Modification of a chemiluminescent ozone monitor for the measurement of gaseous unsaturated hydrocarbons

A chemiluminescent ozone monitor using the ozone-ethylene reaction has been adapted for measuring unsaturated hydrocarbons. The only change in the monitor was a replacement of the ethylene supply system with an electric discharge ozone source. Chemiluminescence was detected for all olefin-ozone reactions studied, including ethylene, substituted ethylenes (vinyl fluoride, chloride and cyanide), propylene, the butenes, 1,3-butadiene and several higher olefins. The intensity of chemiluminescence differed for the different olefins and appeared related to the ozone-olefin reaction rate. Saturated hydrocarbons and aromatics did not give a response. The minimum detectability for ethylene was 0.003 ppm and this value was somewhat lower for the higher olefins.Several important implications of the findings are discussed. These include the development of a more sensitive ozone monitor and the application of a total olefin monitor for the measurement of reactive hydrocarbons.     

Properties of 220Rn progeny (212Pb) in the presence of trace gases.

The charge neutralization of 220Rn progeny (212Pb) was studied in nitrogen and argon environments containing trace concentrations of ethylene, propylene and propane. The diffusion coefficient of 212Pb atoms in the presence and in the absence of oxygen and hydrocarbons was determined using a diffusion tube method which measured the penetration fraction of the 220Rn decay products. The results are explained in terms of the formation of lead dioxide with an ionization potential in the range of 10.5-11.1 eV. The ionization potential of 212PbO2 was found to be higher than that of 218PoO2. Charge neutralization was found to occur in a gas mixture of argon and oxygen containing 600 ppm ethylene (C2H4) and also in a mixture of nitrogen and oxygen containing 600 ppm propylene (C3H6). Charge neutralization was not found to occur in a mixture of argon and oxygen containing up to 5000 ppm propane (C3H8) and in a mixture of argon and nitrogen containing 600 ppm ethylene. In pure oxygen, nitrogen, argon, dry air and a mixture of nitrogen and oxygen, no neutralization was observed to occur through charge transfer from neutral molecules. The 220Rn concentration was found to influence the neutralization mechanism. Diffusion coefficients for partially neutralized and neutralized 212Pb ranged from 0.050 to 0.067 cm2 s-1 at a 220Rn concentration of 3.7 x 10(4) atoms cm-3 and a relative humidity of less than 5%.     

Flame size, heat release, and smoke points in materials flammability

The concept of using the flame size as a surrogate for heat release rate (HRR) has been explored. A technique for simultaneously obtaining the HRR, flame size (height and area), and the smoke point of the flame solely from visual images has been developed. The technique has been demonstrated on gaseous flames (methane, propane, ethylene, and propylene) and explored for five burning solid polymers. Estimations of the flame area from images of the stoichiometric contour based on the CH chemiluminescent region of the flames yielded a good linear correlation with measured HRR, valid for all of the gaseous and solid compounds tested, for burning rates above or below the smoke point. In contrast, flame heights and luminous images (i.e., from soot emission) were confounded by differing behavior above and below the smoke point.     

Sampling Rate Evaluation Of NO2 Badge: (I) In Indoor Environments

The sampling rate of a nitrogen dioxide (NO²) passive sampling badge was evaluated in indoor environments including an unoccupied research house, residential houses, and an office. Measurements from the NO² badges were compared with those of a chemiluminescent analyzer the EPA reference method, by placing them near to the sample inlet of the chemiluminescent analyzer In this study, we used a new sampling rate for the NO² badge placed in indoor environments (an overall mass transfer coefficient of 0.10 cm/s) smaller than the rate previously reported for the badge when used outdoors. The new rate provides more accurate measurements of NO, concentrations in indoor environments. Indoor NO² concentrations were also measured with the NO² badges exposed to a constant wind velocity provided by a wind tunnel. Since the measurements of the badge with a constant wind velocity agreed well with the reference method, the badges could be assumed to be a secondary reference measurement. With the badges used as the secondary reference measurement, we developed a portable wind tunnel to evaluate a personal exposure measurement by the badge. The results are presented in Environment International (Lee et al., 1993). Precision of the badge measurements was as good as an intraclass correlation coefficient of 0.9779. It was determined that placement of the badge should be at least 10 cm out from an indoor wall surface to avoid undersampling due to NO² gradients near the surface.     

Trends in ozone concentrations in Jerusalem

Ozone concentrations have been measured in Jerusalem since 1977 by a chemiluminescent ozone meter. During the last five years ozone levels have increased considerably. In order to test whether this increase reflected the growth in the number of motor vehicles or was caused by atmospheric conditions, the summer data of the last five years were analyzed. Ozone levels were characterized by the daily one-hour maxima; the atmospheric factors considered were temperature, insolation and stability. A multiple regression equation was computed and a correlation coefficient r = 0.77 obtained. The yearly mean reduced ozone levels showed a definite trend, which reflected the corresponding trend in the number of motor vehicles.     

