Advanced Materials Research Vols. 356-360

Abstract: The hydraulic characteristics of constructed wetland are vital to its performance for pollutant removal. Hydraulic characteristics of a pilot scale vertical flow constructed wetland were studied by tracer experiments with the method of moments (MoM) analyzing. From the residence-time distribution (RTD) of tracer during the experiment, the mean detention time, average water velocity and dispersion coefficients were obtained for the constructed wetland. The results showed that the mean residence time was approximately 15% shorter than nominal residence time indicating 85% of total available pore volume was active in pollutant removal processes. The two peaks observed on the RTD curves suggested short-circuiting flows or dead zones exist in the constructed wetland. The relatively large Peclet number of 11.8 suggested that dispersive processes dominated in the tracer movement. Comparison of tracer profiles at different sampling locations indicated that large amount of tracer transported through the upper portion of the constructed wetland.

Abstract: Building engineering in China is divided into civil building and industry building. Civil building engineering includes residential building and public building. There are many types of public building: shopping malls, office buildings, hotels and so on. In this thesis, architecture test and investigation are processed for the large public building such as hotel type, which focus on its characteristic features of energy consumption. Then energy conservation schemes are propounded and applied in real buildings.

Abstract: Reaumuria songarica (Pall.) Maxim and Nitraria tangutorum Bobr. are two species growing on nebkhas in dune system. But N. tangutorum distributes more widely than R. songarica does. Sand burial and drought are two major disturbing factors in the field. Experiments were conducted under controlled conditions to investigate sand burial depth and simulated precipitation amount on seed germination, seedling emergence and seedling mass of the two shrubs to explain the dominance of N. tangutorum over R. songarica. Seeds were buried at 6 depths (0, 0.5, 1.5, 3, 5, 8 cm) and irrigated with 3 water regimes (5, 7, 10 mm) in plastic pots (8 cm in diameter and 11 cm in height) under the same light intensity and alternating temperature in an environment controlled growth chamber. R. songarica has a greater germination percentage than N. tangutorum under each burial depth with any water regime. R songarica seed germination increased with burial depth at each water regime and when depth is deeper than 1.5 cm all the seeds germinated under 7 and 10 mm water treatment. N. tangutorum seed germination increased until an optimal burial depth and then decreased. The optimal burial depth shifts with water regime. Seedling emergence of R songarica did not occur at depth deeper than 1.5 cm under any water regime. N. tangutorum seedling emergence maximized at 3, 1.5 and 0.5 cm with 5, 7 and 10 mm water supply regime respectively. Under all the treatments, N. tangutorum seedlings had larger dry mass than R. songarica seedlings. Higher N. tangutorum seedling emergence percentage and seedling mass with given water supply enhance its possibility to appear on nebkhas in the study area.

Abstract: Soil and water loss from sloped farmland is a mainly environmental and agricultural issue worldwide. Many management practices have been selected and are effective to reduce sediment and associated nutrient losses. Fallout ²¹⁰Pb_ex tracer technique was used to quantity the soil erosion in terrace cultivation and contour farming field. The soil erosion rate from up-and-down slope field was estimated by RUSLE2 model. The sediment yields from contouring and terraces were reduced 63% and 95%, respectively, by comparison with up-and-down tillage. Terraces could reduce soil erosion 74% and intercept runoff 45% than contouring tillage. However, the concentrations of nitrogen and phosphorus with runoff from terraces were greater than those from contouring field. Transport loads of TP, DTP, and phosphate (PO₄^3- -P) through water from terraces increased 4.54, 1.34, and 2.53 times than those from contouring tillage, respectively. It is concluded that no single mitigation option can reduce all pollutants. Terrace can achieve pollutants reduction target in tandem with other soil and water conservations.

Abstract: The Beijing-Tianjin sandstorm source control project started formal implementation in 2001, This paper construct a set of ecological benefit evaluation system about the Beijing-Tianjin sandstorm source control engineering of Beijing, using the monitoring data of Beizhuang monitoring stations of Miyun country of Beijin, Choosing analytic hierarchy process(AHP) to evaluate the ecological environment of Beijing, The result shows that Beijing ecological environment is becoming better year after year and the Beijing-Tianjin sandstorm source control project effect is remarkable.

