Bioremediation of Phenanthrene by Mycoplana sp. MVMB2 Isolated from Contaminated Soil

The effect of nutrient and surfactant addition on the biodegradation of phenanthrene was studied in a batch scale soil–slurry system using isolated Mycoplana sp. MVMB2strain. The study was conducted using an artificially phenanthrene spiked and as well as contaminated soil from petrochemical industrial site. Maximum phenanthrene degradation and subsequent high microbial growth were observed at optimum pH (pH 6) and C/N/P ratio (100:20:3). To investigate maximum substrate degradation potential of Mycoplana sp. MVMB2, very high concentrations of phenanthrene (50–200 mg/kg soil) were used. The organism was capable of degrading >60% for a concentration below 20 mg/kg soil and >40% for concentrations up to 200 mg/kg within 8 days. Further the influence of five different surfactants namely Span 80, Tween 20, Triton X‐100, cetyl trimethyl ammonium bromide, and sodium dodecyl sulfate were tested at their critical micelle concentration (CMC) levels for phenanthrene degradation in the soil. The addition of surfactant enhanced the biodegradation and a maximum of 84.49% was obtained for Triton X‐100. Complete phenanthrene degradation by Mycoplana sp. MVMB2 was observed at 3 CMC concentration of Triton X‐100. The optimized parameters obtained were used for the degradation of phenanthrene present in the contaminated soil and 98.6% biodegradation was obtained. Thus, the results obtained in the study suggested that biodegradation of phenanthrene by Mycoplana sp. MVMB2 appeared to be feasible to remediate phenanthrene rich contaminated sites.     

Coupling Interactions between Electrokinetics and Bioremediation for Pyrene Removal from Soil under Polarity Reversal Conditions

This paper investigates the hybrid technology of electrokinetics (EK) coupled with bioremediation (Bio) in the removal of pyrene (PYR) in a soil matrix. Five different treatments were conducted to investigate the coupling interactions between EK and Bio on PYR degradation. A simulated removal curve was obtained by combining the degradation curves in EK‐ and Bio‐only experiments. The results show that the simulated curve fitted well with the actual degradation curve in electro‐bioremediation (EK‐Bio) experiments for the first 30 days of the experiment, while at later stages a discrepancy was found. This discrepancy was caused by adverse effects of low soil pH (3.6) near the anode on bacteria health during EK treatments. With polarity reversal (PR) to control the soil pH, the simulated curve fitted very well (r > 0.99) with the actual degradation curve during the whole treatment period. At the end of the experiment, PYR removal amounted to 63% with EK‐Bio treatments in PR electric fields, which was 1.7 times that of Bio‐only. Moreover, the bacteria counts under electric fields were more than that without EK. The spatial distributions of PYR degradation and bacterial counts were also investigated. The results show that they were both higher nearer the electrodes under PR electric fields.     

土体剪切带的模拟与机理分析

采用修正剑桥模型,研究在平面应变条件下正常固结土剪切带的产生机理和剪切带形状的多样性。研究结果表明,剪切带是由材料的不均匀变形引起,并由试样局部应变能释放的冲击作用形成的;试样端部摩擦约束与试样内部初始缺陷都能够引起试样的不均匀变形进而诱发剪切带。分析了不同边界约束条件、初始缺陷设置方式及二者共同作用对剪切带形式的影响,平面应变条件下土体的剪切带有单一型、交叉型和多段型等3种形式,多段剪切带的发展具有先后顺序。     

Bioremediation perspective of historically contaminated sediment with polycyclic aromatic hydrocarbons

The purpose of the current study is to compare the influence of different aerobic conditions(biostimulation(BS),bioaugmentation(BA),and a combination of biostimulation and bioaugmentation(BB))on polycyclic aromatic hydrocarbons(PAH)degradation and compare the degraded amount with single step XAD-4 extraction as a new tool for bioavailability assessment for chronically contaminated sediment samples obtained from territory of Autonomous Province Vojvodina of Serbia(S1,S2,and S3).A great number of papers dealing with biodegradation of PAHs in spiked sediment or soil have been published,but to the authors’knowledge,a limited number of papers studied aged,historically polluted sediment and a sum of chosen U.S.Environmental Protection Agency(USEPA)PAHs.A significant reduction(up to67%)in PAH concentration was observed,while the percentage of reduction varied depending on the sediment sample and treatment used.BS treatment successfully stimulated growth of indigenous bacteria.Further,PAH-degrading strain Sphingomonas paucimobilis F8 inoculated in BA and BB treatment survived for up to 7 weeks after it was suppressed by unfavorable conditions or native microbes.Degraded amounts generally showed good correlation with results obtained from XAD-4 extraction.Results obtained in the current study represent a good start for standardizing a XAD-4 extraction technique as a simplified,easier,and lower cost method for bioavailability assessment.     

Simulation of Groundwater Level in Ephemeral Streams with an Improved Groundwater Hydraulics Model

As a component of arid ecosystems, groundwater plays an important role in plant growth; therefore, it is essential to use deterministic models to reconstruct the process of groundwater level change. Typically, the linearized solution of the one-dimensional (1-D) Boussinesq equation yields acceptable performance in simulating transient conditions over short recharge periods in ephemeral stream systems, but the ability of this solution to simulate multiyear changes in groundwater levels is limited. In this study, an improved groundwater hydraulics (GH-D2) model is built based on the groundwater hydraulics (GH) solution of the 1-D Boussinesq equation to simulate multiyear changes in the groundwater level in ephemeral stream systems. The model is validated in the lower reaches of the Tarim River to simulate groundwater level fluctuations within the scope of influence of the river (300, 500, 750, 1050 m) over a 16-year period (2000 to 2015). To evaluate the performance of the models, the bias, mean absolute error, root mean squared error, Nash-Sutcliffe efficiency (NSE), and coefficient of determination (R²) are calculated. The results show that the improved GH-D2 model, which considers ephemeral streamflow, unsteady flow theory and the delayed response effect of groundwater level changes, performs well in simulating multiyear changes in the groundwater level in the ephemeral stream system. The observed and simulated values of the groundwater level at different river distances are consistent, and the model provides a new basis for multiyear simulations of groundwater level fluctuations in ephemeral stream systems.     

