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991.
Laura W. Lackey Johnny R. Gamble Jeffrey L. Boles 《Journal of the Air & Waste Management Association (1995)》2013,63(10):1248-1255
Abstract This project demonstrated the biofiltration of a trichloroethylene (TCE)-contaminated airstream generated by air stripping groundwater obtained from several wells located at the Anniston Army Depot, Anniston, AL. The effects of several critical process variables were investigated to evaluate technical and economic feasibility, define operating limits and preferred operating conditions, and develop design information for a full-scale biofilter system. Long-term operation of the demonstration biofilter system was conducted to evaluate the performance and reliability of the system under variable weather conditions. Propane was used as the primary substrate necessary to induce the production of a nonspecific oxygenase. Results indicated that the process scheme used to introduce propane into the biofiltration system had a significant impact on the observed TCE removal efficiency. TCE degradation rates were dependent on the inlet contaminant concentration as well as on the loading rate. No microbial inhibition was observed at inlet TCE concentrations as high as 87 parts per million on a volume basis. 相似文献
992.
Verne L. Rhodes George Kriek Nelson Lazear Jean Kasakevich Marie Martinko R.P. Heggs 《Journal of the Air & Waste Management Association (1995)》2013,63(7):781-788
Abstract Emission factors for selected volatile organic compounds (VOCs) and particulate emissions were developed while processing eight commercial grades of polycarbonate (PC) and one grade of a PC/acrylonitrile-butadiene-styrene (ABS) blend. A small commercial-type extruder was used, and the extrusion temperature was held constant at 304 °C. An emission factor was calculated for each substance measured and is reported as pounds released to the atmosphere/million pounds of polymer resin processed [ppm (wt/wt)]. Scaled to production volumes, these emission factors can be used by processors to estimate emission quantities from similar PC processing operations. 相似文献
993.
Isaac Schifter Luis Díaz Esteban López-Salinas 《Journal of the Air & Waste Management Association (1995)》2013,63(9):1289-1297
Abstract Environmental agencies are currently in the process of implementing a new air management program, which includes the improvement of fuel quality. In this work, exhaust emissions data and estimated relative risk for various fuels testing in-use vehicles, equipped with three different exhaust emission control technologies, are presented. Aromatics, sulfur, and olefins contents; type of oxygenated compound; and Reid vapor pressure were varied. The aim also includes calculating the ozone (O3)of forming potential and a relative cancer risk of emissions from current and formulated gasoline blends in Mexico. The proposed gasoline decreases carbon monoxide, total hydrocarbons (THC), and nitrogen oxides emissions by 18 and 14%, respectively, when compared with gasoline sold in the rest of the country and within ozone nonattainment metropolitan areas in Mexico, respectively. 相似文献
994.
Bret A. Schichtel William C. Malm Marc L. Pitchford 《Journal of the Air & Waste Management Association (1995)》2013,63(5):539-546
Abstract The goal of the Regional Haze Rule (RHR) is to return visibility in class I areas (CIAs) to natural levels, excluding weather-related events, by 2064. Whereas visibility, the seeing of scenic vistas, is a near instantaneous and sight-path-dependent phenomenon, reasonable progress toward the RHR goal is assessed by tracking the incremental changes in 5-yr average visibility. Visibility is assessed using a haze metric estimated from 24-hr average aerosol measurements that are made at one location representative of the CIA. It is assumed that, over the 5-yr average, the aerosol loadings and relative humidity along all of the site paths are the same and can be estimated from the 24-hr measurements. It is further assumed that any time a site path may be obscured by weather (e.g., clouds and precipitation), there are other site paths within the CIA that are not. Therefore, when calculating the haze metric, sampling days are not filtered for weather conditions. This assumption was tested by examining precipitation data from multiple monitors for four CIAs. It is shown that, in general, precipitation did not concurrently occur at all monitors for a CIA, and precipitation typically occurred 3-8 hr or less in a day. In a recent paper in this journal, Ryan asserts that the haze metric should include contributions from precipitation and conducted a quantitative assessment incorrectly based on the assumption that the Optec NGN-2 nephelometer measurements include the effects of precipitation. However, these instruments are programmed to shut down during rain events, and any data logged are in error. He further assumes that precipitation occurs as often on the haziest days as the clearest days and that precipitation light scattering (bprecip) is independent of geographic location and applied an average bprecip derived for Great Smoky Mountains to diverse locations including the Grand Canyon. Both of these assumptions are shown to be in error. 相似文献
995.
