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821.
David A. Wampler Shelly Miller-Leiden William W. Nazaroff Ashok J. Gadgil Andres Litvak K.R.R. Mahanama 《Journal of the Air & Waste Management Association (1995)》2013,63(6):494-500
Abstract Most environmental tobacco smoke (ETS) issues from the tips of smoldering cigarettes between puffs. Smokeless ashtrays are designed to reduce ETS exposure by removing particulate and/or gas-phase contaminants from this plume. This paper describes an experimental investigation of the effectiveness of four smokeless ashtrays: two commercial devices and two prototypes constructed by the authors. In the basic experimental protocol, one or more cigarettes was permitted to smolder in a room. Particulate or gas-phase pollutant concentrations were measured in the room air over time. Device effectiveness was determined by comparing pollutant concentrations with the device in use to those obtained with no control device. A lung deposition model was applied to further interpret device effectiveness for particle removal. The commercial ashtrays were found to be substantially ineffective in removing ETS particles because of the use of low-quality filter media and/or the failure to draw the smoke through the filter. A prototype ashtray using HEPA filter material achieved better than 90% particle removal efficiency. Gasphase pollutant removal was tested for only one prototype smokeless ashtray, which employed filters containing activated carbon and activated alumina. Removal efficiencies for the 18 gas-phase compounds measured (above the detection limit) were in the range of 70 to 95%. 相似文献
822.
Frederick W. Lipfert Ronald E. Wyzga 《Journal of the Air & Waste Management Association (1995)》2013,63(12):949-966
Abstract Results from 31 epidemiology studies linking air pollution with premature mortality are compared and synthesized. Consistent positive associations between mortality and various measures of air pollution have been shown within each of two fundamentally different types of regression studies and in many variations within these basic types; this is extremely unlikely to have occurred by chance. In this paper, the measure of risk used is the elasticity, which is a dimensionless regression coefficient defined as the percentage change in the dependent variable associated with a 1% change in an independent variable, evaluated at the means. This metric has the advantage of independence from measurement units and averaging times, and is thus suitable for comparisons within and between studies involving different pollutants. Two basic types of studies are considered: time-series studies involving daily perturbations, and cross-sectional studies involving longer-term spatial gradients. The latter include prospective studies of differences in individual survival rates in different locations and studies of the differences in annual mortality rates for various communities. For a given data set, time-series regression results will vary according to the seasonal adjustment method used, the covariates included, and the lag structure assumed. The results from both types of cross-sectional regressions are highly dependent on the methods used to control for socioeconomic and personal lifestyle factors and on data quality. Amajor issue for all of these studies is that of partitioning the response among collinear pollution and weather variables. Previous studies showed that the variable with the least exposure measurement error may be favored in multiple regressions; assigning precise numerical results to a single pollutant is not possible under these circumstances. We found that the mean overall elasticity as obtained from timeseries studies for mortality with respect to various air pollutants entered jointly was about 0.048, with a range from 0.01 to 0.12. This implies that about 5% of daily mortality is associated with air pollution, on average. The corresponding values from population-based cross-sectional studies were similar in magnitude, but the results from the three recent prospective studies varied from zero to about five times as much. Long-term responses in excess of short-term responses might be interpreted as showing the existence of chronic effects, but the uncertainties inherent in both types of studies make such an interpretation problematic. 相似文献
823.
Robert C. Pegnam Michael J. Pilat 《Journal of the Air & Waste Management Association (1995)》2013,63(3):303-308
Particulate mass concentration, particle size distribution, and particle chemical composition measurements have been conducted on the gases exhausting from a chromic acid anodizing process tank. Particle mass concentrations in the 200 to 20,000 μg/m3 range were measured using open-faced filters (47 mm diameter) adjacent to the process tank liquid and with closed filters (90 mm diameter) in the exhaust duct. Particle size distributions, measured using University of Washington Mark 3 and Mark 20 Cascade Impactors, showed the particle aerodynamic mass median diameter was about 3 microns. Chemical analysis of the particle samples obtained by the Modified EPA Method 5 sampling train, the Mark 20 UW Cascade Impactors, and by the 47 mm and 90 mm diameter filters showed Cr+6 concentrations in the 20 to 1,500 μg/m3 range with over 99 percent of the chromium in particles larger than 1.0 microns diameter. An integrating nephelometer was used to measure the light scattering coefficient of the exhaust gases upstream of the wet scrubber. The light scattering coefficient increased by a factor of about 2–3 over the background level during the 40 minute time period while a part was being anodized. The bscat values ranged from 3 × 10?5 to 3 × 10?4 meters?1 for the aerosol particles less than about 6 microns aerodynamic diameter. 相似文献
824.
Nigel J. Tapper Aidan W. Sudbury 《Journal of the Air & Waste Management Association (1995)》2013,63(4):433-441
Odor is acknowledged as a major community air pollution nuisance, but the problems of analysis, particularly in Identifying the origin of odor, are also well recognised. One approach to the problem has been the development of computational schemes which use wind directions at the times of odor observations to locate the likely source of odor. An earlier technique, PONG, has now been superseded by a more sophisticated version, PONG2, which incorporates Gaussian plume modeling techniques. This paper describes the operation of PONG2 in the odor source mapping mode and provides an analysis of the Insensitivity of the technique to errors in input. Then, using specific Australian examples of community odor nuisance emanating from a large sewage treatment complex near Melbourne, and an irrigated golf course within metropolitan Darwin, the paper outlines the utility of PONG2 in resolving problem odor sources at a range of scales and levels of complexity. 相似文献
825.
