Pathways and Kinetics on Photocatalytic Destruction of Aqueous Phenol

In this study, the TiO₂ photocatalytic decomposition process of aqueous phenol was investigated. The intermediate products generated in the elementary reaction steps in the mineralization process were experimentally identified as hydroquinone, catechol and hydroxyhydroquinone. The concentration variations of these intermediate products with time passage were traced by high performance liquid chromatograph. The pathways of the decomposition process were given. Based on Langmuir isothermal theory and Langmuir-Hinshelwood mechanism, the multi-compounds competition kinetic model was established. In this model, the observed time-dependent concentrations of phenol and the intermediate products were simulated.     

燃料NO生成的总包反应速率

基于全面化学反应体系,对燃料ＮＯ的反应特性进行了详细的数值计算和理论分析,指出了目前应用较多的ＤｅＳｏｅｔｅＮＯ总反应模型的不足,同时,通过引入燃料氮氧化过程中关联组分Ｏ与ＯＨ离子的浓度和,用多元回归的方法得到了燃料ＮＯ生成的总包反应速率表达式。     

Degradation of atrazine by catalytic ozonation in the presence of iron scraps: performance,transformation pathway,and acute toxicity

Degradation of atrazine by catalytic ozonation in the presence of iron scraps (ZVI/O₃) was carried out. The key operational parameters (i.e., initial pH, ZVI dosage, and ozone dosage) were optimized by the batch experiments, respectively. This ZVI/O₃ system exhibited much higher degradation efficiency of atrazine than the single ozonation, ZVI, and traditional ZVI/O₂ systems. The result shows that the pseudo-first-order constant (0.0927?min^?1) and TOC removal rate (86.6%) obtained by the ZVI/O₃ process were much higher than those of the three control experiments. In addition, X-ray diffraction (XRD) analysis indicates that slight of γ-FeOOH and Fe₂O₃ were formed on the surface of iron scrap after ZVI/O₃ treatment. These corrosion products exhibit high catalytic ability for ozone decomposition, which could generate more hydroxyl radical (HO^?) to degrade atrazine. Six transformation intermediates were identified by liquid chromatography-mass spectrometry (LC-MS) analysis in ZVI/O₃ system, and the degradation pathway of atrazine was proposed. Toxicity tests based on the inhibition of the luminescence emitted by Photobacterium phosphoreum and Vibrio fischeri indicate the detoxification of atrazine by ZVI/O₃ system. Finally, reused experiments indicate the approving recyclability of iron scraps. Consequently, the ZVI/O₃ system could be as an effective and promising technology for pesticide wastewater treatment.     

Effects of growth substrate on triclosan biodegradation potential of oxygenase-expressing bacteria

Triclosan is an antimicrobial agent, an endocrine disrupting compound, and an emerging contaminant in the environment. This is the first study investigating triclosan biodegradation potential of four oxygenase-expressing bacteria: Rhodococcus jostii RHA1, Mycobacterium vaccae JOB5, Rhodococcus ruber ENV425, and Burkholderia xenovorans LB400. B. xenovorans LB400 and R. ruber ENV425 were unable to degrade triclosan. Propane-grown M. vaccae JOB5 can completely degrade triclosan (5 mg L⁻¹). R. jostii RHA1 grown on biphenyl, propane, and LB medium with dicyclopropylketone (DCPK), an alkane monooxygenase inducer, was able to degrade the added triclosan (5 mg L⁻¹) to different extents. Incomplete degradation of triclosan by RHA1 is probably due to triclosan product toxicity. The highest triclosan transformation capacity (T_c, defined as the amount of triclosan degraded/the number of cells inactivated; 5.63 × 10⁻³ ng triclosan/16S rRNA gene copies) was observed for biphenyl-grown RHA1 and the lowest T_c (0.20 × 10⁻³ ng-triclosan/16S rRNA gene copies) was observed for propane-grown RHA1. No triclosan degradation metabolites were detected during triclosan degradation by propane- and LB + DCPK-grown RHA1. When using biphenyl-grown RHA1 for degradation, four chlorinated metabolites (2,4-dichlorophenol, monohydroxy-triclosan, dihydroxy-triclosan, and 2-chlorohydroquinone (a new triclosan metabolite)) were detected. Based on the detected metabolites, a meta-cleavage pathway was proposed for triclosan degradation.     

