In agricultural systems, maintenance of soil organic matter has long been recognized as a strategy to reduce soil degradation. Manure amendments and green manures are management practices that can increase some nutrie...In agricultural systems, maintenance of soil organic matter has long been recognized as a strategy to reduce soil degradation. Manure amendments and green manures are management practices that can increase some nutrient contents and improve soil aggregation. We investigated the effects of 28 yr of winter planted green manure on soil aggregate-size distribution and aggregateassociated carbon（C） and nitrogen（N）. The study was a randomized completed block design with three replicates. The treatments included rice-rice-fallow, rice-rice-rape, rice-rice-Chinese milk vetch and rice-rice-ryegrass. The experiment was established in 1982 on a silty light clayey paddy soil derived from Quaternary red clay（classified as Fe-Accumuli-Stagnic Anthrosols） with continuous early and late rice. In 2009, soil samples were collected（0-15 cm depth） from the field treatment plots and separated into water-stable aggregates of different sizes（i.e., 〉5, 2-5, 1-2, 0.5-1, 0.25-0.5 and 〈0.25 mm） by wet sieving. The long-term winter planted green manure significantly increased total C and N, and the formation of the 2-5-mm water-stable aggregate fraction. Compared with rice-rice-rape, rice-rice-Chinese milk vetch and rice-rice-ryegrass, the rice-rice-fallow significantly reduced 2-5-mm water-stable aggregates, with a significant redistribution of aggregates into micro-aggregates. Long-term winter planted green manure obviously improved C/N ratio and macro-aggregate-associated C and N. The highest contribution to soil fertility was from macro-aggregates of 2-5 mm in most cases.展开更多
We investigated the size distribution of water-stable aggregates and the soil carbon, nitrogen and phosphorus concentration over aggregate size fractions based on a long-term （1990-2006） fertilization experiment in ...We investigated the size distribution of water-stable aggregates and the soil carbon, nitrogen and phosphorus concentration over aggregate size fractions based on a long-term （1990-2006） fertilization experiment in a reddish paddy soil. The results showed that the largest water-stable aggregate （WSA） （〉5 mm） and the smallest WSA （〈0.25 mm） took up the first largest proportion （38.3%） and the second largest proportion （23.3%）, respectively. Application of organic materials increased the proportion of the large WSA （〉2 mm） and decreased the proportion of the small WSA （〈1 ram）, resulting in an increase in the mean weight diameter of WSA, whereas application of chemical fertilizer had little effect. Application of organic materials, especially combined with chemical fertilizers, increased total carbon, nitrogen and phosphorus concentrations in all sizes of WSA, and total carbon, nitrogen and phosphorus were prone to concentrate in the large WSA. Further more, application of organic materials improved the supply effectiveness of available phosphorus, whereas had little influence on the labile carbon in WSA. Application of chemical fertilizers improved concentrations of total and available phosphorus in all sizes of WSA, whereas had little influence on total carbon and nitrogen contents. Economical fertilization model maintained the soil fertility when compared with full dose of chemical fertilizers, indicating that using organic materials could reduce chemical fertilizers by about one third.展开更多
Soil aggregate stability,as an important indicator of soil functions,may be affected by seasonal freezing and thawing(SFT)and land use in high cold and wet regions.Therefore,comprehensive understanding the effects of ...Soil aggregate stability,as an important indicator of soil functions,may be affected by seasonal freezing and thawing(SFT)and land use in high cold and wet regions.Therefore,comprehensive understanding the effects of SFT on aggregate stability in orchards during winter and spring is crucial to develop appropriate management strategies that can effectively alleviate the degradation of soil quality to ensure sustainable development of orchard ecosystems.To determine the mechanism of degradation in orchard soil quality,the effects of SFT on the stability of water-stable aggregates were examined in apple-pear orchards(Pyrus ussuriensis var.ovoidea)of four different ages(11,25,40,and 63 yr)on 0 to 5%slopes before freezing and after thawing from October 2015 to June 2016 in Longjing City,Yanbian Prefecture,Northeast China,involving a comparison of planted versus adjacent uncultivated lands(control).Soil samples were collected to investigate water-stable aggregate stability in three incremental soil layers(0–20,20–40 and 40–60 cm).In the same samples,iron oxide,organic matter,and clay contents of the soil were also determined.Results showed that the destructive influences of SFT on water-stable aggregates were more pronounced with the increased orchards ages,and SFT exerted severe effects on water-stable aggregates of older orchards(40 and 63 yr)than juvenile orchards.Undergoing SFT,the soil instability index and the percentage of aggregate destruction increased by mean 0.15 mm and 1.86%,the degree of aggregation decreased by mean 1.32%,and the erosion resistance weakened,which consequently led to aggregate stability decreased.In addition,soil free,amorphous,and crystalline iron oxide as well as soil organic matter and clay contents are all important factors affecting the stability of water-stable aggregates,and their changes in their contents were consistent with those in the stability of water-stable aggregates.The results of this study suggest that long-term planting fruit trees can exacerbate the damaging effects of SFT on aggregate stability and further soil erosion increases and nutrient losses in an orchard,which hider sustainable use of soil and the productivity orchards.展开更多
The distribution of light fraction carbon （LF-C） in the various size classes of aggregates and its relationship to water- stable aggregates as well as the influence of cultivation on the organic components in virgin...The distribution of light fraction carbon （LF-C） in the various size classes of aggregates and its relationship to water- stable aggregates as well as the influence of cultivation on the organic components in virgin and cultivated black soils were studied by wet sieving and density separation methods. The total organic carbon （TOC） and LF-C were significantly higher （P≤ 0.05） in the virgin soils than in the cultivated soils. The LF-C in aggregates of different size classes varied from 0.9 to 2.5 g kg^-1 in the cultivated soils and from 2.5 to 7.1 g kg^-1 in the virgin soils, whereas the ratio of LF-C to TOC varied from 1.9% to 7.3% and from 5.0% to 12.2%, respectively. After being incubated under constant temperature and controlled humidity for three months, the contribution of LF-C to TOC sharply decreased to an amount （1.7%4.5%） close to the level in soils that had been cultivated for 20 to 25 years （1.3%-8.8%）. As a result, the larger water-stable macro-aggregates （especially 〉 1 mm） decreased sharply, indicating that the LF-C pool in virgin soils declined quickly after cultivation, which reduced the water stability of soil aggregates.展开更多
Soil organic matter content in water-stable aggregates（WSA） in the arid ecosystems（abandoned agricultural lands especially） of China is poorly understood. In this study, we examined the WSA sizes and stability, an...Soil organic matter content in water-stable aggregates（WSA） in the arid ecosystems（abandoned agricultural lands especially） of China is poorly understood. In this study, we examined the WSA sizes and stability, and soil organic carbon（OC） and nitrogen（N） contents in agricultural lands with abandonment ages of 0, 3, 12, 20, 30 and 40 years, respectively, in the Minqin Oasis of Northwest China. The total soil OC and N contents at depths of 0–20, 20–40 and 40–60 cm in abandoned agricultural lands were compared to those in cultivated land（the control）. Agricultural land abandonment significantly（P0.25 mm） as the age of agricultural land abandonment increased. The effect of abandonment ages of agricultural lands on MWD was determined by the changes of OC and N accumulation in WSA sizes ＆gt;2 mm. The total OC and N contents presented a stratification phenomenon across soil depths in this arid ecosystem. That is, both of them decreased significantly at depths of 0–20 and 40–60 cm while increased at the depth of 20–40 cm. The WSA sizes ＆lt;0.053 mm had the highest soil OC and N contents（accounting for 51.41%–55.59% and 42.61%–48.94% of their total, respectively）. Soil OC and N contents in microaggregates（sizes 0.053–0.25 mm） were the dominant factors that influenced the variations of total OC and N contents in abandoned agricultural lands. The results of this study suggested that agricultural land abandonment may result in the recovery of WSA stability and the shifting of soil organic matter from the silt＋clay（＆lt;0.053 mm） and microaggregate fractions to the macroaggregate fractions. However, agricultural land abandonment did not increase total soil OC and N contents in the short-term.展开更多
