Effect of bromide ions on genotoxicity of halogenated by-products from chlorination of humic acid in water

Genotoxicity of halogenated by-products obtained by chlorination of humic acid in water was evaluated in the presence of bromide ions (Br⁻). After the halogenated humic acid solution was made to flow through CSP800 cartridge, absorbed substances were eluted with dimethyl sulfoxide or acetone, and subjected to mutagenicity assays and to analysis of trihalomethanes (THMs). Mutagenic activity was measured by Ames tests using S. typhimurium TA100 strain without metabolic activation, and by the frequencies of micronuclei formation using cultured Chinese hamster lung cells (CHL/IU) in vitro. A powerful effect of bromide ions in chlorinated humic acid solutions was observed on the reverse mutation and micronuclei formations. The formations of total THMs and more brominated THMs were also enhanced in the presence of bromide ions. The ratio of [Br⁻/Cl⁻] regulated the composition and concentrations of THMs intensely, and the rate of substitution of Br⁻ was greater than that of chloride ions (Cl⁻). The increments of the mutagenicity and total THMs formed in chlorinated solutions were observed in parallel with the concentration of Br⁻ or Cl⁻. From the observations, it was concluded that the increasing mutagenicity might be caused by the increasing chlorinated and/or brominated by-products.     

Continuous flow method for determination of total trihalomethanes in drinking water with membrane-separation

A double-tube separation system with an inner tube of microporous poly(tetrafluoroethylene) (PTFE) and an outer tube of PTFE, is proposed for the continuous determination of TTHMs (total trihalomethanes) in drinking water. The TTHMs in the sample after mixing sodium sulfite solution, are separated with the double-tube system at 50°C and are mixed with alkaline nicotinamide solution, and then heated to 98°C. After cooling in an ice bath, the reaction product is fed to a fluorometer and the fluorescence intensity excited at 372 nm is measured at 467 nm. There was no interference from unknown species existing in drinking water and river water by using the membrane separation system. A response was obtained within 8 min. The detection limit (S/N = 3) was 0.8 μg/1. The present method was applied to the determination of the TTHMs in drinking water.     

确定性数学模型方法预测隧道涌水量研究

本文介绍了确定性数学模型预测隧道涌水量的常用方法,认为数值模拟方法是隧道涌水量预测的有效方法。并基于有限单元数值法对石太客运专线南梁隧道可能集中涌水区段进行了预测,结果表明其预测结果与实际情况基本吻合。     

Impact of water stagnation in residential cold and hot water plumbing on concentrations of trihalomethanes and haloacetic acids

This study demonstrates that levels of trihalomethanes (THMs) increase considerably when cold water stagnates in residential pipes and, more significantly, when water remains in the hot water tank. Levels of haloacetic acids (HAAs) increase as well in both cases, but less significantly in comparison to THMs. The study also demonstrates that in both the plumbing system and residential hot water tank, chlorinated and brominated DBP species do not behave in the same manner. Finally, the study shows that sustained use of water in households helps to maintain THM and HAA levels close to those found in water of the distribution system. The results are useful to identify methods of indoor water use that minimize population exposure to DBPs and improve DBP exposure assessment for epidemiological studies.     

混凝土真实细观模型的生成及氯离子传输的数值模拟

基于改进的遗传算法和8邻域边界跟踪法,对混凝土断面的数字图像进行处理,得到二值图像并提取粗骨料的边界坐标;根据提取的坐标编写程序,生成浆体集料界面过渡区（ITZ）,得到真实的混凝土细观模型;将得到的混凝土细观模型导入COMSOL软件,模拟海洋水下区氯离子侵入混凝土内部过程,得到不同时刻混凝土内部氯离子浓度云图。研究结果表明：使用的建模和模拟方法所得结果与长期实海暴露混凝土实验结果一致,可以用来研究和评价海洋环境下混凝土的耐久性能;ITZ的存在会加速氯离子向混凝土内部扩散,其厚度越大,扩散过程越快,界面区厚度增大1倍,混凝土表观氯离子扩散系数增大12.3%;对比真实混凝土细观模型与参数化生成的圆形随机骨料模型中氯离子传输模拟结果发现,圆形随机骨料模型中氯离子的浓度总是小于真实细观模型中氯离子的浓度。     