Monitoring of indoor volatile organic compounds and polycyclic aromatic hydrocarbons arising from kerosene cooking fuel.

Air samples, representing indoor environments of a kitchen in which a kerosene stove was used were collected and analysed for volatile organic compounds (VOCs) viz., n-hexane, benzene, heptane, toluene, p- and o-xylene and n-decane using a cryogenic preconcentration system and a gas chromatograph with a flame-ionisation detector. Simultaneous outdoor samples were also collected to determine indoor to outdoor (I/O) ratios for each compound. Reversed phase high performance liquid chromatography (HPLC) with ultra violet absorption detection was optimised for separation and quantification of polycyclic aromatic hydrocarbons (PAHs) in air particulate matter. Concentration of total suspended particulate matter (TSPM), benzene soluble organics and the PAHs in air samples collected in indoor environment of some tenements at Trombay, Mumbai where kerosene is used as cooking fuel are discussed in relation to the concentration of the same in outdoor environment in vicinity of the tenement. VOCs and PAHs results from samples collected in kitchens in Trombay are discussed in relation to indoor air pollution.     

Composition and sources of aerosols at Trombay, Bombay

Using energy dispersive X-ray fluorescence analysis, the concentrations of Si, S, Cl, K, Ca, Ti, Fe, Zn and Pb in aerosols, at Trombay (Bombay) have been measured. Factor analysis of the data showed that four sources other than seasalt are necessary to explain the observed aerosol composition. The levels in air of anthropogenic elements varied widely during diurnal cycles; the maximum variation, by a factor of 15, occurred for Pb concentrations. The local basalt weathered soil is suggested as the source material for the major elements of crustal origin measured in the aerosols.     

隧道设计模型、理论与试验

本文作者把围岩应变法、孔洞位移法和衬砌内力法三种地下结构设计模型与圆形隧道的弹、塑、粘性三种衬砌计算理论结合起来,通过室内的模型试验和现场量测验证后,得到了地层压力与衬砌刚度以及地层本构关系有关的设计公式;得出了侧压力系数随衬砌与地层的刚度比而变化,且比静止侧压力系数大。将此法运用于新奥法或盾构法隧道设计中,即可减薄衬砌,节省投资。     

Distribution of structural collapses and optimum reliability for infrequent environmental loads

Structures located in a particular zone of interest may be subjected to the same environmental events or the same natural phenomena that occur infrequently. That is, the structures are subjected to the same environmental loading parameters such as the peak ground acceleration, the reference wind velocity pressure, and the total ice accumulation. Therefore, the structural collapses are dependent or correlated. The correlation may affect the probability distribution of the number of structural collapses and the optimum reliability level for upgrading the exiting structures and infrastructures. This is investigated in this paper. It is shown that the coefficient of variation of the number of structural collapses is an increasing function of the correlation coefficient. This increase can be important to the selection of optimum reliability level for retrofitting of existing structures and infrastructures when the risk aversion factor is considered. An approach by taking the correlation among structural collapses into account in selecting the optimum upgrading level of a group of existing structures is presented and illustrated by a numerical example.     

Determination of dioxins and polychlorinated biphenyls in breast milk, maternal blood and cord blood from residents of Tohoku, Japan

Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) are bioaccumulative chemicals that are considered to be toxic contaminants based on several epidemiological studies. To elucidate exposure levels of these chemicals in the present study, concentrations of PCDD/DFs, dioxin-like PCBs (DL-PCBs) and PCBs in breast milk, maternal blood and cord blood obtained from the same participants registered in a birth cohort study in Tohoku, Japan, were measured. Congener-specific analysis revealed several differences in minor congeners of these compounds among the three specimen types, although major congeners were detected in the specimens. The toxicity equivalence quantity concentrations (1998 WHO-TEF) and PCBs in breast milk, maternal blood and cord blood on the whole and on a lipid basis were in the order of breast milk > maternal blood > cord blood. Pearson's correlation coefficients of TEQs and total PCBs among the three specimens were high, with the correlation coefficient of TEQ between breast milk and maternal blood being the highest (r=0.94, p<0.001). On the other hand, the TEQ between breast milk and cord blood was the lowest (r=0.79, p<0.001). Pearson's correlation coefficient between the TEQ and PCBs in each specimen was also high (r=0.82-0.95, p<0.001). The associations of chemical concentrations with maternal age, parity, fish intake, BMI and the rate of body weight increase during pregnancy were analyzed with multiple linear regression analysis. TEQ concentrations and PCBs were negatively associated with parity (p<0.05), and maternal age was positively associated with PCBs (p<0.05). However, the associations with BMI and fish intake during pregnancy were not significant. These results suggest that parity is an important factor affecting the concentrations of dioxins and PCBs in these specimens.     

