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The major challenge in accurately determining ultratrace gold in high-purity graphite is how to achieve effective separation and high enrichment of it (0.1−1ng/mL) in the sample solution, while minimizing the secondary pollution introduced by vessels, reagents, materials, environment, and equipment during the sample pretreatment process. A new method for the analysis of ultratrace gold in high-purity graphite is established by ashing and acid dissolution in a platinum dish, followed by microextraction with a hanging droplet of tributyl phosphate. Firstly, the fixed carbon in the sample was removed by high-temperature burning in a platinum vessel; then, the ash was completely dissolved into a sample solution using hydrofluoric acid-aqua regia-perchloric acid; next, micro-upgraded tributyl phosphate droplets were used as an extractant to separate and enrich gold from the sample solution; finally, gold in the droplets was determined using high-resolution continuum source graphite furnace atomic absorption spectrometry. The experimental results showed that by using 2.5μL of tributyl phosphate (chloroform volume fraction 20%) as the extractant, gold can be extracted from a sample solution in 10% hydrochloric acid medium for 2min, and the enrichment factor for gold can reach up to 283 times. Under the selected experimental conditions, the mass concentration of gold showed a good linear relationship with its absorbance values in the range of 0.1 to 2.0ng/mL. The correlation coefficient (r) was 0.999, and the detection limit of the method was 0.11ng/g. Interference tests showed that the presence of certain coexisting elements such as sodium, magnesium, and aluminum in the sample solution had no effect on the determination of gold. According to the experimental method, the gold content in five high-purity graphite samples was measured. The relative standard deviation (RSD, n=6) of the results was 1.5%−4.9%, and the recovery rate was 94.9%−105.3%. [ABSTRACT FROM AUTHOR]

In order to find safe and low-cost salt-activated materials to prepare soil polymers, light burned metakaolin was obtained after firing Guangxi kaolin at 850 °C for 4 h and added with different amounts of condensed aluminum phosphate, lithium phosphate and lithium silicate (3%, 4% and 5% of the metakaolin mass, respectively) as the additives to prepare soil polymers. Subsequently, the mixtures of metakaolin with lithium silicate, lithium phosphate or condensed aluminum phosphate were added to the corundum castable system, respectively, and the performance of the castables was compared with that of calcium aluminate bonded corundum castables. The effects of the additives on the solidification time, phase composition and microstructure of the obtained soil polymers as well as the soil polymers on the properties of the castables were explored. The results show that: (1) the solidification time of the soil polymers increases from 2 h to 5 h with the increasing additive addition, and the preferred addition is 4%; (2) at 20 °C, condensed aluminum phosphate reacts with metakaolin to form gelling SiP2O7, while lithium silicate and lithium phosphate react with metakaolin to form LiAISiO4, forming a layered structure or a gelling film attached to the surface of metakaolin, thus resulting in a gelation effect of soil polymers; (3) at 1 100 °C, soil polymers gradually form mullite, and layered metakaolin becomes thinner and cross connected; at 1 600 °C, the mull-itization of soil polymers is complete, forming needle and rod structures that cross connect with each other, and a small amount of liquid is generated, densifying the sample; (4) replacing calcium aluminate cement with soil polymers in the same proportion as the binder, the castable has a certain gap in performance compared to the calcium aluminate cement bonded castable. [ABSTRACT FROM AUTHOR]

Copyright of China Synthetic Fiber Industry is the property of Sinopec Baling Petrochemical Company and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Nonferrous Metals (Mineral Processing Section) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, magnesium aluminate spinel (MgAl2O4) materials were prepared by traditional solid-phase sintering method with high purity fused magnesia and calcined active aluminum powder as raw materials, and NiO as additive. The MgO and Al2O3 powders were mixed in a theoretical molar ratio of 1:1, and NiO with mass fraction of 0%, 0. 5%, 1. 0%, 1. 5%, and 2. 0% NiO were introduced into the system, respectively. The effects of NiO addition on sintering properties, phase composition and microstructure of MgAl2O4 were studied by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The results show that the introduction of appropriate amount of NiO can significantly promote the formation of MgAl2O4 phase and grain growth. At 1 600 °, when the NiO content is lower than 1. 5%, NiO can completely dissolve into MgAl2O4 crystal lattice and preferentially replace Al3+, which improves the defect concentration in MgAl2O4 crystal and activates the lattice, thus promoting the sintering of MgAl2O4. When the NiO content is higher than 1.5%, more second phase NiO appears in the MgAl2O4, which hinders the mass migration and transmission, and it is not conducive to the improvement of sintering performance of MgAl2O4. [ABSTRACT FROM AUTHOR]

In this paper, magnesium aluminate spinel (MgAl2O4) materials were prepared by traditional solid-phase sintering method with high purity fused magnesia and calcined active aluminum powder as raw materials, and NiO as additive. The MgO and Al2O3 powders were mixed in a theoretical molar ratio of 1:1, and NiO with mass fraction of 0%, 0. 5%, 1. 0%, 1. 5%, and 2. 0% NiO were introduced into the system, respectively. The effects of NiO addition on sintering properties, phase composition and microstructure of MgAl2O4 were studied by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The results show that the introduction of appropriate amount of NiO can significantly promote the formation of MgAl2O4 phase and grain growth. At 1 600 °, when the NiO content is lower than 1. 5%, NiO can completely dissolve into MgAl2O4 crystal lattice and preferentially replace Al3+, which improves the defect concentration in MgAl2O4 crystal and activates the lattice, thus promoting the sintering of MgAl2O4. When the NiO content is higher than 1.5%, more second phase NiO appears in the MgAl2O4, which hinders the mass migration and transmission, and it is not conducive to the improvement of sintering performance of MgAl2O4. [ABSTRACT FROM AUTHOR]

ZSM-5 Zeolites were economically synthesized with industrial solid waste(red mud) and water glass as the raw materials.The effects of alkali fusion activation of red mud(AF-RM) and the addition amounts of AF-RM and templates(tetrapropylammonium bromide(TPABr),glucose) on the formation of zeolites were investigated.The catalytic performance of the synthesized zeolites were tested by cracking of low-density polyethylene.The results show that aluminum silicate in red mud can be transferred into sodium aluminate and sodium silicate by alkali fusion activation.ZSM-5 Can be obtained at a AF-RM∶TPABr∶glucose∶water glass∶deionized water mass ratio of 1.5∶0.8∶3.6∶24∶18.The obtained liquid and gaseous yields at catalyst-to-feed ratio of 5∶3 and 500 ℃ are 13% and 84%,respectively.Thereinto, the selectivity to the monocyclic aromatics and light olefins(C2-4=) are 47% and 75%,respectively, suggesting good application prospect in production of benzene, toluene, xylene, ethylene and propylene. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Unburned magnesium aluminate spinel refractories were prepared using sintered magnesium aluminate spinel as the main raw material, phenolic resin as the binder, aluminum powder (2%, 4%, and 6%, by mass) and silicon powder (when Al powder addition is 4%, Si powder addition varies:1% and 2%, by mass) as additives. The effects of the aluminum powder and silicon powder addition on the properties and the microstructure of the refractories heat treated at different temperatures (1 000,1 400,and 1 600 °C for 3 h) were studied. The results show that the Al powder addiiion can greatly enhance the cold modulus of rupture of the samples fired at 1 000 or 1 400 °C,and meanwhile AlN reinforcement phase forms in the matrix, which greatly improves the hot modulus of rupture of the samples at 1 400 °C; however, the heat treatment at 1 600 °C has liitle influence on the strength; the addition of aluminum powder and silicon powder result in the formation of low melting point phases, greatly reducing the hot modulus of rupture. However, the low melting point phases promote sintering, which enhances the density and the cold modulus of rupture, and decreases the volume change during heating. The specimens added with aluminum and silicon all have higher cold modulus of rupture than those added with Al powder only. [ABSTRACT FROM AUTHOR]

