Applied Mechanics and Materials Vol. 700

Abstract: Soil particle size distribution (PSD) is one of the most important physical properties of soil due to its strong influence on hydraulic characteristic, fertility condition and erosion of soil, etc. Sewage irrigation causes the differences in soil PSD. Thus, there may be massive organic contaminants and suspended particles in soil. In this paper, the frequency and multifractal necessity of soil PSD under sewage irrigation in different years were analyzed. Soil PSD demonstrates a heterogeneous characteristic under sewage irrigation, and this heterogeneity can be characterized using the multifractal technique, which calculates the multifractal spectrum parameters. The results showed that the width of multifractal spectrum ∆α is directly proportional to clay content; a remarkable effect of sewage irrigation on multifractal parameters was observed. The soil structure quality decreased with increasing sewage irrigation years. However, the soil structure improved when the soil was irrigated with freshwater for a long period after sewage irrigation. Therefore, multifractal parameters may be potential indicators for the physical property and quality of soil.

Abstract: The zero-valent iron (ZVI) particles were synthesized by the aqueous phase reduction, and the tapping mode image of atomic force microscope (AFM) showed that the diameter of the ZVI particles was in the range of 90 nm - 400 nm. By comparison of the debromination of BDE-47 by sunlight, ZVI, ZVI impregnated activated carbon (ZVI/AC) and ZVI impregnated ion exchange resin (ZVI/IER), the debromination effect was found to descend in the following order: ZVI/IER > ZVI/AC > ZVI > sunlight. Second order and first order kinetic models were used for the fitting of the debromination data of BDE-47. Results show that the debromination data of BDE-47 by the sunlight, ZVI, ZVI/AC and ZVI/IER in the current study are generally best described by the pseudo first order equation. Meanwhile, the debromination data of BDE-47 by the ZVI and ZVI/IER can also be described by the pseudo second order equation.

Abstract: Composite magnetic microspheres of chitosan (CTS) and quaternary ammonium chitosan derivative (HTCC) were prepared by inverse suspension method. Tripolyphosphate (TPP) and glutaraldehyde were used successively to co-crosslink the microsphere matrix. The morphology was analyzed using optical microscopy and scanning electron microscopy (SEM), while the chemical composition was characterized using Fourier transform infrared spectroscopy (FTIR). The adsorption of humic acid (HA) by the composite magnetic microspheres (CHMMs) was investigated in terms of adsorption capacity and kinetics in order to optimize preparation conditions. Both CTS/HTCC mass ratio and crosslinker dosage greatly affected the properties of the microspheres. A batch of CHMMs was prepared when the mass ratio of CTS and HTCC was 1:1 and TPP and glutaraldehyde were17% and 30% of total mass of CTS and HTCC, respectively. These CHMMs were between 150 and 800 μm. 85% HA was able to be removed in 60 min using this proposed absorbent. It was fast and efficient for HA removal from aqueous solution.

Abstract: NOx damages to the environment. It also endangers human body health. It has become a major air pollutant. Only the nitric oxide emissions could be reduced by the improvement of combustion. The economical and reasonable technical measures, which is through selecting rational parameters and combustion process, could decrease the formation of NOx in fuel combustion phase. According to the national bureau of statistics data released, the national NOx emissions will reach 29.14 million ~ 42.96 million t in 2030,what is more ,China will surpass the United States to be the world's largest NOx emissions country. Environmental pollution has become one of the main factors restricting the development of economy in China [1].

Abstract: Dissolution behavior of ²³⁸U from low-level contaminated soil was investigated by Acidithiobacillus ferrooxidans (A. ferrooxidans) . It was found that the removal rate of ²³⁸U by A. ferrooxidans was much higher than that of deionized water. The A. ferrooxidans can promote the dissolution of ²³⁸U and the removal rate can achieve 94.50 %. Furthermore, the turnover rate of soil nutrients of A. ferrooxidans treated sample was much lower than that of dissolution by deionized water, and the soil fertility was maintained. This work illustrated the efficacy of leaching of uranium by the involvement of bacteria by indirect mechanism.

