In situ formed Mg(BH_(4))_(2) for improving hydrolysis properties of MgH_(2)

The hydrolysis of MgH_(2) delivers high hydrogen capacity(15.2 wt%),which is very attractive for real-time hydrogen supply.However,the formation of a surface passivation Mg(OH)_(2) layer and the large excess of H_(2)O required to ensure complete hydrolysis are two key challenges for the MgH_(2) hydrolysis systems.Now,a low-cost method is reported to synthesize MgH_(2)@Mg(BH_(4))_(2) composite via ball-milling MgH_(2) with cheap and widely available B_(2)O_(3)(or B(OH)_(3)).By adding small amounts of B_(2)O_(3),the in-situ formed Mg(BH_(4))_(2) could significantly promote the hydrolysis of MgH_(2).In particular,the MgH_(2)–10 wt%B_(2)O_(3) composite releases 1330.7 mL·g^(−1) H_(2)(close to 80%theoretical hydrogen generation H_(2))in H_(2)O and 1520.4 mL·g^(−1) H_(2)(about 95%)in 0.5 M MgCl_(2) in 60 min at 26℃ with hydrolysis rate of 736.9 mL·g^(−1)·min^(−1) and 960.9 mL·g^(−1)·min^(−1) H_(2) during the first minute of the hydrolysis,respectively.In addition,the MgCl_(2) solution allows repeated use by filtering and exhibits high cycle stability(20 cycles),therefore leading to much reduced capacity loss caused by the excess H_(2)O.We show that by introducing B_(2)O_(3) and recycling the 0.5 M MgCl_(2) solution,the system hydrogen capacity can approach 5.9 wt%,providing a promising hydrogen generation scheme to supply hydrogen to the fuel cells.

Selective leaching of lithium from spent lithium-ion batteries using sulfuric acid and oxalic acid

Traditional hydrometallurgical methods for recovering spent lithium-ion batteries(LIBs)involve acid leaching to simultaneously extract all valuable metals into the leachate.These methods usually are followed by a series of separation steps such as precipitation,extraction,and stripping to separate the individual valuable metals.In this study,we present a process for selectively leaching lithium through the synergistic effect of sulfuric and oxalic acids.Under optimal leaching conditions(leaching time of 1.5 h,leaching temperature of 70°C,liquid-solid ratio of 4 mL/g,oxalic acid ratio of 1.3,and sulfuric acid ratio of 1.3),the lithium leaching efficiency reached89.6%,and the leaching efficiencies of Ni,Co,and Mn were 12.8%,6.5%,and 21.7%.X-ray diffraction(XRD)and inductively coupled plasma optical emission spectrometer(ICP-OES)analyses showed that most of the Ni,Co,and Mn in the raw material remained as solid residue oxides and oxalates.This study offers a new approach to enriching the relevant theory for selectively recovering lithium from spent LIBs.

Examination of Resource Curse Hypothesis: Mineral Resources Exploitation and Economic Growth in Xinjiang Autonomous Region

The mineral resources exploitation stage and the economic growth rate are various in different regions of Xinjiang Autonomous region. Using the method of location quotient, this paper identifies and classifies the intensive regions of three types of mineral resources, known as coal, oil and natural gas, respectively. The intensive regions of economic growth were also identified, according to the rate of per capita GDP growth at prefecture, autonomous prefecture and city. The relationships between different mineral resources and economic growth are different, for example, the relationship between economic growth and coal resource is positive, while the relationship between economic growth and oil resource, or natural gas resource is negative. This study empirically examines the effects of natural resources on economic growth of Xinjiang. The results show that whilst natural resources have a positive impact on growth, and can make a negative impact on growth through the transmission channels, such as investment, manufacture, human capital, and scientific and technologic innovation. Moreover, it studies the transmission channels, that is, the effect of natural resources on the other explanatory variables, and calculates the indirect effect of natural resources on growth for each transmission channel, and comprehensive effects of natural resources on growth. The calculated result of comprehensive effects indicates that the positive direct effects of natural resources on growth are shown to outweigh the negative indirect effect of Xinjiang autonomous region.

