Effects of sheet flow rate and slope gradient on sediment load

Sheet erosion is known as one of the most important forms of erosion, particularly in agricultural land. The purpose of this study was to investigate the effect of flow rate and slope gradient on runoff and sediment discharges in two different soils. Experiments were conducted using a tilting flume facility with the test area of 0.2?×?1.0 m. Overall, 24 experiments on two soils (clay loam and sandy clay loam textures) including six flow rates (75, 100, 125, 150, 175, and 200 ml/s) and two slope gradients (1.5 and 2 %) were performed. The selected flow rates and flume slopes were generated to simulate sheet erosion. The results showed that for both soils and slopes, unit flow discharge (q) and sediment concentration increased with increasing flow rate; however, the effect of slope gradient on flow discharge depends on soil type. In addition, sandy clay loam exhibited higher values of q and sediment concentration and consequently, it showed greater amounts of sediment load. At the start of event, sediment concentration was high but it decreased to approach a steady state. In addition, the time needed to reach a steady state condition was shorter for sandy clay loam than that for clay loam soil and in lower flow rates than higher flow rates. For each soil and slope, there was a direct relationship between sediment load and flow rate. The result implied that the effect of slope gradient on sediment load was almost greater in sandy clay loam soil than clay loam soil. Moreover, the differences between sediment loads of two soils are enlarged at slope 2 %.     

Evaluating the production and bio-stimulating effect of 5-methyl 1, hydroxy phenazine on microbial fuel cell performance

The role of endogenous redox mediators has considerable importance in electron shuttling reactions and associated performance of microbial fuel cell. Single-chamber microbial fuel cell-II with dual air-cathode assembly (area = 18.84 cm²) supported highest bacterial (Pseudomonas aeruginosa) density (6.7 × 10⁹) and active biomass [4.4 ± 0.3 mg cm^?2 (carbon content = 0.48 ± 0.1 mg cm^?2)] on anode thereby resulting in maximum production of redox metabolite, 5-methyl 1, hydroxy phenazine (301 ppm) and voltage (595 ± 5 mV) than similar cells with relatively less surface area of cathode. It was further revealed that 5-methyl 1, hydroxy phenazine production was positively correlated with chemical oxygen demand removal rate (77 ± 2.5%) and power generation (66.6 ± 2.2 mW cm^?2) efficiency of single-chamber microbial fuel cell-II. Maximum power density of 258 ± 4.5 mW cm^?2 was generated when reactor was supplemented with 2 ml crude extract of 5-methyl 1, hydroxy phenazine metabolite, whereas power output was about 229 ± 2.5 mW cm^?2 when reactor was bio-stimulated with 1 ml pure extract of 5-methyl 1, hydroxy phenazine. With this concentration, the electrochemical response of mixed culture biofilm (sediment) was enhanced by 99.3%. However, further increase in concentration of endogenous mediator proved to be limiting on reactor performance. Pyrosequencing and phylogenetic analysis on the basis of partial 16S rRNA sequences demonstrated both culturable and unculturable bacterial species in anodic biofilm and relative abundance of family Pseudomonadaceae was found to be maximum, i.e., 61.7% followed by Rhodocyclaceae 19.2%, Xanthomonadaceae 6.3% and Opitutaceae 3.18%.     

Natural aggregates in the performance and durability of concrete: chemical characteristics

This article continues from the earlier feature in Geology Today (2011, v.27, n.4) and looks at the influence of chemical reactivity within concrete due to the presence of unsound aggregates or deleterious material incorporated in the aggregate used in the concrete mix. Some of the more disruptive problems from chemical unsoundness come from the presence of chlorides, which cause rusting in reinforced concrete or, sulphate attack from ground waters. Both of these reactions are relatively common in Britain. Alkali–silica reactions with aggregates and cement is not too prevalent in Britain but can be very prevalent and disruptive elsewhere in the world.     

