共查询到20条相似文献,搜索用时 0 毫秒
1.
Keith C. Heidorn Anton E. Davies Michael C. Murphy 《Journal of the Air & Waste Management Association (1995)》2013,63(11):1469-1475
The assessment of air quality impacts from roadways is a major concern to urban planners. In order to assess future road and building configurations, a number of techniques have been developed, including mathematical models, which simulate traffic emissions and atmospheric dispersion through a series of mathematical relationships and physical models. The latter models simulate emissions and dispersion through scaling of these processes in a wind tunnel. Two roadway mathematical models, HIWAY-2 and CALINE-4, were applied to a proposed development in a large urban area. Physical modelling procedures developed by Rowan Williams Davies & Irwin Inc. (RWDI) in the form of line source simulators were also applied, and the resulting carbon monoxide concentrations were compared. The results indicated a factor of two agreement between the mathematical and physical models. The physical model, however, reacted to changes in building massing and configuration. The mathematical models did not, since no provision for such changes was included in the mathematical models. In general, the RWDI model resulted in higher concentrations than either HIWAY-2 or CALINE-4. Where there was underprediction, it was often due to shielding of the receptor by surrounding buildings. Comparison of these three models with the CALTRANS Tracer Dispersion Experiment showed good results although concentrations were consistently underpredicted. 相似文献
2.
M. Matti Maricq Richard E. Chase Ning Xu 《Journal of the Air & Waste Management Association (1995)》2013,63(11):1529-1537
ABSTRACT Comparison between particle size distributions recorded directly at the tailpipes of both diesel and gasoline vehicles and measurements made using a conventional dilution tunnel reveals two problems incurred when using the latter method for studying particle number emissions. One is the potential for particulate matter (PM) artifacts originating from hydrocarbon material stored in the transfer hose connecting the tailpipe to the dilution tunnel, and the other is the particle coagulation (as well as condensation and chemical changes) that occurs during the transport. Both are potentially generic to current PM emissions measurement practices. The artifacts typically occur as a nanoparticle mode (10–30 nm) that is 2–4 orders of magnitude larger than what is present in the vehicle exhaust and can easily be mistaken for a similar mode that can arise from the nucleation of hydrocarbon or SO4 2-components in the exhaust under appropriate dilution rates. Wind tunnel measurements are in good agreement with those made directly from the tailpipe and substantiate the potential for artifacts. They reveal PM levels for the recent model port fuel injection (PFI) gasoline vehicles tested that are small compared with the ambient background particle level during steady-state driving. The PM emissions recorded for drive cycles such as the Federal Test Procedure (FTP) and US06 occur primarily during acceleration, as has been previously noted. Light-duty diesel vehicle emissions normally exhibit a single lognormal mode centered between 55 and 80 nm, although a nonartifact nanoparticle mode in some cases appears at a 70-mph cruise up a grade. 相似文献
3.
A Wind Tunnel Study of Gaseous Pollutants in City Street Canyons 总被引:1,自引:0,他引:1
James B. Wedding David J. Lombardi Jack E. Cermak 《Journal of the Air & Waste Management Association (1995)》2013,63(6):557-566
Steady state mean concentrations of tracer gas were measured in a 400:1 scale model of an idealized city with variable geometry placed within a wind tunnel at various orientations to the mean flow for a free stream velocity of 6.8 ft/sec. The tracer gas was released from two parallel line sources to simulate lanes of traffic in an effort to quantify the persistence of pollution as well as the mean values realized at street levels. An aerodynamically rough turbulent boundary layer of neutral thermal stratification was employed to simulate the atmosphere. Values of concentration measured in the model city were converted to prototype concentrations in ppm and compared to National Ambient Air Quality Standards. It was shown that single isolated structures may cause favorable mixing of pollution downwind but very high concentrations exist in the immediate leeward vicinity of the building. Two favorable geometries for city blocks tested were found to reduce pedestrian exposure to pollution both near heavy traffic congestion and downwind. It was concluded that the pollutant dilution was controlled by the mean flow rather than by turbulent diffusion and that the lateral spread of the plume was slight as one proceeded downwind of the line source. The combination of favorable geometry and higher dilution velocities may bring pollution levels down to existing Air Quality Standards. The body of information presented in this paper should interest city planners and air quality monitoring personnel, as well as those researchers attempting to study and model flow in city street canyons. It provides order of magnitude estimates on pedestrian and office worker exposure to pollutants under a wide range of conditions. 相似文献
4.