To study the formation process of feldspathic sandstone and sand compound soil in the Mu Us Desert,1∶ 1,1∶ 2 and 1∶ 5 ratios of feldspathic sandstone and sand were mixed to obtain compound soil to plant crops,and a...To study the formation process of feldspathic sandstone and sand compound soil in the Mu Us Desert,1∶ 1,1∶ 2 and 1∶ 5 ratios of feldspathic sandstone and sand were mixed to obtain compound soil to plant crops,and analyze the rules of changes in water-stable aggregates of the compound soil among the 4 years crops growing process. The results showed,before crop planting,the order of mass percent of> 0. 25 mm and 0. 25-2. 00 mm water-stable aggregates in three kinds of compound soil was 1∶ 1 > 1∶ 2 > 1∶ 5,showing that the overall content was low; the mass percent of > 0. 25 mm water-stable aggregates remained at 18. 38%-28. 22%; the mass percent of 0. 25-0. 50 mm,0. 50-2. 00 mm,2. 00-5. 00 mm,and > 5. 00 mm water-stable aggregates was close with each other in each kind of compound soil. After4 years of planting,the mass percent of > 0. 25 mm water-stable aggregates in 1∶ 2 compound soil increased significantly and exceeded other2 kinds of compound soil,reached 32. 34%; the main components of > 0. 25 mm water stable aggregates in 1∶ 1,1∶ 2,and 1∶ 5 compound soil were 0. 25-0. 50 mm( 53. 54%),0. 25-0. 50 mm( 59. 43%),0. 05-2. 00 mm( 52. 16%),aggregates; 0. 25-2. 00 mm aggregates increased significantly in all three kinds of compound soil,with the highest increase in 1∶ 2 compound soil; the organic matters of 1∶ 2 compound soil were significantly correlated with 0. 25-0. 50 mm and 0. 25-2. 00 mm water-stable aggregates. The results showed that the ratio of 0. 25-2. 00 mm aggregates in the three kinds of compound soil was increased after 4 years of crop planting and 1∶ 2 compound soil was most favorable for the formation of aggregates.展开更多
Soil water-stable aggregates (WSAs) are the basic unit of soil constitution and can contribute to remaining the stable soil constitution. The objective of this study was to clarify the distribution and stability of WS...Soil water-stable aggregates (WSAs) are the basic unit of soil constitution and can contribute to remaining the stable soil constitution. The objective of this study was to clarify the distribution and stability of WSAs and the soil organic carbon (SOC), the total nitrogen (TN), and the total phosphorus (TP) concentrations in 0 - 20 cm and 20 - 40 cm soil layers under the different ages of Robinia pseudoacacia plantations. The 20, 25, 40, and 50 years-old Robinia pseudoacacia plantations were selected. Stepwise regression analysis showed that >5 mm and 1 - 2 mm WSAs, SOC concentration in 2 - 5 mm WSAs, and TN and TP concentrations in < 0.25 mm WSAs were dominant independent variables affecting aggregate stability and that SOC in 0.25 - 0.5 mm WSAs, TN in <0.25 mm and 1 - 2 mm WSAs and TP in 2 - 5 mm WSAs were dominant independent variables affecting SOC, TN, and TP concentrations in bulk soils.展开更多
Polycyclic aromatic hydrocarbons (PAHs) pollution in mangroves has drawn much attention, but knowledge of the sorption of PAHs in mangrove sediment is limited. This study investigated the particles and water-stable ag...Polycyclic aromatic hydrocarbons (PAHs) pollution in mangroves has drawn much attention, but knowledge of the sorption of PAHs in mangrove sediment is limited. This study investigated the particles and water-stable aggregates (WSA) of mangrove sediment in Jiulong River Estuary, China, and the characteristics of anthracene adsorption to them. The adsorption of anthracene was strongly influenced by the physicochemical and structural properties of sediment particles and WSA. The main sorbents of mangrove sediment were carbonized particles and clays. The porous structure of carbonized particles made it easy to sequestrate sequester the anthracene, and the aging allowed anthracene to move into deeper sites of the carbonized particles. Clays had high anthracene-fixing capacities, and they included organic matters and formed aggregates. The sorption contents coefficient <i>K<sub>f</sub></i> of anthracene with WSA of different sizes increased in the order 0.063 - 0.25 mm > 0.063 mm > 0.25 - 1.0 mm > 1.0 mm. The order was correlated with which due to the contents and characteristics of organic matters in the aggregates.展开更多
The accumulation of soil organic carbon(SOC)and total nitrogen(TN)is easily accomplished by returning crop straw,which strongly affects the formation and pore structure of aggregates,especially in black soil.We return...The accumulation of soil organic carbon(SOC)and total nitrogen(TN)is easily accomplished by returning crop straw,which strongly affects the formation and pore structure of aggregates,especially in black soil.We returned maize straw at different rates(6,000,9,000,12,000 and 15,000 kg ha^(-1))for nine years to investigate its influence on the SOC and TN contents in the SOC fractions of aggregates by combining size and density fractionation.Their subsequent influences on pore morphology and size distribution characteristics were examined using X-ray microcomputed tomography scanning(μCT).The results showed that returning straw significantly increased the contents of C and N in the SOC fractions of aggregates,especially at the return rates of 12,000 and 15,000 kg ha^(-1),which in turn promoted aggregate formation and stability,and ultimately amended pore structure.The pore size>100μm,porosity(>2μm),and morphological characteristics(anisotropy,circularity,connectivity and fractal dimension)significantly increased,but the total number of pores significantly decreased(P<0.05).Our results indicated that the amendment of the pore morphology and size distribution of soil aggregates was primarily controlled by the higher contents of C and N in the density fractions of aggregates,rather than in the aggregate sizes.Furthermore,this pore network reconfiguration favored the storage of C and N simultaneously.The findings of this study offer valuable new insights into the relationships between C and N storage and the pore characteristics in soil aggregates under straw return.展开更多
This paper introduces a method for modeling the entire aggregated electric vehicle(EV)charging process and analyzing its dispatchable capabilities.The methodology involves developing a model for aggregated EV charging...This paper introduces a method for modeling the entire aggregated electric vehicle(EV)charging process and analyzing its dispatchable capabilities.The methodology involves developing a model for aggregated EV charging at the charging station level,estimating its physical dispatchable capability,determining its economic dispatchable capability under economic incentives,modeling its participation in the grid,and investigating the effects of different scenarios and EV penetration on the aggregated load dispatch and dispatchable capability.The results indicate that using economic dispatchable capability reduces charging prices by 9.7%compared to physical dispatchable capability and 9.3%compared to disorderly charging.Additionally,the peak-to-valley difference is reduced by 64.6%when applying economic dispatchable capability with 20%EV penetration and residential base load,compared to disorderly charging.展开更多
