Disinfection byproducts in chlorinated or brominated swimming pools and spas: Role of brominated DBPs and association with mutagenicity

Although the health benefits of swimming are well-documented, health effects such as asthma and bladder cancer are linked to disinfection by-products (DBPs) in pool water. DBPs are formed from the reaction of disinfectants such as chlorine (Cl) or bromine (Br) with organics in the water. Our previous study (Daiber et al., Environ. Sci. Technol. 50, 6652; 2016) found correlations between the concentrations of classes of DBPs and the mutagenic potencies of waters from chlorinated or brominated swimming pools and spas. We extended this study by identifying significantly different concentrations of 21 individual DBPs in brominated or chlorinated pool and spa waters as well as identifying which DBPs and additional DBP classes were most associated with the mutagenicity of these waters. Using data from our previous study, we found that among 21 DBPs analyzed in 21 pool and spa waters, the concentration of bromoacetic acid was significantly higher in Br-waters versus Cl-waters, whereas the concentration of trichloroacetic acid was significantly higher in Cl-waters. Five Br-DBPs (tribromomethane, dibromochloroacetic acid, dibromoacetonitrile, bromoacetic acid, and tribromoacetic acid) had significantly higher concentrations in Br-spa versus Cl-spa waters. Cl-pools had significantly higher concentrations of Cl-DBPs (trichloroacetaldehyde, trichloromethane, dichloroacetic acid, and chloroacetic acid), whereas Br-pools had significantly higher concentrations of Br-DBPs (tribromomethane, dibromoacetic acid, dibromoacetonitrile, and tribromoacetic acid). The concentrations of the sum of all 4 trihalomethanes, all 11 Br-DBPs, and all 5 nitrogen-containing DBPs were each significantly higher in brominated than in chlorinated pools and spas. The 8 Br-DBPs were the only DBPs whose individual concentrations were significantly correlated with the mutagenic potencies of the pool and spa waters. These results, along with those from our earlier study, highlight the importance of Br-DBPs in the mutagenicity of these recreational waters.     

Life cycle assessment of hot mix asphalt and zeolite-based warm mix asphalt with reclaimed asphalt pavement

A comprehensive life cycle assessment of asphalt pavements was conducted including hot mix asphalt (HMA), warm mix asphalt (WMA) with the addition of synthetic zeolites, and asphalt mixes with reclaimed asphalt pavement (RAP). The environmental impacts associated with energy consumption and air emissions were assessed, as well as other environmental impacts resulting from the extraction and processing of minerals, binders and chemical additives; asphalt production; transportation of materials; asphalt paving; road traffic on the pavement; land use; dismantling of the pavement at the end-of-life and its landfill disposal or recycling. Monte Carlo simulations were also conducted to take into account the variability of critical input parameters. Taking into account the entire life cycle, the impacts of zeolite-based WMA pavements were almost equal to the impacts of HMA pavements with the same RAP content. The reduction in the impacts of WMA resulting from the lowering of the manufacturing temperature was offset by the greater impacts of the materials used, especially the impacts of the synthetic zeolites. Moreover, by comparing asphalt mixes with different RAP contents, it was shown that the impacts of asphalt mixes were significantly reduced when RAP was added. All endpoint impacts as well as climate change, fossil depletion and total cumulative energy demand were decreased by 13–14% by adding 15% RAP. A key advantage of WMA is the potentially greater use of RAP. Thus, the decrease in the impacts achieved by adding large amounts of RAP to WMA could turn these asphalt mixes into a good alternative to HMA in environmental terms.     

Consumer reflections on the usage of plastic bags to parcel hot edible items: an empirical study in Malaysia

The packaging industry offers a wide range of pouching products to their clients in the food and beverage industries, healthcare industries and households as well. It is observed that pouching products are widely used and seemingly making them indispensable. Such practices are commonly found in Malaysia especially to parcel hot or cold food. The use of pouches raises two concerns namely solid waste disposal and food safety. The present study found more than 62% of the consumers purchase hot edible items in plastic bags daily or weekly because of its cost effectiveness and storage convenience. Consumers apparently are unperturbed by public campaigns against the use of plastic bags and neither do government regulations have any influence to reduce the use of plastic bags to parcel hot edible items. On the other hand, consumers are optimistic that the environmental and health hazards from the use of plastic bags to store hot edible items would only see a positive impact in the future.     