J. M. Davis H. H. Rogers 《Journal of the Air & Waste Management Association (1995)》2013,63(8):905-908
ABSTRACT This study reports the first field measurements of airborne exavalent chromium (Cr(vi)) in southwestern Ontario. Hexavalent chromium was identified as an inhalation carcinogen and an air toxic of concern during the 1991-93 Windsor Air Quality Study. The results of that study indicated that approximately 20% of the routinely monitored ambient airborne chromium (Cr) was in the hexavalent form. In addition, the range of carcinogenic health risks attributable to airborne Cr(vi) was determined to be between 1.4 x IO6 and 3.0 x 10-4 for people living in the Windsor area. During the summer of 1993, analyses of concurrent indoor and outdoor 24-hour air quality samples taken at 33 residences in Hamilton resulted in geometric mean Cr(vi) concentrations of 0.20 r|g/m3 and 0.55 r|g/m3, respectively, and little or no relationship between the indoor and outdoor sample sets. During the summer of 1994, an airborne Cr(vi) size-fractionation study was conducted in Hamilton, the results of which suggested that the majority of the Cr(vi) was in the inhalable fraction. 相似文献
5.
Perry J. Samson Garry Neighmond Andrew J. Yencha 《Journal of the Air & Waste Management Association (1995)》2013,63(12):1232-1237
Linear regression of high volume air sampler data and various meteorological parameters was used to determine a suspended particulate air pollution climatology for Albany, NY. A new method for exhibiting associations between wind direction and pollutant levels using correlation coefficients is presented. Correlations between wind direction distribution frequency and other meteorological parameters is employed to help explain differences in correlations for direction with suspended particulate levels. Results show that high particulate concentrations correlate well with southerly wind flow throughout the study area, regardless of relative location of receptor to local sources. This suggests that ambient background concentrations inherent in different air masses more consistently affected suspended particulate levels than did the diffusion from local sources during the study period. Maximum particulate advection occurs under conditions of good mixing of the boundary layer and moderate wind speeds and is enhanced further in the absence of removal processes such as rainout and washout. Trajectory analysis of selected days indicates a definite relationship between path and origin of the wind flow and regional average particulate concentration. 相似文献
6.
7.
8.
T.L. Montgomery W.B. Norris F.W. Thomas S.B. Carpenter 《Journal of the Air & Waste Management Association (1995)》2013,63(5):388-394
A simplified method which is used by the Tennessee Valley Authority to estimate ambient concentrations of atmospheric emissions from its large power plants is presented. The technique requires the use of three nomogrdms for the rapid graphic solution of three dispersion models—coning, inversion breakup, and trapping. A discussion of the meteorological conditions that are associated with these dispersion models, supporting appendices, and a worked example are also presented. 相似文献
9.
Fuga A Saiki M Marcelli MP Saldiva PH 《Environmental pollution (Barking, Essex : 1987)》2008,151(2):334-340
The Canoparmelia texana epiphytic lichenized fungi was used to monitor atmospheric pollution in the S?o Paulo metropolitan region, SP, Brazil. The cluster analysis applied to the element concentration values confirmed the site groups of different levels of pollution due to industrial and vehicular emissions. In the distribution maps of element concentrations, higher concentrations of Ba and Mn were observed in the vicinity of industries and of a petrochemical complex. The highest concentration of Co found in lichens from the S?o Miguel Paulista site is due to the emissions from a metallurgical processing plant that produces this element. For Br and Zn, the highest concentrations could be associated both to vehicular and industrial emissions. Exploratory analyses revealed that the accumulation of toxic elements in C. texana may be of use in evaluating the human risk of cardiopulmonary mortality due to prolonged exposure to ambient levels of air pollution. 相似文献
10.