Objective A new COS hydrolysis catalyst was developed to ensure the COS content in natural gas meeting the requirements of GB 17820-2018 Natural gas. Methods Using carbon nitride prepared from industrial grade urea as carrier, magnesium nitrate and aluminum nitrate as raw materials, magnesium aluminum composite oxide was grown on the surface of carbon nitride by co-precipitation method, and 150 L carbon nitride COS hydrolysis catalyst was produced in industrial pilot scale. The industrial side-stream line test of catalyst was carried out in the desulfurization unit of Yuanba Gas Purification Plant, SINOPEC Southwest Oil and Gas Company. Results The hydrolysis activity of the catalyst for carbonyl sulfur reached 97.0%-99.5% at the temperature of 80-120 ℃, the pressure of 4.8 MPa and the space velocity of 1 200-2 000 h-1. Conclusions The carbon nitride composite magnesium aluminum oxide prepared in this study, as a COS hydrolysis catalyst, has good low-temperature activity, strong water and hydrogen sulfide resistance, high mechanical strength and good stability. It is expected to realize industrial application. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Energy Chemical Industry is the property of Energy Chemical Industry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Inorganic anchoring adhesive is mainly used for reinforcement of building structures, which has high quality requirements for the bonding strength of materials. Through experiments, the effects of water retaining agent, expansion agent and toughening materials on the bonding strength and mechanical properties of inorganic anchoring adhesive are analyzed. The results show that the addition of inorganic water retaining agent can improve the bonding performance of inorganic anchoring adhesive, and the amount of inorganic water retaining agent should be controlled at 0.1%. When the expansion agent replaces the cementitious material by 6.0%, the expansion rate of inorganic anchoring adhesive can meet the technical requirements of JG/T 340-2011 "Anchoring adhesive for concrete structure engineering", and the bonding strength can be increased by 11.7%. The combination of three materials is used to effectively improve the bonding strength of inorganic anchoring adhesive. When the content of magnesium aluminum silicate is 0.1%, the expansion agent replaces 6.0%, and the amount of steel wool fiber is 6.0%, the bond strength between the ribbed steel bar and the concrete of the inorganic anchor adhesive under the restrained drawing condition reaches 11.2 MPa, which is 30.2% higher than that without steel wool fiber. [ABSTRACT FROM AUTHOR]

Fixed ammonium is commonly defined as the ammonium ion not replaced by neutral salts, particularly between the layers of 2:1 clay mineral. It is also an important component of soil nitrogen pool, and plays a significant role in plant growth. However, the content of fixed ammonium in aeolian sandy soil and its influencing factors are largely unexplored, which limit understanding of the formation of soil fertility and nitrogen cycle in sandy lands. In this study, soil fixed ammonium was determined in three sampling plots (bare sandy land, Salix psammophila land, and Artemisia ordosica land) in the Mu Us Sandy Land, and further to examine the effects of soil particle size and mineral composition on fixed ammonium. In June 2019, ten 5 m × 5 m subplots were randomly selected in each sampling plot. In each subplot, ten soil cores at 0~20 cm depths were randomly collected, and mixed to create one composite sample. All soil samples were air-dried and divided into three fractions (> 0.25 mm, 0.1-0.25 mm, < 0.1 mm). The contents of fixed ammonium in all soil fractions were measured by the Silva-Bremner method. Soil total nitrogen was analyzed using a vario EL III elemental analyzer (Elementar, Germany). The soil mineral composition was determined by the X-ray diffraction (D8 Advance, Bruker Biospin, Germany). The results showed that the average content of soil fixed ammonium in the research site was 18.63 mg/kg, accounting for 8.77% of the soil nitrogen pool, where the soil fixed ammonium and total nitrogen content were most distributed in the Artemisia ordosica land (23.03 ± 1.88 mg/kg and 274.71 ± 8.38 mg/kg, respectively), followed by the Salix psammophila land (16.82 ± 1.25 mg/kg and 197.15 ± 6.74 mg/kg, respectively), and the least in the bare sandy land (16.63 ± 0.61 mg/kg and 145.99 ± 9.45 mg/kg, respectively). The composition of soil particle significantly differed among three different plots, with more fine-textured soils in Artemisia ordosica land than that in Salix psammophila land and bare sandy land. In addition, the content of fine-textured soils in Salix psammophila was higher than that in bare sandy land. Soil particle composition was significantly correlated to fixed ammonium, indicating the finer the soil particle size, the higher the fixed ammonium content. Seven dominant minerals were found in the three sampling plots soil, including quartz, calcite, plagioclase, orthoclase, albite, anorthitic, and calcium aluminum silicate. Three sampling plots were characterized by different soil mineral composition. Specifically, Artemisia ordosica land had the greatest content of calcite, and orthoclase; Salix psammophila land had the greatest quartz content; and the bare sandy land showed the highest plagioclase content. The relationship between soil mineral composition and fixed ammonium was not significant. It infers that that soil fixed ammonium in the Mu Us Sandy Land largely depended on the soil physical composition rather than the mineral composition. The vegetation primarily affected soil fixed ammonium by changing soil particle composition, suggesting that the increase of soil fine-grained matter via vegetation rehabilitation can contribute to the content of fixed ammonium. The findings can offer a significant theoretical support to land desertification control, and further to increase the biological productivity. [ABSTRACT FROM AUTHOR]

BACKGROUND: When the rare earth oxides in bauxite are determined by inductively coupled plasma - optical emission spectrometry ( ICP - OES), acid dissolution often results in incomplete dissolution of samples, and a large amount of fluxes at high temperature alkali fusion will reduce the emission intensity of rare earth elements. Moreover, due to the low content of rare earth oxides ( 0. 0010% -0. 050%) and the matrix interferences such as aluminum and iron, accurate determination of them is difficult. OBJECTIVES: To develop an accurate method to determine the contents of rare earth oxides m bauxite by ICP - OES. METHODS: The bauxite was fused with sodium hydroxide, and the melt was extracted with hot water. A triethanolamine solution was used to eliminate the interferences of aluminum and iron, and ethylenediamine tetraacetate disodium solution was used to complex with calcium, magnesium and other elements. Rare earth hydroxide was retained in the precipitation, which was dissolved into the liquid hydrochloric acid digestion. Rare earth elements can be effectively separated from fluxes and matrix elements by the proposed procedure. RESULTS: The standard solution did not need matrix matching. The linear correlation coefficient of calibration curve was not less than 0. 9999, and the detection limits were 0. 0002% - 0. 0015%. The relative standard deviations of rare earth elements in the sample were 2. 0% -4. 6%, and recoveries were 85. 2% -104. 4%. CONCLUSIONS: There are no obvious differences for analytical results between ICP - OES and inductively coupled plasma - mass spectrometry ( ICP - MS). [ABSTRACT FROM AUTHOR]

