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551.
Tom F. Dann Daniel K. Wang 《Journal of the Air & Waste Management Association (1995)》2013,63(9):695-702
Abstract Since 1987, the Pollution Measurement Division of the Environmental Protection Service, Environment Canada, has operated a field program for measuring benzene in ambient air. With the cooperation of provincial and municipal environmental agencies, samples have been collected at over 30 urban and rural monitoring sites across the country. Samples are collected in evacuated canisters and analyzed by gas chromatography with a mass-selective detector. Using data from all sites, the composite average benzene concentration for Canada over the years 1989 to 1993 was 3.6 μg/m3 and the composite median was found to be 2.6 μ/m3. Benzene concentrations are highest at urban sites near major streets and at sites influenced by industrial sources. For eighteen urban and suburban trend sites (those with no nearby industrial sources), composite annual median benzene concentrations decreased by 20% between 1989 and 1993. For the same period, median benzene concentrations decreased by 33% at four trend sites with nearby industries. At most monitoring sites the parameters for benzene and CO are highly correlated; supporting the inventory estimate that most emissions of benzene are due to vehicle exhaust. For sites with nearby industrial sources of benzene, the industries are estimated to account for 35 to 70% of the benzene dose experienced at the sites. These site specific contributions are much more significant than the estimated national emissions assigned to industrial sources. 相似文献
552.
John A. Willemin Carl C. Nesbitt George R. Dewey John F. Sandell Lawrence L. Sutler 《Journal of the Air & Waste Management Association (1995)》2013,63(11):871-876
Abstract A completely mixed batch reactor leaching method utilizing flow injection analysis (the CMBR-FIA method) was developed to study the lead leaching characteristics of municipal waste combustor fly ash. Flow injection analysis (FIA) coupled with atomic absorption spectrophotometry enabled the determination of lead concentrations at one minute intervals. The pH and oxidation-reduction potential of the solution were continuously monitored to characterize the leaching conditions. Automatic titration was used to alter the solution pH to defined endpoints. The CMBR-FIA method offers the ability to immediately observe alterations to the leaching solution, and grants the freedom to study a number of parameters concurrently. The CMBR-FIA method is a rapid and reliable means to investigate leaching characteristics. This paper describes the method and demonstrates its use to monitor the leaching of lead from municipal solid waste combustor fly ash as a function of pH. Soluble lead concentrations are shown to increase quickly with decreasing pH. A maximum of 50% of the total lead concentration was available in solution at pH 2. This value gradually decreased with time to over 35% of the total. 相似文献
553.
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
554.
Jeffrey R. Brook Tom F. Dann 《Journal of the Air & Waste Management Association (1995)》2013,63(2):193-199
ABSTRACT At a variety of Canadian monitoring sites, carbonaceous compounds were estimated to account for an average of 50% of fine particle mass. These estimates were determined by subtracting the total fine particle mass associated with inorganic compounds from the total fine mass determined gravimetrically. This approach, which yields an upper limit estimate of the total amount of carbon-related mass was necessary since particulate carbon was not measured in the Canadian National Air Pollution Surveillance (NAPS) network. In this paper, total carbon estimates are evaluated against organic and elemental carbon measurements at locations in the Greater Vancouver area and Toronto. In addition, particle nitrate measurements at seven Canadian locations are used to determine the importance of nitrate relative to total mass and to examine the sampling artifacts due to the loss of particle nitrate from Teflon filters used in the NAPS di-chotomous samplers. Measurements of organic and elemental carbon indicated that the total carbon estimation approach provides representative estimates of the average contribution by carbonaceous material to the total fine and coarse mass. The average total carbon among all Vancouver area measurements (N = 225) was 4.28 μg m-3, while the estimated value was 4.34 μg m-3. There was a larger discrepancy between Toronto total carbon measurements (12.1 μg m-3) and estimates (8.8 μg m-3), which is attributed in part to sampling of particles above 10 mm in diameter. However, the R2 relating the measurements and estimates was about 0.71 for both areas. Linear regression slopes of 0.98 for Vancouver and 0.78 for Toronto (nonsignificant intercepts) indicate little bias in the Vancouver estimates, but a tendency for underestimation as the observed total carbon concentration increased in Toronto. Annually, nitrate was responsible for 17% and 12% of the fine mass in the Vancouver area and Ontario, respectively. In contrast, at two rural locations in southern Quebec and Nova Scotia, only 6% of fine mass was associated with nitrate. Due to filter losses, nitrate concentrations determined through the NAPS dichot sampling were much lower than actual concentrations (0.44 μg m-3 vs. 2.63 μg m-3). As a result of these losses (attributed mostly to loss during laboratory storage), previous total carbon estimates for the Canadian NAPS sites were likely to have been overestimated on average by about 10%. 相似文献
555.
Jitendra A. Joshi John A. Hogan Robert M. Cowan Peter F. Strom Melvin S. Finstein 《Journal of the Air & Waste Management Association (1995)》2013,63(9):1647-1654
ABSTRACT Gaseous NH3 removal was studied in laboratory-scale biofilters (14-L reactor volume) containing perlite inoculated with a nitrifying enrichment culture. These biofilters received 6 L/min of airflow with inlet NH3 concentrations of 20 or 50 ppm, and removed more than 99.99% of the NH3 for the period of operation (101, 102 days). Comparison between an active reactor and an autoclaved control indicated that NH3 removal resulted from nitrification directly, as well as from enhanced absorption resulting from acidity produced by nitrification. Spatial distribution studies (20 ppm only) after 8 days of operation showed that nearly 95% of the NH3 could be accounted for in the lower 25% of the biofilter matrix, proximate to the port of entry. Periodic analysis of the biofilter material (20 and 50 ppm) showed accumulation of the nitrification product NO3 - early in the operation, but later both NO2 - and NO3 - accumulated. Additionally, the N-mass balance accountability dropped from near 100% early in the experiments to ~95 and 75% for the 20- and 50-ppm biofilters, respectively. A partial contributing factor to this drop in mass balance accountability was the production of NO and N2O, which were detected in the biofilter exhaust. 相似文献
556.