GM（1,1）等维新息模型在某市需水量预测中的应用

用GM（1,1）等维新息模型对孟州市2010年,2015年,2020年的需水量进行了预测,得出需水量分别为7 759.6万m3,8 823.5万m3,9 015.3万m3。对预测结果的精度校验表明,模型的预测精度等级为一级,模型可靠、合理。     

Evaluation of the EUROSEM model for predicting the effects of erosion-control blankets on runoff and interrill soil erosion by water

The European Soil Erosion Model (EUROSEM, Morgan et al., 1998) is an event-based soil erosion model which predicts runoff and sediment discharge for different environmental conditions. Applying geotextiles or erosion-control blankets (ECB’s) on the soil surface significantly affects surface seal formation and topsoil properties and therefore controls runoff and soil erosion rates during a rainfall event. Since these within-storm changes of soil surface characteristics and hydrological conditions are not incorporated in EUROSEM, errors in runoff and soil erosion predictions may occur for soil surfaces covered with ECB’s.Therefore, the objective of this paper is to evaluate and improve the performance of a research version of the physically-based erosion model EUROSEM (EUROSEM-2010; Borselli and Torri, 2010) for simulating the effects of ECB’s on runoff and interrill soil erosion by water during intense simulated rainfall events. Results of model simulations are compared with experimental results of interrill erosion using biological (i.e. natural) ECB’s and simulated rainfall. Because ECB’s applied on the soil surface retard seal formation, the differences between observed and predicted runoff rates and sediment discharges are rather high during the first 20-30 min of the simulated rainstorm. Therefore, a simple approach is proposed to cope with the dynamic evolution of some soil characteristics, i.e. saturated hydraulic conductivity, soil erodibility and soil cohesion, during an intense rainfall event. This time-dependent approach improves the predictions of runoff rate and sediment discharge during the first 20-30 min of a rainfall event and increases the model efficiency (i.e. a measure for the goodness of fit) from 0.84 to 0.98 and from 0.48 to 0.68 for the total runoff volume and soil loss, respectively. For most conditions, the predicted final sediment discharge is still considerably larger than the observed values, which can be partly attributed to the deposition of sediment in the bare soil patches (i.e. inter-weave open areas) of the ECB’s, which is not simulated by EUROSEM in this study. This model approach increases our understanding of the effects of ECB’s on within-storm changes in hydrological conditions and soil surface characteristics.     

Impacts of blending ground, surface, and saline waters on lead release in drinking water distribution systems

The impacts of distribution water quality changes caused by blending different source waters on lead release from corrosion loops containing small lead coupons were investigated in a pilot distribution study. The 1-year pilot study demonstrated that lead release to drinking water increased as chlorides increased and sulfates decreased. Silica and calcium inhibited lead release to a lesser degree than sulfates. An additional 3-month field study isolated and verified the effects of chlorides and sulfates on lead release. Lead release decreased with increasing pH and increasing alkalinity during the 1-year pilot study; however, the effects of pH and alkalinity on lead release, were not clearly elucidated due to confounding effects. A statistical model was developed using nonlinear regression, which showed that lead release increased with increasing chlorides, alkalinity and temperature, and decreased with increasing pH and sulfates. The model indicated that primary treatment processes such as enhanced coagulation and RO (reverse osmosis membrane) were related to lead release by water quality. Chlorides are high in RO-finished water and increase lead release, while sulfates are high following enhanced coagulation and decrease lead release.     

Removal of low-molecular weight DBPs and inorganic ions for characterization of high-molecular weight DBPs in drinking water

High-molecular weight (MW) halogenated disinfection byproducts (DBPs) may cause adverse health effects. In this work several issues related to the better separation and characterization of the high MW halogenated DBPs (MW>500Da) were studied. Ultra-filtration (UF) coupled with a nominal 500-Da membrane was employed to flush out low MW DBPs and inorganic ions. Two procedures, intermittent UF and continuous UF, were used and compared. The results demonstrate that haloacetic acids, chloride and sodium ions could be effectively flushed out, and most of phosphate ions could be flushed out for a given dilution number or sufficient Milli-Q water. The size exclusion chromatograms indicate that haloacetic acids and trihalomethanes were not bound to Suwannee River fulvic acid (SRFA); 2,4,6-trichlorophenol might form some binding with SRFA, but it appeared to be very weak and readily broken up when passing along the size exclusion column. The octanol-water partition coefficients of low MW DBPs and the properties of humic substances seem to play key roles in determining the formation of possible bindings between low MW DBPs and humic substances.     