BACKGROUND: The identification of leptite is usually based on microscopic identification technology, but it is very difficult to distinguish tiny feldspar, quartz, and layered silicate minerals such as chlorite, montmorillonite and mica using a microscope. There could be a large error in the naming of leptite by microscopic identification methods, which will cause errors in geological mapping and original rock recovery,leading to incorrect geological conclusions. The development of X-ray diffraction analysis technology has led to its wide use in the study of mineralogy and petrology. OBJECTIVES: To identify tiny minerals that are difficult to distinguish under the microscope by using X-ray powder diffraction technology. METHODS: A total of 23 leptite samples were selected. The mineral composition of leptite was detected by X-ray powder diffraction analysis and microscopic rock thin section identification technology. Semi-quantitative X-ray powder diffraction was used to verify the accuracy of the rock slice identification results. RESULTS: The comparison between the identification results of the microscopic rock slices and the X-ray powder diffraction phase analysis results showed that 10 out of 23 samples had the same name. Analyzing the reasons for the difference, it can be found that the advantage of microscopic rock identification was that it can be used to determine rock texture and structure, as well as common mineral components. The advantage of the X-ray powder diffraction method was that it can be used to detect the relative content of tiny quartz and feldspar particles that were difficult to distinguish under the microscope, and can detect tiny layered silicate minerals such as chlorite, montmorillonite and mica, which was effective for detecting minerals with less content and finer particles. CONCLUSIONS: Only by combining the microscopic rock thin identification technology and the X-ray powder diffraction technology can the leptite be named and classified more accurately. The combination of two techniques provides more objective technical data and analytical conclusions for geoscience research. [ABSTRACT FROM AUTHOR]

Copyright of China Surfactant Detergent & Cosmetics (1001-1803) is the property of China Surfactant Detergent & Cosmetics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

BACKGROUND: Sepiolite is a widely used fibrous magnesium-rich silicate clay mineral. Sepiolite is mainly composed of silicon and magnesium, with minor aluminum, potassium, sodium and other impurities. Determination of the major element of sepiolite usually adopts the classical chemical analytical method. After the alkali melting treatment, the sample is determined by volumetric method, photometry and atomic absorption spectrometry, which is inefficient and time-consuming. Moreover, potassium and sodium cannot be simultaneously determined.OBJECTIVES: To find an efficient method for the determination of seven major elements in sepiolite.METHODS: The samples were digested by hydrofluoric acid, nitric acid, and perchloric acid. Contents of major elements such as Al2O3 were determined by inductively coupled plasma-optical emission spectrometry（ICP-OES）. The dosage of hydrofluoric acid was optimized. The analytical spectral lines were Al 396.153 nm, Ti 334.940 nm, K 766.490 nm, Na 589.592 nm, Ca 422.673 nm, Mg 285.213 nm and Fe 238.204 nm, and elements were determined by axial observation. The content of magnesium in sepiolite was high, and there was a certain matrix effect during ICP-OES analysis. A series of high magnesium mixed standard solutions were prepared to match the matrix.RESULTS: The linear correlation coefficient of the standard curve of each element was greater than 0.9990, the detection limits of the method were 0.53-3.25μg/g, the relative standard deviations（RSD, n=10） of the measured results were 0.66%-5.65%, and the recoveries of each element were 95.3%-108.5%.CONCLUSIONS: Acid dissolution is easy to operate compared with the alkali fusion method. The results are consistent with those obtained by classical chemical analytical methods and thus meet the analytical requirements of sepiolite samples. [ABSTRACT FROM AUTHOR]

Copyright of Rock & Mineral Analysis is the property of Editorial Board of Rock & Mineral Analysis and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A detailed study on a high-iron red mud from Shandong province in the perspective of process mineralogy were conducted through chemical analysis, XRD, optical microscope, laser particle size analysis, energy spectrum analysis and BPMA automatic analyzer. The results show that the red mud has a fine particle size, and the chemical composition and mineral ( phase) composition are complex. The main minerals ( phases) in red mud are particulate silicon slag, hematite, iron-aluminum oxide, limonite, as well as trace amounts of sodium aluminosilicate, iron-titanium oxide, quaitz, gibbsite, bauxite, feldspar, and mica, etc. Iron occurs in the form of hematite, limonite, iron-aluminum oxide and particulate silicon slag. There is a large amount of particulate silicon slag in red mud, but the mineral ( phase) particle size is fine. The key to taking full advantage of the red mud is how to make use of iron, aluminum, titanium and sodium in the particulate silicon slag. [ABSTRACT FROM AUTHOR]

Copyright of Journal of the Chinese Society of Rare Earths is the property of Editorial Department of Journal of the Chinese Society of Rare Earths and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A research was conducted on the micro mechanism of the creep mechanical behavior of aluminum silicate short fiber-reinforced AZ91D magnesium matrix composite. The unit cell model was applied together with the finite element method (FEM) of ABAQUS to simulate the composite. The FEM results show that the distribution of stress and strain in the fiber and matrix is roughly uniform in each segment, the fiber assumes far higher equivalent Mises stress than the matrix, and there is distinct stress concentration around the interface between the matrix and the fiber. The creep fracture of the composite goes through three microscopic processes. With the increase of creep deformation, the short fiber bears and transfers the load with various damages, fracture and multiple fracture, which strengthens the creep resistance of the matrix. The micro-cracks generated at the weak interface continue to expand, causing sharp fall of the creep resistance and in turn fracture of the composite. [ABSTRACT FROM AUTHOR]

Numerical investigations are carried out to study the energy absorption behavior of multi-layers Aluminum tube without any fill, it is found that multi-layers Aluminum tube has more energy absorption and higher specific energy absorption (SEA) than that of the single layer tube. Based on these results, several types of foam-filled multi-layers tubes with different layers are designed and their crushing behaviors have been studied by numerical simulations. It shows that, the distortions of Aluminum foam are not only subjected to the axial crushing, but also to the interaction between layers in the radial direction. Then, three multi-layers Aluminum tubes filled by Aluminum foams with different densities have been modeled and parametric studies are conducted to determine the effect of the layer number and foam density on the energy absorption behavior. The results demonstrate that the energy absorption and the SEA of foam-filled multi-layers tube are increased with the increasing of layer number, but the SEA will begin to decrease when the foam density is increased to a certain value, while the SEA is still higher than that of single tube filled with the same foam. [ABSTRACT FROM AUTHOR]