Gary F. Evans Ross V. Highsmith Linda S. Sheldon Jack C. Suggs Ronald W. Williams Roy B. Zweidinger 《Journal of the Air & Waste Management Association (1995)》2013,63(11):1887-1896
ABSTRACT Two collaborative studies have been conducted by the U.S. Environmental Protection Agency (EPA) National Exposure Research Laboratory (NERL) and National Health and Environmental Effects Research Laboratory to determine personal exposures and physiological responses to par-ticulate matter (PM) of elderly persons living in a retirement facility in Fresno, CA. Measurements of PM and other criteria air pollutants were made inside selected individual residences within the retirement facility and at a central outdoor site on the premises. In addition, personal PM exposure monitoring was conducted for a subset of the participants, and ambient PM monitoring data were available for comparison from the NERL PM research monitoring platform in central Fresno. Both a winter (February 1-28, 1999) and a spring (April 19-May 16, 1999) study were completed so that seasonal effects could be 相似文献
557.
Jon M. Heuss Dennis F. Kahlbaum George T. Wolff 《Journal of the Air & Waste Management Association (1995)》2013,63(7):772-788
Abstract A national analysis of weekday/weekend ozone (O3) differences demonstrates significant variation across the country. Weekend 1-hr or 8-hr maximum O3 varies from 15% lower than weekday levels to 30% higher. The weekend O3 increases are primarily found in and around large coastal cities in California and large cities in the Midwest and Northeast Corridor. Both the average and the 95th percentile of the daily 1-hr and 8-hr maxima exhibit the same general pattern. Many sites that have elevated O3 also have higher O3 on weekends even though traffic and O3 precursor levels are substantially reduced on weekends. Detailed studies of this phenomenon indicate that the primary cause of the higher O3 on weekends is the reduction in oxides of nitrogen (NOx) emissions on weekends in a volatile organic compound (VOC)-limited chemical regime. In contrast, the lower O3 on weekends in other locations is probably a result of NOx reductions in a NOx-limited regime. The NOx reduction explanation is supported by a wide range of ambient analyses and several photochemical modeling studies. Changes in the timing and location of emissions and meteorological factors play smaller roles in weekend O3 behavior. Weekday/weekend temperature differences do not explain the weekend effect but may modify it. 相似文献
558.
L.-W. Antony Chen Judith C. Chow Bruce G. Doddridge Russell R. Dickerson William F. Ryan Peter K. Mueller 《Journal of the Air & Waste Management Association (1995)》2013,63(8):946-956
Abstract Observations of the mass and chemical composition of particles less than 2.5 μm in aerodynamic diameter (PM2.5), light extinction, and meteorology in the urban Baltimore-Washington corridor during July 1999 and July 2000 are presented and analyzed to study summertime haze formation in the mid-Atlantic region. The mass fraction of ammoniated sulfate (SO4 2-) and carbonaceous material in PM2.5 were each ~50% for cleaner air (PM2.5 < 10 μg/m3) but changed to ~60% and ~20%, respectively, for more polluted air (PM2.5 > 30 μg/m3). This signifies the role of SO4 2- in haze formation. Comparisons of data from this study with the Interagency Monitoring of Protected Visual Environments network suggest that SO4 2? is more regional than carbonaceous material and originates in part from upwind source regions. The light extinction coefficient is well correlated to PM2.5 mass plus water associated with inorganic salt, leading to a mass extinction efficiency of 7.6 ± 1.7 m2/g for hydrated aerosol. The most serious haze episode occurring between July 15 and 19, 1999, was characterized by westerly transport and recirculation slowing removal of pollutants. At the peak of this episode, 1-hr PM2.5 concentration reached ~45 μg/m3, visual range dropped to ~5 km, and aerosol water likely contributed to ~40% of the light extinction coefficient. 相似文献
559.
D. Bruce Henschel Roy C. Fortmann Nancy F. Roache Xiaoyu Liu 《Journal of the Air & Waste Management Association (1995)》2013,63(5):708-717
ABSTRACT A laboratory thermal desorption apparatus was used to measure emissions from a number of nominally identical photocopier toners—manufactured to meet the specifications of one specific model copier—when these toners were heated to fuser temperature (180-200 °C). The objective was to assess how potential volatile organic compound (VOC) emissions from the toner for a given copier can vary, depending upon the production run and the supplier. Tests were performed on a series of toner (and associated raw polymer feedstock) samples obtained directly from a toner manufacturer, representing two production runs using a nonvented extrusion process, and on toner cartridges purchased from two local retailers, representing three different production lots (histories unknown). The results showed that the retailer toners consistently had up to 350% higher emissions of some major compounds (expressed as |ig of compound emit-ted/g of toner), and up to 100% lower emissions of others, relative to the manufacturer toners (p ≤ 0.01). The manufacturer toners from one production run had emissions of certain compounds, and of total VOCs, that were modestly higher (13-18%) than those from the other run (p ≤ 0.01). The emission differences between the retailer and manufacturer toners are probably due to differences 相似文献
560.