铸铁管输配再生水铁溶出颗粒物特征研究

针对输配水过程中产生的"红水"现象及铁颗粒物溶出对水质的影响,开展了初步的模拟管网中试研究.实验采用内径为100 mm的铸铁管搭建了120 m长管网中试模拟系统,并以北京某再生水厂生产的再生水为水源,进行了单向连续流动和密闭循环流动模拟管网输配实验,并对管网出水水质进行了的连续跟踪监测.中试结果表明,两种方式的实验都发生了"红水"现象;出水水质的p H、总溶解性固体(TDS)、电导率及总铁都有明显升高;实验过程中得到的两种不同颜色颗粒物,它们都包括α-Fe OOH、γ-Fe OOH、Fe CO3、Fe2O3、Fe3O4及Fe O等矿物质;颗粒物颜色可能与颗粒中羟基氧化铁与碳酸亚铁的含量有关;水流速度对于管网中颗粒物的沉积和释放要一定影响;不带内衬的铸铁管不适合作为输配腐蚀性极强水质再生水的管材.     

Identifying the major fluorescent components responsible for ultrafiltration membrane fouling in different water sources

Three-dimensional fluorescence excitation–emission matrix(EEM) coupled with parallel factor analysis(PARAFAC) was performed for a total of 18 water samples taken from three water sources(two lakes and one wastewater treatment plant(WWTP) secondary effluent),with the purpose of identifying the major ultrafiltration(UF) membrane foulants in different water sources. Three fluorescent components(C1, C2 and C3) were identified,which represented terrestrially derived humic-like substances(C1), microbially derived humic-like substances(C2), and protein-like substances(C3). The correlations between the different fluorescent components and UF membrane fouling were analyzed. It was shown that for the WWTP secondary effluent, all three components(C1, C2 and C3) made a considerable contribution to the irreversible and total fouling of the UF membrane.However, for the two lakes, only the C3 exhibited a strong correlation with membrane fouling, indicating that the protein-like substances were the major membrane foulants in the lake waters. Significant attachment of C1, C2 and C3 to the UF membrane was also confirmed by mass balance analyses for the WWTP secondary effluent; while the attachment of C1 and C2 was shown to be negligible for the two lakes. The results may provide basic formation for developing suitable fouling control strategies for sustainable UF processes.     

Polycyclic aromatic hydrocarbon concentrations, compositions, sources, and associated carcinogenic risks to humans in farmland soils and riverine sediments from Guiyu, China

The concentrations of 16 priority polycyclic aromatic hydrocarbons(PAHs) were measured in 23 farmland soil samples and 10 riverine sediment samples from Guiyu, China, and the carcinogenic risks associated with PAHs in the samples were evaluated. Guiyu is the largest electronic waste(EW) dismantling area globally, and has been well known for the primitive and crude manner in which EWs are disposed, such as by open burning and roasting. The total PAH concentrations were 56–567 ng/g in the soils and 181–3034 ng/g in the sediments.The Shanglian and Huamei districts were found to be more contaminated with PAHs than the north of Guiyu. The soils were relatively weakly contaminated but the sediments were more contaminated, and sediments in some river sections might cause carcinogenic risks to the groundwater system. The PAHs in the soils were derived from combustion sources,but the PAHs in the sediments were derived from both combustion and petroleum sources.     

Reducing the risk of rear-end collisions with infrastructure-to-vehicle (I2V) integration of variable speed limit control and adaptive cruise control system

Objective: Adaptive cruise control (ACC) has been investigated recently to explore ways to increase traffic capacity, stabilize traffic flow, and improve traffic safety. However, researchers seldom have studied the integration of ACC and roadside control methods such as the variable speed limit (VSL) to improve safety. The primary objective of this study was to develop an infrastructure-to-vehicle (I2V) integrated system that incorporated both ACC and VSL to reduce rear-end collision risks on freeways.

Methods: The intelligent driver model was firstly modified to simulate ACC behavior and then the VSL strategy used in this article was introduced. Next, the I2V system was proposed to integrate the 2 advanced techniques, ACC and VSL. Four scenarios of no control, VSL only, ACC only, and the I2V system were tested in simulation experiments. Time exposed time to collision (TET) and time integrated time to collision (TIT), 2 surrogate safety measures derived from time to collision (TTC), were used to evaluate safety issues associated with rear-end collisions. The total travel times of each scenario were also compared.

Results: The simulation results indicated that both the VSL-only and ACC-only methods had a positive impact on reducing the TET and TIT values (reduced by 53.0 and 58.6% and 59.0 and 65.3%, respectively). The I2V system combined the advantages of both ACC and VSL to achieve the most safety benefits (reduced by 71.5 and 77.3%, respectively). Sensitivity analysis of the TTC threshold also showed that the I2V system obtained the largest safety benefits with all of the TTC threshold values. The impact of different market penetration rates of ACC vehicles in I2V system indicated that safety benefits increase with an increase in ACC proportions.