Triethylamine removal using biotrickling filter (BTF): effect of height and recirculation liquid rate on BTFs performance

This study investigated the removal of triethylamine using a biotrickling filter. The influence of affecting parameters, such as height and recirculation liquid rate (V _L) on contaminant removal efficiency, was examined in detail. The results demonstrated that in the constant empty bed residence time (EBRT), when V _L was increased, the removal efficiency (RE) increased. Also, for a specific V _L, increasing EBRT could also increase RE values. However, it seems that an increasing V _L is a more cost-effective way to enhance RE as compared to an increasing EBRT. The obtained outcomes represented that for a constant EBRT, an increase in inlet loading (IL) could decrease RE. For lower ILs, the removal of the contaminant could be carried out faster in height. The first part of the bed contributed the most to contaminant removal, and for the lower ILs, the contribution was even further. For the first section of bed in a constant IL, increasing EBRT could increase RE. In a constant IL and EBRT, increasing V _L could increase RE, as well as the removed mass loading by at least 20–25 g/m³/h. Also, the effect of the V _L increase on removal amount in the second and third sections of the bed was negligible.     

应变率与含水率对冻土单轴压缩特性影响研究

通过对泥浆制样法制备的冻结粉质砂土的单轴压缩试验,系统地研究了冻结砂土在一个宽泛应变率以及含水率范围内的单轴压缩破坏应变特性和线弹模量特性。结果表明：随着应变率的增加,当含水率为12.0%,破坏应变逐渐增大;当含水率在16.7%～24.0%范围内时,破坏应变先增大后减小;当含水率大于等于30.6%时,破坏应变逐渐减小,3种情况下破坏应变最终都逐渐趋于稳定。破坏应变随含水率增加而先急剧增大到一个最大值,然后急剧减小,当含水率超过41.5%时,基本趋于冰的破坏应变。线弹模量先随着应变率的增大而非线性增大到一个最大值,然后应变率的继续增大使线弹模量逐渐减小,线弹模量与应变率的关系满足二次抛物函数规律。在温度为 2.0 ℃,应变率小于4.67×10-3 s-1的条件下,线弹模量随着含水率的增大而非线性增大,直至最后趋于冰的线弹模量;而在大于等于该应变率的条件下,随着含水率的增大,线弹模量先增大到一个最大值,然后减小趋于冰的线弹模量。当温度为 5.0 ℃时,类似的应变率临界值为1.00×10-2 s-1。     

Risk assessment of bottom ash from fuel oil power plant of Italy: mineralogical,chemical and leaching characterization

The main aim of the present study is to contribute to the field of environmental research by providing new data on bottom ash samples derived from an oil power plant located in Southern Italy. To achieve this purpose, the mineralogical and chemical properties of representative bottom ash samples were investigated through the integrated employment of different analytical techniques, i.e., X-ray powder diffraction, scanning electron microscopy, X-ray fluorescence and atomic absorption spectrometry. The obtained experimental results show that quartz, alunogen, rhomboclase and potassium hydrogen silicate are the major crystalline phases of all the analyzed samples. Furthermore, the revealed main ash constituents are SiO₂ and SO₃, with low contents of Fe₂O₃ and Al₂O₃, and little amounts of CaO, Na₂O, K₂O, MgO, P₂O₅ and TiO₂. Among the trace elements, very high amounts of heavy metals, i.e., V, Cr, Ni, La, Pb and Mo, were detected. The comparison of the obtained heavy metal abundance data with those reported in the literature highlights significant differences. Leaching test evidenced V, Ni and Cr values that make these ashes a potential contamination source for groundwater quality and for soil, nearby the ash disposal landfills area. All the obtained findings show that these materials are highly harmful for the human health, with a greater extent for the heavy metal concentrations.     

Effects of plants development and pollutant loading on performance of vertical subsurface flow constructed wetlands

The influent concentration has a great effect on nutrients removal efficiency in vertical subsurface flow constructed wetland systems, but treatment performance response to different C: N: P ratios in the influent are unclear at present. At the first growing seasons, the effects of the plants present or not, season, the different C: N: P ratio in influent condition and their interaction on treatment performances were studied in the planted or the unplanted wetlands in greenhouse condition. Each set of units was operated at hydraulic loading rates of 40 L/d. Low, medium and high-strength (100, 200, 400 mg/L of chemical oxygen demand or 20, 40, 80 mg/L total nitrogen) synthetic sewage were applied as influent. According to the first growing season results, the average removal efficiencies for the unplanted and the planted wetlands were as follows: chemical oxygen demand (44–58 % and 55–61 % respectively), total nitrogen (26–49% and 31–54 %) and total phosphorus (36–64 % and 70–83 %). The both wetlands system was operated as an efficient treatment system of highest average removal rates of both chemical oxygen demand and total phosphorus when medium-strength synthetic sewage were applied. When high strength synthetic sewage was applied, the planted wetlands usually had a higher nutrients removal rates than the unplanted over the study period. The plants grew well under any high loading treatment over the study period. Anyhow, it also proved that the wetland systems have a good capacity to treat different strength wastewater in greenhouse condition.     