Crystal K. Reul-Chen Charles Ross Nancy L.C. Steele Arthur M. Winer 《Journal of the Air & Waste Management Association (1995)》2013,63(2):241-247
Abstract To reduce public exposure to diesel particulate matter (DPM), the California Air Resources Board has begun adoption of a series of rules to reduce these emissions from in-use heavy-duty vehicles. Passive diesel particulate filter (DPF) after-treatment technologies are a cost-effective method to reduce DPM emissions and have been used on a variety of vehicles worldwide. Two passive DPFs were interim-verified in California and approved federally for use in most 1994–2002 engine families for vehicles meeting min engine exhaust temperature requirements for successful filter regeneration. Some vehicles, however, may not be suited to passive DPFs because of lower engine exhaust temperatures. The purpose of this study was to determine the applicability of two types of passive DPFs to solid waste collection vehicles, the group of vehicles for which California recently mandated in-use DPM reductions. We selected 60 collection vehicles to represent the four main types of collection vehicle duty cycles—roll-offs, and front-end, rear, and side loaders—and collected second-by-second engine exhaust temperature readings for one week from each vehicle. As a group, the collection vehicles exhibited low engine exhaust temperatures, making the application of passive DPFs to these vehicles difficult. Only 35% of tested vehicles met the temperature requirements for one passive DPF, whereas 60% met the temperature requirements for the other. Engine exhaust temperatures varied by vehicle type. Side and front-end loaders met the engine exhaust temperature requirements in the greatest number of cases with ~50–90% achieving the required regeneration temperatures. Only 8–25% of the rear loader and roll-off collection vehicles met the engine exhaust temperature requirements. Solid waste collection vehicles represent a diverse fleet with a variety of duty cycles. Low engine exhaust temperatures will need to be addressed for successful use of passive DPFs in this application. 相似文献
996.
Daniel P. Connell Jeffrey A. Withum Stephen E. Winter Robert M. Statnick Richard A. Bilonick 《Journal of the Air & Waste Management Association (1995)》2013,63(4):467-480
Abstract Average concentrations of particulate matter with an aerodynamic diameter less than or equal to 2.5 μm (PM2.5) in Steubenville, OH, have decreased by more than 10 μg/m3 since the landmark Harvard Six Cities Study1 associated the city’s elevated PM2.5 concentrations with adverse health effects in the 1980s. Given the promulgation of a new National Ambient Air Quality Standard (NAAQS) for PM2.5 in 1997, a current assessment of PM2.5 in the Steubenville region is warranted. The Steubenville Comprehensive Air Monitoring Program (SCAMP) was conducted from 2000 through 2002 to provide such an assessment. The program included both an outdoor ambient air monitoring component and an indoor and personal air sampling component. This paper, which is the first in a series of four that will present results from the outdoor portion of SCAMP, provides an overview of the outdoor ambient air monitoring program and addresses statistical issues, most notably autocorrelation, that have been overlooked by many PM2.5 data analyses. The average PM2.5 concentration measured in Steubenville during SCAMP (18.4 μg/m3) was 3.4g/m3 above the annual PM2.5 NAAQS. On average, sulfate and organic material accounted for ~31% and 25%, respectively, of the total PM2.5 mass. Local sources contributed an estimated 4.6 μg/m3 to Steubenville’s mean PM2.5 concentration. PM2.5 and each of its major ionic components were significantly correlated in space across all pairs of monitoring sites in the region, suggesting the influence of meteorology and long-range transport on regional PM2.5 concentrations. Statistically significant autocorrelation was observed among time series of PM2.5 and component data collected at daily and 1-in-4-day frequencies during SCAMP. Results of spatial analyses that accounted for autocorrelation were generally consistent with findings from previous studies that did not consider autocorrelation; however, these analyses also indicated that failure to account for autocorrelation can lead to incorrect conclusions about statistical significance. 相似文献
997.
