真菌对土壤团聚体形成的影响研究进展

针对真菌转化秸秆等有机物料促进土壤团聚体形成、提升土壤保水保肥能力这一研究热点,回顾了土壤团聚体的定义、特征指标和形成理论,分析了外源秸秆碳在团聚体中的周转,创新地将土壤孔隙分级与土壤团聚体的逐级形成联系起来,重点考察了真菌的生长方式、分解代谢、合成代谢在土壤团聚体形成中的作用,明确了真菌在土壤团聚体形成中的作用对于完善土壤团聚体形成理论、优化土壤团聚体组成的重要意义,并指出真菌促进土壤团聚体形成的研究将为土壤物理学和微生物学的交叉研究提供新的思路。

高能球磨对Al-Ti-C粉料混合物粒度和组织的影响

随着高能球磨时间的增加 ,Al,Ti和 C粉料混合物颗粒的尺寸不断细化 ,各元素的分布也愈均匀 ,并且粉料相互团聚成团聚体。颗粒内的晶粒也不断细化 ,晶粒畸变 ,晶体内部缺陷增多 ;球磨一定时间后 ,形成纳米晶 ,甚至产生非晶组织。这些因素都有助于扩散 。

Agglomeration−aggregation and leaching properties of mechanically activated chalcopyrite

The effect of mechanical activation on the granulometric parameters,microstructure,and leaching efficiency of chalcopyrite was evaluated,and the occurrence/transition of agglomeration and aggregation was discussed.The results showed that in 8 h of milling treatment,the agglomeration and the microstructure did not affect each other.However,with prolonging milling time,the crystallite size tended to reach a saturation value,and the stagnating microstructural changes led to the replacement of agglomeration by aggregation.The leaching results indicated that the mechanical activation can strongly enhance the reactivity of chalcopyrite and the hindering effect of aggregation on leaching was considerably greater than that of agglomeration.Consequently,after 8 h of milling,the maximum Cu leaching rate of 80.13%was achieved after 4 h of acid leaching.

Numerical Predication of Cracking Reaction of Particle Clusters in Fluid Catalytic Cracking Riser Reactors

Behavior of catalytic cracking reactions of particle cluster in fluid catalytic cracking （FCC） riser reactors was numerically analyzed using a four-lump mathematical model. Effects of the cluster porosity, inlet gas velocity and temperature, and coke deposition on cracking reactions of the cluster were investigated. Distributions of temperature, gases, and gasoline from both catalyst particle cluster and an isolated catalyst particle are presented. The reaction rates from vacuum gas oil （VGO） to gasoline, gas and coke of individual particle in the cluster are higher than those of the isolated particle, but it reverses for the reaction rates from gasoline to gas and coke. Less gasoline is produced by particle clustering. Simulated results show that the produced mass fluxes of gas and gasoline increase with the operating temperature and molar concentration of VGO, and decrease due to the formation of coke.

Effect of substrate amendment on alkaline minerals and aggregate stability in bauxite residue

Bauxite residue is an alkaline waste material in the process of alumina production due to its characteristics of higher salinity and alkalinity,which results in environmental issues and extremely restricts the sustainable development of alumina industries.In this work,we conduct a column experiment to study the effects of two amendments on aggregate stability and variations in alkaline minerals of bauxite residue.The two amendments are phosphogypsum(PG)and phosphogypsum and vermicompost(PVC).The dominant fraction in aggregate is 1–0.25 mm in diameter on the surface,which takes up 39.34%,39.38%,and 44.51%for CK,PG,and PVC,respectively.Additions of PG and PVC decreased pH,EC,ESP,exchangeable Na^+concentration and the percentage of alkaline minerals,and then increased exchangeable Ca^2+concentration in bauxite residue.There was significant positive correlation between pH and exchangeable Na^+concentration,the percentage of cancrinite,tricalcium aluminate and calcite;while negative correlation was found in pH value versus exchangeable Ca^2+concentration.Theses findings confirmed that additions of phosphogypsum and vermicompost have a stimulative effect on aggregate stability in bauxite residue.In particular,amendment neutralization(phosphogypsum+vermicompost)in column represents an advantage for large-scale simulation of vegetation rehabilitate in bauxite residue disposal areas.

