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431.
为综合利用黄磷尾气中的CO,通过计算平均活化能和测定XPS、TG/DTA和氮吸附特性的方法,研究了Cu2+和某金属离子Mn+改性碳脱除PH3和H2S的动力学和反应机理问题。结果表明:H2S在金属改性碳上反应时平均活化能为134.4 J/mol为-0.76级反应,PH3在金属改性碳上反应时平均活化能为1 247.6 J/mol为-0.8级反应;减小改性碳粒径增加流量可以显著提高其脱除PH3和H2S的速率;XPS、TG/DTA和孔径分布分析证明,改性碳净化H2S和PH3是一个催化吸附过程,H2S和PH3首先与氧在改性碳表面进行催化氧化反应,然后生成S和P2O5沉积吸附在改性碳表面。 相似文献
432.
纳米TiO2光催化降解硝基酚类污染物动力学及机理的研究 总被引:1,自引:0,他引:1
采用纳米TiO2(P25)粉末作为催化剂,研究了几种典型硝基取代酚在TiO2/UV悬浮体系下的光催化降解。研究表明,这些化合物的降解过程符合Langmuir-Hinshelwood动力学方程,其表观速率常数(kapp)的大小为:2-氨基-4硝基酚(2-A,4-NP)>4-硝基酚(4-NP)>2-硝基酚(2-NP)>3-硝基酚(3-NP)>2,4-二硝基酚(2,4-DNP)>2,4,6-三硝基酚(2,4,6-TNP),而吸附平衡常数(KL)却与kapp成反比。苯环上取代基的种类和数目对有机物光催化降解活性有很大的影响,硝基的加入降低了光催化活性,并且kapp与Hammett常数(σ)具有较好的线性关系。 相似文献
433.
434.
Canada responded to the Global Biodiversity Convention by completing the Canadian Biodiversity Strategy in 1995. At the same time, Environment Canada also completed a national Science Assessment on Biodiversity. During this period, the Smithsonian Institution, in partnership with Parks and Environment Canada, initiated the implementation of a global biodiversity monitoring program in Canada. Under the auspices of the United Nations Man and the Biosphere Program, the SI/MAB monitoring protocols and plots have spread across Canada at an unprecedented rate. National champions in the science and educational sectors, working within an inter-disciplinary ecological framework, have guided the development, education, quality control and sharing of atmosphere-biodiversity observations electronically.Atmospheric-Biodiversity Networks and Networking have traditionally operated within separate mandates with little degree of integration. Air-Bio Networks were designed within an integrated framework to better understand the atmospheric stress on biodiversity and the adaptation actions, nationally and regionally. Detailed examples of the cumulative effects of climate change, stratospheric ozone depletion, acid deposition, ground-level ozone, suspended particulate matter and hazardous air pollutants on biodiversity will be discussed using a Southern Ontario case study. In addition, recommendations will be presented for future paired SI/MAB plots, linked networks and networking for adaptation within the context of climate, chemical and ecological gradients. 相似文献
435.
A new all season passive sampling system for monitoring O3 in the atmosphere has been developed in the laboratory and validated in the field. The unique features for this system include a newly designed passive sampler and a rain shelter, which allow the passive sampler to be installed in the field facing downwards. An equation associated with meteorological parameters is used to calculate the passive sampling rates. This system has been extensively tested in the lab (temperature from –18 to 20°C, relative humidity from 13 to 81%, and wind speed from 0.5 to 150 cm/s) and validated in the field in climates of all seasons. The accuracy of the ozone concentrations in the atmosphere obtained with the use of the new passive sampling system was higher than 85% compared to those obtained with continuous ozone analyzers. The new ozone passive sampling system can be used to measure ambient O3 concentrations ranging from 3 ppb to 1000 ppb based on one-day exposure and 0.1 ppb to 140 ppb for a monthly exposure period. It is also reasonable to conclude that the new passive sampling system can be used for eight-hour exposure study because of the low field blanks and high sampling rates. 相似文献
436.
Enhanced photocatalytic activity of TiO2 by surface fluorination in degradation of organic cationic compound 总被引:3,自引:2,他引:1
Experiments were carried out to investigate the influence of TiO2 surface fluorination on the photodegradation of a representative organic cationic compound, Methylene Blue (MB). The eleetropositive MB shows poor adsorption on TiO2 surface; its degradation performs a HO. radical-mediated mechanism. In the F-modified system, the kinetic reaction rate enlarged more than 2.5 fold that was attributed mainly to the accumulating adsorption of MB and the increased photogenerated hole available on the F-modified TiO2 surface. 相似文献
437.