Accumulation of hydroxylated polychlorinated biphenyls (OH-PCBs) and implications for PCBs metabolic capacities in three porpoise species

The present study investigated polychlorinated biphenyls (PCBs) and hydroxylated metabolites of PCBs (OH-PCBs) in blood from three porpoise species: finless porpoises (Neophocaena phocaenoides), harbor porpoises (Phocoena phocoena), and Dall’s porpoises (Phocoenoides dalli). The porpoises were found stranded or were bycaught along the Japanese coast. Concentrations of OH-PCB were the highest in Dall’s porpoises (58 pg g⁻¹ wet wt), second highest in finless porpoises (20 pg g⁻¹ wet wt), and lowest in harbor porpoises (8.3 pg g⁻¹ wet wt). The concentrations in Dall’s porpoises were significantly higher than the concentrations in finless porpoises and harbor porpoises (p < 0.05 and p < 0.01, respectively). There was a positive correlation between PCB and OH-PCB concentrations (r = 0.67, p < 0.001), suggesting the possible concentration-dependent induction of CYP enzymes. The three porpoise species may have exceptionally low metabolic capacities compared with other marine and terrestrial mammals, because low OH-PCB/PCB concentration ratios were found, which were 0.0016 for Dall’s porpoises, 0.0013 for harbor porpoises, and 0.00058 for finless porpoises. Distinct differences in the OH-PCB congener patterns were observed for the three species, even though they are taxonomically closely related.     

The Valuation of Health Effects Caused by Stationary Sources–Related SO2 Emissions: The Adaptation of Impact Pathway Approach in Taiwan

This paper presents the externalities of sulfur dioxide (SO₂) in the Taichung metropolitan, Taiwan. The human effects of SO₂ from stationary sources are a key element for local air quality management. A methodology to evaluate those effects in monetary term had been adapted and applied. This method was modified from the EU-based impact pathway approach link to the skill of geographic information systems. The studied area was divided into 66 districts and the quantity of SO₂ was allocated to each district. Then, the ambient concentration of SO₂ was estimated by using the ordinary kriging method. A risk analysis was employed to characterize the health impacts caused by SO₂. Finally, a monetary transfer approach based on the European data was conducted to estimate local damage costs per ton of SO₂. Health impacts, especially acute mortality, dominate in term of costs. The calculation showed that damage costs ranged from 0.56 to 7.38 USD/kg SO₂ based on the 2002 emission data. The results could be used in the internalization of SO₂ externalities and management of the stationary sources in the studied area. This paper also concludes that the externalities caused by stationary-related SO₂ emissions are some 28.5 million US dollars in Taichung metropolitan (Taiwan) in 2002.     

SBR单级自养脱氮系统氮素转化途径

利用氮素计量关系和批式实验研究了SBR系统中基于短程硝化的单级自养脱氮特性和脱氮途径。结果表明,SBR系统获得良好脱氮效果,TN最高去除负荷和去除速率分别达0.49 kg N/(m3.d)和0.20 kg N/(kg VSS.d);系统中82%的氨氮转化成气体脱除,10%的氨氮转化成硝酸盐氮。批式实验结果表明,SBR系统中的污泥同时具有厌氧氨氧化、亚硝酸盐氧化和自养反硝化活性,三者的反应速率分别为0.12 kg NH4+-N/(kg VSS.d)、0.04 kg NO2--N/(kg VSS.d)和0.03 kg NO2--N/(kg VSS.d)。综上,SBR系统中氮的脱除是短程硝化、厌氧氨氧化和反硝化共同作用的结果,产生的硝酸盐是厌氧氨氧化和硝化作用所致。     

可持续发展视角下的中央商务区低碳发展路径和策略探讨

随着城市建设的不断推进,中央商务区(CBD)的可持续发展受到越来越多关注。随着全球气候变化的日益加剧,低碳CBD作为一种新型的CBD发展模式被提出。基于国内外已有的CBD建设研究,以可持续发展理念为指引,在解析CBD发展历程的基础上,探究了中国CBD低碳建设的路径和策略。CBD的碳排放特征分析表明,"低碳CBD"的发展路径必须将低碳理念贯彻到规划期、建设期及运营期等各个阶段,坚持全生命周期的低碳管理。最后,从量化低碳目标、创新低碳政策和持续改进地管理低碳建设3个方面提出了低碳CBD的发展策略。     

Decomposition of 2,2',4,4',5,5'-hexachlorobiphenyl with iron supported on an activated carbon from an ion-exchange resin

An activated carbon (AC) containing a high concentration (374 mg g⁻¹) of Fe was prepared by carbonization of an ion-exchange resin. To examine its chemical reactivity as a catalyst to decompose 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB-153), the decomposition parameters of temperature and time were varied under air or N₂. Decomposition at 350 °C was achieved within 15 min under air and 30 min under N₂, and the efficiency of PCB-153 decomposition was 99.7% and 98.0%, respectively. An analysis of inorganic chloride ions revealed that PCB-153 was mineralized effectively during the decomposition. The Brunauer-Emmett-Teller (BET) surface area and pore volume of the AC were measured to assess the adsorption capacity before and after the decomposition. The differences between decomposition under air and N₂ reflected the differences in the BET surface and pore volume measurements. A decomposition pathway was postulated, and the reactive characteristics of chlorine atoms loaded on the benzene rings followed the order of para > meta > ortho, which agrees with the calculated results from a density functional theory study.