改性沸石处理含氟水的试验研究

用氧化铝改性沸石制备了一种除氟材料,其最佳制备工艺参数为:在200℃下焙烧1.5 h对沸石进行预处理的基础上,用pH=9的Al(OH)3悬浮液对沸石进行覆盖沉淀改性,并在400 ℃下焙烧1 h涂层,最后用质量分数为4%的Al2(SO4)3溶液浸渍12 h.改性后的沸石对氟离子的吸附量可达0.84 mg/g.改性前后除氟性能的对比试验结果表明,活性氧化铝成分与氟离子的络合作用对氟的去除起主要作用.     

Impact of source waters,disinfectants, seasons and treatment approaches on trihalomethanes in drinking water: a comparison based on the size of municipal systems

This study compares concentrations of trihalomethanes (THMs) in municipal water for 2001–2007 from the small and large systems in two provinces in Canada (Newfoundland and Quebec) based on source waters, disinfectants, seasons and treatment approaches. Approximately 71 and 94%, respectively, of the municipal systems in Quebec and Newfoundland are small systems (serving fewer than 3000 people). The small systems serve approximately 8.6% (0.57 million) and 44.1% (0.18 million) of the populations in Quebec and Newfoundland, respectively. Concentrations of THMs and its variability are much higher in the small systems (Quebec: 0–941 μg/L; Newfoundland: 0–875 μg/L) than in the systems with populations 10 000 or more (Quebec: 0–364 μg/L; Newfoundland: 2.3–205 μg/L). The study reveals that the differences in THMs between the small and medium/large systems are because of different types of source waters, treatments, disinfection strategies and seasons. The results emphasize that regulatory agencies must focus more on the occurrence of DBPs in small systems and identify strategies to reduce their levels in drinking water.     

铁锰超标对天然河床潜流水水质影响及处理

研究了铁锰离子超标对天然河床潜流水水质的影响及相应的处理技术，分析了潜流水中铁锰的危害及迁移富集规律，通过对除铁锰技术进行比选，得出接触氧化法是去除潜流水中铁锰的最佳方法，并对其工艺流程作了具体介绍，以期指导实践。     

考虑环境与荷载长期共同作用的木材本构模型研究

针对木材的变形易受周围环境温湿度变化影响的问题,提出了一种能描述木材在外界环境和荷载长期共同作用下的本构模型和力学性能研究方法.首先基于Tsai-Wu屈服准则、Drucker公设和一致性理论提出了考虑蠕变、机械吸附蠕变的木材本构模型;然后采用Fortran语言将推导的本构模型编写成UMAT子程序模块并嵌入到ABAQUS...     

A suitable model of combined effects of temperature and initial condition on chlorine bulk decay in water distribution systems

Maintaining a chlorine residual is a major disinfection goal in many water distribution systems. A suitable general model of chlorine decay in the transported bulk water is an essential component for efficiently modelling chlorine concentration in distribution systems. The two-reactant model meets basic suitability criteria, including accurate prediction of chlorine residual over hundreds of hours, commencing with chlorine concentration 0-4 mg/L. This model was augmented with an equation that increases the decay coefficients with temperature according to Arrhenius theory. The augmented model was calibrated against decay-test data sets to obtain a single invariant set of parameters for each water. Model estimates of chlorine residuals over time closely matched decay-test data, over the usual operating ranges of initial chlorine concentration (1-4 mg/L) and temperature (3.5-28 °C). When the augmented model was fitted to partial data sets, it also predicted the data reserved for validation very well, suggesting that this model can accurately predict the combined effect of initial chlorine concentration and temperature on chlorine bulk decay in distribution systems, using a single set of invariant parameters for a given source water.     