In this study, the surface chemical functional groups of Bacillus cereus biomass were identified by Fourier transform infrared (FTIR) analytical technique. It had been shown that the B. cereus cells mainly contained carboxyl, hydroxyl, phosphate, amino and amide functional groups. The potentiometric titration was conducted to explain the surface acid-base properties of aqueous B. cereus biomass. The computer program FITEQL 4.0 was used to perform the model calculations. The optimization results indicated that three sitesthree pKas model, which assumed the cell surface to have three distinct types of surface organic functional groups based on the IR analysis results, simulated the experimental results very well. Moreover, batch adsorption experiments were performed to investigate biosorption behavior of Cu(Ⅱ) and Pb(Ⅱ) ions onto the biomass. Obviously, the adsorption equilibrium data for the two ions were reasonably described by typical Langmuir isotherm. 相似文献
438.
Temperature dependence of the absolute rate constant for the reaction of ozone
with dimethyl sulfide
Absolute rate constants for the reaction of ozone with dimethyl sulfide (DMS) were measured in a 200-L Teflon chamber over the temperature range of 283-353 K. Measurements were carried out using DMS in large excess over ozone of 10 to 1 or greater. Over the indicated temperature range,the data could be fit to the simple Arrhenius expression as KDMS = (9.96±3.61)×10-11exp(-(7309.7±1098.2)/T)cm3/(molecule·s). A compared investigation of the reaction between ozone and ethene had a kc2H4 value of(1.35±0.11)×10-18 cm3/(molecule·s) at room temperature. 相似文献
439.
HAN Hai-yan HUANG Guo-dong JIN Shun-ping ZHENG Pei-chao XU Guo-hu LI Jian-quan WANG Hong-mei CHU Yan-nan 《环境科学学报(英文版)》2007,19(6):751-755
Ion mobility spectrometry (IMS) is a very fast, highly sensitive, and inexpensive technique, it permits efficient monitoring of volatile organic compounds like alcohols. In this article, positive ion mobility spectra for six alcohol organic compounds have been systematically studied for the first time using a high-resolution IMS apparatus equipped with a discharge ionization source. Utilizing protonated water cluster ions (H2O)nH^+ as the reactant ions and clean air as the drift gas, alcohol organic compounds, ethanol, 1- propanol, 2-propanol, 1-butanol, 1-pentanol and 2-octanol, all exhibit product ion characteristic peaks in their respective ion mobility spectrometry, that is a result of proton transfer reactions between the alcohols and reaction ions (H2O)nH^+. The mixture of these alcohols, including two isomers, has been detected, and the results showed that they could be distinguished effectively in the ion mobility spectrum. The reduced mobility values have been determined, which are in very well agreement with the traditional ^63Ni-IMS experimental values. The exponential dilution method was used to calibrate the alcohol concentrations, and a detection limit available for the alcohols is in order of magnitude of a few ng/L. 相似文献
440.
CAI Peng HUANG Qiao-yun LU Yan-du CHEN Wen-li JIANG Dai-hu LIANG Wei 《环境科学学报(英文版)》2007,19(11):1326-1329
Polymerase chain reaction(PCR)was used to amplify a 600-base pair(bp)sequence of plasmid pGEX-2T DNA bound on soil colloidal particles from Brown soil(Alfisol)and Red soil(Ultisol),and three different minerals(goethite,kaolinite,montmorillonite). DNA bound on soil colloids,kaolinite,and montmorillonite was not amplified when the complexes were used directly but amplification occurred when the soil colloid or kaolinite-DNA complex was diluted,10- and 20-fold.The montmorillonite-DNA complex required at least 100-fold dilution before amplification could be detected.DNA bound on goethile was amplified irrespective of whether the complex was used directly,or diluted 10- and 20-fold.The amplification of mineral-bound plasmid DNA by PCR is,therefore,markedly influenced by the type and concentration of minerals used.This information is of fundamental importance to soil molecular microbial ecology with particular reference to monitoring the fate of genetically engineered microorganisms and their recombinant DNA in soil environments. 相似文献