低温等离子体技术改善生物膜反应器载体表面性能的研究 总被引:4,自引:0,他引:4
通常,微生物及广为应用的多聚体型生物载体表面均带有有负电荷。两者间产生的静电斥力严重阻碍了载体表面生物膜的形成。为强化微生物的载体上附着,提出了载体表面电荷改性新技术;低温等离子体氧化-Fe离子沉积技术。研究了4种等离子体对4种聚合载体(PE、PP、PS和PVC)的氧化强度及Fe^3+在处理后载体上的沉积。实验表明,处理后的载体表面生物膜形成速度加快,生物量显著增加,这项新技术为开发生物膜反应器新 相似文献
11.
Frank P. Terraglio Raymond M. Manganelli 《Journal of the Air & Waste Management Association (1995)》2013,63(6):403-406
Results of a laboratory study indicate that the rate of solution of atmospheric sulfur dioxide in distilled water, over the range of atmospheric concentrations of 0.81?8.73 mg SO2/M3, is a function of the concentration of SO2 in the atmosphere, with saturation being reached more rapidly at the higher concentrations. This would indicate that rain water, with constantly renewed surfaces, can be very effective in the removal of atmospheric SO2. The pH of the exposed water samples reached values of 4.0 or less, comparable to values observed in fog and cloud water near large industrial areas. Overall solubility of sulfur dioxide in distilled water did not follow the law of partial pressure. At the atmospheric concentrations used it was found that over 98.5% of the sulfite in solution was in the form of the bisulfite ion with, the remainder present as unionized sulfurous acid. Computations using the concentration of unionized sulfurous acid in the solution showed that the solubility of this portion of dissolved sulfite did follow the law of partial pressure. 相似文献
12.
Lawrence J. Hagen Neil P. Woodruff 《Journal of the Air & Waste Management Association (1995)》2013,63(8):860-861
Dust is always present in the air, but when wind erosion occurs, both the flux of soil particles into the air and the particulate concentration increase by orders of magnitude. Previous research1 indicated that median duststorm concentration was 4.85 mg/m3 and median annual hours with duststorms was 45 in the Great Plains during the 1950’s. Of the total soil moved by wind, the suspended particulates probably represent 10% or less.2-3 相似文献
13.
The behavioral distribution of the atmospheric turbulence flow over the terrain with changes in a rough surface has become one of the most important topics of air pollution research, among such other topics as transportation and dispersion pollutants. In this study, a computational model on atmospheric turbulence flow over a terrain hill shaped with rough surface was investigated under neutral atmospheric conditions. The flow was assumed to be 2D and modeled using computational fluid dynamics (CFD) models, which were numerically solved using Reynolds-averaged Navier-Stokes equations. Rough surface conditions were modeled using a number of windbreak fences regularly spaced on the hill. The mean velocity and turbulent structures such as turbulence intensity and turbulent kinetic energy were investigated in the upwind and downwind regions over the hill, and the numerical models were validated against the wind-tunnel results to optimize the turbulence model. The computational results agreed well with the results obtained from the wind tunnel experiments. The computational results indicate that the mean velocity was observed to increase dramatically around the crest of the upwind slope of the hill. A thick internal boundary layer was observed with a fence on the crest and downwind region of the hill. The reversed flow and recirculation zone were formed in the wake region behind the hill. It was thus determined that turbulent kinetic energy decreases as the mean velocity increases. 相似文献
14.