软黏土双层地基堆载预压固结空间概率分析

根据工程地质资料,分析固结系数的概率统计值;以双层地基为对象,研究堆载预压固结的概率分析方法和空间概率特性;采用正交试验方法,分析固结参数的不确定性及其分布对固结概率特性的影响;推导固结度均值和方差的解析计算公式,据此分析固结的空间概率特性与自相关距离的相关性;探讨方差折减系数的相关函数选取问题。研究表明,在固结后期双层软黏土地基固结系数的不确定性和概率分布对固结概率特性的影响比较显著,而压缩模量的影响不显著;固结度的均值随着固结系数的变异系数增大而减小,而它的方差则随着固结系数的变异系数增大而增大;固结系数的自相关性对固结概率特性具有一定程度的影响;方差折减系数对于自相关函数形式的选取不敏感。     

基于颗粒椭球体理论的隧道松动土压力计算方法

基于颗粒椭球体理论认为隧道上部松动区滑动面为椭圆形,据此推导出受滑动面倾角影响的侧土压力系数计算方法;在椭圆形松动区内竖向荷载沿水平向呈梯形分布,推导出隧道松动土压力计算方法。结果表明:当埋深低于极限椭圆高度时,松动区域为地面线以下的极限椭圆区域;当埋深达到极限椭圆高度时,松动区为整个极限椭圆,松动土压力不再增加。滑动面侧土压力系数是变化的,与滑动面倾角和土的摩擦角有关,随着内摩擦角增大而减小,随着滑动面倾角增大而增大。取值范围为0.2~0.8,介于主动土压力系数和Krynine侧土压力系数之间。本模型计算结果与实测数据较为吻合,可以用于隧道设计和施工中。     

基于响应面法的LRB基础隔震结构地震易损性分析

提出了一种基于响应面法的LRB基础隔震结构地震易损性分析方法,考虑了LRB基础隔震结构中各子结构之间(即上部结构和LRB隔震支座)地震需求的相关性。分析中考虑地震动与LRB基础隔震结构物理参数的不确定性,以均匀设计法建立地震动-LRB基础隔震结构样本,通过对有限元模型进行非线性时程分析,分别建立各子结构响应均值、方差及其相关系数与不确定参数之间的响应面模型。在此基础上,采用蒙特卡罗模拟得到LRB基础隔震结构在不同性能水准下的地震易损性曲线。分析结果表明,所建立的响应面模型精度高、结构可靠,减小了复杂有限元模型非线性时程分析计算的工作量,有效提高了LRB基础隔震结构地震易损性分析的时效性。为了准确建立LRB基础隔震结构的地震易损性曲线,应考虑各子结构地震响应需求之间的相关性。     

Radon exhalation from the ground; Method of measurements and preliminary results

The paper will present a method for measurements of radon exhalation from the ground. The method is based on a combination of activated charcoal and TLD. This method is superior to the traditional charcoal method, because it yields a mean value for the exhalation rate during the whole in-growth time. Furthermore, by using the activated charcoal/TLD method, the decay time is not critical, because the TLD is irradiated from absorbed radon during the decay time. In this way, the method is usable for remote measurements by mail.The method has been tested in areas with “normal” ground and in areas where high indoor radon concentrations previously have been measured. Exhalation measurements were performed near to houses where the indoor radon concentrations were known, and in most cases there was a strong correlation between exhalation rate and indoor radon concentrations. The method thus seems to be usable for classification of building ground.     

Detailed evaluation of three chemiluminescent ozone monitors

A detailed evaluation of three gas phase chemiluminescent ozone analyzers was undertaken. Experiments were carried out to study the characteristics of the gas flow systems and significant differences were found in certain areas. The instrument response was measured as a function of sample and ethylene flow-rates and the dependences were found to be different for each monitor. Errors introduced by using particulate filters on the input stream were also investigated. Response times were measured and compared with those given by the manufacturers. An analysis of the output signals was performed using a standard strip chart recorder and a storage oscilloscope. The latter provided an indication of the noise content at various frequencies; in some cases significant high frequency noise was found.The study also included a comparison of operating characteristics over an extended period. The instruments sampled ambient air for one month and flow-rate changes and zero- and span-drifts were noted. Measurement data from each monitor were compared and correlation coefficients calculated. The correlation between each pair was better than 0.97.     