Abstract: Cultivation in the tropical mountainous regions by using hedgerow systems as erosion control measures is recommended due to its effectiveness in reducing soil erosion and in supplying N. However, competition for nutrients and water between crops and hedges reduces crop performance and yield response. ¹³C stable isotope signature in combination with data on N and water availability and uptake in soil and plants framework was used to assess whether N or water function as a main driving force for spatial variability of crop yield along the alleys. The leaf δ¹³C values of maize were significantly (p<0.05) less depleted close to the hedges, suggesting that water stress was not the main driving force for spatial variability along the alleys. In the opposite, significant (p<0.05) N concentration depleted in maize leaf of plot with L. Leucocephala hedges, in particular at the row closed to hedgerow, in combination with significant (p<0.05) increase in δ¹³C values of leaf of the corresponding plot indicating the influence of N stress on poor maize performance and yield decrease. In addition, the significant (p<0.05) negative correlation between leaf δ¹³C values of maize, leaf N concentration and yield confirmed that N plays as a major role in crop decline towards hedgerows. Therefore, increasing amount of N fertilization to cropped area close to the hedgerows should be recommended for farmers, in order to encourage the acceptance of hedges system in tropical mountainous regions.

Abstract: Facing up to problem that the extant freezer is not convenient to disassemble and transport, we design a demountable freezer which is based on the concept “modularization”. The volume and shape of newly-designed freezer is modulated by the addition and remove of the modules. Demountable freezer could be widely utilized in daily life, military field and emergency aid e.t.c. Its demountability is dramatically beneficial to the user’s need, not only because it can be assembled when it is needed, but because it could save more space for people when it is set aside. The convenience, its economic and social effect and its optional structure because of the current high-tech of demountable freezer is unmatched by the traditional freezer.

Abstract: This paper did simulated erosion experiment indoors to study influence of precipitation intensity, grass density, slope gradient, protection type on erosion modulus of pebbly clay slope in airport. The results show that anti-erosion of slope is better and influence of slope on erosion modulus is smaller as grass density is higher. Compared with protecting slope only with grass, erosion modulus decreases about 60%~80% when slope is protected with geosynthetics. Geocell is slightly better than the geogrid.

Abstract: In the paper, the total contents of Pb, Zn, Cd, Cu, Cr in sediment samples which were systematically collected from Yin-dong Liang lead-zinc mine area located at Feng country in Shaanxi province were determined by air-acetylene flame atomic spectrophotometer and the morphology of heavy metal in sediment was further investigated. Based on system testing, pollution load index was applied to assess the pollution situation of sediment. The results show that the pollution load index of mine area was up to 14.22, indicating the pollution situation is severe. Moreover, the most heavy metals are in residual state in comparison with the less water soluble, leading to relative low bioavailability and ecological risk. However, the higher proportion of reducible and oxidizable could be released to the environment under appropriate conditions, resulting in severe potential ecological risk.

Abstract: In order to improve the rate of degradation of cellulose in corn straw, the study has an important significance that compost corn straw with inoculating high-efficient microbe agents. The experiment inoculated a cellulose-degrading strain F2 which was screened from compost into compost pretreatment, the VS of corn straw reduced from 93.14% to 71.69% after 15 days, the content of cellulose reduced from 34.12g·kg-1 to 25.66g·kg-1, the rate of degradation was 24.79% which was 10.60% higher than those without the strain. An anaerobic fermentation experiment was carried out with the two groups of composted corn straw and mixed pig feces with a certain ratio, and investigations of biogas production, pH, content of volatile fatty acids(VFA) and rate of methane production were conducted. The results were that the corn straw composted with the cellulose-degrading strain peaked 4 days earlier, the maximal daily biogas production was 1470mL, the cumulative biogas production reached 23641mL which was 16.87% higher and operated stably earlier. The study showed that the cellulose-degrading strain had a strong capacity to degrade cellulose in corn straw, and then improved the performance of anaerobic digestion.