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701.
Zhishi Guo Ronald B. Mosley Shirley J. Wasson Roy C. Fortmann Jenia A. McBrian 《Journal of the Air & Waste Management Association (1995)》2013,63(4):616-622
ABSTRACT As an odorless, nontoxic, and inert compound, sulfur hexafluoride (SF6) is one of the most widely used tracer gases in indoor air quality studies in both controlled and uncontrolled environments. This compound may be subject to reactions with water vapor under elevated temperature to form acidic inorganic compounds such as HF and H2SO4. Thus, in the presence of unvented combustion sources such as kerosene heaters, natural gas heaters, gas log fireplaces, candles, and lamps, the SF6 dissociation may interfere with measurements of the emissions from these sources. Tests were conducted in a research house with a vent-free natural gas heater to investigate these potential interferences. It was observed that the heater operation caused about a 5% reduction of SF6 concentration, which can be an error source for the ventilation rate measurement and consequently the estimated pollutant emission rates. Further analysis indicates that this error can be much greater than the observed 5% under certain test conditions because it is a function of the ventilation flow rate. Reducing the tracer gas concentration has no effect on this error. A simple theoretical model is proposed to estimate the magnitude of this error. The second type of interference comes from the primary and secondary products of the SF6 dissociation, mainly H2SO4, SO2, HF, and fine particulate matter (PM). In the presence of ~5 ppm SF6, the total airborne concentrations of these species increased by a factor of 4-10. The tests were performed at relatively high SF6 concentrations, which is necessary to determine the interferences quantitatively. The second type of interference can be significantly reduced if the SF6 concentration is kept at a low ppb level. 相似文献
702.
ABSTRACT Methylcyclopentadienyl manganese tricarbonyl (MMT) has been used in Canada since 1976 as an antiknock agent in gasoline, completely replacing Pb in 1990. An early study of much higher Mn concentrations in gasoline showed that the combustion of MMT leads to the formation of inorganic manganese oxides, especially Mn3O4. Recent emission testing by Lawrence Livermore National Laboratory for Ethyl Corp. has shown that Mn is primarily emitted as a phosphate or sulfate along with minor amounts of oxides. The main objective of this research was to analyze the deposition of Mn from MMT to the terrestrial environment beside the major highways in the greater Toronto area (GTA), Canada. The results were compared with Pb and other trace elements such as Al, Ca, Fe, Mg, Cu, Zn, Na, and the Cl- ion (water extractable) to study the behavior of Mn in soil. The study area was located near major Toronto highways 401 (urban) and 400 (rural), at 43° 67′ N and 79° 37′ W (latitude and longitude) (278,560 and 47,835 cars/day), respectively. Surface soil samples (0–5 cm depth) were collected at distances up to 40 m from the roadside. Parameters evaluated included total and available Mn and other trace elements, particle size, pH, organic content, and cation exchange capacity. 相似文献
703.
Kerry E. Kelly David A. Wagner JoAnn S. Lighty Adel F. Sarofim Brad Bretecher Bruce Holden 《Journal of the Air & Waste Management Association (1995)》2013,63(1):83-92
Abstract In-service diesel engines are a significant source of particulate matter (PM) emissions, and they have been subjected to increasingly strict emissions standards. Consequently, the wide-scale use of some type of particulate filter is expected. This study evaluated the effect of an Engelhard catalyzed soot filter (CSF) and a Rypos electrically heated soot filter on the emissions from in-service diesel engines in terms of PM mass, black carbon concentration, particle-bound polycyclic aromatic hydrocarbon concentration, and size distribution. Both filters capture PM. The CSF relies on the engine's exhaust to reach the catalyst regeneration temperature and oxidize soot, whereas the electrically heated filter contains a heating element to oxidize soot. The filters were installed on several military diesel engines. Particle concentrations and compositions were measured before and after installation of the filter and again after several months of operation. Generally, the CSF removed at least 90% of total PM, and the removal efficiency improved or remained constant after several months of operation. In contrast, the electrical filters removed 44-69% of PM mass. In addition to evaluating the soot filters, the sampling team also compared the results of several real-time particle measurement instruments to traditional filter measurements of total mass. 相似文献
704.
Hebi Li Yongsheng Chen John Crittenden David Hand Roy Taylor 《Journal of the Air & Waste Management Association (1995)》2013,63(8):1155-1166
Abstract A high-efficiency particulate air (HEPA)-carbon filtration system was developed by the Access Business Group, LLC, to reduce the indoor levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). The HEPA filter removes the particle-bound PCDD/Fs, and the carbon filter removes the gaseous fraction. Because of the toxicity of PCDD/Fs, it is very difficult to handle them in the laboratory. In this study, mathematical modeling was performed to evaluate the performance of the HEPA-carbon filtration system for PCDD/Fs removal and to optimize its design and operation. The model was calibrated with experimental data conducted with toluene in a sealed room. Model simulations with four selected congeners demonstrated that it takes ~1 hr for the indoor air treatment system to reach the maximum removal efficiency and that the carbon air filter has a life time of 107 yr for dioxin removal. Given a zero emission from the HEPA filter, the overall removal efficiency is 78.7% for 2,3,7,8-tetrachloro dibenzo-p-dioxins, 89.8% for octa-chlorodibenzodioxin, 78% for tetra-chlorodibenzofuran, and 89.8% for octachlorodibenzofuran. The larger the mass emission from the HEPA filter, the lower the overall removal efficiency, and the larger the ratio of the filter flow rate (Qf) to the room flow rate (Q), the higher the overall removal efficiency. When the ratio of Qf/Q is 15, an overall removal efficiency of 90% can be reached for all four of the selected compounds. The removal of the four selected compounds does not change as the relative humidity increases ≤90%. 相似文献
705.
