紫外/亚硫酸盐高级还原工艺加速降解水中难降解含碘造影剂

紫外/亚硫酸盐（UV/SO₃^2-）是一种基于紫外活化SO₃^2-离子依靠生成还原性自由基——水合电子降解目标污染物的高级还原工艺.本文研究了UV/SO₃^2-加速降解含碘造影剂泛影酸钠（DTZ）的效能、机制与影响因素以及UV/SO₃^2-降解DTZ的路径.结果表明,UV/SO₃^2-降解DTZ符合一级动力学模型,降解速率快于单独UV和紫外/过氧化氢工艺,且降解速率随SO₃^2-浓度的增加而升高.弱碱性或碱性水质可强化UV/SO₃^2-降解效率,背景有机物对降解DTZ有一定抑制作用.DTZ降解机制包括直接光解和还原性自由基攻击,其中自由基攻击占主要部分.DTZ在UV/SO₃^2-的降解路径包括取代、脱羧基羟基化和酰胺键断裂等.     

基于网络模拟的岩体边坡稳定性概率分析

介绍了基于网络模拟的岩体边坡潜在滑动面随机搜索及其破坏概率计算的基本原理和实现过程。首先通过统计分析得到岩体边坡结构的统计性质参数及分布的密度函数,应用蒙特卡洛方法,采用随机参数模拟生成边坡岩体的结构面网络模型;然后以结构面网络模型为基础,在研究岩体边坡断裂失稳问题中,结合优势面理论,并考虑岩桥破坏机理,建立了新的使用动态规划方法寻求潜在滑动面及破坏概率计算的随机模拟技术,完成了相应计算程序。     

Elimination of antibiotic resistance genes and control of horizontal transfer risk by UV-based treatment of drinking water: A mini review

Antibiotic-resistant bacteria and antibiotic resistance genes are in water bodies. UV/chlorination method is better to remove ARGs than UV or chlorination alone. Research on UV/hydrogen peroxide to eliminate ARGs is forthcoming. UV-based photocatalytic processes are effective to degrade ARGs. Antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) have been recognized as one of the biggest public health issues of the 21st century. Both ARB and ARGs have been determined in water after treatment with conventional disinfectants. Ultraviolet (UV) technology has been seen growth in application to disinfect the water. However, UV method alone is not adequate to degrade ARGs in water. Researchers are investigating the combination of UV with other oxidants (chlorine, hydrogen peroxide (H₂O₂), peroxymonosulfate (PMS), and photocatalysts) to harness the high reactivity of produced reactive species (Clž·, ClOž·ž, Clž₂·ž⁻, žž·OH, and SOž₄ž·⁻€) in such processes with constituents of cell (e.g., deoxyribonucleic acid (DNA) and its components) in order to increase the degradation efficiency of ARGs. This paper briefly reviews the current status of different UV-based treatments (UV/chlorination, UV/H₂O₂, UV/PMS, and UV-photocatalysis) to degrade ARGs and to control horizontal gene transfer (HGT) in water. The review also provides discussion on the mechanism of degradation of ARGs and application of q-PCR and gel electrophoresis to obtain insights of the fate of ARGs during UV-based treatment processes.     