Regeneration of spent LiFePO4 as a high-performance cathode material by a simultaneous coating and doping strategy

With the number of decommissioned electric vehicles increasing annually,a large amount of discarded power battery cathode material is in urgent need of treatment.However,common leaching methods for recovering metal salts are economically inefficient and polluting.Meanwhile,the recycled material obtained by lithium remediation alone has limited performance in cycling stability.Herein,a short method of solid-phase reduction is developed to recover spent LiFePO4 by simultaneously introducing Mg2+ions for hetero-atom doping.Issues of particle agglomeration,carbon layer breakage,lithium loss,and Fe3+defects in spent LiFePO4 are also addressed.Results show that Mg2+addition during regeneration can remarkably enhance the crystal structure stability and improve the Li+diffusion coefficient.The regenerated LiFePO4 exhibits significantly improved electrochemical performance with a specific discharge capacity of 143.2 mAh·g^(−1)at 0.2 C,and its capacity retention is extremely increased from 37.9%to 98.5%over 200 cycles at 1 C.Especially,its discharge capacity can reach 95.5 mAh·g^(−1)at 10 C,which is higher than that of spent LiFePO4(55.9 mAh·g^(−1)).All these results show that the proposed regeneration strategy of simultaneous carbon coating and Mg2+doping is suitable for the efficient treatment of spent LiFePO4.

Oxidative exfoliation of spent cathode carbon:A two-in-one strategy for its decontamination and high-valued application

Spent cathode carbon(SCC)from aluminum electrolysis is a potential graphite resource.However,full use of the SCC remains a challenge,since it contains many hazardous substances(e.g.,fluoride salts,cyanides),encapsulated within the thick carbon layers and thus posing serious environmental concerns.This work presents a chemical oxidative exfoliation route to achieve the recycling of SCC and the decontaminated SCC with high-valued graphene oxide(GO)-like carbon structures(SCC-GO)is applied as an excellent adsorbent for organic pollutants.Specifically,after the oxidative exfoliation,the embedded hazardous constituents are fully exposed,facilitating their subsequent removal by aqueous leaching.Moreover,benefiting from the enhanced specific surface areas along with abundant O-containing functional groups,the as-produced SCC-GO,shows an adsorption capacity as high as 347 mg·g^(-1)when considering methylene blue as a pollutant model,which exceeds most of the recently reported carbon-based adsorbents.Our study provides a feasible solution for the efficient recycling of hazardous carbonaceous wastes.

Techno-economic assessment of a chemical looping splitting system for H2 and CO Co-generation

The natural gas(NG)reforming is currently one of the low-cost methods for hydrogen production.However,the mixture of H2 and CO_(2) in the produced gas inevitably includes CO_(2) and necessitates the costly CO_(2) separation.In this work,a novel double chemical looping involving both combustion(CLC)and sorption-enhanced reforming(SE-CLR)was proposed towards the co-production of H2 and CO(CLC-SECLRHC)in two separated streams.CLC provides reactant CO_(2) and energy to feed SECLRHC,which generates hydrogen in a higher purity,as well as the calcium cycle to generate CO in a higher purity.Techno-economic assessment of the proposed system was conducted to evaluate its efficiency and economic competitiveness.Studies revealed that the optimal molar ratios of oxygen carrier(OC)/NG and steam/NG for reforming were recommended to be 1.7 and 1.0,respectively.The heat integration within CLC and SECLRHC units can be achieved by circulating hot OCs.The desired temperatures of fuel reactor(FR)and reforming reactor(RR)should be 850
C and 600
C,respectively.The heat coupling between CLC and SECLRHC units can be realized via a jacket-type reactor,and the NG split ratio for reforming and combustion was 0.53:0.47.Under the optimal conditions,the H2 purity,the H2 yield and the CH4 conversion efficiency were 98.76%,2.31 mol mol-1 and 97.96%,respectively.The carbon and hydrogen utilization efficiency respectively were 58.60% and 72.45%in terms of the total hydrogen in both steam and NG.The exergy efficiency of the overall process reached 70.28%.In terms of the conventional plant capacity(75 × 103 t y^(-1))and current raw materials price(2500$t^(-1)),the payback period can be 6.2 years and the IRR would be 11.5,demonstrating an economically feasible and risk resistant capability.