Conclusions: Compared to VSL-only and ACC-only scenarios, this integrated I2V system is more effective in reducing rear-end collision risks. The findings of this study provide useful information for traffic agencies to implement novel techniques to improve safety on freeways.     

Modeling level-of-safety for bus stops in China

Objective: Safety performance at bus stops is generally evaluated by using historical traffic crash data or traffic conflict data. However, in China, it is quite difficult to obtain such data mainly due to the lack of traffic data management and organizational issues. In light of this, the primary objective of this study is to develop a quantitative approach to evaluate bus stop safety performance.

Methods: The concept of level-of-safety for bus stops is introduced and corresponding models are proposed to quantify safety levels, which consider conflict points, traffic factors, geometric characteristics, traffic signs and markings, pavement conditions, and lighting conditions. Principal component analysis and k-means clustering methods were used to model and quantify safety levels for bus stops.

Results: A case study was conducted to show the applicability of the proposed model with data collected from 46 samples for the 7 most common types of bus stops in China, using 32 of the samples for modeling and 14 samples for illustration. Based on the case study, 6 levels of safety for bus stops were defined. Finally, a linear regression analysis between safety levels and the number of traffic conflicts showed that they had a strong relationship (R² value of 0.908).

Conclusions: The results indicated that the method was well validated and could be practically used for the analysis and evaluation of bus stop safety in China. The proposed model was relatively easy to implement without the requirement of traffic crash data and/or traffic conflict data. In addition, with the proposed method, it was feasible to evaluate countermeasures to improve bus stop safety (e.g., exclusive bus lanes).     

WO_3/Ag_3VO_4复合光催化剂的制备及其可见光催化性能

采用超声辅助沉淀法—浸渍法制备了WO3/Ag3VO4复合光催化剂,对其进行了表征,考察了其在可见光条件下对罗丹明B的催化降解性能,并对催化机理进行了探讨。表征结果显示:WO3紧密包覆在Ag3VO4颗粒的表面,并未改变Ag3VO4的晶体结构;与Ag3VO4和WO3相比,WO3/Ag3VO4的吸收带边发生了红移。实验结果表明:w(WO3)为3.5%时,WO3/Ag3VO4对罗丹明B的可见光催化降解效果最好;在光催化剂加入量0.8 g/L、初始罗丹明B质量浓度10 mg/L的条件下,于室温下光照180 min时的罗丹明B去除率达95.76%,TOC去除率达96.5%;WO3与Ag3VO4在能带间的耦合作用下形成异质结结构,很好地抑制了光生电子-空穴对的复合。     

温岭市高架道路交通噪声空间分布规律与防治对策研究

为评价温岭市东环高架道路交通噪声的环境影响,采用实测法对东环高架附近代表性点位及不同时间段进行噪声监测,记录等效连续A声级(Leq),以及同步监测车流量、车型等相关数据.根据《声环境质量标准》(GB 3096-2008),由所得监测数据,推测其交通噪声空间分布规律.结果表明,噪声最大值发生于上下班高峰期,交通噪声则随距离的增加而衰减,而道路两侧高层建筑交通噪声随着高度的增加先由小变大后变小.此外,还为该高架道路交通噪声的防治提供一定的参考依据.     

上海市西部郊区PM2.5污染状况及影响因素

通过2014年上海市西部郊区PM2.5的浓度变化分析了该地区的PM2.5污染分布状况,并且从温度、湿度和风向等方面讨论了PM2.5浓度与气象因子的关联性.结果表明:该地区2014全年超标天数有112天,超标率为30.7％,PM2.5月均浓度呈夏低冬高的趋势状态,并且PM2.5浓度与气象条件有密切的联系.该地区气温在5～15℃、湿度在60～70％时PM2.5浓度最高;在以东风为主导风盛行时,该地区PM2.5浓度较低,而在以西风为主导风盛行时,该地区易受到周边区域的高污染因素影响,形成PM2.5高浓度累积现象.     

基于降低温室效应的航空器运行策略

以航空器运行对环境造成温室效应的两个主要因素—CO_2和凝结尾为研究对象,通过绝对全球温变潜势(AGTP)建立科学统一的衡量标准,将CO_2和凝结尾对环境的影响转换为全球地表温度的改变,为降低温室效应提供依据。最后结合典型高空的探空资料对实际增温进行计算,对比分析25、50、100年时间水平下CO_2和凝结尾对全球地表温度造成的影响,为航空器降低温室效应提供飞行高度指导。