Hot water flushing for immiscible displacement of a viscous NAPL

Thermal remediation techniques, such as hot water flooding, are emerging technologies that have been proposed for the removal of nonaqueous phase liquids (NAPLs) from the subsurface. In this study a combined laboratory and modeling investigation was conducted to determine if hot water flooding techniques would improve NAPL mass removal compared to ambient temperature water flushing. Two experiments were conducted in a bench scale two-dimensional sandbox (55 cmx45 cmx1.3 cm) and NAPL saturations were quantified using a light transmission apparatus. In these immiscible displacement experiments the aqueous phase, at 22 degrees C and 50 degrees C, displaced a zone with initial NAPL saturations on the order of 85%. The interfacial tension and viscosity of the selected light NAPL, Voltesso 35, are strongly temperature-dependent. Experimental results suggest that hot water flooding reduced the size of the high NAPL saturation zone, in comparison to the cold water flood, and yielded greater NAPL mass recovery (75% NAPL removal vs. 64%). Hot water flooding did not, however, result in lower residual NAPL saturations. A numerical simulator was modified to include simultaneous flow of water and organic phases, energy transport, temperature and pressure. Model predictions of mass removal and NAPL saturation profiles compared well with observed behavior. A sensitivity analysis indicates that the utility of hot water flooding improves with the increasing temperature dependence of NAPL hydraulic properties.     

热锻-冷锻复合塑性成形技术

热锻-冷锻复合塑性成形技术将热锻和冷锻技术结合起来使用，可成形高精度的复杂形状零计，且降低了成本，取得了良好的效果。介绍了热锻冷报技术的概况及其在工业生产中的若干应用实例。     

Ignition tests for electrical and mechanical equipment subjected to hot surfaces

This paper reports some experimental work on hot surface ignition temperatures of dust deposits. Dust layers up to 75 mm in depth were ignited using a modified version of the standard 5 mm layer apparatus. The measured ignition temperatures show good agreement with predictions using the method given in EN 50281-2-1. Ignition temperatures of conical dust deposits over an electrically heated box were not predictable, but were not too dissimilar from the ignition temperatures of the thick layers. Both tests gave adequate reproducibility in round robin tests. Rotating steel wheels in contact, immersed in a dust deposit produce the frictional hot surfaces. A relation between the power lost by friction and the surface temperature developed has been derived. The surface temperatures leading to ignition were close to the ignition temperatures for the conical deposits on the heated box. The similarities between the ignition temperatures of dust deposits in several configurations indicate that a simple test for ignition temperature measurement could have wide application in dusty environments.     

基于改进达标检测法的跨区域排污权交易体系研究

由于污染排放存在时空与行业"热点"(hot spots)问题,针对非均匀污染物建立跨区域排污权交易体系具有一定困难。基于一种新的污染外部性度量系数,本文对传统的达标检测方法进行了改进,在此改进达标检测法上构建的跨区域排污权交易体系,能够在简化交易机制和管理工作的同时较好地解决"热点"问题,在社会总产出和总排污量不变的情况下实现社会福利的帕累托改进。     

热颗粒和热辐射共同作用阴燃点燃松针燃料床：数值研究

建立了热颗粒和热辐射共同作用下阴燃点燃松针燃料床的二维数值模型,计算得到了热颗粒和热辐射单独点燃以及共同作用点燃的临界条件,分析了燃料床的点燃过程。与前人实验数据对比表明数值模型能够较好预测临界点燃条件。金属热颗粒单独作用时点火所需的临界温度与颗粒直径呈双曲线关系。金属热颗粒与热辐射共同作用时,临界辐射热通量呈现出随颗粒温度和直径的增加而显著减小的趋势。热辐射持续供热能有效维持表层炭氧化反应,两者共同作用下点燃危险性增加。研究同时发现,燃料含水率对共同作用下的临界辐射热通量有较大影响。     

热爆炸研究的主题聚类、趋势与影响

为全面认识国际热爆炸研究的主题聚类、趋势与影响,使用科技文本挖掘工具VOSviewer对科睿唯安SCI数据库中的1 415篇热爆炸研究论文进行了分析。结果表明:国际热爆炸研究的热点主要分布在燃烧合成、分解、点火、晶体结构、含能材料等方面;以高频关键词为中心形成了5个主要聚类,分别为热爆炸理论基础、热合成、热分解、热行为及含能材料与晶体结构。主题趋势显示热爆炸研究在整体上首先经历了热爆炸理论基础研究,并渗透到了热合成、热分解、热行为和含能材料与晶体结构等方面,高影响主题集中在热合成和热分解两个领域。热合成研究的高影响主题相比其他领域要更加显著,高影响主题涉及传播、镍铝化物、钛镍、铝、碳化及致密化等方面。相比而言,作为热爆炸研究的基础领域,热爆炸理论研究的热度及对应聚类主题的整体引用次数要显著低于目前活跃的领域。     

火灾中摩擦火花和热表面引燃能力的研究

用摄影和热点偶等方法在一个有磨削轮的容器中研究了机械摩擦火花和热表面的引燃能力。在本研究中发现,对于某些材料,如碳钢等,由摩擦产生的磨屑可以被周围空气中的氧氧化而放出大量的热,从而使屑粒温度升高,达到白热程度。通常我们把一簇这样的颗粒中做“摩擦火花”。