Paddy Soil Stability and Mechanical Properties as Affected by Long-Term Application of Chemical Fertilizer and Animal Manure in Subtropical China

Wet stability, penetration resistance （PR）, and tensile strength （TS） of paddy soils under a fertilization experiment for 22 years were determined to elucidate the function of soil organic matter in paddy soil stabilization. The treatments included no fertilization （CK）, normal chemical fertilization （NPK）, double the NPK application rates （2NPK）, and NPK mixed with organic manure （NPK＋OM）. Compared with CK, Fertilization increased soil organic carbon （SOC） and soil porosity. The results of soil aggregate fragmentation degree （SAFD） showed that fast wetting by water was the key fragmentation mechanism. Among the treatments, the NPK＋OM treatment had the largest size of water-stable aggregates and greatest normal mean weight diameter （NMWD） （P ≤ 0.05）, but the lowest PR and TS in both cultivated horizon （Ap） and plow pan. The CK and 2NPK treatments were measured with PR 〉 2.0 MPa and friability index 〈 0.20, respectively, in the Ap horizon, suggesting that the soils was mechanically unfavourable to root growth and tillage. In the plow pan, the fertilization treatments had greater TS and PR than in CK. TS and PR of the tested soil aggregates were negatively correlated to SOC content and soil porosity. This study suggested that chemical fertilization could cause deterioration of mechanical properties while application of organic manure could improve soil stability and mechanical properties.

Self-magnetization of pyrite and its application in flotation

Pyrite is a special weakly magnetic mineral containing Fe(II). Its self-magnetization only by adjusting slurry temperatureand pH value was able to enhance its magnetism, producing the so-called the magnetized pyrite, which was further used as magneticseeds in the flotation of pyrite ore to promote flotation recovery. Tests, such as self-magnetization, vibrating sample magnetometer(VSM), XPS, size analysis and flotation were carried out. The optimal conditions of the pyrite self-magnetization were pulp pH of11.81 and temperature of 65 °C. The magnetized pyrite was characteristic of the valence change of elemental iron, resulting instronger magnetism of the magnetized pyrite than that of the original pyrite. Then, this magnetized pyrite was applied to the magneticseeding flotation (MSF) of pyrite ore. It was found that the recovery of pyrite flotation grew with the increase of magneticsusceptibility of the magnetic seeds?the magnetized pyrite; and the proper dosage of the magnetized pyrite was 100 g/t. The reasonbehind the increased recovery lies in that the magnetized pyrite promoted the magnetic agglomeration between fine pyrite particles;and the fact that the stronger the magnetism of the magnetized pyrite, the larger the aggregate size, indicates that the agglomeration issomewhat in line with the flotation, also confirming that the MSF is more suitable for fine particles than traditional flotation.

Analysis of Particle Size Control in the Preparation of Nano-size CaCO_3 Particles

Cubic shaped CaCO3 particles with mean size of 30-40nm were prepared by intermittent carbonation process without any additives. It was found that the flow rate of CO2 has no distinct influence on the particle size in the range of 30 120ml·min^-1 under conditions of 13℃ and stirring rate of 680r·min^-1. A further increase of flow rate makes the particles larger. When CO2 flow rate is 70ml·min^-1, a high agitation rate is in favor of the reduction of the crystal size in the range of 70-680 r·min^-1. When flow rate is 120 ml·min^-1, the particles prepared at agitation rates of 680r·min^-1 and 280r·min^-1 have similar sizes, while products prepared at 90r·min^-1 have larger size.

Carbon Mineralization Associated with Soil Aggregates as Affected by Short-term Tillage

Abstract： Tillage practice has received much attention due to its effects on greenhouse gas emissions from agricultural fields. The understanding of carbon mineralization associated with soil aggregates helps to explore the influence mechanisms of tillage practice on soil carbon dynamics. Total carbon and carbon mineralization rates associated with various sizes of soil aggregates under no-tillage and tillage treatments were studied with a volcanic ash soil. Total carbon content in microaggregates （〈0.25 mm） was higher than that in macroaggregates （〉0.25 mm） for both the no-tillage and tillage treatments, since microaggregates of the volcanic ash soil include more fine silts and clay particles absorbing more organic agents. The carbon mineralization rate and total carbon were highly correlated （R2 = 0.6552, P= 0.002） for both treatments, suggesting that soil aggregate size is an important factor to influence the carbon mineralization rate. The no-tillage system showed the advantage of improving soil structure for volcanic ash soil. A larger proportion of microaggregates with relatively high carbon mineralization might contribute to the greater carbon loss from tilled soils. Unlike aggregate size, short-term tillage showed no significant effects on carbon mineralization rates associated with aggregates in a specific size class.