Effects of pH and temperature on dimerization rate of glycine: Evaluation of favorable environmental conditions for chemical evolution of life

To evaluate favorable environmental conditions for the chemical evolution of life, we studied the effects of pH and temperature on the dimerization rate of glycine (Gly: NH₂-CH₂-COOH), one of the simplest amino acids. Gly dimerizes to form glycylglycine (GlyGly), and GlyGly further reacts to form diketopiperazine (DKP). Gly solutions with pH ranging from 3.1 to 10.9 were heated for 1-14 days at 140 °C, and changes in concentrations of Gly, GlyGly, and DKP were evaluated. At pH 9.8, the experiments were conducted at 120, 140, 160, and 180 °C. The dimerization rate of Gly was nearly constant at pH 3-7 and increased with increasing pH from 7 to 9.8 and then decreased with further increases in pH. To elucidate the reason for this pH dependency, we evaluated the role of the three dissociation states of Gly (cationic state: Gly⁺, zwitterionic state: Gly^±, and anionic state: Gly⁻). For pH >6, the dominant forms are Gly^± and Gly⁻, and the molar fraction of Gly^± decreases and that of Gly⁻ increases with increasing pH. The dimerization rate was determined for each dissociation state. The reaction between Gly^± and Gly⁻ was found to be the fastest; the rate constant of the reaction between Gly^± and Gly⁻ was 10 times the size of that between Gly⁻ and Gly⁻ and 98 times that between Gly^± and Gly^±. The dimerization rate became greatest at pH 9.8 because the molar fractions of Gly^± and Gly⁻ are approximately equal at this pH. The dimerization rate increased with temperature, and an activation energy of 88 kJ mol⁻¹ was obtained. Based on these results and previous reports on the stability of amino acids under hydrothermal conditions, we determined that Gly dimerizes most efficiently under alkaline pH (∼9.8) at about 150 °C.     

Non-parallelism between the effect of microbial flocculants on sewerage disposal and the flocculation rate

1 IntroductionMicrobial flocculant (MBF) is one of the naturalmacromolecular organic compounds, which is producedby some microorganisms and has a high flocculationfunction ( Cheng Wen et al., 2003). It has beencalled“the third-generation flocculant”beca…     

悬板开孔对排沙漏斗流场特性的影响

排沙漏斗的水沙分离性能取决于其流场特性,为了弄清楚悬板开孔对流场特性的影响,利用粒子图像测速技术和数值模拟方法,分别对悬板溢流段和非溢流段同时均匀布孔、仅在非溢流段布孔和无孔时的排沙漏斗流场特性开展研究。结果表明:①布孔位置不影响涡流性质但影响其强度,均匀布孔时涡流强度最小,不利于水沙离心分离;②无孔和仅在非溢流段布孔时的流场特性有利于泥沙径向输移、沉降和排出,均匀布孔径向速度和二次流流速减小不利于泥沙输移和排出;③仅在悬板非溢流段布孔时悬板表面速度大于其他方案,泥沙不易淤积于悬板。为减少悬板上的泥沙淤积量且同时要保证较高的泥沙截除率时可采用仅在悬板非溢流段布孔的方案优化悬板体型。     

悬板开孔对排沙漏斗流场特性的影响

排沙漏斗的水沙分离性能取决于其流场特性,为了弄清楚悬板开孔对流场特性的影响,利用粒子图像测速技术和数值模拟方法,分别对悬板溢流段和非溢流段同时均匀布孔、仅在非溢流段布孔和无孔时的排沙漏斗流场特性开展研究。结果表明：①布孔位置不影响涡流性质但影响其强度,均匀布孔时涡流强度最小,不利于水沙离心分离;②无孔和仅在非溢流段布孔时的流场特性有利于泥沙径向输移、沉降和排出,均匀布孔径向速度和二次流流速减小不利于泥沙输移和排出;③仅在悬板非溢流段布孔时悬板表面速度大于其他方案,泥沙不易淤积于悬板。为减少悬板上的泥沙淤积量且同时要保证较高的泥沙截除率时可采用仅在悬板非溢流段布孔的方案优化悬板体型。     