The influence of bioturbation on sandy reservoirs: the delta front sand of the lower Zhujiang Formation, Baiyun Depression, Zhujiang River Mouth Basin

Ichnofossils are well developed in clastic rock reservoirs in marine and transitional facies, which can considerably change the physical properties of the reservoir. However, this influence is not well understood, raising an important problem in the effective development of petroleum reservoirs. This paper analyzes continental shelf margin delta reservoirs through core observation, cast thin section observation and reservoir physical property test. Some important scientific insights are obtained:(1) The presence of Cruziana ichnofacies, including Asterosoma, Ophiomorpha, Planolites, Skolithos, Thalassinoides, and other ichnofossils can be used to identify in subaqueous distributary channels, subaqueous levee, frontal sheet sand, abandoned river channels, crevasse channels, main channels and channel mouth bars. Considerable differences in the types of ichnofossils and the degree of bioturbation can be observed in the different petrofacies.(2) Ichnofossils and bioturbation play a complex role in controlling reservoir properties. The reservoir physical properties have the characteristics of a decrease–increase–decrease curve with increasing bioturbation degree. This complex change is controlled by the sediment mixing and packing of bioturbation and the diagenetic environment controlled by the ichnofossils.(3) Sea-level cycle changes affect the modification of the reservoir through sediment packing. Bioturbation weakens the reservoir's physical property when sea level slowly rises and improves the reservoir's physical property when base level slowly falls.

Effect of fluoride ions on coordination structure of titanium in molten NaCl–KCl

The effects of fluoride ions(F^(-)) on the electrochemical behavior and coordination properties of titanium ions(Ti^(n+)) were studied in this work,by combining electrochemical and mathematical analysis as well as spectral techniques.The α was taken as a factor to indicate the molar concentration ratio of F^(-) and Ti^(n+).Cyclic voltammetry(CV),square wave voltammetry(SWV),and open circuit potential method(OCP)were used to study the electrochemical behavior of titanium ions under conditions of various α,and in-situ sampler was used to prepare molten salt samples when α equal to 0.0,1.0,2.0,3.0,4.0,5.0,6.0,and 8.0.And then,samples were analyzed by X-ray photoelectron spectroscopy(XPS) and Raman spectroscopy.The results showed that F^(-) in molten salt can reduce the reduction steps of titanium ions and greatly affects the proportion of valence titanium ions which making the high-valence titanium content increased and more stable.Ti^(2+) cannot be detected in the molten salt when α is higher than 3.0 and finally transferred to titanium ions with higher valence state.Investigation revealed that the mechanism behind those phenomenon is the coordination compounds(TiCl_(j) F_(i)^(m-)) forming.

Reaction characteristics of magnesium production under argon flow by silicothermic reduction and numerical simulation of argon entrainment process

In this study, the reaction characteristics of reduction of calcined dolomite with ferrosilicon under argon flow to produce magnesium were studied by conducting experiments Pidgeon pellets were used to study the effect of reduced temperature, argon flow, and reduced time on the conversion of calcined dolomite reduction by ferrosilicon. The results show that the conversion significantly increases with the increase in the reduction temperature and reduction time. The conversion first increases and then decreases with the increase in argon flow. The highest conversion was obtained when the argon flow rate was 3 L·min^(-1), and a nearly spherical shape, nanoscale magnesium powder was obtained. Then the characters of the circulating argon entrainment process were numerically studied by ANSYS Fluent 17. A physical model of multilayer pellet arrangement was established, and a numerical calculation model of chemical reaction, radiation, heat conduction, and convection heat transfer was constructed. This confirms that high-temperature argon can effectively strengthen the heat exchange between pellets, improve the heat transfer efficiency, and facilitate the pellets to react quickly. When the conversion is 80%, the production efficiency increased by about 28.6%. In addition, the magnesium production efficiency showed an increase tendency with the increase of the argon inlet flow rate.