Abstract: This study was performed to determine the feasibility of enhancing removal of zinc ions from aqueous solutions using an iron-carbon internal micro-electrolysis (ICIME) followed by iron hydroxide self-flocculation (IHSF) process. Results shown that the Zn²⁺ removal using ICIME was improved by IHSF significantly. The pH=3, mass ratio of Fe/AC=2: 1, hydraulic reaction time=30min of ICIME and pH=9, both aeration time and static placing time were 60min of IHSF were proposed as the optimum conditions. Under these conditions, the removal efficiency and residual concentration of Zn²⁺ from lead and zinc smelting wastewater were reached 99.10%, 1.32mg/L. Meanwhile, other metal ions and the F^- also were removed effectively. Lead and zinc smelting wastewater could meet the discharging standard (integrated wastewater discharge standard (GB8978-1996)) of China. The Zn²⁺ removal was significantly influenced by other metal ions existing in aqueous solutions. Contrast and breakthrough time experiment indicated the Compare with single Fe and ICIME, ICIME followed by IHSF have a higher efficiency and bearing capacity for Zn²⁺ removal. ICIME removal of Zn²⁺ enhanced by IHSF is a feasible method.

Abstract: Soil enzyme activity is closely related to ecosystem course and function.Tendency and intensity of different biochemical course carried on in the soil was reflected by enzyme activity. This paper deals with the soil enzyme activity, content of organic matter, N,P 'and the relation of the enzyme activity with soil organic matter, N,P in soil of Liangzi Lake wetland by soil samples analyzed. The results shows that in the wetland soil,the urease activity is 0.397-0.652 mg/g ;the phosphatase activity is phenol6.52-11.53 mg/g; The activity of Cellulase in the soil is 0.397 - 0.652 mg/g. The change trend of Cellulase and phosphatase activity throughout the year is summer > autumn > winter > spring. The change trend of urinary enzyme throughout the year is summer > spring > autumn > winter. There is notably positive correlation between the urease activity and soil available nitrogen. There is notably positive corelation between the phosphatase activity and soil available P in the paddy field.There is notably positive correlation between the Cellulase activity and soil organic matter.

Abstract: Everyday there are about 7 million passengers commuting by subway in Shanghai, China. Although Shanghai has one of the largest subway networks in the world, yet this subway system is still full of passengers during the rush hours. Extracting air and smoke is important part of the station ventilation system which supplies enough fresh air in the crowded station. As we know, the underground subway stations are built in an enclosed space where needs air circulation far more than other type of station. This paper focuses on the designs of duct layout and valve control in an underground subway station. The authors give three solutions to return air and exhaust smoke in the underground station platform area and entrance area. The goal of this paper is to compare these three ventilation solutions in the normal time and in the fire accident. The result of analyzing and applying these solutions are concluded in the paper.

Abstract: The paper presents a novel method for the separation/enrichment of trace Zn²⁺ using NH₄SCN –dodecyl dimethyl benzyl ammonium bromide (DDBAB)-water system.The effects of different parameters on the enrichment yield of Zn²⁺ have been investigated. The possible enrichment mechanism of Zn²⁺ was discussed.The results show that under the optimum conditions, Zn (SCN)₄^2- produced by Zn²⁺ and SCN^- reacts with DDBAB cation (DDBAB ⁺) to form the water-insoluble ternary association complex of [Zn (SCN)₄](DDBAB)₂, so Zn²⁺ was enriched quantitatively.While Al³⁺,Mn²⁺,Ni²⁺ and Pb²⁺ could not be enriched. Thereby, the quantitative separation of Zn²⁺ from the above metal ions could be achieved.A new method for the separation/enrichment of trace zinc was established. The proposed method has been successfully applied to the separation/enrichment of trace Zn²⁺ in the samles of synthetic water, and the enrichment yield is 96.4%-99.5%.

Abstract: The mechanism of resistance enhanced by composite endomycorrhizal and ectomycorrhizal fertilizers under stresses had been studied. The results showed that under water stress, the seedling height, ground diameter, aboveground and underground dry weight, relative water content, WUEof WS+F treatment group were higher than that of WS+NF treatment group, to which were respectively higher 55.09%, 59.22%, 29.98%, 75%, 26.49%、142.86%. The RWD, Pro and MDA content of the inoculation of composite mycorrhizal fungi treatment under the stresses were all significantly decreased. In the aspect of antioxidant enzymes activity, SOD, CAT and POD activity of WS+F treatment group increased than that of WS+NF treatment group to 13.45%、59.88%、45.58%. Because of the series responses of Chinese fir seedling inoculated with the composite mycorrhizal fungi, which were benefit for promoting growth, improving water use efficiency, improving the physicochemical character of soil, etc, the resistance of plant had been improved to stress.