基于蒙特卡罗法的白家包滑坡库水位消落可靠度分析

可靠度理论考虑了滑坡岩土体本身的复杂性、离散型、不确定性,相比传统确定单一的滑坡稳定系数算法,通过可靠度指标、失效概率、各参数敏感性等对滑坡稳定性进行综合评价,更加符合工程实际。基于蒙特卡罗随机抽样算法,通过3 000次模拟抽样对三峡库区白家包滑坡在库水位消落两种工况下的可靠度和参数敏感性进行了对比分析。滑坡可靠度分析表明:两种工况下滑坡整体都表现出随着库水位快速消落其稳定系数均值减小、失效概率增大,且库水位消落速率越大这种现象越明显;当以工况2运行时滑坡失效概率超过50%,滑坡整体有失稳的可能。滑坡参数敏感性分析表明:两种工况下该滑坡滑带土体的重度(γ)与滑坡稳定系数呈现微弱的正相关性,且随着库水位消落其相关性呈现增大的趋势;滑带土体的内摩擦角(φ)与滑坡稳定系数的正相关性远大于内聚力(c),且随着库水位快速消落这种正相关性呈现微小的削弱;对比两种工况,工况2参数敏感性"增幅"、"降幅"都大于工况1。     

Calculation of the minimum ecological water requirement of an urban river system and its deployment: A case study in Beijing central region

The minimum ecological water requirements of an urban river system and water deployment are key elements in integrated water resources planning and urban ecological construction. Based on a review of ecological water requirement calculation methods and considering the different ecological functions of an urban river system, the ecological function method was used in this paper to calculate the components of the ecological water requirements of an urban river. An envelope curve-based method was proposed for assessing the minimum ecological water requirements of an urban river system. Water resources deployment strategies designed to meet the minimum ecological water requirements were described. Then, the minimum ecological water requirements of the urban river system in Beijing central region, selected as a case study, were investigated. The key parameters for assessing the minimum ecological water requirement in the Beijing urban river system were determined. Based on the ecological objectives and the current status of the different urban river systems within the Beijing central region, the minimum ecological water requirements were calculated. Different types of water sources, including rainwater, upstream water, and reclaimed water, were deployed to meet the ecological water requirements for the urban river system in the Beijing central region.     

Ca2+、Mg2+共存对SBR工艺生物脱氮和微生物群落结构的影响

为了研究共存的硬度金属离子在废水生物处理中的作用,在进水Ca~(2+)为1.1 mmol·L~(-1)的条件下,通过改变Mg~(2+)的浓度,考察Ca~(2+)/Mg~(2+)物质的量比对SBR工艺污染物去除和微生物群落的影响,采用高通量测序技术分析微生物优势种群的变化,以期从微生物角度明确Ca~(2+)、Mg~(2+)共存对生物脱氮的影响机制.结果表明:当Ca~(2+)/Mg~(2+)物质的量比分别为2、1和0.5时,COD去除率由88%分别升高至90%、91%和93%;NH~+_4-N去除率由74%分别升高至91%、93%和96%;TN去除率由44%分别升高至58%、62%和69%.随着进水Ca~(2+)/Mg~(2+)物质的量比的降低,微生物群落的丰富度升高,Ca~(2+)/Mg~(2+)物质的量比为2的微生物群落结构与Ca~(2+)/Mg~(2+)物质的量比为1和0.5的微生物群落结构差异显著.变形菌门、拟杆菌门和放线菌门一直为SBR工艺的优势菌门,有利于有机污染物的去除.参与脱氮过程的Niabella和Dechloromonas在反应器内富集,保证了良好的脱氮效果.Ca~(2+)/Mg~(2+)物质的量比的降低促进了有机物和总氮的去除及微生物多样性的提高.     

柴油表征燃料在高浓度CO2氛围下燃烧机理的分析

为研究高浓度CO₂在高温高压情况下对柴油燃烧特性的影响,提出了柴油表征燃料在CO₂/O₂氛围下的燃烧反应机理.通过量子化学计算了化学反应路径并对反应路径进行分析,最后进行柴油表征燃料燃烧的仿真.通过搭建定容燃烧弹试验台架和可视化系统进行试验与仿真分析,结果表明：在50% CO₂+50% O₂氛围下,对仿真与实验的火焰燃烧极限长度和火焰纵截面面积进行对比,最小误差分别为0.39%和0.64%,最大误差分别为8.54%和4.94%,说明此机理适用于高浓度CO₂氛围下柴油燃烧特性的研究;CO₂的化学效应在柴油表征燃料燃烧时具有促进作用,CO₂在2600 K时发生热解,热解产物CO与H自由基等发生反应可以生成着火促进剂·OH;柴油在50% CO₂+50% O₂、43% CO₂+57% O₂和35% CO₂+65% O₂氛围下的燃烧效率比空气氛围分别提高了28.2%、30.4%和33.3%.     