Soil carbohydrates constitute an important component of soil organic matter(SOM),and substantially contribute to the stabilization of soil aggregates.Here,we aimed to investigate the distribution of water-stable aggre...Soil carbohydrates constitute an important component of soil organic matter(SOM),and substantially contribute to the stabilization of soil aggregates.Here,we aimed to investigate the distribution of water-stable aggregates and carbohydrates within water-stable aggregates of soil in tea plantations located in Zhongfeng Township of Mingshan County,Sichuan,which is in southwest China.Samples were collected from tea plantations of different ages(18,25,33,and 55 years old)and an area of abandoned land was used as a control(CK).We also examined correlations between soil carbohydrates fractions and aggregate stability.The results showed that the mean weight diameter(MWD)of soil aggregates in the tea plan-tations was significantly higher than that the control.Furthermore,the soil aggregate stability was significantly enhanced in tea plantations,with the 25-year-old plantation showing the most pronounced effect.Soils in the plantations were also characterized by higher concentrated acid-extracted carbohy-drate content,and carbohydrate content in both surface and sub-surface layers were higher in the 25-year-old plantation.We also detected a significant positive correlation between the carbohydrate con-tent of soil and MWD after tea plantation(P<0.01).Notably,the association between dilute-acid extracted carbohydrate and the aggregate stability showed the highest correlation,indicating this car-bohydrate fraction could be used as an index to reflect changes in soil quality during tea plantation development.We should develop a potential fertilisation programme to maintain SOM-Carbohydrates within aggregates and the appropriate pH for preventing soil structure degradation after 25 years of tea planting.展开更多
Both soil organic carbon (SOC) and iron (Fe) oxide content, among other factors, drive the formation and stability of soil aggregates.However, the mechanism of these drivers in greenhouse soil fertilized with organic ...Both soil organic carbon (SOC) and iron (Fe) oxide content, among other factors, drive the formation and stability of soil aggregates.However, the mechanism of these drivers in greenhouse soil fertilized with organic fertilizer is not well understood.In a 3-year field experiment, we aimed to investigate the factors which drive the stability of soil aggregates in greenhouse soil.To explore the impact of organic fertilizer on soil aggregates, we established four treatments:no fertilization (CK);inorganic fertilizer (CF);organic fertilizer (OF);and combined application of inorganic and organic fertilizers(COF).The application of organic fertilizer significantly enhanced the stability of aggregates, that is it enhanced the mean weight diameter, geometric mean diameter and aggregate content (%) of>0.25 mm aggregate fractions.OF and COF treatments increased the concentration of SOC, especially the aliphatic-C, aromatic-C and polysaccharide-C components of SOC, particularly in>0.25 mm aggregates.Organic fertilizer application significantly increased the content of free Fe(Fed), reactive Fe (Feo), and non-crystalline Fe in both bulk soil and aggregates.Furthermore, non-crystalline Fe showed a positive correlation with SOC content in both bulk soil and aggregates.Both non-crystalline Fe and SOC were significantly positively correlated with>2 mm mean weight diameter.Overall, we believe that the increase of SOC, aromatic-C, and non-crystal ine Fe concentrations in soil after the application of organic fertilizer is the reason for improving soil aggregate stability.展开更多
Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may ...Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may exacerbate these limitations.To address these issues,this study introduced a novel cement-stabilized permeable recycled aggregate material.A total of 162 beam specimens prepared with nine different levels of cement-aggregate ratio were tested to evaluate their permeability,bending load,and bending fatigue life.The experimental results indicate that increasing the content of recycled aggregates led to a reduction in both permeability and bending load.Additionally,the inclusion of recycled aggregates diminished the energy dissipation capacity of the specimens.These findings were used to establish a robust relationship between the initial damage in cement-stabilized permeable recycled aggregate material specimens and their fatigue life,and to propose a predictive model for their fatigue performance.Further,a method for assessing fatigue damage based on the evolution of fatigue-induced strain and energy dissipation was developed.The findings of this study provide valuable insights into the mechanical behavior and fatigue performance of cement-stabilized permeable recycled aggregate materials,offering guidance for the design of low-carbon-emission,permeable,and durable roadways incorporating recycled aggregates.展开更多
Soil aggregate plays a critical role in the sequestration of soil organic carbon(SOC)on the Qinghai-Tibetan Plateau(QTP).However,the impact of plateau pika(Ochotona curzoniae)on these processes remains uncertain.In th...Soil aggregate plays a critical role in the sequestration of soil organic carbon(SOC)on the Qinghai-Tibetan Plateau(QTP).However,the impact of plateau pika(Ochotona curzoniae)on these processes remains uncertain.In this study,we examined both control and pika disturbed alpine grasslands across various degradation levels,including undegraded(UDM),lightly(LDM),moderately(MDM)and severely(SDM)degraded sites.Through analyzing variations in aggregate size distribution,stability,aggregate associated SOC(ASOC)and bulk SOC(BSOC)concentration,we investigated the influence of plateau pika disturbance on SOC,and compared these effects across varying degradation levels.The results indicate that:(i)pika disturbance decreases soil water content(SWC)by 26.3%and 22.2%in LDM and SDM at the surface soil layer,while increasing SWC by 34.1%and 30.4%in LDM and MDM at the subsurface soil layer.It significantly reduces bulk density(BD)across all soil depths and grassland types,with most significant effect in LDM;(ii)Plateau pika disturbance increases the macroaggregate proportion in both drysieved aggregate(DSA)and water-stable aggregate(WSA),particularly in LDM.It enhances mean weight diameter(MWD)and geometric mean diameter(GMD)for both DSA and WSA,especially in MDM;(iii)Pika disturbance mitigates the negative effect of soil properties on aggregate stability,particularly in LDM and MDM,thereby enhancing the positive effect of aggregate stability on ASOC and improving BSOC content,especially in LDM.These findings provide novel insights into the effects of plateau pika disturbance on SOC dynamics in alpine grasslands.展开更多
Exploring alternative aggregates or recycled aggregates to substitute traditional concrete aggregates,particularly sand aggregates,which are becoming more limited and must comply with environmental protection standard...Exploring alternative aggregates or recycled aggregates to substitute traditional concrete aggregates,particularly sand aggregates,which are becoming more limited and must comply with environmental protection standards,is essential.Research has explored various alternative materials to sand in concrete,including concrete from demolished buildings,and broken glass from projects,among others.Investigating the use of recycled broken glass to substitute sand aggregates and implementing this research in compression columns is crucial.This paper examines the compressive behavior of reinforced concrete columns that utilize recycled glass particles as a substitute for sand in concrete.The research findings establish the relationships:load and vertical displacement,load and deformation at the column head,mid-column,and column base;the formation and propagation of cracks in the column,while considering factors such as the percentage of recycled glass,the arrangement of stirrups,and the amount of load-bearing steel influencing the performance of square reinforced concrete columns under compression.The feasibility of using recycled glass as a substitute for sand in column structures subjected to compression has been demonstrated,with the ideal replacement content for sand aggregate in reinforced concrete columns in this study ranging from 0%to 10%.The column’s load-bearing ability dropped from 250 kN to 150 kN when 100%recycled glass was used instead of sand.This is a 40%drop,and cracks started to show up sooner.The research will support recycling broken glass instead of using sand in building,improving the environment and reducing natural sand use.展开更多