Quantitative morphometric analysis of a deep-water channel in the Taranaki Basin, New Zealand

The morphological changes of deep-water channels have an important influence on the distributions of channel sand reservoirs,so it is important to explore the morphological change process of deep-water channel for the exploration and development of deep-water oil and gas.Based on a typical sinuous Quaternary channel(Channel I)in the Taranaki Basin,New Zealand,a variety of seismic interpretation techniques were applied to quantitatively characterize the morphological characteristics of the Channel I,and the relationships between the quantitative parameters and the morphological changes of the Channel I,as well as the controlling factors affecting those morphological changes,were discussed.The results are as follows:(1)in the quantitative analysis,six parameters were selected:the channel depth,width,sinuosity,and aspect ratio(width/depth),the channel swing amplitude(λ)and the channel bend frequency(ω);(2)according to the quantitative morphological parameters of the channel(mainly including three parameters such as channel sinuosity,ωandλ),the Channel I was divided into three types:the low-sinuous channel(LSC),the high-sinuous channel(HSC),the moderate-sinuous channel(MSC).U-shaped channel cross-sections developed in the LSC,V-shaped channel cross-sections developed in the HSC,including inclined-V and symmetric-V cross-sections,and dish-shaped channel cross-sections developed in the MSC;(3)the morphological characteristics of the LSC and MSC were related to their widths and depths,while the morphology of the HSC was greatly affected by the channel width,a change in depth did not affect the HSC morphology;(4)the morphological changes of the Channel I were controlled mainly by the slope gradient,the restricted capacity of the channel and the differential in fluid properties.

Metallurgical properties of CaO–SiO_(2)–Al_(2)O_(3)–4.6wt%MgO–Fe_(2)O_(3)slag system pertaining to spent automotive catalyst smelting

The metallurgical properties of the CaO–SiO_(2)–Al_(2)O_(3)–4.6wt%Mg O–Fe_(2)O_(3)slag system,formed by the co-treatment process of spent automotive catalyst(SAC)and copper-bearing electroplating sludge(CBES),were studied systematically in this paper.The slag structure,melting temperature,and viscous characteristics were investigated by Fourier transform infrared(FTIR)spectroscopy,Raman spectroscopy,Fact Sage calculation,and viscosity measurements.Experimental results show that the increase of Fe_(2)O_(3)content(3.8wt%–16.6wt%),the mass ratio of CaO/SiO_(2)(m(CaO)/m(SiO_(2)),0.5–1.3),and the mass ratio of SiO_(2)/Al_(2)O_(3)(m(SiO_(2))/m(Al_(2)O_(3)),1.0–5.0)can promote the depolymerization of silicate network,and the presence of a large amount of Fe_(2)O_(3)in form of tetrahedral and octahedral units ensures the charge compensation of Al^(3+)ions and makes Al_(2)O_(3)only behave as an acid oxide.Thermodynamic calculation and viscosity measurements show that with the increase of Fe_(2)O_(3)content,m(Ca O)/m(SiO_(2)),and m(SiO_(2))/m(Al_(2)O_(3)),the depolymerization of silicate network structure and low-melting-point phase transformation first occur within the slag,leading to the decrease in melting point and viscosity of the slag,while further increase causes the formation of high-melting-point phase and a resultant re-increase in viscosity and melting point.Based on experimental analysis,the preferred slag composition with low polymerization degree,viscosity,and melting point is as follows:Fe_(2)O_(3)content of 10.2wt%–13.4wt%,m(CaO)/m(SiO_(2))of 0.7–0.9 and m(SiO_(2))/m(Al_(2)O_(3))of 3.0–4.0.This work provides a theoretical support for slag design in co-smelting process of SAC and CBES.