Viney P. Aneja Jeffrey S. Brittig Deug-Soo Kim Adel Hanna 《Journal of the Air & Waste Management Association (1995)》2013,63(6):681-688
Abstract An analysis of ozone (O3) concentrations and several other air quality-related variables was performed to elucidate their relationship with visibility at five urban and semi-urban locations in the southeast United States during the summer seasons of 1980-1996. The role and impact of O3 on aerosols was investigated to ascertain a relationship with visibility. Regional trend analysis over the 1980s reveals an increase in maximum O3 concentration coupled with a decrease in visibility. However, a similar analysis for the 1990s shows a leveling-off of both O3 and visibility; in both cases, the results were not statistically significant at the 5% level. A case study of site-specific trends at Nashville, TN, followed similar trends. To better understand the relationships between O3 concentration and visibility, the analysis was varied from yearly through daily to hourly averaged values. This increased temporal resolution showed a statistically significant inverse relationship between visibility and O3. Site-specific hourly r2 values ranged from 0.02 to 0.43. Additionally, by performing back-trajectory analysis, it was found that the visibility degraded by air mass migration over polluted areas. 相似文献
998.
Christopher D. Simpson Russell L. Dills Bethany S. Katz David A. Kalman 《Journal of the Air & Waste Management Association (1995)》2013,63(6):689-694
Abstract A microanalytical method suitable for the quantitative determination of the sugar anhydride levoglucosan in low-volume samples of atmospheric fine particulate matter (PM) has been developed and validated. The method incorporates two sugar anhydrides as quality control standards. The recovery standard sedoheptulosan (2,7-anhydro-β-D-altro-heptulopyranose) in 20 μL solvent is added onto samples of the atmospheric fine PM and aged for 1 hr before ultrasonic extraction with ethylacetate/ triethylamine. The extract is reduced in volume, an internal standard is added (1,5-anhydro-D-mannitol), and a portion of the extract is derivatized with 10% by volume N-trimethylsilylimidazole. The derivatized extract is analyzed by gas chromatography/mass spectrometry (GC/MS). The recovery of levoglucosan using this procedure was 69 ± 6% from five filters amended with 2 μg levoglu-cosan, and the reproducibility of the assay is 9%. The limit of detection is ~0.1 μg/mL, which is equivalent to ~3.5 ng/m3 for a 10 L/min sampler or ~8.7 ng/m3 for a 4 L/min personal sampler (assuming 24-hr integrated samples). We demonstrated that levoglucosan concentrations in collocated samples (expressed as ng/m3) were identical irrespective of whether samples were collected by PM with aerodynamic diameter ≤2.5 μm or PM with aerodynamic diameter ≤10 μm impactors. It was also demonstrated that X-ray fluorescence analysis of samples of atmospheric PM, before levoglucosan determinations, did not alter the levels of levoglucosan. 相似文献
999.