Understanding long-term effects of agricultural management on soil organic carbon(C)(SOC)dynamics and aggregate stability is essential for crop production sustainability.In this study,effects of crop rotation,cover cr...Understanding long-term effects of agricultural management on soil organic carbon(C)(SOC)dynamics and aggregate stability is essential for crop production sustainability.In this study,effects of crop rotation,cover crop,and nitrogen(N)fertilization on SOC physical and molecular fractions and water-stable aggregate stability were evaluated by characterizing soils of the world's oldest,century-long(>120 years)continuous cotton experiment located in the southern USA.Field treatments included continuous cotton with no winter legume and no mineral N fertilizer(control,CK),continuous cotton with winter legume(CWL),cotton-corn rotation with winter legume(CCWL),cotton-corn rotation with winter legume and mineral N fertilizer(CCWLN),and continuous cotton with mineral N fertilizer(CN).Total organic C(TOC),total nitrogen(TN),acid-hydrolysis C(AHC),and water-extractable organic C(WEOC)in both bulk soils and different aggregate fractions were determined.Soil organic matter(SOM)composition was characterized using pyrolysis-gas chromatography/mass spectrometry(Py-GC/MS).Results showed that CCWL and CCWLN increased bulk soil TOC,AHC,and TN by 150%–165%,300%–315%,and 198%–223%,respectively,as well as aggregate-associated C by 180%–246%over CK.The CWL and CN treatments also increased TOC,AHC,and TN compared to CK but to a lesser degree.The CCWL treatment increased macroaggregates(250–2000μm)by 92%followed by CCWLN by 46%,whereas CWL and CN had limited effects in increasing macroaggregates(by 1%–7%)compared to CK.Moreover,SOM showed more diversified polysaccharide-derived compounds,aliphatic compounds,aromatic compounds,lignin,and phenols in CCWL and CCWLN followed by CWL,CN,and CK.Across different field treatments,aggregate stability indices,mean weight diameter(MWD)and geometric mean diameter(GMD),were positively related to TOC and TN(R2=0.57–0.65),and N-containing compounds and phenols(R^(2)=0.71–0.89),as well as polysaccharide-derived and aliphatic compounds(R^(2)=0.53–0.71).It was concluded that the diversified inputs of SOM composition brought by synergistic interactions between corn rotation and winter legume inclusion were mainly responsible for the observed TOC accumulation and aggregate formation and stability in these subtropical cotton production systems.展开更多
oil aggregates profoundly impact soil sustainability and crop productivity, and they are influenced by complexinteractions between minerals and organics. This study aimed to elucidate the alterations in mineralogy and...oil aggregates profoundly impact soil sustainability and crop productivity, and they are influenced by complexinteractions between minerals and organics. This study aimed to elucidate the alterations in mineralogy and soilorganic carbon(SOC) following long-term green manure incorporation and the effect on soil aggregates. Based on 5-and 36-year field experiments, surface soil samples(0–20 cm) were collected from Alfisol and Ferrisol soilssubjected to rice–rice–winter fallow(CK) and rice–rice–Chinese milk vetch(MV) treatments to investigate aggregatestability, mineralogy, SOC composition, and soil microstructural characteristics. The results showed that high clay-content Ferrisol exhibited greater aggregate stability than low clay-content Alfisol. The phyllosilicates in Alfisolprimarily comprised illite and vermiculite, whereas those in Ferrisol with high-content free-form Fe oxides(Fed) weredominated by kaolinite. Additionally, the clay fraction in Ferrisol contained more aromatic-C than the clay fraction inAlfisol. The 36-year MV incorporation significantly increased the Ferrisol macroaggregate stability(9.57–13.37%),and it also facilitated the transformation of vermiculite into kaolinite and significantly increased the clay, Fed, and aromatic-C contents in Ferrisol. Backscattered electron(BSE)-scanning electron microscopy/energy dispersive X-ray spectroscopy(SEM/EDS) revealed a compact aggregate structure in Ferrisol with co-localization of Feoxides and kaolinite. Moreover, the partial least path model(PLS-PM) revealed that clay content directly improvedmacroaggregate stability, and that kaolinite and Fed positively and directly affected clay or indirectly modulated clay formation by increasing the aromatic-C levels. Overall, long-term MV incorporation promotes clay aggregation by affecting mineral transformation to produce more kaolinite and Fe oxides and retain aromatic-C, and it ultimately improves aggregate stability.展开更多
The homogeneity of aggregate blend has a significant influence on the performance of asphalt mixture.The composition of aggregate blend,including the size combination and the mass ratio between each size particles(MRE...The homogeneity of aggregate blend has a significant influence on the performance of asphalt mixture.The composition of aggregate blend,including the size combination and the mass ratio between each size particles(MRESP),is an important factor affecting the homogeneity.This study investigated the influence of the size combination and MRESP on the distribution homogeneity of particles in aggregate blend using discrete element method(DEM).An indicator quantifying the distribution homogeneity was established according to the coefficient of variation(CV)for particle number.Two-size,three-size,and four-size aggregate blends with various compositions were designed.Laboratory tests show the DEM simulation is feasible.The particle distribution homogeneity in various blends was analyzed.The results showed the distribution homogeneity of each size particles in a blend is closely related to their mass fraction.The higher the mass fraction of the particles,the more homogeneous the distribution of them.The MRESP has no significant influence on the homogeneity of the blend composed of only coarse aggregates.However,the homogeneity of the blend composed of coarse and fine aggregates improves gradually with the increase of the mass fraction of fine aggregates.The smaller the maximum particle size in a blend,the better the homogeneity.It is suggested that the mass fraction of fine aggregates should be between 33%and 50%for achieving good homogeneity of aggregate blends.The research results can provide a reference for gradation design of asphalt mixture.展开更多
The effects of various fly ash(FA)contents on the durability and mechanical properties of recycled fine aggregate high ductility cementitious composites(RFA-HDCC)prepared with recycled fine aggregates(RFA)to fully rep...The effects of various fly ash(FA)contents on the durability and mechanical properties of recycled fine aggregate high ductility cementitious composites(RFA-HDCC)prepared with recycled fine aggregates(RFA)to fully replace natural fine aggregates was investigated.The results indicated that a 50% FA content significantly increased the compressive strength of RFA-HDCC by 13.93%.However,a?further increase in FA content led to a drastic decrease.The increased fly ash content substantially reduced the flexural and tensile strength;however,it markedly increased the matrix strain capacity,resulting in a 53.73% increase in the peak strain when FA was raised to 70%.Regarding durability,the increase in FA content negatively affected the chloride ion permeability and carbonation resistance.However,the increase in FA content initially improved the frost resistance of RFA-HDCC,peaking at 50% FA and deteriorating at 60% and 70% FA content.展开更多
基金funded by the Special Fund for AgroScientific Research in the Public Interest of China (20110300508, 201203030)supported in partial by the Key Technologies R&D Program of China during the 12th Five-Year Plan period (2012BAD05B05-3, 2013BAD07B11)the International Plant Nutrition Institute, Canada (IPNI China Program: Hunan-17)
文摘In agricultural systems, maintenance of soil organic matter has long been recognized as a strategy to reduce soil degradation. Manure amendments and green manures are management practices that can increase some nutrient contents and improve soil aggregation. We investigated the effects of 28 yr of winter planted green manure on soil aggregate-size distribution and aggregateassociated carbon（C） and nitrogen（N）. The study was a randomized completed block design with three replicates. The treatments included rice-rice-fallow, rice-rice-rape, rice-rice-Chinese milk vetch and rice-rice-ryegrass. The experiment was established in 1982 on a silty light clayey paddy soil derived from Quaternary red clay（classified as Fe-Accumuli-Stagnic Anthrosols） with continuous early and late rice. In 2009, soil samples were collected（0-15 cm depth） from the field treatment plots and separated into water-stable aggregates of different sizes（i.e., 〉5, 2-5, 1-2, 0.5-1, 0.25-0.5 and 〈0.25 mm） by wet sieving. The long-term winter planted green manure significantly increased total C and N, and the formation of the 2-5-mm water-stable aggregate fraction. Compared with rice-rice-rape, rice-rice-Chinese milk vetch and rice-rice-ryegrass, the rice-rice-fallow significantly reduced 2-5-mm water-stable aggregates, with a significant redistribution of aggregates into micro-aggregates. Long-term winter planted green manure obviously improved C/N ratio and macro-aggregate-associated C and N. The highest contribution to soil fertility was from macro-aggregates of 2-5 mm in most cases.