澜沧江里底水电站坝库区泥石流物质来源及堆积特征研究

云南澜沧江上游里底水电站地处滇西北山区,地势陡峻、沟谷深切、降雨丰富,是泥石流活动相对频繁的地段。对坝库区泥石流沟的调查研究表明,泥石流物源类型丰富,有坍塌、崩塌、滑坡及人工破坏等多种成因类型,广泛分布于泥石流沟各区段,其中以坍塌型和崩塌型最为普遍。泥石流沟谷发育特征与其发育程度有关,其中“V”型沟谷多处于泥石流发育早-中期,规模不大但发生频率相对较高;“U”型谷多处于泥石流发育的中-晚期,规模较大,发生频率相对较低。此外,泥石流沟口堆积扇的形态特征在一定程度上也可以反映泥石流的活动性强弱程度;外凸型扇缘多出现在发育期泥石流沟沟口;内凹型扇缘多见于衰退期泥石流沟沟口;“S”型扇缘则多见于成熟期泥石流沟沟口。该研究为从形态特征方面对泥石流的发育程度进行宏观判断提供了素材和依据。     

Effects of transient uplift/erosion on the surface heat flow and heat generation relationship in presence of small scale asthenospheric convection

In this paper the effect of transient uplift/erosion on the relationship between surface heat flow and heat generation for truncated exponential model of radiogenic heat source distribution and basal asthenospheric convection is investigated. Asthenospheric convection is described by a parameterized model, in the form of a nonlinear heat flux boundary condition involving basal temperature and mantle internal temperature. This boundary condition has been linearized and the analytical solution of the problem is obtained by the eigenvalue-eigenfunction expansion method. The analytical solution is used to derive the nature of surface heat flow and heat generation relationship. The results show that the linear relationship is maintained during the uplift/erosion and the estimates of the slope of the linear relationship are different from the depth scale of the exponential model and increase with the rate of uplift/erosion. The estimates of the reduced heat flow also increase with the rate of uplift/erosion. These results would find applications in the interpretation of linear surface heat flow and heat generation relationship which is observed in different tectonic environment.     

The effect of opium poppy oil diesel fuel mixture on engine performance and emissions

Recently, decreasing of fossil fuel reserves and their negative effect on environment have increased the interest in alternative energy sources. One of the alternative energy sources is vegetable oils. In this study, blends of 50 % opium poppy oil — 50 % diesel fuel mixture are tested as alternative fuel on a single cylinder, 4-stroke, air cooled, pre-combustion chamber diesel engine at different speeds and its effects on engine performance and emissions are investigated. When compared to the diesel fuel as average, engine torque and power decrease at 4 % and 5.73 %, respectively. Specific fuel consumption increases by using of 50% opium poppy oil — 50 % diesel fuel mixture. When compared to the diesel fuel as average, carbon monoxide and nitrogen oxides emissions of 50 % opium poppy oil — 50 % diesel fuel mixture decrease to 15.5 % and 5.9 %, respectively. Diesel fuel-opium poppy oil mixture has been found notably successful and environment friendly as an alternative fuel for diesel engines.     

Effects of regional groundwater flow on the performance of an aquifer thermal energy storage system under continuous operation

Numerical investigations and a thermohydraulic evaluation are presented for two-well models of an aquifer thermal energy storage (ATES) system operating under a continuous flow regime. A three-dimensional numerical model for groundwater flow and heat transport is used to analyze the thermal energy storage in the aquifer. This study emphasizes the influence of regional groundwater flow on the heat transfer and storage of the system under various operation scenarios. For different parameters of the system, performances were compared in terms of the temperature of recovered water and the temperature field in the aquifer. The calculated temperature at the producing well varies within a certain range throughout the year, reflecting the seasonal (quarterly) temperature variation of the injected water. The pressure gradient across the system, which determines the direction and velocity of regional groundwater flow, has a substantial influence on the convective heat transport and performance of aquifer thermal storage. Injection/production rate and geometrical size of the aquifer used in the model also impact the predicted temperature distribution at each stage and the recovery water temperature. The hydrogeological-thermal simulation is shown to play an integral part in the prediction of performance of processes as complicated as those in ATES systems.     