Leaf metabolic influence of glyphosate and nanotubes on the Arabidopsis thaliana phyllosphere

Chemical exposure can indirectly affect leaf microbiota communities, but the mechanism driving this phenomenon remains largely unknown. Results revealed that the co-exposure of glyphosate and multi-carbon nanotubes (CNTs) caused a synergistic inhibitory effect on the growth and metabolism of Arabidopsis thaliana shoots. However, only a slight inhibitory effect was induced by nanotubes or glyphosate alone at the tested concentrations. Several intermediate metabolites of nitrogen metabolism and fatty acid synthesis pathways were upregulated under the combined treatment, which increased the amount of energy required to alleviate the disruption caused by the combined treatment. Additionally, compared with the two individual treatments, the glyphosate/nanotube combination treatment induced greater fluctuations in the phyllosphere bacterial community members with low abundance (relative abundance (RA) <1%) at both the family and genus levels, and among these bacteria some plant growth promotion and nutrient supplement related bacteria were markable increased. Strikingly, strong correlations between phyllosphere bacterial diversity and metabolites suggested a potential role of leaf metabolism, particularly nitrogen and carbohydrate metabolism, in restricting the range of leaf microbial taxa. These correlations between phyllosphere bacterial diversity and leaf metabolism will improve our understanding of plant-microbe interactions and the extent of their drivers of variation and the underlying causes of variability in bacterial community composition.     

Disinfection by-product (DBP) research in China: Are we on the track?

Disinfection by-products (DBPs) formed during water disinfection has drawn significant public concern due to its toxicity. Since the first discovery of the trihalomethanes in 1974, continued effort has been devoted on DBPs worldwide to investigate the formation mechanism, levels, toxicity and control measures in drinking water. This review summarizes the main achievements on DBP research in China, which included: (1) the investigation of known DBP occurrence in drinking water of China; (2) the enhanced removal of DBP precursor by water treatment process; (3) the disinfection optimization to minimize DBP formation; and (4) the identification of unknown DBPs in drinking water. Although the research of DBPs in China cover the whole formation process of DBPs, there is still a challenge in effectively controlling the drinking water quality risk induced by DBPs, an integrated research framework including chemistry, toxicology, engineering, and epidemiology is especially crucial.     

钯基催化剂电催化氢解处理氯代有机物的研究进展

氯代有机物(COPs)是一类重要的化工生产原料和中间体,但其高持久性、高生物累积性、致癌性及遗传毒性将对生态环境和人体健康造成巨大危害. 开发消除COPs毒性的新型技术,实现人与自然和谐共生,成为国际学术界和工业界共同关注的焦点. 电催化氢解技术(ECH)因具有高反应活性、结构简单、二次污染风险小等优势而备受青睐. 本文系统综述了钯(Pd)基催化剂上的ECH反应机制,探究强还原性氢自由基(H*)的定量分析方法,揭示脱氯反应与析氢副反应间的竞争关系. 通过分析H*产量、污染物脱附、电场等因素对脱氯速率的影响规律,建立晶面与效能间构效关系,识别不同反应条件下制约ECH速率的因素. 聚焦阴极催化活性低、易受脱氯产物毒化的关键问题,通过暴露Pd活性中心位点、强化水裂解、调控电子效应和配体效应及几何效应等策略增强催化剂产H*量和抗毒化性能. 开展ECH脱氯反应路径识别、脱氯性能影响因素探讨以及生物安全性评价,并基于当前存在的关键科学问题,展望ECH技术的发展趋势,为设计和发展实用型环境催化新技术和新型催化材料指明方向.      

Scenario analysis of water pollution control in the typical peri-urban river using a coupled hydrodynamic-water quality model

The water quality pollution and ecological deterioration in peri-urban rivers are usually serious under rapid urbanization and economic growth. In the study, a typical peri-urban river, Nansha River, was selected as a case study to discuss the scheme of peri-urban river rehabilitation. Located in the north part of the Beijing central region, the Nansha River watershed has been designated as an ecologically friendly garden-style area with high-tech industry parks and upscale residential zones. However, the Nansha River is currently seriously contaminated by urban and rural pollutants from both nonpoint sources (NPS) and point sources (PS). In this study, the pollutant loads from point sources and nonpoint sources in the Nansha River watershed were first assessed. A coupled model, derived from the Environmental Fluid Dynamics Code and Water Quality Analysis Simulation Program, was developed to simulate the hydrodynamics and water quality in the Nansha River. According to the characteristics of the typical peri-urban river, three different PS and NPS control scenarios were designed and examined by modeling analyses. Based on the results of the scenario analysis, a river rehabilitation scheme was recommended for implementation.     

三江源地区基于植被生长季的NDVI对气候因子响应的差异性研究

采用1999—2008年NDVI和三江源地区及周边31个气象站点的温度和降水旬数据,在确定每年5月中旬至9月底作为三江源地区植被生长季（14旬）的基础上,分析NDVI对气候因子变化响应的区域差异。结果显示：以巴颜喀拉山为界,三江源西部生长季内NDVI指数对温度、降水的线性相关性明显比中东部普遍,同时,不同海拔地段响应程度存在着明显的差异,且海拔5300m左右为线性响应的最高限,NDVI对气候因子的线性响应主要表现为对温度正相关和降水负相关。因此,对三江源生长季内植被生长而言,水条件明显好于温度条件,并且温度对植被覆盖的影响通过直接正相关和降水负相关表现出来,温度是三江源地区植被生长的主导因子。     

Evaluation of aquatic rehabilitation technologies for polluted urban rivers and the case study of the Foshan Channel

An index system for evaluation of technologies for urban river rehabilitation was proposed and discussed. The index system includes indicators of cost, resources, environmental improvement, and social effects. The calculation method for an objective value of each index based on its attributes and weights was presented. The Foshan Channel, which is a seriously polluted, black and malodorous urban river in Foshan City, China, was selected as a case study. The values of the attributes and the weights of the indices for the Foshan Channel were determined. The technologies for the rehabilitation of the Foshan Channel were evaluated based on this index system. Finally, a rehabilitation scheme for the Foshan Channel was proposed.