基金funded by the Knowledge Innovativation Program of the Chinese Academy of Sciences (KZCX2-YW-423)the National Basic Research Program of China (2005CB121106)
文摘We investigated the size distribution of water-stable aggregates and the soil carbon, nitrogen and phosphorus concentration over aggregate size fractions based on a long-term （1990-2006） fertilization experiment in a reddish paddy soil. The results showed that the largest water-stable aggregate （WSA） （〉5 mm） and the smallest WSA （〈0.25 mm） took up the first largest proportion （38.3%） and the second largest proportion （23.3%）, respectively. Application of organic materials increased the proportion of the large WSA （〉2 mm） and decreased the proportion of the small WSA （〈1 ram）, resulting in an increase in the mean weight diameter of WSA, whereas application of chemical fertilizer had little effect. Application of organic materials, especially combined with chemical fertilizers, increased total carbon, nitrogen and phosphorus concentrations in all sizes of WSA, and total carbon, nitrogen and phosphorus were prone to concentrate in the large WSA. Further more, application of organic materials improved the supply effectiveness of available phosphorus, whereas had little influence on the labile carbon in WSA. Application of chemical fertilizers improved concentrations of total and available phosphorus in all sizes of WSA, whereas had little influence on total carbon and nitrogen contents. Economical fertilization model maintained the soil fertility when compared with full dose of chemical fertilizers, indicating that using organic materials could reduce chemical fertilizers by about one third.
基金Under the auspices of National Natural Science Foundation of China(No.31460117,41877024)。
文摘Soil aggregate stability,as an important indicator of soil functions,may be affected by seasonal freezing and thawing(SFT)and land use in high cold and wet regions.Therefore,comprehensive understanding the effects of SFT on aggregate stability in orchards during winter and spring is crucial to develop appropriate management strategies that can effectively alleviate the degradation of soil quality to ensure sustainable development of orchard ecosystems.To determine the mechanism of degradation in orchard soil quality,the effects of SFT on the stability of water-stable aggregates were examined in apple-pear orchards(Pyrus ussuriensis var.ovoidea)of four different ages(11,25,40,and 63 yr)on 0 to 5%slopes before freezing and after thawing from October 2015 to June 2016 in Longjing City,Yanbian Prefecture,Northeast China,involving a comparison of planted versus adjacent uncultivated lands(control).Soil samples were collected to investigate water-stable aggregate stability in three incremental soil layers(0–20,20–40 and 40–60 cm).In the same samples,iron oxide,organic matter,and clay contents of the soil were also determined.Results showed that the destructive influences of SFT on water-stable aggregates were more pronounced with the increased orchards ages,and SFT exerted severe effects on water-stable aggregates of older orchards(40 and 63 yr)than juvenile orchards.Undergoing SFT,the soil instability index and the percentage of aggregate destruction increased by mean 0.15 mm and 1.86%,the degree of aggregation decreased by mean 1.32%,and the erosion resistance weakened,which consequently led to aggregate stability decreased.In addition,soil free,amorphous,and crystalline iron oxide as well as soil organic matter and clay contents are all important factors affecting the stability of water-stable aggregates,and their changes in their contents were consistent with those in the stability of water-stable aggregates.The results of this study suggest that long-term planting fruit trees can exacerbate the damaging effects of SFT on aggregate stability and further soil erosion increases and nutrient losses in an orchard,which hider sustainable use of soil and the productivity orchards.
基金Project supported by the State Key Basic Research Development Program (No. G1999011804) the Knowledge Innovation Program of the Chinese Academy of Sciences (No. KZCXZ-SW-416).
文摘The distribution of light fraction carbon （LF-C） in the various size classes of aggregates and its relationship to water- stable aggregates as well as the influence of cultivation on the organic components in virgin and cultivated black soils were studied by wet sieving and density separation methods. The total organic carbon （TOC） and LF-C were significantly higher （P≤ 0.05） in the virgin soils than in the cultivated soils. The LF-C in aggregates of different size classes varied from 0.9 to 2.5 g kg^-1 in the cultivated soils and from 2.5 to 7.1 g kg^-1 in the virgin soils, whereas the ratio of LF-C to TOC varied from 1.9% to 7.3% and from 5.0% to 12.2%, respectively. After being incubated under constant temperature and controlled humidity for three months, the contribution of LF-C to TOC sharply decreased to an amount （1.7%4.5%） close to the level in soils that had been cultivated for 20 to 25 years （1.3%-8.8%）. As a result, the larger water-stable macro-aggregates （especially 〉 1 mm） decreased sharply, indicating that the LF-C pool in virgin soils declined quickly after cultivation, which reduced the water stability of soil aggregates.
