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排序方式: 共有857条查询结果,搜索用时 437 毫秒
101.
Kai LIU Fengkui DUAN Kebin HE Yongliang MA Yuan CHENG 《Frontiers of Environmental Science & Engineering》2014,8(2):284-292
Polycyclic aromatic hydrocarbons (PAHs) are complex organic compounds which are identified as significant carcinogenic to human health. PAHs (mainly in particle phase) are susceptible to atmospheric oxidant gases, especially ozone, nitrogen oxides (NOx), hydroxyl radical (OH), and could be degraded on filters during sampling process, leading to an underestimation of ambient PAH concentrations. The goal of this work was to investigate particle associated PAHs sampling artifacts caused by ozone in summer of Beijing. Comparative sampling systems were operated simultaneously during the whole campaign, one with activated carbon ozone denuder, the other being set as conventional sampling system. Activated carbon denuder was testified to be highly efficient to eliminate ozone from air stream. In general, nine particle-bound PAHs observed from conventional sampler were all lower than those from ozone denuder system. The total PAHs (particle phase) concentration was averagely underestimated by 35.9% in conventional sampling procedure. Benzo[a]pyrene (BaP) had the highest percentage of mass loss. founded to have influences Ambient temperature was on PAHs sampling artifacts. High temperature can increase loss of particle associated PAHs during sampling. 相似文献
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103.
Yao CHEN Jinhui LI Huabo DUAN Zhishi WANG 《Frontiers of Environmental Science & Engineering》2011,5(2):167-174
Mechanical waste-processing methods, which combine crushing and separation processes for the recovery of valuable materials, have been widely applied in waste printed wiring board (PWB) treatment. However, both the high impact toughness and the tensile and flexural strengths of whole PWB with a laminated structure result in great energy consumption and severe abrasion of the cutters during multi-level crushing. In addition, the high temperatures occurring in continual crushing probably cause the decomposition of the polymer matrix. A thermal-crack method using residual steam as the heating medium has been developed to pre-treat waste PWBs. This treatment reduces the mechanical strength in order to improve the recovery rate of valuable materials in subsequent mechanical recycling. The changes of the PWBs’ macro-mechanical properties were studied to evaluate thermal expansion impacts associated with changes in temperature, and the dynamic dislocation micro-structures were observed to identify the fracture mechanism. The results showed that thermal cracking with steam at the temperature of 500 K can effectively attenuate the mechanical properties of waste PWBs, by reducing the impact, tensile and flexural strengths respectively, by 59.2%, 49.3% and 51.4%, compared to untreated PWB. Thermal expansion can also facilitate the separation of copper from glass fiber by reducing peel resistance by 95.4% at 500 K. It was revealed that the flexural fracture was a transverse cracking caused by concentrated stress when the heating temperature was less than 500 K, and shifted to a vertical cracking after exceeding 500 K. 相似文献
104.
Guangzhou has ambitions to build itself into a world class metropolis by 2010. Sustainable development is the only way to achieve this magnificent goal. Based on the ecological perspective of sustainable development and the principles of ecosystem integrity, this paper develops an approach for evaluation of sustainable development in Guangzhou between 1986 and 1995. A hierarchical evaluation system of four tiers of sustainability indicators was established. Using the method of fuzzy multistage synthetic evaluation, sustainability development level index, QIx, was calculated for the indicators at the B, C, D, and E tiers. Development stages were identified based on these index values. The coordination degree among the economic, social, and natural subsystems was also computed. Further, an overall sustainability index for each year was computed by combining the development level index and the coordination degree. It was found that the urban ecosystem in Guangzhou had generally become more sustainable, in spite of fluctuations in coordination degree. The development level index of the economic subsystem has surpassed that of social and natural subsystems since 1995. Appropriate measures must be taken to ensure coordinated development among the subsystems for the purpose of sustainable development. 相似文献
105.
水稻基因类型与生长环境对精米中砷积累的影响 总被引:6,自引:0,他引:6
砷(As)是动植物非必需的有毒类金属。水稻是对As有较强吸收和富集能力的大宗粮食作物,大米的食用是我国及东南亚地区人体暴露As的最主要途径,严重威胁人体健康。水稻籽粒中As的积累与水稻的基因型及众多环境因子密切相关,而且表现出复杂的交互作用。在浙江省选择了不同土壤砷背景值的5块水稻田,同时在嘉兴市农科院布置了人工添加As的盆栽实验,比较了20个水稻品种在这6个实验点的精米中As含量。结果表明,水稻基因型与环境及其相互作用对水稻籽粒中As的积累均有极显著影响,并且筛选得到了5个精米中As含量较低的基因型:秀水128、秀水09、秀水134、甬粳16和Y-05-8。 相似文献
106.
Lei Yuan Xiang Zheng Kaijiao Duan Hao Hu Jinggang Wang Seong Ihl Woo Zhiming Liu 《Frontiers of Environmental Science & Engineering》2013,7(3):457-463
Selective catalytic reduction of NO x by H2 in the presence of oxygen has been investigated over Pt/ Al2O3 catalysts pre-treated under different conditions. Catalyst preparation conditions exert significant influence on the catalytic performance, and the catalyst pre-treated by H2 or H2 then followed by O2 is much more active than that pre-treated by air. The higher surface area and the presence of metallic Pt over Pt/Al2O3 pre-treated by H2 or pretreated by H2 then followed by O2 can contribute to the formation of NO2, which then promotes the reaction to proceed at low temperatures. 相似文献
107.
基于湖南省97个地面气象观测站观测资料,根据所选定的阴雨天气评价指标,运用数理统计方法,对2012年上半年湖南省阴雨天气特征及强度进行分析评估,结果表明,阴雨天气阶段性特征显著,属隆冬至初春历史罕见的寡照低温多雨事件与初春至初夏的极端多雨寡照事件的组合。同时根据社会调查数据对阴雨天气的影响展开多方位分析,得出低温阴雨天气不仅对农业造成了重大影响,而且对水利、交通、建筑业等多行业和人们身体健康也有较大影响,以此提出了应对极端天气气候事件的对策建议。 相似文献
108.
Acrylamide (AA) is a potential human carcinogen, genotoxicant, and neurotoxicant. Thus, the aim of this study was to examine the ability of mercapto flavor compounds to remove AA released from consumer packaging into food products. Four mercapto flavor compounds including 1,2-ethanedithiol, 1-butanethiol, 2-methyl-3-furanthiol, and 2-furanmethanethiol were employed to extract AA in model system using high temperature and low humidity. Our study showed that mercaptans were effective in eliminating AA in our model system. In order to remove 0.2 μmol AA, the optimal conditions in the reaction system were mercaptan flavor chemicals at 5 μmol, temperature 180 °C, and reaction time 25 min. In the presence of a higher pH, the greater was the amount of AA eliminated. Evidence indicates that employment of mercapto flavor chemicals under certain temperature and pH conditions is a reliable method to remove any unwanted AA from food products. 相似文献
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110.