Jeffrey S. Gaffney Nancy A. Marley Mary M. Cunningham V. Rao Kotamarthi 《Journal of the Air & Waste Management Association (1995)》2013,63(8):1228-1235
Abstract Natural radionuclides have been proposed as a means of assessing the transport of ozone (O3) and aerosols in the troposphere. Beryllium-7 (7Be) is produced in the upper troposphere and lower stratosphere by the interaction of cosmogenic particles with atmospheric nitrogen and oxygen. 7Be has a 53.29-day half-life (478 keV γ) and is known to attach to fine particles in the atmosphere once it is formed. It has been suggested that O3 from aloft can be transported into rural and urban regions during stratospheric–tropospheric folding events leading to increased background levels of O3 at the surface. 7Be can be used as a tracer of upper atmospheric air parcels and the O3 associated with them. Aerosol samples with a 2.5-µm cutoff were collected during 12-hr cycles (day/night) for a 30-day period at Deer Park, TX, near Houston, in August– September of 2000, and at Waddell, AZ, near Phoenix, in June–July of 2001. A comparison of 7Be levels with 12-hr O3 averages and maxima shows little correlation. Comparison of nighttime and daytime O3 levels indicate that during the day, when mixing is anticipated to be higher, the correlation of 7Be with O3 in Houston is approximately twice that observed at night. This is consistent with mixing and with the anticipated loss of O3 by reaction with nitric oxide (NO) and dry deposition. At best, 30% of the O3 variance can be explained by the correlation with 7Be for Houston, less than that for Phoenix where no significant correlation was seen. This result is consistent with the intercept values obtained for 7Be correlations with either O3 24-hr averages or O3 12-hr maxima and is also in the range of the low O3 levels (25 ppb) observed at Deer Park during a tropical storm event where the O3 is attributable primarily to background air masses. That is, maximum background O3 level contributions from stratospheric sources aloft are estimated to be in the range of 15–30 ppb in the Houston, TX, and Phoenix, AZ, area, and levels above these are because of local tropospheric photochemical production. 相似文献
1000.
Laura A. Geer Jeremy Weedon Michelle L. Bell 《Journal of the Air & Waste Management Association (1995)》2013,63(11):1285-1295
Previous studies have explored the association between air pollution levels and adverse birth outcomes such as lower birth weight. Existing literature suggests an association, although results across studies are not consistent. Additional research is needed to confirm the effect, investigate the exposure window of importance, and distinguish which pollutants cause harm. We assessed the association between ambient pollutant concentrations and term birth weight for 1,548,904 births in TX from 1998 to 2004. Assignment of prenatal exposure to air pollutants was based on maternal county of residence at the time of delivery. Pollutants examined included particulate matter with aerodynamic diameter ≤10 and ≤2.5 µm (PM10 and PM2.5), sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and ozone (O3). We applied a linear model with birth weight as a continuous variable. The model was adjusted for known risk factors and region. We assessed pollutant effects by trimester to identify biological exposure window of concern, and explored interaction due to race/ethnicity. An interquartile increase in ambient pollutant concentrations of SO2 and O3 was associated with a 4.99-g (95% confidence interval [CI], 1.87–8.11) and 2.72-g (95% CI, 1.11–4.33) decrease in birth weight, respectively. Lower birth weight was associated with exposure to O3 in the first and second trimester, whereas results were not significant for other pollutants by trimester. A positive association was exhibited for PM2.5 in the first trimester. Effects estimates for PM10 and PM2.5 were inconsistent across race/ethnic groups. Current ambient air pollution levels may be increasing the risk of lower birth weight for some pollutants. These risks may be increased for certain racial/ethnic groups. Additional research including consideration of improved methodology is needed to investigate these findings. Future studies should examine the influence of residual confounding.
Implications: This is one of the most comprehensive studies examining criteria air pollutants and lower birth weight in Texas. Our findings confirm results found previously for adverse effects of the air pollutant SO2 on lower birth weight. Results from our study suggest that adverse pregnancy outcomes such as lower birth weight can occur even while maintaining air pollution levels below regulatory standards. Future studies should incorporate the assessment of differential pollutant exposure as well as effect estimates by race/ethnicity with individual and community-level social factors in order to enhance our understanding of how physical, social, and host factors influence birth outcomes. Supplemental Materials: Supplementary information relating to characteristics of excluded births, distribution of air pollutant monitors by pollutant, and correlation coefficients of the air pollutants is available in the publisher's online edition of the Journal of the Air & Waste Management Association. 相似文献