基金funded by the Science & Technology Pillar Program of Gansu Province (1104FKCH162, 1204FKCH164, 1304FKCH102)the National Natural Science Foundation of China (31560170)
文摘Soil organic matter content in water-stable aggregates（WSA） in the arid ecosystems（abandoned agricultural lands especially） of China is poorly understood. In this study, we examined the WSA sizes and stability, and soil organic carbon（OC） and nitrogen（N） contents in agricultural lands with abandonment ages of 0, 3, 12, 20, 30 and 40 years, respectively, in the Minqin Oasis of Northwest China. The total soil OC and N contents at depths of 0–20, 20–40 and 40–60 cm in abandoned agricultural lands were compared to those in cultivated land（the control）. Agricultural land abandonment significantly（P0.25 mm） as the age of agricultural land abandonment increased. The effect of abandonment ages of agricultural lands on MWD was determined by the changes of OC and N accumulation in WSA sizes ＆gt;2 mm. The total OC and N contents presented a stratification phenomenon across soil depths in this arid ecosystem. That is, both of them decreased significantly at depths of 0–20 and 40–60 cm while increased at the depth of 20–40 cm. The WSA sizes ＆lt;0.053 mm had the highest soil OC and N contents（accounting for 51.41%–55.59% and 42.61%–48.94% of their total, respectively）. Soil OC and N contents in microaggregates（sizes 0.053–0.25 mm） were the dominant factors that influenced the variations of total OC and N contents in abandoned agricultural lands. The results of this study suggested that agricultural land abandonment may result in the recovery of WSA stability and the shifting of soil organic matter from the silt＋clay（＆lt;0.053 mm） and microaggregate fractions to the macroaggregate fractions. However, agricultural land abandonment did not increase total soil OC and N contents in the short-term.
基金Supported by Special Project of Public Welfare Industry of Ministry of Land and Resources(201411008)
文摘To study the formation process of feldspathic sandstone and sand compound soil in the Mu Us Desert,1∶ 1,1∶ 2 and 1∶ 5 ratios of feldspathic sandstone and sand were mixed to obtain compound soil to plant crops,and analyze the rules of changes in water-stable aggregates of the compound soil among the 4 years crops growing process. The results showed,before crop planting,the order of mass percent of> 0. 25 mm and 0. 25-2. 00 mm water-stable aggregates in three kinds of compound soil was 1∶ 1 > 1∶ 2 > 1∶ 5,showing that the overall content was low; the mass percent of > 0. 25 mm water-stable aggregates remained at 18. 38%-28. 22%; the mass percent of 0. 25-0. 50 mm,0. 50-2. 00 mm,2. 00-5. 00 mm,and > 5. 00 mm water-stable aggregates was close with each other in each kind of compound soil. After4 years of planting,the mass percent of > 0. 25 mm water-stable aggregates in 1∶ 2 compound soil increased significantly and exceeded other2 kinds of compound soil,reached 32. 34%; the main components of > 0. 25 mm water stable aggregates in 1∶ 1,1∶ 2,and 1∶ 5 compound soil were 0. 25-0. 50 mm( 53. 54%),0. 25-0. 50 mm( 59. 43%),0. 05-2. 00 mm( 52. 16%),aggregates; 0. 25-2. 00 mm aggregates increased significantly in all three kinds of compound soil,with the highest increase in 1∶ 2 compound soil; the organic matters of 1∶ 2 compound soil were significantly correlated with 0. 25-0. 50 mm and 0. 25-2. 00 mm water-stable aggregates. The results showed that the ratio of 0. 25-2. 00 mm aggregates in the three kinds of compound soil was increased after 4 years of crop planting and 1∶ 2 compound soil was most favorable for the formation of aggregates.
文摘Soil water-stable aggregates (WSAs) are the basic unit of soil constitution and can contribute to remaining the stable soil constitution. The objective of this study was to clarify the distribution and stability of WSAs and the soil organic carbon (SOC), the total nitrogen (TN), and the total phosphorus (TP) concentrations in 0 - 20 cm and 20 - 40 cm soil layers under the different ages of Robinia pseudoacacia plantations. The 20, 25, 40, and 50 years-old Robinia pseudoacacia plantations were selected. Stepwise regression analysis showed that >5 mm and 1 - 2 mm WSAs, SOC concentration in 2 - 5 mm WSAs, and TN and TP concentrations in < 0.25 mm WSAs were dominant independent variables affecting aggregate stability and that SOC in 0.25 - 0.5 mm WSAs, TN in <0.25 mm and 1 - 2 mm WSAs and TP in 2 - 5 mm WSAs were dominant independent variables affecting SOC, TN, and TP concentrations in bulk soils.
文摘Polycyclic aromatic hydrocarbons (PAHs) pollution in mangroves has drawn much attention, but knowledge of the sorption of PAHs in mangrove sediment is limited. This study investigated the particles and water-stable aggregates (WSA) of mangrove sediment in Jiulong River Estuary, China, and the characteristics of anthracene adsorption to them. The adsorption of anthracene was strongly influenced by the physicochemical and structural properties of sediment particles and WSA. The main sorbents of mangrove sediment were carbonized particles and clays. The porous structure of carbonized particles made it easy to sequestrate sequester the anthracene, and the aging allowed anthracene to move into deeper sites of the carbonized particles. Clays had high anthracene-fixing capacities, and they included organic matters and formed aggregates. The sorption contents coefficient <i>K<sub>f</sub></i> of anthracene with WSA of different sizes increased in the order 0.063 - 0.25 mm > 0.063 mm > 0.25 - 1.0 mm > 1.0 mm. The order was correlated with which due to the contents and characteristics of organic matters in the aggregates.
基金the Chinese Academy of Sciences for their financial support and research facilitiesfunded by the National Key Research and Development Program of China(2022YFD1500100)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA28070100)the China Agriculture Research System of MOF and MARA(CARS04)。
文摘The accumulation of soil organic carbon(SOC)and total nitrogen(TN)is easily accomplished by returning crop straw,which strongly affects the formation and pore structure of aggregates,especially in black soil.We returned maize straw at different rates(6,000,9,000,12,000 and 15,000 kg ha^(-1))for nine years to investigate its influence on the SOC and TN contents in the SOC fractions of aggregates by combining size and density fractionation.Their subsequent influences on pore morphology and size distribution characteristics were examined using X-ray microcomputed tomography scanning(μCT).The results showed that returning straw significantly increased the contents of C and N in the SOC fractions of aggregates,especially at the return rates of 12,000 and 15,000 kg ha^(-1),which in turn promoted aggregate formation and stability,and ultimately amended pore structure.The pore size>100μm,porosity(>2μm),and morphological characteristics(anisotropy,circularity,connectivity and fractal dimension)significantly increased,but the total number of pores significantly decreased(P<0.05).Our results indicated that the amendment of the pore morphology and size distribution of soil aggregates was primarily controlled by the higher contents of C and N in the density fractions of aggregates,rather than in the aggregate sizes.Furthermore,this pore network reconfiguration favored the storage of C and N simultaneously.The findings of this study offer valuable new insights into the relationships between C and N storage and the pore characteristics in soil aggregates under straw return.
基金State Grid Henan Power Company Science and Technology Project‘Key Technology and Demonstration Application of Multi-Domain Electric Vehicle Aggregated Charging Load Dispatch’(5217L0240003).
文摘This paper introduces a method for modeling the entire aggregated electric vehicle(EV)charging process and analyzing its dispatchable capabilities.The methodology involves developing a model for aggregated EV charging at the charging station level,estimating its physical dispatchable capability,determining its economic dispatchable capability under economic incentives,modeling its participation in the grid,and investigating the effects of different scenarios and EV penetration on the aggregated load dispatch and dispatchable capability.The results indicate that using economic dispatchable capability reduces charging prices by 9.7%compared to physical dispatchable capability and 9.3%compared to disorderly charging.Additionally,the peak-to-valley difference is reduced by 64.6%when applying economic dispatchable capability with 20%EV penetration and residential base load,compared to disorderly charging.
