in a basal salts medium （BSM）, with the combined potential to degrade pyrene and volatilize arsenic. Bacillus sp. PY1, Sphingomonas sp. PY2 and Fusarium sp. PY3 were isolated from the consortium and were shown to degrade pyrene and volatilize arsenic independently and in combination. Fungal-bacterial cocul- ture has shown that the most effective removal of pyrene was 96.0% and volatilized arsenic was 84.1% after incubation in liquid medium after 9 days culture, while bioremediation ability was 87.2% in contaminated soil with 100 mg-kg-1 pyrene. The highest level of arsenic volatilization amounted to 13.9% of the initial As concentration in contaminated soil after 63 days. There- fore, a synergistic degradation system is the most effective approach to degrade pyrene and remove arsenic in contaminated soil. These findings highlight the role of these strains in the bioremediation of environments contaminated with pyrene and arsenic.
基金supported by the Second Qinghai-Xizang Plateau Scientific Expedition and Research Program(2019QZKK0306 and 2019QZKK0308)
文摘Alpine forest soil in the southeastern Qinghai–Xizang Plateau plays a crucial role in regional and global climate and biogeochemical cycles,yet the elevational distribution of soil nitrogen(N)availability and losing risk is unresolved.In this study,we characterized soil N composition and key N transformation processes across different elevations in 3 typical mounts of the Qinghai–Xizang Plateau.In contrast to previous suggestions,soil total N and ammonium are found to accumulate in high elevation zones.This accumulation of N at higher altitudes is due to a consistent soil net N mineralization rate coupled with an extremely low net nitrification rate,which is suppressed by low p H and high soil moisture in high elevation zones.Moreover,the elevated rates of biological N fixation along the elevation further contribute to N accumulation in high elevation regions in which the acid-tolerant Bradyrhizobium,plant-associated Herbaspirillum,and Klebsiella are identified as the key diazotrophic microbial taxa responsible for active N fixation.Collectively,our results suggest that total N and NH_(4)^(+)-N accumulation in higher altitude zone is a ubiquitous phenomenon in the southeast Qinghai–Xizang Plateau,with lower nitrification rates and higher biological nitrogen fixation being key processes enabling this occurrence.