Nancy E. Greene John H. Shaw 《Journal of the Air & Waste Management Association (1995)》2013,63(6):468-470
Lines of the 1-0 band of NO near 5.3 jum have been observed in spectra of approximately 500 m of ground-level air at Columbus, Ohio, on several occasions between October 1970 and January 1971. The estimated NO abundances lie between 0.0 and 0.08 ppm with uncertainties of ±0.01 ppm. 相似文献
15.
Philip W. West J. Jaime Chiang 《Journal of the Air & Waste Management Association (1995)》2013,63(7):671-673
A method is described for determining acidity by means of the spectrophotometric determination of the displacement of the equilibrium of açid-base indicators. The method is simple, sensitive and free of known interferences. There is no dependence on costly or sophisticated equipment and the results obtained are reliable and reproducible. 相似文献
16.
S. Sıddık Cindoruk Erman Ozturk 《Environmental science and pollution research international》2016,23(24):24504-24513
Wet deposition fluxes of organochlorine pesticides (OCPs) were determined for rain samples collected in a coastal area of Turkey. Seventeen precipitation samples were collected over a 1-year period from 2008 to 2009. Rainwater was accumulated at the beginning of rain events using real time monitoring. Atmospheric concentrations were also measured in parallel with deposition samples. Both atmospheric concentrations and deposition fluxes were determined as particle and gas phases. The particle phase and dissolved phase deposition fluxes were 794.26?±?756.70 ngm?2 day?1 and 800.77?±?672.63 ngm?2 day?1, respectively. The washout ratios for OCP compounds were calculated separately for the particle and dissolved phases using the atmospheric concentrations and rain concentrations. The minimum washout ratio for the particle phase was 2339.47 for Endrin aldehyde, whereas the maximum washout ratio was 497593.34 for Methoxychlor. The maximum washout ratio for the dissolved phase was 247523.89 for Endosulfan beta, whereas the minimum washout ratio was 10169.69 for p,p′-DDT. The dry deposition velocities ranged from 0.01 to 1.67 cms?1. The partitioning of wet deposition between the particle and dissolved phases was 50 % in terms of total OCP deposition. 相似文献
17.
George H. Farrah 《Journal of the Air & Waste Management Association (1995)》2013,63(11):738-741
Manual methods for the determination of air-borne fluorides, including the discrimination of gaseous and particulate forms, have been reviewed. Published methods have been re-examined and comparative sampling data presented, to point out advantages of some newer techniques in sampling, separation, and quantitation. 相似文献
18.
19.
Atmospheric contamination by pesticides: Determination in the liquid, gaseous and particulate phases
Maurice Millet Henri Wortham Astrid Sanusi Philippe Mirabel 《Environmental science and pollution research international》1997,4(3):172-180
Between 1991 and 1993, 18 fogwater samples, 31 rainwater samples and 17 atmosphere (gas and particles) samples were analysed for 13 pesticides (pp’DDT,pp’DDD,pp’DDE, aldrin, dieldrin, lindane, hexachlorobenzene, fenpropathrin, mecoprop, methyl-parathion, atrazine, isoproturon and aldicarb). The samples were collected in a rural area where some of the compounds are in use (experimental INRA farm, “Institut National de la Recherche Agronomique” in Colmar, Eastern France, 80,000 inhabitants). This paper briefly presents the analytical methodology used and, in detail, the contamination level of the different atmospheric phases. The contamination levels are roughly constant throughout the year in all the atmospheric phases and the most abundant pesticides are those commonly used on the experimental INRA farm and other surrounding farms. Nevertheless, some pesticides not used since the 1970s such as 1,1-Bis(4-chlorophenyl)-2,2,2-trichloroethane (pp’DDT) and 2,2-Bis(4-chlorophenyl)-1,1-dichloroethane (pp ’DDD) are also detected in the atmosphere of Colmar. A small increase in the pesticide concentrations in the atmosphere (gas and particles) was observed during treatments. 相似文献