Soil Aggregate Stability and Iron and Aluminium Oxide Contents Under Different Fertiliser Treatments in a Long-Term Solar Greenhouse Experiment

Soil in greenhouses is likely to suffer a gradual decline in aggregate stability. Determination of the effects of different fertiliser practices on soil aggregate stability is important for taking advantage of solar greenhouses. Soil aggregate stability and iron （Fe） and aluminium （A1） oxide contents were investigated in a 26-year long-term fertilisation experiment in greenhouse in Shenyang, China, under eight fertiliser treatments： manure （M）, fertiliser N （FN）, fertiliser N with manure （MN）, fertiliser P （FP）, fertiliser P with manure （MP）, fertiliser NP （FNP）, fertiliser NP with manure （MNP）, and control without any fertiliser （CK）. A wet sieving method was used to determine aggregate size distribution and water-stable aggregates （WSA）, mean weight diameter and geometric mean diameter as the indices of soil aggregate stability. Different fertiliser treatments had a statistically significant influence on aggregate stability and Fe and A1 oxide contents. Long-term application of inorganic fertilisers had no obvious effects on the mass proportion of aggregates. By contrast, manure application significantly increased the mass proportion of macroaggregates at the expense of microaggregates. All treatments, with the exception of FNP, significantly increased the stability of macroaggregates but decreased that of microaggregates when compared with CK. Aggregation under MP and MN was better than that under M and MNP; however, no significant differences were found among inorganic fertiliser treatments （i.e., FN, FP, and FNP）. A positive relation was found between pyrophosphate-extractable Fe and WSA （r=0.269）, but no significant relations were observed between other Fe and Al oxides and aggregate stability.

Enzyme Activity in Water-Stable Soil Aggregates as Affected by Long-Term Application of Organic Manure and Chemical Fertiliser

The activities of invertase, protease, urease, acid phosphomonoesterase, dehydrogenase, and catalase in different fractions of waterstable aggregates (WSA) were examined in long-term (26 years) fertilised soils. The long-term application of organic manure (OM) with chemical fertiliser (CF) significantly increased macroaggregate and decreased microaggregate percentages, enhanced the mean weight diameter, and significantly increased soil total carbon (TC) and total nitrogen (TN) contents of WSA in different size fractions. Combined fertilisation with OM and CF also increased invertase, protease, urease, acid phosphomonoesterase, dehydrogenase, and catalase activities of WSA in different size fractions. Enzyme activities were higher in macroaggregates than in microaggregates. The distribution of enzyme activities generally followed the distribution of TC and TN in WSA. The geometric mean of the enzyme activities in different WSA of OM-treated soils was significantly higher than that in soils treated with 100% CF or no fertiliser. The results indicated that the long-term combined application of OM with CF increased the aggregate stability and enzyme activity of different WSA sizes, and consequently, improved soil physical structure and increased soil microbial activity.

Hydrophobicity and carbonation treatment of earthen monuments in humid weather condition

Water stability of soil is crucial to the durability of earthen monuments,especially those located in the humid weather condition.This paper discusses the selection reason of materials(tung oil and quicklime) for earthen monument treatment,and then validates the applicability of these materials with tests of soil-water characteristic curve(SWCC),aggregate stability test(AST) and scanning electron microscope(SEM).The soil tested was sampled from Da Bao'en temple in Nanjing,Jiangsu province,China.The test results indicate that the carbonation reaction of quicklime offers a favorable environment for the formation of tung oil film.Meanwhile,the regulatory function of tung oil restricts the crystallinity of calcium carbonate(CaCO3) and forms fine crystals.Soil treated with both of tung oil and quicklime has good water repellency and aggregate stability without obvious changing in aesthetic appearance.Hydrophobicity and carbonation treatment can be applied prospectively in the conservation of earthen monument located in humid weather condition.