Applied Mechanics and Materials Vols. 316-317

Abstract: Headspace solid phase microextraction combined with gas chromatography (HS-SPME–GC) method has been studied for determination of 7 polychlorinated biphenyls (PCBs) in seawater samples. To perform the HS-SPME polydimethylsiloxane (PDMS) (7, 30 and 100 µm film thickness) fibers were compared on the basis of their absorption capacities for the selected compounds, and PDMS 100 µm film thickness was selected. The influence of various parameters on PCBs extraction efficiency by HS-SPME was studied using GC-electron capture detector (ECD) compared with solid phase. The performance of proposed HS-SPME–GC methodology with respect to linearity, reproducibility and limit of detection (LOD) was evaluated by water spiked with target compounds. The linear range of most compounds was found to be between 0.1 and 100 µgL−1 and the limits of detection were between 15.2 and 63.8 ngL−1. The reproducibility of the method (n = 6), expressed as relative standard deviation (RSD), was between 4 and 10%. Finally, developed procedure was applied to determine selected PCBs in seawater samples.

Abstract: Ultrasonic-assisted supported Fe/γ-Al2O3, fluoride; γ-Al2O3; adsorption Abstract: γ-Al2O3 adsorbent modified with iron (Fe/γ-Al2O3) was prepared by impregnation and ultrasonic wave-assisted oxidation. The optimum pH range for fluoride adsorption was 3.0–9.0, which is preferable for actual application. The maximum adsorption capacity of the Fe/γ-Al2O3 adsorbent was 2.51 mg g-1 and about 2 times of the plain γ-Al2O3 (γ-Al2O3). A column experiment was performed at an initial fluoride concentration of 30 mg l-1, space velocity of 1.7 h-1 and pH of 5.9, and the breakthrough time of the Fe/γ-Al2O3 was more than 210 min with the effluent fluoride under 10 mg l-l and was about 5 times of the plain one. The samples were measured by X-ray diffraction (XRD) patterns and scanning electron microscope (SEM) images.

Abstract: Magnetic chitosan/yeast(MCY) composites were prepared and applied to adsorb Ce(III) ions from aqueous solutions. The effects of pH, contact time and initial concentration were examined, and the hematite leakage was also studied. The optimum pH was 5.5. MCY composites had magnetic stability (especially over pH range of 4.5~7.0). The kinetic data were investigated by pseudo-first-order and pseudo-second-order models. The kinetic data were better fitted to the pseudo-second-order model. Experimental data were fitted with the Langmuir and Freundlich models to analyze the equilibrium isotherms. The Freundlich model was better to describe the experimental data. The maximum adsorption capacity calculated by Langmuir isotherm was 73.53 mg/g.

Abstract: The 30 years’ annual variations of major nutrients dissolved inorganic nitrogen(DIN) and dissolved inorganic phosphorus(DIP) in Xiangshan Bay East China Sea between 1982 and 2011 were reported. The results showed that the concentrations of nitrogen and phosphorus nutrients increased year by year, consistent with the trend of nitrogen and phosphorus consumption in our country. Inorganic nitrogen was the main pollutant, then was inorganic phosphorus in Xiangshan harbor. The annual average change of DIN ranged from 0.21 to 0.76 mg∙dm^-3 while DIP ranged from 0.018 to 0.054 mg∙dm^-3. And the change trend of DIN and DIP was as following: winter > autumn > summer > spring. The DIN and DIP in Xiangshan horbor exceeded the standard limits greatly, the water quality in culture areas exceeded national criteria for sea water Level IV and most water qualities were inferior Level IV.

Abstract: System science and debris flow prediction theory are adopted to analyze external environmental conditions of the system which influence the occurrence of flush flood and debris flow in the area. The external environmental conditions are introduced as model indexes and a set of prediction models is then established. By checking the model with oneself validation and cross validation, the accuracy for judging is 93.75%, which meets the requirement of Bayes discriminatory analysis that the accuracy of judged model should be more than 80%. Two validation results are consistent with each other and the model is stable.