Projection Pursuit Evaluation Model: Optimizing Scheme of Crop Planning for Agricultural Sustainable Development and Soil Resources Utilization

Planting structure influences the economic, social, and ecological benefits of crop farming as well as the use efficiency of water and arable land resources, and so crop planning (CP) benefits for agricultural sustainable development and soil resources utilization. The projection pursuit evaluation (PPE) model is put forward to solve the problem of selecting an optimizing scheme for CP by considering the indices of water‐saving and economic, social, and ecological benefits. The real‐coding‐based accelerating genetic algorithm (RAGA) is introduced to accelerate the calculation process. The model can translate multi‐indices into a single index by transforming high‐dimensional data to low‐dimensional space, which helps evaluate CP optimizing schemes. For example, the model is used to evaluate and select an optimal scheme of CP in the middle reaches of the Heihe mainstream basin in the arid area of northwest China. According to four criteria (high efficiency of resources use, economic rationality, social equity, and ecological security) 19 indices were chosen to evaluate 12 optimizing schemes of four kinds (economic‐benefit, food‐security, ecological‐benefit, and water‐saving programs) in 2006, 2020, and 2030. The result shows that, in the 3 years, the water‐saving program is always the optimized scheme in an arid region with water deficiency and fragile ecology. The evaluated results match up to the developmental conditions of crop farming in recent years. Moreover, the direction of the optimal projection could reflect the weight and orientation of indices objectively and accurately.     

Analysis of Flow and Sediment Transport Characteristics in Sand Beds

Analysis of flow velocities in stable beds is used to recognize the zones of eroding, transferring, and nontransferring velocities. The profiles of cross-sections in a pool and a rift are constructed using the author's formula.     

小应变硬化土模型参数的确定与敏感性分析

地下工程施工引起的土体扰动区可分为剧烈扰动区、扰动区、微扰动区和未扰动区。为全面反映土体在扰动下的应力路径和力学响应,必须考虑全应变范围的土体特性,尤其是小应变范围内的力学响应,因此对小应变硬化土本构模型关键参数(初始剪切模量和剪应变阀值)的确定方法进行介绍。开展上海典型软土的三轴固结排水剪切试验和固结试验研究,给出确定上海软土小应变硬化土模型(HSSmall)参数的方法,建议采用原位测试的方法确定土体的初始弹性模量。基于土单元数值模拟进行初始弹性模量和剪应变阀值的参数敏感性分析。随着初始弹性模量的增大,初始压缩曲线与卸载-再压缩曲线的斜率均增大。由于对应的回弹模量不变,初始弹性模量与回弹模量的差值增大,应变与偏应力试验曲线的回滞环宽度也随之增大。随着剪应变阀值的增大,初始压缩曲线和再压缩曲线的近似直线段增长,在同样剪应力情况下,土体的应变值减小,土体保持初始弹性模量刚度的区间增大。     

考虑土结构性损伤的小应变模型

结合叠合小应变模型和结构性土的损伤理论,提出了可以考虑土的结构性损伤对小应变下刚度的影响的小应变模型。该模型可作为其他常规土体本构模型的数据接口模型,从而使其他常规本构模型能充分反映土体的小应变特性。通过与实验资料比较分析表明模型可以有效模拟结构性土体的小应变特性。     

Numerical Simulation of Mesoscale Circulations in a Region of Contrasting Soil Types

Mesoscale processes that form due to changes in surface characteristics play a dominant role in the development of the planetary boundary layer structure and the formation of convection. In this study, effects of the Sandhills region of North and South Carolina on mesoscale processes are examined. Climatological analyses indicate increased convective precipitation in this location as compared to the surrounding region. This is believed to be due to enhanced convection induced by horizontal heat flux gradients caused by sharp changes in soil type and hence the heat capacity of the soil. Simulations using a non-hydrostatic mesoscale model (MM5 version 3.3) were made for a non-precipitation case with a 5-km resolution domain centered over the Carolinas from August 15, 2000 to August 18, 2000. The results showed the existence of a mesoscale circulation over the Sandhills region. Differential heating induced by contrasting soil types dividing the Coastal Plain from the central Piedmont causes this circulation. Sea-breeze circulation often combines with the Sandhills circulation to initiate convection in this region. Diurnal variations are handled well by the model indicating that the thermodynamic structure of the atmosphere is well simulated.     

移动荷载作用下土体动力反应数值模拟

在研究轨道振动荷载的产生机理基础上,归纳出一个能够涵盖速度、线路不平顺、轮重、轨枕对轮载的分散作用等因素在内的轨道荷载解析表达式,以此作为输入施加到土体模型上,利用ANSYS模拟地基土在轨道移动荷载作用下的三维瞬态弹塑性反应。通过计算得到土体不同位置位移和加速度时程曲线,并得出如下结论:荷载刚施加时地面位移会有一个突变,但是随着荷载的移动会达到一个稳定值,并随着水平面内远离轨道,该值逐渐衰减;荷载刚刚施加时加速度会有一个突变值,随着荷载的移动逐渐趋于零。轨道机车速度对竖向方向的位移和加速度影响不大。