Sedimentary elements,evolutions and controlling factors of the Miocene channel system:a case study of the deep-water Taranaki Basin in New Zealand

Deep-water channel systems are important petroleum reservoirs,and many have been discovered worldwide.Understanding deep-water channel sedimentary elements and evolution is helpful for deep-sea petroleum exploration and development.Based on high-resolution 3D seismic data,the Miocene channel system in the deep-water Taranaki Basin,New Zealand,was analyzed by using seismic interpretation techniques such as interlayer attribute extraction and strata slicing.The channel system was divided into five composite channels(CC-I to CC-V)according to four secondary level channel boundaries,and sedimentary elements such as channels,slump deposits,inner levees,mass transport deposits,and hemipelagic drape deposits were identified in the channel system.The morphological characteristics of several composite channels exhibited stark variances,and the overall morphology of the composite channels changed from relatively straight to highly sinuous to relatively straight.The evolution of the composite channels involved a gradual and repeated process of erosion and filling,and the composite channels could be divided into three evolutionary stages:initial erosion-filling,later erosion-filling(multistage),and channel abandonment.The middle Miocene channel system may have formed as a consequence of combined regional tectonic activity and global climatic change,and its intricate morphological alterations may have been influenced by the channel's ability to self-regulate and gravity flow properties.When studying the sedimentary evolution of a large-scale deep-water channel system in the Taranaki Basin during the Oligocene-Miocene,which transitioned from a passive margin to plate convergence,it can be understood how tectonic activity affected the channel and can also provide a theoretical reference for the evolution of the deepwater channels in areas with similar tectonic conversion environments around the world.

The whole-genome survey of Acer griseum,its polymorphic simple sequence repeats development and application

Background:Acer griseum Pax is an endangered species endemic to China with both ornamental and economic value.However,the lack of information on its genome size and characteristics hinders further work at the genome level.Methods:This paper applied bioinformatics methods to predict the characteristics and patterns of the A.griseum genome,providing an important basis for formulating its whole-genome sequencing scheme.This study also characterized the simple sequence repeats(SSRs)of A.griseum,laying the foundation for the development and application of genome-wide SSR markers.In this study,PE150 sequencing was performed by the BGI MGISEQ platform,and the sequence files were analyzed by the K-mer method to estimate the characteristic information by GCE software.Results:The genome size was finally determined to be 739.63 Mb,its heterozygosity ratio was 1.33%,and the repetition ratio was 65.68%.A total of 825,960 SSR loci were identified in the assembled genome sequence,and primers were successfully designed for 526,020 loci.To verify the effectiveness of these primers,100 pairs of primers were randomly selected and synthesized,and 81 pairs successfully amplified the target fragments.Fourteen pairs of primers with good polymorphism were selected for principal component analysis of 31 A.griseum individuals from two populations,showing favorable heterozygosity and PIC values.According to the findings,these SSRs might identify genetic variations based on geographic areas.Conclusion:It is suggested that Illumina+PacBio assembly strategy should be used for whole-genome sequencing due to the high heterozygosity rate and high repetition rate of the genome.In addition,the SSR primers designed in batches in this study laid a foundation for the in-depth study of population structure and population maintenance mechanism of A.griseum,which is helpful for the effective conservation and sustainable utilization of this germplasm resource.

Flotation separation of wolframite from calcite using a new trisiloxane surfactant as collector

Since wolframite is usually associated with calcite,the separation and enrichment of wolframite by froth flotation remains a great challenge.Herein,a novel trisiloxane surfactant N-(2-aminoethyl)-3-ami nopropyltrisiloxane(AATS)was successful synthesized,which was used for the separation of wolframite from calcite for the first time.The flotation separation performance of AATS was studied by flotation test,and its adsorption mechanism was explored based on contact angle,infrared spectrum analysis(FTIR),zeta potential and density functional theory(DFT)calculation.The results of microflotation test and binary mixed ore flotation test pointed that AATS had excellent selectivity and more prominent collection capacity for the flotation of wolframite when compared with industrial reagent sodium oleate(NaOL).The measurement results of contact angle proved that AATS improved the hydrophobicity of the wolframite surface.The highly selective adsorption mechanism of AATS surfactant on mineral surfaces were further researched and analyzed by FTIR and zeta potential.The results revealed that AATS surfactant had significant adsorption effect on wolframite,yet almost no adsorption on calcite.DFT calculation indicated that AATS produced electrostatic adsorption with wolframite surface through—N+H3 group.