Abstract: Salt deposition from supercritical water has been identified as a key issue in the development of supercritical water technologies. In order to better understand salt deposition behavior, the salt particle – supercritical water flow in a 90° bend pipe with smooth walls was simulated using discrete element method (DEM) coupled with computational fluid dynamics (CFD). The transport behavior of pure supercritical water flow and salt particle-supercritical water flow with diiferent particle sizes were both simulated. The numerical results indicates that for the pure supercritical water flow, the primary flow accelerated near the inner wall and a secondary flow moving from the outer to the inner wall of the bend. The salt particle accumulation in the inner wall of horizontal pipe is the most notable feature in the salt - supercritical water flow.

Abstract: Reclaimed water contains lots of contaminants such as nitrogen and phosphorus, which may cause eutrophication of reclaimed water reused as river-lake water. Growing aquatic plants and application of compound microbiological preparations is expected to become a feasible method for purifying reclaimed water in situ. Based on this, a comparison test was taken to studying the water purification ability of reclaimed water by emergent plants, floating plants and compound microbiological preparations with a method of simulation of artificial wetlands. The results show that, Emergent plants in the purifying effect of the nitrogen are better than floating plants, and it also can effectively reduce the pH value of water. The suitable varieties on the purification of recycled water by aquatic plant were chosen, which were emergent plant cattail and floating plant water hyacinth. The purifying effect of nitrite bacteria preparation is the best of all, which is able to increase the number and types of microorganisms in water, and when the applied concentration is 8 ~16g/m3, the purifying effect is the best one. But the pH is generally above 9.5 in water using compound microbiological preparations, which may cause the increase of the alkalinity of water. Therefore, it is advised to prudently use compound microbiological preparations.

Abstract: An approach for establishment of soil environmental assessment model to evaluate the environmental quality level for soil environmental quality is proposed, in which the GIS and self-organizing map (SOM) techniques are integrated through investigation of soil environmental quality. In this model, self-organizing maps (SOM) and spatial interpolation were applied to cluster a concentration data set of pollutants of soil environmental quality and mapping anomaly region. An application of heavy metal concentrations in soils were surveyed to indicate the status of heavy metal contents and assess environmental quality of soils basing on spatial extraction model. The concentration of 9 metals (Cu, Pb, Zn, Cd, Ni, Cr, Hg, As and Mn) in topsoil were investigated based on samples. The samples were clustered into 3 classes by SOM. According to the concentration level of the samples, the different environmental quality levels were discriminated. The results indicate that SOM as the spatial extraction model was effective to assess the soil environmental quality.

Abstract: The navigation system of the AUV usually takes SINS as the core, and is supplemented by GPS and DVL. While the output speed of the DVL is relative to the water, and the relative speed is taken as the observed quantity to assist SINS, the navigation accuracy will be declined. In order to solve the problem, SINS/GPS/DVL integrated navigation method is proposed to estimate the ocean current model. In this method, the Kalman filter is used to estimate the ocean current based on the ocean current model, and then the speed relative to the seabed is gained and taken as the measurements for assisting the SINS. Simulation results show that the proposed method can estimate accurately the ocean current speed.

Abstract: Slope biotechnique has become a significant method to protect slopes. Vetiveria zizanioides has many biological characteristics, such as resistance to overhead flooding injury; withstand drought, pain resistance and tachyauxesis. The root system has high tensile strength, well adaptability and other features. Through the joint effects of root system and micro-ecological environment, the slope can be well reinforced and protected. This paper studies the basic properties of vetiveria zizanioides and the principle of water and soil maintenance. The tensile strength of single root and the force mechanism of eco-reinforced slope are analyzed. Research shows that vetiveria zizanioides also has many excellent engineering parameters, such as tensile strength and shear strength. With the large and deep pierced root system, the soil mass is effectively fixed, which limits the shift of shallow soil of slopes. Vetiveria zizanioides is easy to grow. Meanwhile, it can control soil erosion effectively and maintain the stability of the highway slope. Therefore, this plant has a greater value in the field of highway slope protection.