降雨与库水位共同作用下近坝库岸边坡滑坡模型试验研究

根据云南省龙江水电站近坝库岸边坡滑坡特点,为了对降雨与库水位共同作用下近坝库岸边坡滑坡有深入的了解,进行了降雨与库水位共同作用下边坡滑坡大型模型试验研究。试验结果表明:降雨是引起近坝库岸边坡滑坡的重要因素,降雨与库水位共同作用下近坝库岸滑坡有效应力减小,研究库水位以下边坡土体的抗剪强度减小;库水位作用使得边坡产生沉降和裂缝,边坡的滑坡是由降雨和库水位共同作用引起,库水位以下边坡土体水分入渗充分,边坡内部孔隙水压力较大,边坡易产生滑坡且滑坡规模较大,近坝库岸边坡滑坡属于浅层牵引式滑坡。     

Development of a system for predicting snow distribution in built-up environments: Combining a mesoscale meteorological model and a CFD model

A system has been developed for predicting snow distribution in built-up environments. This system combines a mesoscale meteorological model that predicts precipitation, including snowfall in an area, and a Computational Fluid Dynamics (CFD) model that predicts snow phenomena on building scale. The system focuses on snow distribution around buildings, which often leads to snow disaster and snow-related difficulties in urban areas. It can be used for predicting snow distribution due to snowfall and snowdrift in a development area and is expected to be a useful design tool for city and architectural planning in snowy regions. This paper outlines the system and examines its performance by comparing its results with measured data. The snowdrift patterns, i.e. erosion around the upwind corners and deposition in front of and behind a building, obtained by the present model show good correspondence with those obtained from field observation. However, the model under-predicted the decrease of snow depth near the building. Further investigations required to comprehensively evaluate the prediction accuracy of the system are discussed.     

盾构隧道预应力管片接头的模型试验研究

盾构隧道普通混凝土管片接头的抗弯刚度主要是通过现场试验确定,目前尚无现成的公式或者图表可遵循,对于预应力管片这一新型的结构型式则更有必要对其接头的正负转角刚度,为此进行了弯曲的预应力管片接头试验.文章介绍了模型试验的设计及试验过程,通过试验数据分析了影响预应力管片接头刚度的各项因素,如施加预应力的大小、偏心距等,并得出了计算其刚度的经验公式.     

断层破碎带隧道突水突泥模型试验系统研制与应用

为研究吉莲高速永莲隧道扰动作用下突水突泥灾变演化过程及破坏特征,以F2断层破碎带为研究对象,研制大型三维地质模型试验系统,该系统由模型架、地应力加载系统、水压加载系统以及信息监测系统组成,通过材料配比试验及物理力学性能参数测试,研制出适用于流–固耦合模型试验的新型断层围岩及正常围岩相似材料。采用该系统进行模型试验,揭示正常围岩开挖过程中及揭露断层后的隧道围岩渗流压力、应力应变、位移以及涌出物等特征参数的变化规律,模型试验结果与实际工程灾变特征具有较好一致性。试验结果表明该系统稳定可靠,可广泛应用于其它地下工程的模型试验研究,其研究方法及结果对类似工程研究具有一定的指导和借鉴意义。     

Effects of temperature and biodegradable organic matter on control of biofilms by free chlorine in a model drinking water distribution system

This study used annular reactors (AR) to investigate, under controlled laboratory conditions, the effects of temperature and biodegradable organic matter (BOM) on the free chlorine residual needed to control biofilm accumulation, as measured by heterotrophic plate count (HPC) bacteria. Biofilm was grown on PVC coupons, initially in the absence of chlorine, at 6, 12, and 18 degrees C, in the presence and absence of a BOM supplement (250 microg C/L) added as acetate. During the early stages of chlorine addition, when no measurable free chlorine residual was present, a reduction in biofilm HPC numbers was observed. Subsequently, once sufficient chlorine was added to establish a residual, the biofilm HPC numbers expressed as log CFU/cm2 fell exponentially with the increase in free chlorine residual. Temperature appeared to have an important effect on both the chlorine demand of the system and the free chlorine residual required to control the biofilm HPC numbers to the detection limit (3.2 Log CFU/cm2). For the water supplemented with BOM, a strong linear correlation was found between the temperature and the free chlorine residual required to control the biofilm. At 6 degrees C, the presence of a BOM supplement appeared to substantially increase the level of free chlorine residual required to control the biofilm. The results of these laboratory experiments provide qualitative indications of effects that could be expected in full-scale systems, rather than to make quantitative predictions.