基金support from the Key R&D Project of Sichuan Province(Grant No.2019YFS0463)for this research.
文摘Soil carbohydrates constitute an important component of soil organic matter(SOM),and substantially contribute to the stabilization of soil aggregates.Here,we aimed to investigate the distribution of water-stable aggregates and carbohydrates within water-stable aggregates of soil in tea plantations located in Zhongfeng Township of Mingshan County,Sichuan,which is in southwest China.Samples were collected from tea plantations of different ages(18,25,33,and 55 years old)and an area of abandoned land was used as a control(CK).We also examined correlations between soil carbohydrates fractions and aggregate stability.The results showed that the mean weight diameter(MWD)of soil aggregates in the tea plan-tations was significantly higher than that the control.Furthermore,the soil aggregate stability was significantly enhanced in tea plantations,with the 25-year-old plantation showing the most pronounced effect.Soils in the plantations were also characterized by higher concentrated acid-extracted carbohy-drate content,and carbohydrate content in both surface and sub-surface layers were higher in the 25-year-old plantation.We also detected a significant positive correlation between the carbohydrate con-tent of soil and MWD after tea plantation(P<0.01).Notably,the association between dilute-acid extracted carbohydrate and the aggregate stability showed the highest correlation,indicating this car-bohydrate fraction could be used as an index to reflect changes in soil quality during tea plantation development.We should develop a potential fertilisation programme to maintain SOM-Carbohydrates within aggregates and the appropriate pH for preventing soil structure degradation after 25 years of tea planting.
基金supported by the Shenyang Municipal Science and Technology Project,China(23-409-2-03)the Liaoning Provincial Department of Science and Technology Project,China(Z20230183)the Liaoning Provincial Applied Basic Research Program,China(2022JH2/101300173).
文摘Both soil organic carbon (SOC) and iron (Fe) oxide content, among other factors, drive the formation and stability of soil aggregates.However, the mechanism of these drivers in greenhouse soil fertilized with organic fertilizer is not well understood.In a 3-year field experiment, we aimed to investigate the factors which drive the stability of soil aggregates in greenhouse soil.To explore the impact of organic fertilizer on soil aggregates, we established four treatments:no fertilization (CK);inorganic fertilizer (CF);organic fertilizer (OF);and combined application of inorganic and organic fertilizers(COF).The application of organic fertilizer significantly enhanced the stability of aggregates, that is it enhanced the mean weight diameter, geometric mean diameter and aggregate content (%) of>0.25 mm aggregate fractions.OF and COF treatments increased the concentration of SOC, especially the aliphatic-C, aromatic-C and polysaccharide-C components of SOC, particularly in>0.25 mm aggregates.Organic fertilizer application significantly increased the content of free Fe(Fed), reactive Fe (Feo), and non-crystalline Fe in both bulk soil and aggregates.Furthermore, non-crystalline Fe showed a positive correlation with SOC content in both bulk soil and aggregates.Both non-crystalline Fe and SOC were significantly positively correlated with>2 mm mean weight diameter.Overall, we believe that the increase of SOC, aromatic-C, and non-crystal ine Fe concentrations in soil after the application of organic fertilizer is the reason for improving soil aggregate stability.
基金Project(2024JJ2073)supported by the Science Fund for Distinguished Young Scholars of Hunan Province,ChinaProjects(2023YFC3807205,2019YFC1904704)+4 种基金supported by the National Key R&D Program of ChinaProject(52178443)supported by the National Natural Science Foundation of ChinaProject(2024ZZTS0109)supported by Fundamental Research Funds for the Central Universities of Central South University,China。
文摘Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may exacerbate these limitations.To address these issues,this study introduced a novel cement-stabilized permeable recycled aggregate material.A total of 162 beam specimens prepared with nine different levels of cement-aggregate ratio were tested to evaluate their permeability,bending load,and bending fatigue life.The experimental results indicate that increasing the content of recycled aggregates led to a reduction in both permeability and bending load.Additionally,the inclusion of recycled aggregates diminished the energy dissipation capacity of the specimens.These findings were used to establish a robust relationship between the initial damage in cement-stabilized permeable recycled aggregate material specimens and their fatigue life,and to propose a predictive model for their fatigue performance.Further,a method for assessing fatigue damage based on the evolution of fatigue-induced strain and energy dissipation was developed.The findings of this study provide valuable insights into the mechanical behavior and fatigue performance of cement-stabilized permeable recycled aggregate materials,offering guidance for the design of low-carbon-emission,permeable,and durable roadways incorporating recycled aggregates.
基金supported by the National Natural Science Foundation of China(41672342)Natural Science Foundation of Sichuan Province(2024NSFSC0101).
文摘Soil aggregate plays a critical role in the sequestration of soil organic carbon(SOC)on the Qinghai-Tibetan Plateau(QTP).However,the impact of plateau pika(Ochotona curzoniae)on these processes remains uncertain.In this study,we examined both control and pika disturbed alpine grasslands across various degradation levels,including undegraded(UDM),lightly(LDM),moderately(MDM)and severely(SDM)degraded sites.Through analyzing variations in aggregate size distribution,stability,aggregate associated SOC(ASOC)and bulk SOC(BSOC)concentration,we investigated the influence of plateau pika disturbance on SOC,and compared these effects across varying degradation levels.The results indicate that:(i)pika disturbance decreases soil water content(SWC)by 26.3%and 22.2%in LDM and SDM at the surface soil layer,while increasing SWC by 34.1%and 30.4%in LDM and MDM at the subsurface soil layer.It significantly reduces bulk density(BD)across all soil depths and grassland types,with most significant effect in LDM;(ii)Plateau pika disturbance increases the macroaggregate proportion in both drysieved aggregate(DSA)and water-stable aggregate(WSA),particularly in LDM.It enhances mean weight diameter(MWD)and geometric mean diameter(GMD)for both DSA and WSA,especially in MDM;(iii)Pika disturbance mitigates the negative effect of soil properties on aggregate stability,particularly in LDM and MDM,thereby enhancing the positive effect of aggregate stability on ASOC and improving BSOC content,especially in LDM.These findings provide novel insights into the effects of plateau pika disturbance on SOC dynamics in alpine grasslands.
文摘Exploring alternative aggregates or recycled aggregates to substitute traditional concrete aggregates,particularly sand aggregates,which are becoming more limited and must comply with environmental protection standards,is essential.Research has explored various alternative materials to sand in concrete,including concrete from demolished buildings,and broken glass from projects,among others.Investigating the use of recycled broken glass to substitute sand aggregates and implementing this research in compression columns is crucial.This paper examines the compressive behavior of reinforced concrete columns that utilize recycled glass particles as a substitute for sand in concrete.The research findings establish the relationships:load and vertical displacement,load and deformation at the column head,mid-column,and column base;the formation and propagation of cracks in the column,while considering factors such as the percentage of recycled glass,the arrangement of stirrups,and the amount of load-bearing steel influencing the performance of square reinforced concrete columns under compression.The feasibility of using recycled glass as a substitute for sand in column structures subjected to compression has been demonstrated,with the ideal replacement content for sand aggregate in reinforced concrete columns in this study ranging from 0%to 10%.The column’s load-bearing ability dropped from 250 kN to 150 kN when 100%recycled glass was used instead of sand.This is a 40%drop,and cracks started to show up sooner.The research will support recycling broken glass instead of using sand in building,improving the environment and reducing natural sand use.