RETRACTED ARTICLE:Sapflow characteristics of three afforestation species during the wet and dry seasons in a dry–hot valley in Southwest China

This article is retracted by the publisher due to duplicate publication caused by technical mishap during the pro-duction process.

Artificial Macrophage with Hierarchical Nanostructure for Biomimetic Reconstruction of Antitumor Immunity

Artificial cells are constructed from synthetic materials to imitate the biological functions of natural cells.By virtue of nanoengineering techniques,artificial cells with designed biomimetic functions provide alternatives to natural cells,showing vast potential for biomedical applications.Especially in cancer treatment,the deficiency of immunoactive macrophages results in tumor progression and immune resistance.To overcome the limitation,a BaSO_(4)@ZIF-8/transferrin(TRF)nanomacrophage(NMΦ)is herein constructed as an alternative to immunoactive macrophages.Alike to natural immunoactive macrophages,NMΦis stably retained in tumors through the specific affinity of TRF to tumor cells.Zn^(2+)as an“artificial cytokine”is then released from the ZIF-8 layer of NMΦunder tumor microenvironment.Similar as proinflammatory cytokines,Zn^(2+)can trigger cell anoikis to expose tumor antigens,which are selectively captured by the BaSO_(4)cavities.Therefore,the hierarchical nanostructure of NMΦs allows them to mediate immunogenic death of tumor cells and subsequent antigen capture for T cell activation to fabricate long-term antitumor immunity.As a proof-of-concept,the NMΦmimics the biological functions of macrophage,including tumor residence,cytokine release,antigen capture and immune activation,which is hopeful to provide a paradigm for the design and biomedical applications of artificial cells.

Habitats shape root-associated fungal and bacterial communities of Minjiang fir saplings

Root-associated microbes play an essentialrole in mediating plant growth,health,and habitat adaptability.However,it is unknown which microbial taxa help develop host fitness and how habitats shape root-associated microbial assembly patterns.As an endemic species of subalpine forests in western Sichuan,China,Minjiang fir(Abies fargesii var.faxoniana)is dominant on cold-shaded northwestern slopes while absent on warm sunlit southwestern slopes.In this study,fungal and bacterial communities were investigated in three spatial compartments(endosphere,rhizosphere,and bulk soil)associated with Minjiang fir saplings on a cold-shaded northwestern slope and a warm sunlit southwestern slope.Habitats differentiated the microbial communities regardless of the spatial compartment and microbial taxa.Slope aspect variations caused shifts in root-associated(rhizosphere and endosphere)microbial compositions.Compared with the southwestern slope,the cold-shaded northwestern slope harbored a higher abundance of the growth-promoting bacteria Burkholderia and ectomycorrhizal fungi Cortinarius and Piloderma.The slope aspect had stronger effects on fungal diversity than bacterial diversity,with higher fungal endemism and lower bacterial endemism.Slope aspect variations were the dominant drivers of root-associated microbial communities,with lower contribution by soil properties and higher contribution by plant traits on the northwestern slope.Findings from this study could improve the understanding of plant habitat adaptability from the perspective of microbial community assembly.It is suggested that forest management should consider root-associated microbiomes for enhancing species fitness and habitat adaptability.

Advances in Molten Salt Synthesis of Non-oxide Materials

The properties of non-oxide materials are continuously revealed,and their applications in the fields of ceramics,energy,and catalysis are increasingly extensive.Regardless of the traditional binary materials or the MAX phases,the preparation methods,which are environmentally friendly,efficient,economical,and easy to scale-up,have always been the focus of attention.Molten salt synthesis has demonstrated unparalleled advantages in achieving non-oxide materials.In addition,with the development of the process in molten salt synthesis,it also shows great potential in scale-up production.In this review,the recent progress of molten salt synthesis in the preparation of binary non-oxide and MAX phase is reviewed,as well as some novel processes.The reaction mechanisms and the influence of synthetic conditions for certain materials are discussed in detail.The paper is finalized with the discussion of the application prospect and future research trends of molten salt synthesis in non-oxide materials.