D. R. van der Vaart W. M. Vatavuk A. H. Wehe 《Journal of the Air & Waste Management Association (1995)》2013,63(4):497-501
In an earlier paper, major commercially available incinerator technologies designed to treat dilute waste gas streams containing volatile organic compounds (VOCs) were described in a qualitative comparison. In addition, a simplified procedure was outlined through which important sizing parameters could be calculated given certain information about the waste gas. This paper describes the use of these parameters in developing a study (±30percent) cost estimate for the total capital investment and the total annual costs incurred in treating a waste stream of volatile organic compounds (VOCs). An illustrative problem used in the former paper is completed here in order to contrast some of the economic differences between thermal and catalytic incinerator systems. 相似文献
826.
W. Alan Bowman 《Journal of the Air & Waste Management Association (1995)》2013,63(9):1124-1128
Equations are derived from the Gaussian plume mode! and prescribe the critical downwind distance, wind speed, and plume rise values that result in maximum ground-level concentrations (MGLC) under downwash conditions. The derivations apply to bent-over plumes and encompass the Schulman-Scire and Huber-Snyder building downwash treatments. 相似文献
827.
Brian K. Gullett Paul W. Groff M. Linda Lin James M. Chen 《Journal of the Air & Waste Management Association (1995)》2013,63(10):1188-1194
Pilot-scale tests were conducted to develop a combined nitrogen oxide (NOx) reduction technology using both selective catalytic reduction (SCR) and selective noncatalytic reduction (SNCR). A commercially available vanadium- and titanium-based composite honeycomb catalyst and enhanced urea (NH2CONH2) were used with a natural-gas-fired furnace at a NOx concentration of 110 ppm. Changes in SNCR chemical injection temperature and stoichiometry led to varying levels of post-furnace ammonia (NH3), which acts as the reductant feed to the downstream SCR catalyst. The urea-based chemical could routinely achieve SNCR plus SCR total NOx reductions of 85 percent with less than 3 ppm NH3 slip at reductant/NOx stoichiometries ranging from about 1.5 to 2.5 and SCR space velocities of 18,000 to 32,000 h?1. This pilot-scale research has shown that SNCR and SCR can be integrated to achieve high NOx removal. SNCR provides high temperature reduction of NOx followed by further removal of NOx and minimization of NH3 slip by a significantly downsized (high-space velocity) SCR. 相似文献
828.
Robert F. Mouradiarn Steven P. Levine Hui-Qiong Ke Herbert H. Alvord 《Journal of the Air & Waste Management Association (1995)》2013,63(8):1067-1072
Direct inlet gas chromatography (GC) is becoming one of the most frequently used techniques for measurement of volatile organics in air. Although GC is an effective tool, its usefulness as a field method can be limited by retention times of several minutes or more, and by the limits of detection. In order to address these issues, a high speed GC system featuring a capillary cold trap inlet and variable speed electrometeramplifier was developed and tested. The gas cooled inlet was used to collect and focus organic vapors from injection volumes of up to 1 ml. Resistance heating of the metal cold trap produced a narrow injection band that allowed simple separations to be completed in 5 to 20 seconds. Use of a variable speed electrometer-amplifier allowed the response time and noise suppression characteristics to be adjusted to the needs of the specific analysis. Simple mixtures of organics including aromatics, alkanes and chlorinated hydrocarbons were separated in 20 seconds or less. The limits of detection for 13 test compounds ranged from less than 1 part per billion by volume (ppbv) to about 50 ppbv. Data presented here indicate that high speed GC using a cold trap inlet may be a feasible approach for near real-time measurement of volatile organics in ambient air. 相似文献
829.
Richard W.Tock 《Journal of the Air & Waste Management Association (1995)》2013,63(10):953-962
Abstract Neural networks have shown tremendous promise in modeling complex problems. This work describes the development and validation of a neural network for the purpose of estimating point source emission rates of hazardous gases. This neural network approach has been developed and tested using experimental data obtained for two specific air pollutants of concern in West Texas, hydrogen sulfide and ammonia. The prediction of the network is within 20% of the measured emission rates for these two gases at distances of less than 50 m. The emission rate estimations for ground level releases were derived as a function of seven variables: downwind distance, crosswind distance, wind speed, downwind concentration, atmospheric stability, ambient temperature, and relative humidity. A backpropagation algorithm was used to develop the neural network and is also discussed here. The experimental data were collected at the Wind Engineering Research Field Site located at Texas Tech University in Lubbock, Texas. Based on the results of this study, the use of neural networks provides an attractive and highly effective tool to model atmospheric dispersion, in which a large number of variables interact in a nonlinear manner. 相似文献
830.
M.W. Poore 《Journal of the Air & Waste Management Association (1995)》2013,63(10):990-992
Abstract The direct Karl Fischer (KF) titration method has known interferences for measuring water content. In addition, in analyzing some paints, KF can fail to produce an accurate analysis. The California Air Resources Board (GARB) staff has developed a KF procedure that can be used to determine the water content of consumer products. The procedure uses an oven accessory to the titration system, and is based on a distillation method developed by the California Polytechnical University at San Luis Obispo (Cal Poly). Samples are diluted in l-methoxy-2-propanol (MPA), and an aliquot is injected into an enclosed oven system, where the MPA/water azeotrope is swept directly into the KF titration vessel. The technique is accurate and precise and, thus far, proves to be a fast and reliable method for analysis. 相似文献