Conservation decision-making in large state spaces

When looking for the best course of management decisions to efficiently conserve metapopulation systems, a classic approach in the ecology literature is to model the optimisation problem as a Markov decision process and find an optimal control policy using exact stochastic dynamic programming techniques. Stochastic dynamic programming is an iterative procedure that seeks to optimise a value function at each timestep by evaluating the benefits of each of the actions in each state of the system defined in the Markov decision process.Although stochastic dynamic programming methods provide an optimal solution to conservation management questions in a stochastic world, their applicability in metapopulation problems has always been limited by the so-called curse of dimensionality. The curse of dimensionality is the problem that adding new state variables inevitably results in much larger (often exponential) increases in the size of the state space, which can make solving superficially small problems impossible. The high computational requirements of stochastic dynamic programming methods mean that only simple metapopulation management problems can be analysed. In this paper we overcome the complexity burden of exact stochastic dynamic programming methods and present the benefits of an on-line sparse sampling algorithm proposed by Kearns, Mansour and Ng (2002). The algorithm is particularly attractive for problems with large state spaces as the running time is independent of the size of the state space of the problem. This appealing improvement is achieved at a cost: the solutions found are no longer guaranteed to be optimal.We apply the algorithm of Kearns et al. (2002) to a hypothetical fish metapopulation problem where the management objective is to maximise the number of occupied patches over the management time horizon. Our model has multiple management options to combat the threats of water abstraction and waterhole sedimentation. We compare the performance of the optimal solution to the results of the on-line sparse sampling algorithm for a simple 3-waterhole case. We find that three look-ahead steps minimises the error between the optimal solution and the approximation algorithm. This paper introduces a new algorithm to conservation management that provides a way to avoid the effects of the curse of dimensionality. The work has the potential to allow us to approximate solutions to much more complex metapopulation management problems in the future.     

HYDROLOGIC DESIGN CONSIDERATIONS OF CONSTRUCTED WETLANDS FOR URBAN STORMWATER RUNOFF1

ABSTRACT: The successful design of constructed wetlands requires a continuous supply of water or vegetation that can withstand drought conditions. Having a constant water source is the best alternative to insure species diversity throughout the season. Consequently, detention structure designs should be based on times between events as well as on hydrologic return periods, since between events is when most evaporation and infiltration losses are likely to occur. In arid or semi-arid environments, this is a difficult process because of long interevent times and seasonal changes in precipitation patterns. This discussion is predicated on the assumption that phytoplankton, epiphytic algae, and emergent vegetation require moist conditions to be effective at removing nutrients, metals and other pollutants. There are drought tolerant species of vegetation that can be used in constructed wetlands but it may take several days to re-establish the attached bacteria communities necessary for optimum pollutant removal. This paper examines a stochastic framework to examine the probability of extended dry periods based on historic rainfall data. The number of consecutive dry days is selected for a specified level of assurance. By multiplying this value by the sum of daily system losses, an overall pond volume can be determined that ensures a minimum depth of water. To illustrate the utility of the approach, the method is applied to a site in Spokane, Washington.     

A stochastic approach for the operation of a wind and pumped storage plant under a deregulated environment

To improve the competiveness in the energy market, it is necessary that the wind power plants provide guaranteed power generation, although, it is not possible to forecast power availability from wind power plant accurately. This paper presents a stochastic model and solution technique for the combined operation of wind and pumped storage power plants to improve the power availability and increasing the profit considering uncertainties of wind power generation. In this model, uncertainties in wind data have been forecasted for grid connected day-ahead market using Weibull distribution model. The imbalances in the forecasted wind data and the market demand have been reduced by operating the pumped storage power plant. In this stochastic mixed integer problem, pumped storage plant can take the supply either from the grid or from the wind power plant for the pumping operation to store the energy in order to utilize this energy during peak hours for increasing the overall revenue. The reliability of the pumped storage is improved by replacing the conventional unit with the adjustable speed type pumped storage unit. In order to prove the optimality of the solution, two case studies were considered. In case study–I, scheduling is provided by operating the conventional pumped storage unit, whereas in case study–II, adjustable speed pumped storage unit has been used. It has been found that the adjustable speed pumped storage unit has further reduced the imbalance between generated power and demand. The complete approach has been formulated and implemented using AMPL software.     

