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Qing Xie Jingwen Chen Jianping Shao Changer Chen Hongxia Zhao Ce Hao 《Chemosphere》2009,76(11):1486-1490
Photolysis of deca-bromodiphenyl ether (BDE-209) was investigated in tetrahydrofuran, dichloromethane, isopropanol, acetone, ethanol, methanol, acetonitrile and dimethylsulfoxide. Noticeable differences of the photolytic rates and quantum yields were found in the diverse solvents. Different to the previous deductions, hydrogen donating efficiency and electron donating efficiency of solvents were not the decisive factors for the photolytic rate in this study, which was proved by the fast photolysis of BDE-209 in CCl4, a solvent without hydrogen and difficult to donate electrons. Besides hydrogen addition process, intermolecular polymerization might occur during the photolysis. Density functional theory (DFT) calculation was performed to understand the molecular properties of BDE-209 in different solvents. The lowest singlet vertical excitation energy (Eex) and the average formal charge on Br () of BDE-209, reflecting the difficulty for the excitation of BDE-209 and for the departing of Br atom, respectively, were changed by the reaction fields formed by the different solvents. Eex and linearly correlated with the photolytic activity (log k). This study is helpful to better understand the photolytic behavior of BDE-209 in different media. 相似文献
163.
Qing Zhou Christine W. Chan Paitoon Tontiwachiwuthikul Raphael Idem Don Gelowitz 《International Journal of Greenhouse Gas Control》2009,3(5):535-544
Post combustion carbon dioxide (CO2) capture is one of the most commonly adopted technologies for reducing industrial CO2 emissions, which is now an important goal given the widespread concern over global warming. Research on amine-based CO2 capture has mainly focused on improving effectiveness and efficiency of the CO2 capture process. Our research work focuses on studying the relationships among the significant parameters influencing CO2 production because an enhanced understanding of the intricate relationships among the parameters involved in the process is critical for improving efficiency of the CO2 capture process. This paper presents a statistical study that explores the relationships among parameters involved in the amine-based post combustion CO2 capture process at the International Centre for CO2 Capture (ITC) located in Regina, Saskatchewan of Canada. A multiple regression technique has been applied for analysis of data collected at the CO2 capture pilot plant at ITC. The parameters have been carefully selected to avoid issues of multicollinearity, and four mathematical models among the key parameters identified have been developed. The models have been tested, and accuracy of the models is found to be satisfactory. The models developed in this study describe part of the CO2 capture process and can help to predict performance of the CO2 capture process at ITC under different conditions. Some results from a preliminary validation process will also be presented. 相似文献
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大型活动生物恐怖应急处置研究与系统开发 总被引:1,自引:1,他引:0
针对非传统安全威胁的现状及其应急处置中的主要问题,以典型的非传统安全事件-大型活动举办过程中生物恐怖事件为背景,通过比较分析,给出了生物恐怖的定义;从大型活动生物恐怖应急指挥与处置的角度,通过应急处置业务流程分析,提出了大型活动生物恐怖事件应急处置的系统框架;根据系统框架和处置功能分析,基于三维GIS和AJAX技术开发了大型活动生物恐怖应急处置原型系统,对复杂的应急处置体系进行了分层模块化和可视化,可为应急救援部门制定更为详细的救援方案和应急决策提供技术参考。 相似文献
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为考察溶胶凝胶法制备的Co-Mo二元硫化物对H_2S气体的电催化活性,通过循环伏安法和Tafel曲线分析对铂载不同Co、Mo掺杂比的电催化剂进行表征.结果表明,不同阳极电催化剂交换电流密度J_0由大到小依次为,铂载n(Co):n(Mo)=2:3、铂载n(Co):n(Mo)=2:1、铂载n(Co):n(Mo)=1:1和铂,即铂载n(Co):n(Mo)=2:3阳极电催化剂具有较好的活性,这与循环伏安曲线测试结果一致.电解质溶液pH值为6~7时,随着温度的升高铂载n(co):n(Mo)=2:3阳极电催化剂活性呈现上升的趋势.优化后的Co、Mo掺杂原子比约为0.66,此类电催化剂在操作温度80℃下,交换电流密度为1.318mA/cm~2,表观活化焙值为616.6 kJ/mol .研究表明,铂载钴钼二元硫化物适合作为低温H_2S燃料电池阳极电催化剂,其中Co、Mo掺杂比对电催化活性影响较大. 相似文献
169.
城市化进程的加快,农村人口大量涌入城市,城市布局及局部气候改变等因素使得城市热岛效应问题日益突出,已成为当前城市环境研究热点之一。以武汉市为例,应用遥感技术与地理信息系统技术,选取2004~2015年5个时相Landsat系列影像数据,利用单窗算法反演地表温度,并以此为基础进行热岛强度分级,获取了近10 a武汉市城市热岛效应变化结果,并分析了武汉市11个辖区城市热岛效应动态变化特征及热岛效应与土地利用变化的关系。研究结果表明:(1)自2007年后,武汉市老城区热岛面积持续减少,而新城区热岛面积则持续增加,呈现出以老城区为中心向新城区扩张的趋势,至2015年,新老城区热岛面积仅相差20.74 km2;(2)东西湖区、蔡甸区、江夏区与洪山区是近些年城市热岛面积增长较为显著的辖区,其中江夏区的热岛面积年际变化最大,最高值达95.42 km2;(3)城市热岛效应与土地利用类型的面积年际平均值拟合关系显示,2004~2015年,城市热岛效应与建筑用地的R2值最大,为0.681 2,建筑用地面积的增加是城市热岛强度面积扩张的重要影响因素。 相似文献
170.
Dong Qing Zhang Tao Hua Richard M. Gersberg Junfei Zhu Wun Jern Ng Soon Keat Tan 《Chemosphere》2013,90(4):1568-1572
Uptake, accumulation and translocation of caffeine by Scirpus validus grown in hydroponic condition were investigated. The plants were cultivated in Hoagland’s nutrient solution spiked with caffeine at concentrations of 0.5–2.0 mg L?1. The effect of photodegradation on caffeine elimination was determined in dark controls and proved to be negligible. Removal of caffeine in mesocosms without plants showed however that biodegradation could account for about 15–19% of the caffeine lost from solutions after 3 and 7 d. Plant uptake played a significant role in caffeine elimination. Caffeine was detected in both roots and shoots of S. validus. Root concentrations of caffeine were 0.1–6.1 μg g?1, while the concentrations for shoots were 6.4–13.7 μg g?1. A significant (p < 0.05) positive correlation between the concentration in the root and the initial concentrations in the nutrient solution was observed. The bioaccumulation factors (BAFs) of caffeine for roots ranged from 0.2 to 3.1, while BAFs for shoots ranged from 3.2 to 16.9. Translocation from roots to shoots was the major pathway of shoot accumulation. The fraction of caffeine in the roots as a percentage of the total caffeine mass in solution was limited to 0.2–4.4% throughout the whole experiment, while shoot uptake percentage ranged from 12% to 25% for caffeine at the initial concentration of 2.0 mg L?1 to 50–62% for caffeine at the initial concentration of 0.5 mg L?1. However, a marked decrease in the concentration of caffeine in the shoots between d-14 and d-21 suggests that caffeine may have been catabolized in the plant tissues subsequent to plant uptake and translocation. 相似文献