We investigated the responses and underlying mechanisms of community composition, and function group of fungi in yellow clayey paddy soil to different long-term fertilization, which may provide scientific basis for rational fertilization and sustainable development in agriculture ecosystems. There were four treatments, including control (CK), inorganic fertilizer (NPK), inorganic fertilizer combined with manure (NPKM), and inorganic fertilizer combined with straw (NPKS). Illumina high-throughput sequencing and FUNGuild were performed to investigate the fungal community structure and functional group, respectively. Ascomycota, Basidiomycota, and Zygomycota were identified as the three dominant ones. The proportion of Ascomycota in NPKM and NPKS were significantly lower (49% and 47%, respectively) compared with CK (71%) and NPK (74%) treatments, with the main reduced orders of Hypocreales, Pleosporales and Eurotiales. While there was higher relative abundance of Basidiomycota in NPKM and NPKS (18% and 28%) compared to CK (14%) and NPK (10%), the orders with enhancement were Tremellales, Trechisporales, and Agaricales. The ratio of Basidiomycota was decreased with sole inorganic fertilizer. Moreover, the relative abundance of Zygomycota was increased after 33 years of fertilization, which was dominated by Mortierellales and Basidiobolales at order level. Diversity indices including Shannon, Simpson, Chao1 and ACE were all significantly declined in NPK compared with CK, NPKM and NPKS treatments, whereas Chao1 index and ACE index in NPKM and NPKS were higher than that in CK and NPK. Saprotroph was the main fungal functional group across all the four treatments (48%-57%). Higher proportion of symbiotroph fungi was identified in soils with NPKS and NPKM (17%) in comparison to CK and NPK. The main guilds with the increasing proportion were arbuscular mycorrhizal fungi and ectomycorrhizal fungi. However, significantly higher proportion of animal pathogen fungi were detected in NPK (10%) than other treatments. Redundancy analysis (RDA) showed that moisture, salinity and porosity in soil were more strongly related with fungal community composition and fungal functional composition than soil organic matter and total nitrogen. Our results suggest that sole application of inorganic fertilizer results in great changes in fungal community compositions and the hazard of over production of pathogen fungi, whereas combined organic-inorganic fertilization would be beneficial to maintain the healthy environment through increasing fungal diversity and the ratio of symbiotrophic fungi in yellow clayey paddy soil.

Addition of urease inhibitors is one of the important measures to increase nitrogen (N) use efficiency of crop, due to retardant of urea hydrolysis and reduction of ammonia volatilization loss. An incubation experiment was conducted to investigate the urease inhibition effect of a new phosphoramide urease inhibitor, NPPT (N-(n-propyl) thiophosphoric triamide) in different texture soils under dark condition at 25 ℃, and NBPT (N-(n-butyl) thiophosphoric triamide) was obtained to compare the inhibition effect on urease in different soil textures by different dosages of urea adding. Results showed that the effective reaction time of urea was less than 9 d in the loamy and clay soil. Addition of inhibitors for retardation of urea hydrolysis was more than 3 d. In sandy soil, urea decomposition was relatively slow, and adding inhibitor significantly inhibited soil urease acti-vity, and reduced NH 4 + -N content. During the incubation time, the inhibition effect of high dosage urea in the soil was better than that of low dosage. At day 6, the urease inhibition rate of NBPT and NPPT (N 250 mg·kg -1 ) were 56.3% and 53.0% in sandy soil, 0.04% and 0.3% in loamy soil, 4.1% and 6.2% in clay soil; the urease inhibition rate of NBPT and NPPT (N 500 mg·kg -1 ) were 59.4% and 65.8% in sandy soil, 14.5% and 15.1% in loamy soil, 49.1% and 48.1% in clay soil. The urease inhibition effects in different texture soil were in order of sandy soil > clay soil> loamy soil. The soil NH 4 + -N content by different inhibitors during incubation time increased at first and then decreased, while soil NO 3 - -N content and apparent nitrification rate both showed rising trends. Compared with urea treatment, addition of urease inhibitors (NBPT and NPPT) significantly increased urea-N left in the soil and reduced NH 4 + -N content. In short, new urease inhibitor NPPT in different texture is an effective urease inhibitor.

The aim of this study was to investigate the effects of carbon sequestration in soil particle-sized fractions during reversion of desertification at Mu Us Sand Land, soil samples were collected from quicksand land, semifixed sand and fixed sand lands that were established by the shrub for 20-55 year-old and the arbor for 20-50 year-old at sand control region of Yulin in Northern Shaanxi Province. The dynamics and sequestration rate of soil organic carbon (SOC) associated with sand, silt and clay were measured by physical fractionation method. The results indicated that, compared with quicksand area, the carbon content in total SOC and all soil particle-sized fractions at bothsand-fixing sand forest lands showed a significant increasing trend, and the maximum carbon content was observed in the top layer of soils. From quicksand to fixed sand land with 55-year-old shrub and 50-year-old arbor, the annual sequestration rate of carbon stock in 0-5 cm soil depth was same in silt by 0.05 Mg·hm -2 ·a -1 . The increase rate of carbon sequestration in sand was 0.05 and 0.08 Mg·hm -2 ·a -1 , and in clay was 0.02 and 0.03 Mg·hm -2 ·a -1 at shrubs and arbors land, respectively. The increase rate of carbon sequestration in 0-20 cm soil layer for all the soil particles was averagely 2.1 times as that of 0-5 cm. At the annual increase rate of carbon, the stock of carbon in sand, silt and clay at the two fixed sand lands were increased by 6.7, 18.1 and 4.4 times after 50-55 year-old reversion of quicksand land to fixed sand. In addition, the average percentages that contributed to accumulation of total SOC by different particles in 0-20 cm soil were in the order of silt carbon (39.7%)≈sand carbon (34.6%) > clay carbon (25.6%). Generally, the soil particle-sized fractions had great carbon sequestration potential during reversion of desertification in Mu Us Sand Land, and the slit and sand were the main fractions for carbon sequestration at both fixed sand lands.

Objective: To study the effect of physicochemical characteristics of soil on Panax notoginseng agronomic character, in order to offer the theory for selecting an appropriate soil to cultivate Panax notoginseng, and to build the production bases., Methods: To test and analyze Panax notoginseng agronomic character, to analyze the form of layered soil particles, p H value and soil fertility. At the same time, the analysis of Panax notoginseng plant height, leaf number, the length of taproot, the width of taproot, stem diameter, the width of residual part of stem, rootlet number, root fresh and dry weight and drying rate were carried out., Results: Panax notoginseng agronomic character had a large difference. The length of roots, the width of roots and a large number of rootlets had a promoting effect on accumulating biological yield. Nevertheless, the numbers of branches had no obvious impact on accumulating biological yield. Most of soil texture were silty clay or light clay of silty clay. Physical clay and coarse silt could promote the growth of Panax notoginseng. Sand grain had significant effect on Panax notoginseng growth. A reasonable use of nitrogenous fertilizer had a prominent promoting effect on the width of the medicine’s root. In fact, the use of phosphorus potassium also had a great impact on Panax notoginseng growth., Conclusion: Panax notoginseng should be planted on the light clay which are loose and can irrigate and drain conveniently and contains many silty. The heavy clay soil which are defective aeration and contain cosmid has a bad influence of the growth of Panax notoginseng. It will cause a decrease of the yield of medicinal materials. Using nitrogenous fertilizer aptly also is an effective way to improve the quality and yield of Panax notoginseng.