Manure substitution improves maize yield by promoting soil fertility and mediating the microbial community in lime concretion black soil

Synthetic nitrogen(N)fertilizer has made a great contribution to the improvement of soil fertility and productivity,but excessive application of synthetic N fertilizer may cause agroecosystem risks,such as soil acidification,groundwater contamination and biodiversity reduction.Meanwhile,organic substitution has received increasing attention for its ecologically and environmentally friendly and productivity benefits.However,the linkages between manure substitution,crop yield and the underlying microbial mechanisms remain uncertain.To bridge this gap,a three-year field experiment was conducted with five fertilization regimes:i)Control,non-fertilization;CF,conventional synthetic fertilizer application;CF_(1/2)M_(1/2),1/2 N input via synthetic fertilizer and 1/2 N input via manure;CF_(1/4)M_(3/4),1/4 N input synthetic fertilizer and 3/4 N input via manure;M,manure application.All fertilization treatments were designed to have equal N input.Our results showed that all manure substituted treatments achieved high soil fertility indexes(SFI)and productivities by increasing the soil organic carbon(SOC),total N(TN)and available phosphorus(AP)concentrations,and by altering the bacterial community diversity and composition compared with CF.SOC,AP,and the soil C:N ratio were mainly responsible for microbial community variations.The co-occurrence network revealed that SOC and AP had strong positive associations with Rhodospirillales and Burkholderiales,while TN and C:N ratio had positive and negative associations with Micromonosporaceae,respectively.These specific taxa are implicated in soil macroelement turnover.Random Forest analysis predicted that both biotic(bacterial composition and Micromonosporaceae)and abiotic(AP,SOC,SFI,and TN)factors had significant effects on crop yield.The present work strengthens our understanding of the effects of manure substitution on crop yield and provides theoretical support for optimizing fertilization strategies.

Topsoil organic carbon mineralization and CO_2 evolution of three paddy soils from South China and the temperature dependence

Carbon mineralization and its response to climatic warming have been receiving global attention for the last decade. Although the virtual influence of temperature effect is still in great debate, little is known on the mineralization of organic carbon （SOC） of paddy soils of China under warming. SOC mineralization of three major types of China＇s paddy soils is studied through laboratory incubation for 114 d under soil moisture regime of 70% water holding capacity at 20℃ and 25℃ respectively. The carbon that mineralized as CO2 evolved was measured every day in the first 32 d and every two days in the following days. Carbon mineralized during the 114 d incubation ranged from 3.51 to 9.22 mg CO2-C/gC at 20℃ and from 4.24 to 11.35 mg CO2-C/gC at 25℃ respectively; and a mineralizable C pool in the range of 0.24 to 0.59 gC/kg, varying with different soils. The whole course of C mineralization in the 114 d incubation could be divided into three stages of varying rates, representing the three subpools of the total mineralizable C： very actively mineralized C at 1-23 d, actively tnineralized C at 24--74 d and a slowly mineralized pool with low and more or less stabilized C mineralization rate at 75-114 d. The calculated Q10 values ranged from 1.0 to 2.4, varying with the soil types and N status. Neither the total SOC pool nor the labile C pool could account for the total mineralization potential of the soils studied, despite a well correlation of labile C with the shortly and actively mineralized C, which were shown in sensitive response to soil warming. However, the portion of microbial C pool and the soil C/N ratio controlled the C mineralization and the temperature dependence. Therefore, C sequestration may not result in an increase of C mineralization proportionally. The relative control of C bioavailability and microbial metabolic activity on C mineralization with respect to stabilization of sequestered C in the paddy soils of China is to be further studied.