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601.
The photocatalytic degradation of gaseous trichloroethylene (TCE) without water has been studied. The degradation products were determined to be CO2, HCl and Cl2, and the reaction stoichiometry, was described as . The degradation rate was found to be linear with 0.16 power of the illumination intensity. When the TCE concentration was low (1014 mol L−1 or a little more), its degradation rate model could be considered as first order kinetics. A mechanism of valence band hole oxidation was proposed. 相似文献
602.
Tracer experiments conducted using a flow field established by injecting water into one borehole and withdrawing water from another are often used to establish connections and investigate dispersion in fractured rock. As a result of uncertainty in the uniqueness of existing models used for interpretation, this method has not been widely used to investigate more general transport processes including matrix diffusion or advective solute exchange between mobile and immobile zones of fluid. To explore the utility of the injection-withdrawal method as a general investigative tool and with the intent to resolve the transport processes in a discrete fracture, two tracer experiments were conducted using the injection-withdrawal configuration. The experiments were conducted in a fracture which has a large aperture (>500 microm) and horizontally pervades a dolostone formation. One experiment was conducted in the direction of the hydraulic gradient and the other in the direction opposite to the natural gradient. Two tracers having significantly different values of the free-water diffusion coefficient were used. To interpret the experiments, a hybrid numerical-analytical model was developed which accounts for the arcuate shape of the flow field, advection-dispersion in the fracture, diffusion into the matrix adjacent to the fracture, and the presence of natural flow in the fracture. The model was verified by comparison to a fully analytical solution and to a well-known finite-element model. Interpretation of the tracer experiments showed that when only one tracer, advection-dispersion, and matrix diffusion are considered, non-unique results were obtained. However, by using multiple tracers and by accounting for the presence of natural flow in the fracture, unique interpretations were obtained in which a single value of matrix porosity was estimated from the results of both experiments. The estimate of porosity agrees well with independent measurements of porosity obtained from core samples. This suggests that: (i) the injection-withdrawal method is a viable tool for the investigation of general transport processes provided all relevant experimental conditions are considered and multiple conservative tracers are used; and (ii) for the conditions of the experiments conducted in this study, the dominant mechanism for exchange of solute between the fracture and surrounding medium is matrix diffusion. 相似文献
603.
Evaluation of PCDD/F congener distributions in MWI flue gas treated with SCR catalysts 总被引:1,自引:0,他引:1
Partitioning of PCDD/F congeners between gaseous and particulate phases and removal efficiencies of the air pollution control devices (APCDs) for PCDD/Fs at an existing municipal waste incinerator (MWI) in Taiwan are evaluated via stack sampling and analysis. The MWI investigated is equipped with electrostatic precipitators (EP), wet scrubbers (WS) and selective catalytic reduction system (SCR) as APCDs. The average PCDD/F concentration of stack gas is 1.49 ng/N m3, and the International Toxic Equivalent Quantity (I-TEQ) is 0.043 ng-I-TEQ/N m3. The EP increases PCDD/F concentration by 174.0% while the average removal efficiency of WS + SCR system for PCDD/Fs reaches 99.1%. In addition, the PCDF removal efficiency achieved with WS + SCR system (97.1–99.8%) is higher than that for PCDDs (96.5–99.3%). The results obtained on gas/particulate partitioning in flue gas indicate that the particulate-phase PCDD/Fs accounted for 65% at the inlet of EP, 20% at the outlet of EP and 50% at the stack, respectively, of the total PCDD/F concentrations. This study also indicates that as the chlorination level of PCDD/F congeners increases, the percentage of PCDD/Fs existing in gas phase decreases in all flue gas samples. 相似文献
604.
甲醇为无色挥发性澄明液体,沸点64.7℃,比重0.792。甲醇对人体有麻醉作用、特别是对眼睛毒害作用明显,易造成失明。空气中甲醇含量达到6.7 ̄36.5%时,形成爆炸性混合物,甲醇为易燃工业原料。甲醇的分析方法常采用比色法(1)和气相色谱法(2)两种方法均需吸收瓶盛装蒸馏水进行采样,因此分析步骤交杂费时间,不适于污染事故的快速监测,使用便携式色谱仪,可以在现场直接开展监测工作。其最低检测浓度为0. 相似文献
605.
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607.
被动扩散技术以其低成本、操作简单、空间覆盖率较高等优点现已在西方发达国家广泛应用于环境空气质量监测及调查研究。作为欧盟——辽宁综合环境项目空气质量管理项目的一部分辽宁省自 2 0 0 0年 9月在沈阳、抚顺两市进行了为期 6个月 (每月采样一次 )的被动扩散管调查 ,所监测的污染物有 NO2 、SO2 、O3和苯系物 相似文献
608.
采用气相色谱法测定工业废水中的4-硝基-2,6-二氯苯胺。研究了样品的提取、色谱分析条件及定量方法。测定了方法的精密度和准确度。以3倍的仪器噪声计算其检出限为4.8×10~(-11)g,进样量为2μL时,最低检出浓度为0.024mg/L,线性范围为0.04~2.0mg/L;精密度实验的变异系数为0.4%~1.7%;加标回收率为97.5%~99.0%。苯胺,对硝基苯胺,邻硝基苯胺,邻氯对硝基苯胺均不干扰测定。 相似文献
609.
以一化工厂作为研究对象,按1/3125缩尺制作模型,在风洞实验室中进行扩散试验,研究该区域的大气污染情况,以及地形和局地气流对大气污染物扩散的影响. 相似文献
610.
本文对大气二氧化硫的流动注射—化学发光法测定进行了研究.基于鲁米诺—碘—二氧化硫无机偶合化学发光反应,建立了测定大气二氧化硫的新方法.采用了流动注射气体扩散在线分离技术,使得经典的化学发光测定的选择性大大提高.对鲁米诺—碘这一化学发光体系有很强催化作用的金属离子及其它酸化后不挥发的物质均不影响本体系的测定.方法具有简单、快速、选择性好的特点.已用于大气环境监测分析,结果较满意. 相似文献