A series of organo-montomorillonites were prepared using Na-montomorillonite and hexadecyl trimethyl ammonium bromide (HDTMA). The organo-montomorillonites were then investigated for the remediation of Cr(VI) contaminated soils. FT-IR, XRD, SEM and N2 -BET, CEC, Zeta potential measurement were conducted to understand the structural changes of montmorillonites as different amounts of HDTMAs were added as modifier. The characterization results indicated that the clay interlayer spacing distance increased from 1. 25 nm to 2. 13 nm, the clay surface roughness decreased, the clay surface area reduced from 38.91 m² · g⁻¹ to 0.42 m² · g⁻¹, the clay exchangeable cation amount reduced from 62 cmol · kg⁻¹ to 9.9 cmol · kg⁻¹ and the clay surface charge changed from -29.1 mV to 5.59 mV as the dosage of HDTMA in montmorillonite was increased. The TCLP (toxicity characteristic leaching procedure) was used to evaluate the leachate toxicity of Cr(VI). The effects of the initial soil Cr(VI) concentration, montmorillonites dosage, reaction time and HDTMA modification amount were investigated, respectively. The results revealed that modification of montmorillonites would manifest an attenuated physical adsorptive effect and an enhanced electrostatic adsorptive effect on Cr(VI), suggesting electrostatic effect was the major force that resulted in improved Cr(VI) adsorption onto HDTMA modified montmorillonites.

Along the 368-591 mm precipitation gradient, 7 survey sites, i.e. a total 63 investigated plots were selected. At each sites, woodland, grassland, and cropland with similar restoration age were selected to investigate soil organic carbon distribution in surface soil (0-30 cm), and the influence of factors, e.g. climate, soil depth, and land uses, on soil organic carbon distribution were analyzed. The result showed that, along the precipitation gradient, the grassland (8.70 g . kg-1) > woodland (7.88 g . kg-1) > farmland (7.73 g . kg-1) in concentration and the grassland (20.28 kg . m-2) > farmland (19.34 kg . m-2) > woodland (17.14 kg . m-2) in density. The differences of soil organic carbon concentration of three land uses were not significant. Further analysis of pooled data of three land uses showed that the surface soil organic carbon concentration differed significantly at different precipitation levels (P<0.00 1). Significant positive relationship was detected between mean annual precipitation and soil organic carbon concentration (r=0.838, P<0.001) in the of pooled data. From south to north (start from northernmost Ordos), i.e. along the 368-591 mm precipitation gradient, the soil organic carbon increased with annual precipitation 0. 04 g . kg-1 . mm-1, density 0.08 kg . m-2 . mm-1. The soil organic carbon distribution was predicted with mean annual precipitation, soil clay content, plant litter in woodland, and root density in farmland.

Objective: To analyze the mineral medicine of Chloriti Lapis, Micae Lapis Aureus and Vermiculitum by X-ray diffraction, then to guide the identification and quality assessment of them., Methods: XRD Fourier patterns were collected from powder samples to analyze phase compositions, and to determine the original mineral resources of Chloriti Lapis, Micae Lapis Aureus and Vermiculitum by comparing with their characteristic traits. First derivative + vector normalization and 21 point smoothing were used to pretreat the selected spectrum band from 0. 68 ~ 1. 77 nm. Then the data were analyzed by fuzzy cluster., Results: It was found that the original mineral resource of seven powder samples of Chloriti Lapis was biotite schist belonging to metamorphic mineral. The original mineral resource of three powder samples of high-quality Micae Lapis Aureus was vermiculite biotite schist belonging to metamorphic mineral. The original mineral resources of three powder samples of Vermiculitum were phlogopite and vermiculite phlogopite., Conclusion: The method of X-ray diffraction analysis is accurate and rapid, which can be used for the identification and quality evaluation of Chloriti Lapis, Micae Lapis Aureus and Vermiculitum.

In this study, four land use types including subtropical evergreen broad-leaved forest (abbreviation: forest), sloping farmland, orchard and abandoned land were selected to collect soil samples from 0 to 60 cm depth at the same altitude in Jinyun Mountain. Four sizes of large macroaggregates (> 2 mm), small macroaggregates (0.25-2 mm), microaggregates (0.053-0.25 mm) and silt + clay (< 0.053 mm) were achieved by wet sieving method and the contents of microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) in each aggregate fraction were measured to study the impacts of the different land use types on MBC and MBN in soil aggregates. The results showed that the contents of MBC and MBN in all aggregates in the four land use types decreased with the increasing soil depth. Except large macroaggregetes, the contents of MBC and MBN in the other three soil aggregates decreased when the forest was reclamated into orchard and sloping farmland. MBC and MBN contents in large macroaggregates, small macroaggregates and microaggregates all increased when the sloping farmland was abandoned. The storages of organic carbon and nitrogen in soil depth of 0-60 cm in the four proportions were calculated by the equivalent soil mass method. The results revealed that MBC storages in the other three sizes except silt + clay were higher in the forest than those in orchard and sloping land. And MBC storages in the all aggregates were higher in the abandoned land than those in the sloping land. MBN storages in small macroaggregates and microaggregates were higher in the forest than those in orchard and sloping land. And MBN storages in the other three aggregates except silt + clay were higher in the abandoned land than those in the sloping land. Generally speaking, the storages of MBC in soil aggregates of forest and abandoned land were higher than in orchard and sloping land, MBN storage in soil aggregates of forest was nearly equal to the storage in orchard. However, the storages of MBN in soil aggregates of forest and abandoned land were higher than those in sloping land. The results showed that the reclamation of the forest resulted in the loss of MBC and MBN in soil aggregates of sloping land. However, the abandon of the sloping land contributed to the acumulation of MBC and MBN in soil aggregates. In the process of land use change, the direction and quantity of change in MBC in the soil aggregates were not consistent with those of the total soil organic carbon, which meant the microbial quotient in soil aggregates was not suitable for using to evaluate the impact of land use change on soil quality, using the total organic carbon as an index to express the sensitivity of the land use change may be better.

Objective: To evaluate the operation time and clinical effect of three types of materials (i.e., total-etching adhesive, self-etching adhesive, resin-modified glass ionomer cement) that are used to bond removable thermoplastic appliances., Methods: Thirty malocclusion patients (156 attachments) with removable thermoplastic appliances were randomly divided into three groups, with 10 individuals each. Attachments of groups A and B were bonded using 3M Adper Single Bond 2 and 3M Adper Easy One, respectively; both adhesives utilized 3M Z350 nano composite resin. Attachments of group C was directly bonded using GC Fuji Ortho LC. The operation time of each attachment was recorded. Failure rates of adhesion were evaluated during adhesion, 1 month after treatment, and 6 months after treatment., Results: The operation time of group C was shorter than those of groups A and B (P<0.01). Significant difference of adhesion failure rates was not found among the three groups (P>0.05). No significant difference of adhesion failure rates was also observed in different times of the same group (P>0.05)., Conclusion: The attachment stability of the three types of materials achieved satisfactory effects. However, the operation method of resin-modified glass ionomer cement is more concise and suitable for clinical promotion.