Nonmethane hydrocarbon measurements at a suburban site in Changsha City, China

The concentration, composition, and variability of nonmethane hydrocarbons (NMHCs) and carbon monoxide (CO) were characterized in a suburban region of south-central China. Weekly samples were collected in 2007 in the Changsha suburban area and analyzed with a three-stage preconcentration method coupled with GC-MS. A time series of NMHC measurements showed seasonal variation, with a higher level occurring in winter and a lower level in summer. Toluene was the most abundant species with an average concentration of 2.51 ± 1.87 ppbv, followed by benzene (2.04 ± 1.30 pptv). According to the level of identified NMHCs, vehicular exhaust appears to be the main source of NMHCs in Changsha. Among alkanes, the highest level is propane with a concentration of 1.31 ± 0.71 ppbv, it indicated an extensive use and leakage of liquefied petroleum gas (LPG) in Changsha. The concentrations of NMHCs were influenced by the wind direction; a high level of NMHCs was carried by winds from southern China. Significant biogenic isoprene emissions were observed, with good correlation between isoprene level and temperature. Finally, when the typical individual NMHC species and CO in the morning and afternoon were compared, the shorter lifetime of NMHC species relative to CO could explain the poorer correlation observed in the afternoon.     

Cytochrome P450 1B1 mRNA levels in peripheral blood cells and exposure to polycyclic aromatic hydrocarbons in Chinese coke oven workers

Cytochrome P450 1B1 (CYP1B1) is induced through the Ah receptor and is involved in the activation of polycyclic aromatic hydrocarbons (PAHs). To determine the validity of a quantitative analysis of CYP1B1 mRNA in peripheral human blood cells for the estimation of PAH exposure, a real-time quantitative polymerase chain reaction method was used to measure the relative levels of CYP1B1 mRNA in 37 Chinese coke oven workers and 13 control workers. A large inter-individual difference in the levels was observed. The average level of the CYP1B1 mRNA in workers at the top work site, where the PAH exposure level from the coke ovens was highest, was significantly higher than in workers at the middle site (P<0.01) or the controls (P=0.02). A non-significant positive correlation was found between the CYP1B1 mRNA levels and urinary 1-hydroxypyrene (R=0.22, P=0.13), and a significant correlation between these mRNA levels and urinary cotinine (R=0.33, P=0.02). It was interesting that a significant positive correlation between CYP1B1 mRNA and 1-hydroxypyrene was observed in subjects with the Leu/Leu type of CYP1B1 Leu432Val polymorphism (R=0.33, P=0.02, n=38) and a non-significant correlation in subjects with the Leu/Val and Val/Val types (R=-0.36, P=0.25, n=12), although the number of subjects in this strata analysis was small. Our preliminary study suggests that PAH exposure in coke ovens and smoking maybe associated with CYP1B1 mRNA levels in peripheral blood cells although mRNA is generally unstable and could be expressed following exposure to other agents.     

The lead, copper and zinc content of tree rings and bark. A measurement of local metallic pollution.

Analysis of samples of wood taken from different tree rings for lead by atomic absorption spectrometry showed that there was little correlation between the sample site or ring age and air borne lead concentrations. However, the concentration of lead in tree bark at several sites was particularly sensitive to traffic flow at that site. The concentration of lead, zinc and copper in the tree bark decreased with increased distance from the road and with height above the ground. The method offers a simple technique for effectively tracing atmospheric metal concentrations.     

Polycyclic Aromatic Hydrocarbons (PAHs) in urban topsoils: Concentration and source analysis in Xuzhou,China

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous organic pollutants in urban environments and are considered as the priority pollutants by the US Environmental Protection Agency (EPA). In this study, surface soils (0–10 cm) samples from 41 sampling sites in Xuzhou (China) were collected and analysed for 16 EPA priority polycyclic aromatic hydrocarbons via gas chromatograph/mass spectrometry (GC-MS). Total PAHs concentrations were in the range of 526 to 8612 ng/g with a mean of 2468 ng/g. Total PAHs concentrations were compared to guideline and results showed that nearly all urban soils in our study can be classified as heavily contaminated (>1000 ng/g). Carcinogenic PAHs were detected in relatively high concentrations and contributed 40.2% of the total PAHs in the urban soils. Multivariate statistical analysis including cluster analysis and factor analysis were performed and grouped the 16 PAHs under 2 clusters, which could indicate that the PAHs had different origins. The values of PAHs isomer indicated that vehicular emission might contribute to the soil PAHs in urban topsoils. The carcinogenic potency of PAH compounds was calculated and was found to be insignificant at the present level of emissions in Xuzhou.