Effects of seawater irrigation on soil microbial community structure and physiological function

Irrigation with diluted seawater would be an alternative water resource which can play an important role under scarce resources of freshwater for promoting agricultural production in coastal areas. Salvadora persica Linn. was irrigated with different concentrations of seawater (0, 10, 20, 40, 60, 80 and 100 % seawater), and their effect on plant growth, nutrient contents in soil and plants, shift in soil microbial community structure (phospholipid fatty acid; PLFA) and community-level physiological profiling (CLPP, Biolog ECO MicroPlate) were studied. Plant dry matter was significantly increased with all seawater treatments, and highest increase was at 20 % seawater treatment. Sodium and chloride contents were significantly increased, whereas ratios of K/Na and Ca/Na were significantly decreased in plants with seawater irrigation. Soil electrical conductivity (EC), available K and Na were significantly increased with increasing the concentration of seawater. Total PLFA concentration and PLFA profile of soils were used as indices of total microbial biomass and community composition, respectively. The concentrations of total PLFA, gram-positive, gram-negative and actinomycetes biomarker PLFAs were significantly reduced at 20, 40, 80 and 40 % concentrations of seawater, respectively. The application of different concentrations of seawater induced a clear shift in the soil microbial community structure toward the bacterial abundance. The microbial community structure and community-level physiological profiling in seawater irrigation treatments had significantly differentiated. It can be concluded that irrigation with different concentrations of seawater had significant impact on soil chemical and microbial properties which is attributed due to the salinity stress.     

黏度时变性注浆材料流动特性与应用研究

浆液的流动性对于浆液的扩散与运移具有重要的影响。通过开展黏度时变性注浆材料流动性正交试验,并选择不同可泵时间黏度时变性浆液进行流动度测试,分析了水灰比、外掺剂对浆液流动性能的影响规律,揭示了黏度时变性浆液流动度时间变化特征,从外掺剂对浆液水化硬化影响基础上,对浆液的流动变化机制性进行了探讨,并以碎裂岩体注浆为例,研究浆液流动性在注浆中的应用。研究结果表明:对于浆液的流动度的影响,随着水灰比、助剂1~#、助剂2~#、助剂3~#量的增加,浆液的流动度增加,水灰比是影响流动度的最大的因素,其次为助剂2~#、助剂3~#、助剂1~#;对于浆液黏度的影响主次关系为助剂3~#、助剂1~#、水灰比、助剂2~#;浆液流动度的变化具有缓慢期、快速期、稳定期3阶段特征,浆液临近可泵时间时,浆液流动度变化具有显著的突变性。碎裂岩体注浆应用结果表明:运用浆液的黏度时变特性进行注浆,减少了普通水泥浆待凝、复灌所带来的工时延长,缩短了注浆时间,节省注浆材料。     

水流交汇区污染物输移扩散特性

为分析水流交汇区污染物输移扩散规律,开展了交汇区污染物浓度分布规律的实验和数值模拟研究。建立了交汇区污染物扩散的水气两相流数学模型,并采用实验结果进行验证,对交汇区不同流量、动量和交汇角情况进行实验和数值模拟研究。结果表明:含高浓度污染物的支流汇入干流后,在交汇口下游支流侧形成较长的污染带,且支流与干流的交汇角和流量比(动量比)越小,污染带越狭长;在污染带范围内,污染物浓度梯度较大;污染物分布主要受随流输移和扩散的综合作用影响,其中在交汇区污染物的扩散作用明显。     

三种人工湿地脱氮除磷效果比较研究

对沸石潜流湿地、砾石潜流湿地和自由表面流人工湿地脱氮除磷性能进行了中试对比试验研究,结果表明在相同进水水质和水力停留时间为1 d的运行条件下,沸石潜流湿地脱氮效果最佳,总氮去除率接近60%;砾石潜流湿地除磷效果最佳,总磷去除率可达70%;自由表面流人工湿地脱氮除磷效果介于沸石和砾石潜流湿地之间.探讨了三种人工湿地脱氮除磷机理方面的差别,并对其进行了经济性、运行方式等方面的比较.