Four land utilization patterns were selected for this study in Jinyun mountain, including subtropical evergreen broad-leaved forest (abbreviation: forest), sloping farmland, orchard and abandoned land. Soil samples were taken every 10 cm in the depth of 60 cm soil and proportions of large macroaggregates (> 2 mm), small macroaggregates (0. 25-2 mm), microaggregates (0. 053 - 0. 25 mm) and silt + clay (<0. 053 mm) were obtained by wet sieving method to measure the content of organic carbon and labile organic carbon in each aggregate fraction and analyze impacts of land uses on organic carbon and labile organic carbon of soil aggregates. LOC content of four soil aggregates were significantly reduced with the increase of soil depth; in layers of 0-60 cm soil depth, our results showed that LOC contents of forest and abandoned land were higher than orchard and sloping farmland. Reserves of labile organic carbon were estimated by the same soil quality, it revealed that forest (3. 68 Mg.hm-2) > abandoned land (1. 73 Mg.hm-2) > orchard (1. 43 Mg.hm-2) >sloping farmland (0.54 Mg.hm-2) in large macroaggregates, abandoned land (7.77, 5. 01 Mg.hm-2) > forest (4. 96, 2.71 Mg.hm-2) > orchard (3. 33, 21. 10 Mg.hm-2) > sloping farmland (1. 68, 1. 35 Mg.hm-2) in small macroaggregates and microaggregates, and abandoned land(4. 32 Mg.hm-2) > orchard(4. 00 Mg.hm-2) > forest(3. 22 Mg.hm-2) > sloping farmland (2.37 Mg.hm-2) in silt + clay, forest and abandoned land were higher than orchard and sloping farmland in other three soil aggregates except silt + clay. It was observed that the level of organic carbon and labile organic carbon were decreased when bringing forest under cultivation to orchard or farmland, and augments on organic carbon and labile organic carbon were found after exchanging farmland to abandoned land. The most reverses of forest and abandoned land emerged in small macroaggregates, orchard and sloping farmland were in microaggregates. That was, during the transformations of land utilization pattern, soil aggregates with bigger size were easier to accumulate or lose labile organic carbon. Allocation ratios of labile organic carbon to soil organic carbon under four land uses were decreased as the soil depth added. Allocation ratios of orchard and sloping farmland were a bit higher than forest and abandoned land, which indicated that organic carbon of forest and abandoned land were more steady and available for soil as a carbon sink, meanwhile, the forest and abandoned land would avoid more CO2 diffusing to the atmosphere from the decomposition of soil organic carbon.

The solidification/stabilization (S/S) of chromite ore processing residue (COPR) was performed using zero-valent iron (ZVI) and lime-activated ground granulated blast furnace slag (GGBFS). The degree of Cr immobilization was evaluated using the leaching procedure, mineral composition analysis and morphology analysis. Semi-dynamic leaching tests were implemented to investigate the potential for reusing the final treatment product as a readily available construction material. The results showed that after reduction, all of the S/S treated COPR samples met the pollution control limit of bricks and building block products (Chinese standard HJ/T 301-2007) produced with COPR for total Cr (0.3 mg x L(-1)), the compressive strength of all the S/S samples could meet the compressive strength standard (15 MPa) for producing clay bricks, and Cr existed as the specie that bound to Fe/Mn oxides in the S/S samples. At the same time, all of the S/S treated specimens tested were suitable for utilization at certain levels.

The characteristics and changes of soil organic carbon (SOC) and total nitrogen (TN) in different size particles of soil under different agricultural practices are the basis for better understanding soil carbon sequestration of mollisols. Based on a 31-year long-term field experiment located at the Heilongjiang Academy of Agricultural Sciences (Harbin) , soil samples under six treatments were separated by size-fractionation method to explore changes and distribution of SOC and TN in coarse sand, fine sand, silt and clay from the top layer (0-20 cm) and subsurface layer (20-40 cm). Results showed that long-term application of manure (M) increased the percentages of SOC and TN in coarse sand and clay size fractions. In the top layer, application of nitrogen, phosphorus and potassium fertilizers combined with manure (NPKM) increased the percentages of SOC and TN in coarse sand by 191.3% and 179.3% compared with the control (CK), whereas M application increased the percentages of SOC and TN in clay by 45% and 47% respectively. For subsurface layers, the increase rates of SOC and TN in corresponding parts were lower than that in top layer. In the surface and subsurface layers, the percentages of SOC storage in silt size fraction accounted for 42%-63% and 48%-54%, TN storage accounted for 34%-59% and 41%-47%, respectively. The enrichment factors of SOC and TN in coarse sand and clay fractions of surface layers increased significantly under the treatments with manure. The SOC and TN enrichment factors were highest in the NPKM, being 2.30 and 1.88, respectively, while that in the clay fraction changed little in the subsurface layer.

The decomposed rate of crop residues is a major determinant for carbon balance and nutrient cycling in agroecosystem. In this study, a constant temperature incubation study was conducted to evaluate CO2 emission and microbial biomass based on four different parts of corn straw (roots, lower stem, upper stem and leaves) and two soils with different textures (sandy loam and clay loam) from the black soil region. The relationships between soil CO2 emission, microbial biomass and the ratio of carbon (C) to nitrogen (N) and lignin of corn residues were analyzed by the linear regression. Results showed that the production of CO2 was increased with the addition of different parts of corn straw to soil, with the value of priming effect (PE) ranged from 215. 53 µmol . g-1 to 335. 17 µmol . g -1. Except for corn leaves, the cumulative CO2 production and PE of clay loam soil were significantly higher than those in sandy loam soil. The correlation of PE with lignin/N was obviously more significant than that with lignin concentration, nitrogen concentration and C/N of corn residue. The addition of corn straw to soil increased the contents of MBC and MBN and decreased MBC/MBN, which suggested that more nitrogen rather than carbon was conserved in microbial community. The augmenter of microbial biomass in sandy loam soil was greater than that in clay loam soil, but the total dissolved nitrogen was lower. Our results indicated that the differences in CO2 emission with the addition of residues to soils were primarily ascribe to the different lignin/N ratio in different corn parts; and the corn residues added into the sandy loam soil could enhance carbon sequestration, microbial biomass and nitrogen holding ability relative to clay loam soil.