基金supported by the United States Department of Agriculture-Natural Resources Conservation Service(No.NR217217XXXXG004)the United States Department of Agriculture National Institute of Food and Agriculture Hatch Project(No.7003969)supported,in part,by a scholarship from China Scholarship Council(No.201206300183)。
文摘Understanding long-term effects of agricultural management on soil organic carbon(C)(SOC)dynamics and aggregate stability is essential for crop production sustainability.In this study,effects of crop rotation,cover crop,and nitrogen(N)fertilization on SOC physical and molecular fractions and water-stable aggregate stability were evaluated by characterizing soils of the world's oldest,century-long(>120 years)continuous cotton experiment located in the southern USA.Field treatments included continuous cotton with no winter legume and no mineral N fertilizer(control,CK),continuous cotton with winter legume(CWL),cotton-corn rotation with winter legume(CCWL),cotton-corn rotation with winter legume and mineral N fertilizer(CCWLN),and continuous cotton with mineral N fertilizer(CN).Total organic C(TOC),total nitrogen(TN),acid-hydrolysis C(AHC),and water-extractable organic C(WEOC)in both bulk soils and different aggregate fractions were determined.Soil organic matter(SOM)composition was characterized using pyrolysis-gas chromatography/mass spectrometry(Py-GC/MS).Results showed that CCWL and CCWLN increased bulk soil TOC,AHC,and TN by 150%–165%,300%–315%,and 198%–223%,respectively,as well as aggregate-associated C by 180%–246%over CK.The CWL and CN treatments also increased TOC,AHC,and TN compared to CK but to a lesser degree.The CCWL treatment increased macroaggregates(250–2000μm)by 92%followed by CCWLN by 46%,whereas CWL and CN had limited effects in increasing macroaggregates(by 1%–7%)compared to CK.Moreover,SOM showed more diversified polysaccharide-derived compounds,aliphatic compounds,aromatic compounds,lignin,and phenols in CCWL and CCWLN followed by CWL,CN,and CK.Across different field treatments,aggregate stability indices,mean weight diameter(MWD)and geometric mean diameter(GMD),were positively related to TOC and TN(R2=0.57–0.65),and N-containing compounds and phenols(R^(2)=0.71–0.89),as well as polysaccharide-derived and aliphatic compounds(R^(2)=0.53–0.71).It was concluded that the diversified inputs of SOM composition brought by synergistic interactions between corn rotation and winter legume inclusion were mainly responsible for the observed TOC accumulation and aggregate formation and stability in these subtropical cotton production systems.
基金supported by the National Natural Science Foundation of China (41977020)the China Agriculture Research System of MOF and MARA (CARS22)。
文摘oil aggregates profoundly impact soil sustainability and crop productivity, and they are influenced by complexinteractions between minerals and organics. This study aimed to elucidate the alterations in mineralogy and soilorganic carbon(SOC) following long-term green manure incorporation and the effect on soil aggregates. Based on 5-and 36-year field experiments, surface soil samples(0–20 cm) were collected from Alfisol and Ferrisol soilssubjected to rice–rice–winter fallow(CK) and rice–rice–Chinese milk vetch(MV) treatments to investigate aggregatestability, mineralogy, SOC composition, and soil microstructural characteristics. The results showed that high clay-content Ferrisol exhibited greater aggregate stability than low clay-content Alfisol. The phyllosilicates in Alfisolprimarily comprised illite and vermiculite, whereas those in Ferrisol with high-content free-form Fe oxides(Fed) weredominated by kaolinite. Additionally, the clay fraction in Ferrisol contained more aromatic-C than the clay fraction inAlfisol. The 36-year MV incorporation significantly increased the Ferrisol macroaggregate stability(9.57–13.37%),and it also facilitated the transformation of vermiculite into kaolinite and significantly increased the clay, Fed, and aromatic-C contents in Ferrisol. Backscattered electron(BSE)-scanning electron microscopy/energy dispersive X-ray spectroscopy(SEM/EDS) revealed a compact aggregate structure in Ferrisol with co-localization of Feoxides and kaolinite. Moreover, the partial least path model(PLS-PM) revealed that clay content directly improvedmacroaggregate stability, and that kaolinite and Fed positively and directly affected clay or indirectly modulated clay formation by increasing the aromatic-C levels. Overall, long-term MV incorporation promotes clay aggregation by affecting mineral transformation to produce more kaolinite and Fe oxides and retain aromatic-C, and it ultimately improves aggregate stability.
基金funded by the National Natural Science Foundation of China(No.51978048).
文摘The homogeneity of aggregate blend has a significant influence on the performance of asphalt mixture.The composition of aggregate blend,including the size combination and the mass ratio between each size particles(MRESP),is an important factor affecting the homogeneity.This study investigated the influence of the size combination and MRESP on the distribution homogeneity of particles in aggregate blend using discrete element method(DEM).An indicator quantifying the distribution homogeneity was established according to the coefficient of variation(CV)for particle number.Two-size,three-size,and four-size aggregate blends with various compositions were designed.Laboratory tests show the DEM simulation is feasible.The particle distribution homogeneity in various blends was analyzed.The results showed the distribution homogeneity of each size particles in a blend is closely related to their mass fraction.The higher the mass fraction of the particles,the more homogeneous the distribution of them.The MRESP has no significant influence on the homogeneity of the blend composed of only coarse aggregates.However,the homogeneity of the blend composed of coarse and fine aggregates improves gradually with the increase of the mass fraction of fine aggregates.The smaller the maximum particle size in a blend,the better the homogeneity.It is suggested that the mass fraction of fine aggregates should be between 33%and 50%for achieving good homogeneity of aggregate blends.The research results can provide a reference for gradation design of asphalt mixture.
基金Funded by the Natural Science Foundation of Jiangsu Province(No.BK20220626)Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX24_3174)Taizhou Science and Technology Support Programme(Social Development)Directive Project(No.TS202432)。
文摘The effects of various fly ash(FA)contents on the durability and mechanical properties of recycled fine aggregate high ductility cementitious composites(RFA-HDCC)prepared with recycled fine aggregates(RFA)to fully replace natural fine aggregates was investigated.The results indicated that a 50% FA content significantly increased the compressive strength of RFA-HDCC by 13.93%.However,a?further increase in FA content led to a drastic decrease.The increased fly ash content substantially reduced the flexural and tensile strength;however,it markedly increased the matrix strain capacity,resulting in a 53.73% increase in the peak strain when FA was raised to 70%.Regarding durability,the increase in FA content negatively affected the chloride ion permeability and carbonation resistance.However,the increase in FA content initially improved the frost resistance of RFA-HDCC,peaking at 50% FA and deteriorating at 60% and 70% FA content.