云南省耕地生产效率的时空差异及影响因素

以第二次全国土地调查完成以来的2009~2013年为研究时段,在测算云南省16个州(市)的耕地生产效率基础上,综合运用ESDA技术、基尼系数等方法系统分析云南省耕地生产效率的时空差异,并构建计量经济模型研究影响不同区域耕地生产效率变化的主要因素。结果表明:(1)2009~2013年,云南省耕地生产效率呈总体上升趋势,但增幅逐年降低;效率低值地区增长明显,高值地区则并不显著;(2)云南省耕地生产效率区域差异呈缩小态势,并表现出由西南向东北递减的空间分布特征;(3)滇中、滇西南等粮食主产区受≤6°耕地面积比重、旱涝保收面积的影响较大,而滇东地区则更易受到6°坡耕地面积和人均GDP的影响,滇西北地区受≤6°耕地面积比重和人均GDP的影响显著。     

武汉城市圈公路沿线土地利用变化规律分析

区域交通土地一体化规划需要明晰公路沿线的土地利用变化过程。基于随机概率的土地转移矩阵模型及相关结构指数,分析了武汉城市圈公路沿线的土地变化规律。结果显示,从变化量而言,武汉城市圈各类型公路沿线耕地转为建设用地的比例最大,且以国道最为明显;从系统的变化方向而言,各公路类型沿线建设用地占用耕地现象显著,此外,高速沿线建设用地占用水域,国道沿线耕地占用林地,以及各类型公路沿线耕地、林地闲置现象也需及时监测和预警。     

重金属Cr(Ⅵ)和Ni对旱伞草富集能力及其生理生化指标的影响

采用水培方法,研究了在不同重金属Cr(Ⅵ)(0~50 mg/L)和Ni(0~50 mg/L)浓度下旱伞草(Cyperus alternifolius)的富集能力及生理生化指标的变化规律。研究结果表明:(1)旱伞草中积累的重金属含量随处理浓度的增加逐渐增加,Cr(Ⅵ)在其地上部和根部富集量分别达到958.00 mg/kg和2 874.44 mg/kg,Ni在其地上部和根部富集量分别达到1 655.46 mg/kg和2 511.20 mg/kg;(2)在Cr(Ⅵ)和Ni胁迫下,随着Cr(Ⅵ)和Ni浓度的增加,旱伞草生物量、叶绿素含量、根系活力均呈先上升后下降的趋势;(3)脯氨酸的含量随着Cr(Ⅵ)胁迫浓度的增加,呈现为先上升后降低的趋势,而随着Ni胁迫浓度的增加,则为先缓慢上升而后急剧升高。旱伞草对Cr(Ⅵ)和Ni具有较强的富集能力且主要分布在根部,虽不是Cr(Ⅵ)和Ni超积累植物,但具有较强的稳定化能力,在污染水体的修复方面有一定应用潜力。     

Improvements in Fluvial Stability Associated with Two‐Stage Ditch Construction in Mower County,Minnesota

Water quality and stream habitat in agricultural watersheds are under greater scrutiny as hydrologic pathways are altered to increase crop production. Agricultural drainage ditches function to remove water quickly from farmed landscapes. Conventional ditch designs lack the form and function of natural stream systems and tend to be unstable and provide inadequate habitat. In October of 2009, 1.89 km of a conventional drainage ditch in Mower County, Minnesota, was converted to an alternative system with a two‐stage channel to investigate the improvements in water quality, stability, and habitat. Longitudinal surveys show a 12‐fold increase in the pool‐riffle formation. Cross‐sectional surveys show an average increase in bankfull width of approximately 10% and may be associated to an increased frequency in large storm events. The average increase in bankfull depth was estimated as 18% but is largely influenced by pool formation. Rosgen Stability Analyses show the channel to be highly stable and the banks at a low risk of erosion. The average bankfull recurrence interval was estimated to be approximately 0.30 years. Overall, the two‐stage ditch design demonstrates an increase in fluvial stability, creating a more consistent sediment budget, and increasing the frequency of important instream habitat features, making this best management practice a viable option for addressing issues of erosion, sediment imbalance, and poor habitat in agricultural drainage systems.