Effects of chemical fertilizers and organic manure on the soil organic carbon (SOC) content in particle size fractions of paddy soil were investigated in a 17-year long-term fertilization field experiment in Zhejiang Province, China. The inherent chemical composition of silt- and clay-associated SOC was evaluated with solid-state 13C-NMR spectroscopy. Compared to CK (no fertilizer treatment), NPKRS (NPK fertilizers plus rice straw) , NPKOM (NPK fertilizers plus organic manure) , NPK (NPK fertilizers) and OM (organic manure alone) treatments significantly (P <0. 05) increased the SOC content of sand- (2-0.02 mm), silt- (0.02-0.002 mm) and clay-sized (< 0.002 mm) fractions. However, no significant difference was observed in the accumulation of silt- and clay-associated SOC between CK and rice straw (RS) treatments. Besides, in comparison with plots applied with NPK fertilizers alone, combined application of organic amendments and NPK fertilizers facilitated the storage of newly sequestered SOC in silt- and clay-sized fractions, which could be more conducive to the stability of SOC. Based on 13C-NMR spectra, both silt and clay fractions were composed of Alkyl-C, O-alkyl-C, Aromatic-C and carbonyl-C. Changes in the relative proportion of different C species were observed between silt and clay fractions: the clay fraction had relatively more Alkyl-C, carbonyl-C and less O-alkyl-C, Aromatic-C than those in the silt fraction. This might be ascribed to the fact that the organic matter complexed with clay was dominated by microbial products, whereas the silt appeared to be rich in aromatic residues derived from plants. The spectra also showed that the relative proportion of different C species was modified by fertilization practices. In comparison with organic amendments alone, the relative proportion of Alkyl-C was decreased by 9.1%-11.9% and 13.7%-19.9% under combined application of organic amendments and chemical fertilizers, for silt and clay, respectively, and that of O-alkyl-C was increased by 2.9%-6.3% and 13.4%-22.1%, respectively. These results indicated that NPKOM and NPKRS treatments reduced the decomposition rate of SOC. The aromaticity, hydrophobicity and, hence, chemical recalcitrance of silt- and clay-associated SOC in the NPK fertilizer treatments were lower than those of the organically amended plots and unfertilized treatments, indicating decreased recalcitrance of SOC against decomposition. We concluded that long-term application of organic manure combined with chemical fertilizers, either through increased accumulation of both recalcitrant compounds and carbohydrates or reduced decomposition of organic matter, was a sustainable strategy for facilitating carbon accumulation of the paddy soil investigated in this study.

Based on the laser particle size and X-ray diffraction (XRD) analysis, 28 sediment samples collected from the inshore region of the Yellow River estuary in October 2013 were determined to discuss the influence of long-term implementation of the flow-sediment regulation scheme (FSRS, initiated in 2002) on the distributions of grain size and clay components (smectite, illite, kaolinite and chlorite) in sediments. Results showed that, after the FSRS was implemented for more than 10 years, although the proportion of sand in inshore sediments of the Yellow River estuary was higher (average value, 23.5%) than those in sediments of the Bohai Sea and the Yellow River, silt was predominated (average value, 59.1%) and clay components were relatively low (average value, 17.4%). The clay components in sediments of the inshore region in the Yellow River estuary were close with those in the Yellow River. The situation was greatly changed due to the implementation of FSRS since 2002, and the clay components were in the order of illite > smectite > chlorite > kaolinite. This study also indicated that, compared to large-scale investigation in Bohai Sea, the local study on the inshore region of the Yellow River estuary was more favorable for revealing the effects of long-term implementation of the FSRS on sedimentation environment of the Yellow River estuary.

In irrigated agricultural ecosystems, the accumulation, distribution and transfer of nitrate nitrogen (NO(3-)-N) in soil profile and groundwater nitrate pollution were influenced by irrigation and fertilization, and were closely related to soil textural characteristics. In this study, a monitoring section with 10 groundwater observation wells along Heihe River flood land-old oasis croplands-newly cultivated sandy croplands-fixed sandy land outside oasis was established in Pingchuan desert-oasis in Linze county in the middle of Heihe river basin, and groundwater NO(3-)-N concentration was continuously monitored. Soil texture and NO(3-)-N concentration in the unsaturated zone at different landscape locations were determined. The NO(3-)-N transfer change in soil profile, nitrate leaching of soils with different texture and fertility levels in the 0-100 cm layer were analyzed. The results indicated that the vertical distribution of soil texture was sandy loam in the 0-130 cm depth, loam in the 130-190 cm and clay loam in the 190-300 cm for the old oasis croplands. For newly cultivated sandy croplands, sand content was more than 80% in each soil layer of the 0-300 cm profile, although a thin clay layer occurred in the 140-160 cm depth. The clay layer occurred 160 cm below the sand-fixing zone outside oasis. There were significant correlations between soil NO(3-)-N concentration and silt + clay content, and the order of significant degree was the natural soils of sandy lands > the newly cultivated sandy croplands > the old oasis croplands. The loss of N leaching was closely correlated to the silt + caly content in the 0-100 cm soil depth. The groundwater NO(3-)-N concentration varied from 1.01 to 5.17 mg · L(-1), with a mean value of 2.65 mg · L(-1) and from 6.6 to 29.5 mg · L(-1), with an average of 20.8 mg · L(-1) in the area of old oasis croplands and the newly cultivated croplands, respectively. The averaged groundwater NO(3-)-N concentration in the area of newly cultivated sandy croplands during the period of May and October, 2013 was 26.5 mg · L(-1), which was increased by 9.5 mg · L(-1) in comparison with the same period of 2012. There was a clear increasing trend in groundwater NO(3-)-N concentration in the sand-fixing zone outside oasis. The textural characteristics of soil unsaturated zone in the shallow groundwater distribution area was the key determining factor for controlling soil NO(3-)-N leaching and groundwater nitrate pollution. The newly cultivated sandy croplands were the nitrate vulnerable zones and high-risk areas of groundwater nitrate pollution. The implementation of cultivation pattern and irrigation and fertilization management that could effectively reduce groundwater NO(3-)-N pollution should be considered in the development of ecological agriculture.

In order to investigate the effects of long-term tea planting on soil pH buffer capacity (pHBC), the variation of pHBC and its influence factors were investigated in tea gardens of 10, 15, 20, 25 and 30 years in Langxi and Qimen of Anhui Province. The results showed that the acid-base titration method was suitable for the determination of soil pHBC of tea gardens. The amount of acid-base added had approximate linear relationship with soil pH value in specific section (pH 4.0-6.0) of acid-base titration curves, so the soil pHBC could be calculated by linear regression equation. Soil pHBC in the tea gardens from the two regions showed a downward trend with increasing the planting years, which decreased at rates of 0.10 and 0.06 mmol · kg(-1) · a(-1) in Langxi and Qimen tea gardens, respectively. Soil pHBC had significant positive correlation with CEC, soil organic matter, base saturation and physical clay content, and significant negative correlation with exchangeable acid and exchange H+.

In this study, topsoil samples were collected from wetlands recovered from farmlands respectively for 3, 5, 9 and 11 years around Caizi Lake, Anhui, China. Their characteristics of adsorption and desorption of phosphorus were examined with comparison to soils sampled from an adjacent vegetable farmland and a non-cultivated wetland. Phosphorus adsorption curves of all studied soils could be modeled by Langmuir and Freundlich equations (P < 0.01). The maximum P adsorption (Xm), adsorption constant K and maximum buffer capacity (MBC) of all the 6 soil samples were in the ranges of 478-1074 mg x kg(-1), 0.14-0.61 and 68.6-661.5 mg x kg(-1), respectively. These three parameters all tented to increase with the recovered years but did not reach the values of the non-cultivated wetland. However, the P desorption rate ranging from 6.2% to 14.6%, increased first and then decreased with the recovered years and was significantly higher than that of the non-cultivated wetland. It was concluded that the P immobilization would increase with the recovery years of cultivated wetlands, which could be affected by the soil organic carbon and clay contents of the wetland soil.