706.
Rui de Abrantes João V. de Assunção Célia R. Pesquero Raimundo P. da Nóbrega Roy E. Bruns 《Journal of the Air & Waste Management Association (1995)》2013,63(12):1344-1352
ABSTRACT The exhaust emissions of 17 polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) were investigated in two spark-ignition light-duty vehicles, one gasohol-fueled and a flexible-fuel one fueled with hydrated ethanol. Gasohol is a mixture of gasoline and 22% ethanol. The influence of fuel type and quality, lubricant oil type, and use of fuel additives on the formation of these compounds was tested using standardized U.S. Federal Test Procedure (FTP)-75 cycle tests. The sampling of the PCDD/Fs followed the recommendations of a modified U.S. Environmental Protection Agency (EPA) Method 23 (http://www.epa.gov/ttn/emc/promgate/m-23.pdf) and the analysis basically followed the U.S. EPA Method 8290 (http://www.epa.gov/osw/hazard/testmethods/sw846/pdfs/8290a.pdf). Results showed that emission factors of PCDD/Fs for the gasohol vehicle varied from undetected to 0.068 pg international toxic equivalency (I-TEQ) km?1 (average of 0.0294 pg I-TEQ km?1), whereas in the ethanol vehicle they varied from 0.004 to 0.157 pg (I-TEQ) km?1 (average of 0.031 pg I-TEQ km?1). In the gasohol-powered vehicle, the use of fuel additive diminished the emission of Octachlorodibenzo-p-dioxin (OCDD) significantly, whereas in the ethanol vehicle no significant associations were observed between the investigated variables and the emissions.
IMPLICATIONS The objective of this work was to analyze differences in emissions from a traditional fossil fuel (gasoline) and an alternative renewable fuel (ethanol from sugarcane), and the influence of fuel additives and lubricant oils on the formation of chlorinated dioxins and furans in spark-ignition light-duty gasohol and ethanol vehicles. Renewable fuels are very important in terms of climate change but the risk to the population's health must not increase. Thus the results of this work could help in the development of environmental impact studies as well as orienting policy-makers in formulating strategies for air pollution control. 相似文献
707.
Geoff Wilson Giovanni Quaranta Claire Kelly Rosanna Salvia 《Journal of Environmental Planning and Management》2016,59(3):518-537
This study analyses social, economic and political “lock-ins” for understanding community resilience and land degradation. The study focuses on lock-ins from within communities, using four case study communities in Italy affected by land degradation. The analysis highlights the complex interrelationships between various lock-ins, and suggests that the communities are on declining resilience pathways that may lead to increasing difficulties in addressing land degradation issues in future. 相似文献
708.
Saheli Pradhan Indrani Roy Gopal Lodh Prasun Patra Samrat Roy Choudhury Arunava Samanta 《Journal of environmental science and health. Part. B》2013,48(7):559-569
This is a report of an experimental study on a nanoencapsulation of the organophosphate acephate. Acephate was encapsulated in polyethylene glycol, using a simple, easy-to-replicate method that required no special equipment or conditions. The nanoencapsulation (nanoacephate) was characterized and its bioefficacy as compared to the regular commercial acephate was tested. The biosafety of the new compound was also tested on a murine model. Our new nanoencapsulation scored over the regular variety on all counts. It was found to successfully incorporate the active pesticidal component, acephate and this compound retained greater functional integrity over time as a nanoencapsulation. It was significantly more efficacious than the regular variety. It was biosafe when tested on murine model. We have reason to believe that this nanoencapsulation would allow the use of an organophosphate in a more targeted manner, thereby making it a cost-effective and eco-friendly alternative to the regular variety in use now. 相似文献
709.
710.
Robert J. Luxmoore William W. Hargrove M. Lynn Tharp Wilfred M. Post Michael W. Berry Karen S. Minser Wendell P. Cropper Jr. Dale W. Johnson Boris Zeide Ralph L. Amateis Harold E. Burkhart V. Clark Baldwin Jr. Kelly D. Peterson 《Environmental Modeling and Assessment》2000,5(2):125-137
Stochastic transfer of information in a hierarchy of simulators is offered as a conceptual approach for assessing forest responses
to changing climate and air quality across 13 southeastern states of the USA. This assessment approach combines geographic
information system and Monte Carlo capabilities with several scales of computer modeling for southern pine species and eastern
deciduous forests. Outputs, such as forest production, evapotranspiration and carbon pools, may be compared statistically
for alternative equilibrium or transient scenarios providing a statistical basis for decision making in regional assessments.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献