The alpine meadow in the source region of the Yangtze and Yellow River is suffering serious deterioration. Though great efforts have been put into, the restoration for the degraded grassland is far from being effective, mainly due to poor understanding of the degradation mechanism of alpine meadow in this region. In order to clarify the formation mechanism of degradation grassland and provide the new ideas for restoration, degradation sequences of the alpine meadow in the source region of the Yangtze and Yellow River were taken as target systems to analyze the soil particle size distribution, the fractal dimension of the soil particle size, and the relationship between soil erosion modulus and fractal dimension. The results showed that, with increasing grassland degradation, the percentage contents of clay increased while the percentage contents of silt sand and very fine sand showed a decreasing trend. The fractal dimension presented a positive correlation with clay among the degradation sequences while negative correlations were found with very fine sand and silt sand. The curvilinear regression of fractal dimension and erosion modulus fitted a quadratic function. Judged by the function, fractal dimension 2.81 was the threshold value of soil erosion. The threshold value has an indicative meaning on predicting the breakout of grazing-induced erosion and on restoration of the degraded grassland. Taking fractal dimension of 2.81 as the restoration indicator, adoption of corresponding measures to make fractal dimension less than 2.81, would an effective way to restore the degradation grassland.

Abstract: A 2-year field experiment with a yellow-clay paddy soil in Zhejiang Province was conducted to study the effects of different planting measures combined with different fertilization practices on rice yield, soil nutrients, microbial biomass C and N and activities of urease, phosphatase, sucrase and hydrogen peroxidase at the maturity stage. Results showed that mechanical transplanting of rice with controlled release bulk blending (BB) fertilizer (BBMT) could achieve a significantly higher mean yield than traditional manual transplanting with traditional fertilizer (TFTM) and direct seeding with controlled release BB fertilizer (BBDS) by 16.3% and 27.0%, respectively. The yield by BBMT was similar to that by traditional manual transplanting with controlled release BB fertilizer (BBTM). Compared with TFTM, BBMT increased the contents of soil total-N, available N, available P and microbial biomass C, and the activities of urease, sucrase and hydrogen peroxidase by 21.5%, 13.6%, 41.2%, 27.1%, 50.0%, 22.5% and 46.2%, respectively. Therefore, BBMT, a simple high-efficiency rice cultivation method with use of a light-weighted mechanical transplanter, should be widely promoted and adopted.

Size fractions of soil aggregates in Lake Tai region were collected by the low-energy ultrasonic dispersion and the freeze-desiccation methods. The dissolution of aluminum and changes of pH in soil solution during sorption of Cu2+ and changes of the dissolution of aluminum at different pH in the solution of Cu2+ by aggregates were studied by the equilibrium sorption method. The results showed that in the process of Cu2+ sorption by aggregates, the aluminum was dissoluted and the pH decreased. The elution amount of aluminum and the decrease of pH changed with the sorption of Cu2+, both increasing with the increase of Cu2+ sorption. Under the same conditions, the dissolution of aluminum and the decrease of pH were in the order of coarse silt fraction > silt fraction > sand fraction > clay fraction, which was negatively correlated with the amount of iron oxide, aluminum and organic matter. It suggested that iron oxide, aluminum and organic matters had inhibitory and buffering effect on the aluminum dissolution and the decrease of pH during the sorption of Cu2+.

Transport behaviors of nano-CeO2, nano-TiO2 and nano-Al2O3 materials in various soils were investigated by column leaching experiment. The relationship between transportability of nanomaterials and soil properties was analyzed and potential transport distances of nanomaterials in soils were estimated by applying the colloid migration dynamic model. The result shows that both nano-CeO2 and nano-TiO2 have strong mobility in most of tested soils. While nano-Al2O3 is almost completely retained in most of tested soils except acidic soil, in which nano-Al2O3 shows relatively strong transportability. The transport mechanisms of nanomaterials in soils are very complicated. Among electrostatic interaction, soil surface charge heterogeneities, aggregation, straining and ripening, each of them plays an important role in the transport of nanomaterials. The transportability of nano-CeO2 is negatively correlated with soil Zeta potential, while that of nano-TiO2 is negatively correlated with soil clay content, and positively correlated with soil permeability coefficients. The transportability of nano-Al2O3 is negatively correlated with soil pH, and positively correlated with soil permeability coefficients. The estimated maximum transport distances of nano-CeO2, nano-TiO2 and nano-Al2O3 materials in soils were 526,9043 cm, 31-332 cm and <10-5,722 cm, respectively. The estimated potential transport distances of nanomaterials in some soils are far more than the surface soil depth of 30 cm, indicating severe risks to deeper soil layers would potentially occur in these soils.

In-situ biological stabilization solidification (SS) technology is an effective ground water risk control method for chromium contaminated sites. Through on-site engineering test, this paper has preliminarily validated the remediation effect of in-situ SS method on a southern chromium contaminated site. The engineering test site has an area of approximately 600 m2, and is located at the upstream of the contaminated area. Due to the severe contamination of chromium, the total chromium concentration reached up to 11,850 mg x kg(-1), while the hexavalent chromium concentration reached up to 349 mg x kg(-1), and the most severely contaminated soil had a depth of -0.5 - -2 m. Variations in hexavalent chromium and total chromium concentration in groundwater were observed through the injection of reducing agents and microbial regulators into the injection wells in the test site, and through the monitoring analysis at different time and different depth under the action of the injection agents. Results of the engineering test showed that the on-site SS technology significantly changed the chromium speciation in soil and then reduced the migration of chromium, thus the groundwater risk was reduced. The injected agents had a good effect of hexavalent chromium remediation in groundwater within the effective range of the injection wells, and the SS rate of hexavalent chromium into trivalent chromium reached 94%-99.9%, the SS rate of total chromium fixation reached 83.9%-99.8%. The test results are of significant reference value for the remediation of contaminated sites with features of shallow groundwater depth and soil mainly consisting of silty clay and sandy clay.

By the methods of space-time substitution and PVC tube closed-top in situ incubation, this paper studied the soil mineralized-N content, N mineralization rate, and N uptake rate in Phyllostachys edulis-broadleaf mixed forest (PBMF) formed by P. edulis expansion and its adjacent evergreen broadleaf forest (EBF) in Dagangshan Mountain of Jiangxi Province, China. There existed the same spatiotemporal variation trend of soil total mineralized-N (TMN) content between the two forests. The annual average N mineralization rate was slightly lower in PBMF than in EBF. In PBMF, soil N mineralization was dominated by ammonification; while in EBF, soil ammonification and nitrification were well-matched in rate, and soil nitrification was dominated in growth season (from April to October). The N uptake by the plants in PBMF and EBF in a year was mainly in the form of NH4+-N, but that in EBF in growth season was mainly in the form of NO3- -N. These findings indicated that the expansion of P. edulis into EBF could promote the ammonification of soil N, weakened soil nitrification and total N mineralization, and also, increased the NH4+-N uptake but decreased the NO3- -N and TMN uptake by the plants.