Characterization of Emissions from a Variable Gasoline/Methanol Fueled Car

In response to the occurrence of the increasingly severe ambient ozone exceedances, regional environmental managers are examining the possibility of a cleaner fuel for automobiles. At this time the leading candidate appears to be methanol. In anticipation of a shift to methanol, flexible-fueled automobiles capable of operating on gasoline and/or methanol are being developed. This study examines both the exhaust and evaporative emissions from a prototype General Motors Variable Fuel Corsica. Results are reported for tests conducted at temperatures of 40°, 75°, and 90° F, and for fuels MO M25, M50, M85, and M100. In addition to regulated emissions and fuel economy, emission rates for methanol, aldehydes, and a large number of hydrocarbon compounds were measured. The data indicate that increasing the fuel's methanol content does not affect the exhaust organic emission rate (calculated in accordance with the regulation) from flexible-fueled cars, but formaldehyde and methanol comprise increasingly greater portions of the organic material while hydrocarbons comprise less. Increasing fuel methanol content has no significant effect on exhaust regulated emission rates (organic material, carbon monoxide, and nitrogen oxides) nor on the composition of total hydrocarbons, except for methane, which increases substantially. The effect of ambient temperature on both exhaust and evaporative emissions is similar to its effect on gasoline cars: organic and carbon monoxide exhaust emissions increase substantially at the lower temperatures, and evaporative emissions increase steadily with increases in temperature.     

Evaluating Sources of Indoor Air Pollution

Evaluation of Indoor air pollution problems requires an understanding of the relationship between sources, air movement, and outdoor air exchange. Research is underway to investigate these relationships. A three-phase program is being implemented: 1) Environmental chambers are used to provide source emission factors for specific indoor pollutants; 2) An IAQ (Indoor Air Quality) model has been developed to calculate indoor pollutant concentrations based on chamber emissions data and the air exchange and air movement within the indoor environment; and 3) An IAQ test house is used to conduct experiments to evaluate the model results. Examples are provided to show how this coordinated approach can be used to evaluate specific sources of indoor air pollution. Two sources are examined: 1) para-dichlorobenzene emissions from solid moth repellant; and 2) particle emissions from unvented kerosene heaters.

The evaluation process for both sources followed the three-phase approach discussed above. Para-dichlorobenzene emission factors were determined by small chamber testing at EPA’s Air and Energy Engineering Research Laboratory. Particle emission factors for the kerosene heaters were developed In large chambers at the J. B. Pierce Foundation Laboratory. Both sources were subsequently evaluated in EPA’s IAQ test house. The IAQ model predictions showed good agreement with the test house measurements when appropriate values were provided for source emissions, outside air exchange, in-house air movement, and deposition on “sink” surfaces.     

Regional Photochemical Measurement and Modeling Studies: A Summary of the Air & Waste Management Association International Specialty Conference

Abstract

This paper summarizes the Air & Waste Management Association’s International Specialty Conference, "Regional Photochemical Measurement and Modeling Studies," held in San Diego, California, on November 8-12,1993. The purpose of the conference was to facilitate exchange of information and to initiate better communication and interaction among scientists, air quality managers, regulators, and others involved in or applying tools (models and measurements to support the modeling efforts) that can be used to develop equitable and effective emissions management practices for attainment of ozone standards. Attendees heard more than 350 presentations from authors representing nearly 30 air quality and meteorological measurement and modeling studies from 18 countries. While the primary emphasis of the conference was technical, two policy sessions were included (Plenary and Concluding Sessions) to place the technical results in perspective with the policy issues. The technical agenda was divided into three subjects: Analysis of Field Measurements (results and interpretation), Modeling (status and results), and Other Topics. Papers presented at the conference are being published in a variety of journals or books to meet the needs of the scientific and policy communities. A complete bibliographical listing of the papers presented at the conference is included with this paper.

An unexpected outcome of the conference has been the development of an initiative for continuing the intercomparison of goals and scientific findings from regional air quality studies in Europe and North America, entitled “Regional Oxidants Programs Intercomparison” (ROxPIn). This paper will also discuss the goals and objectives of ROxPIn.     

Spatial Variation in Acidic Sulfate and Ammonia Concentrations within Metropolitan Philadelphia

Abstract

Acidic sulfate concentrations were measured in metropolitan Philadelphia during the summers of 1992 and 1993, as part of a continuing effort to characterize particle concentrations in urban environments. Sampling was performed simultaneously at eight sites located within and around metropolitan Philadelphia. Sites were selected based on their population density and on their distance and direction from the city center. Air pollution sampling was conducted every other day during the summer of 1992 and every day during the summer of 1993. All samples were collected for 24-h periods beginning at 9 a.m. (EDT). All acidic sulfate and ammonia samples were collected using modified Harvard-EPA Annular Denuder Systems (HEADS).

In this paper, we examine the spatial variation in acidic sulfate and ammonia concentrations within the metropolitan Philadelphia area. We also identify factors that may influence their variation and develop models to predict their concentrations. Outdoor sulfate (SO₄ ^2?) concentrations were uniform within metropolitan Philadelphia; however, aerosol strong acidity (H⁺) concentrations varied spatially. This variation generally was independent of wind direction, but was related to local factors, such as the NH₃ concentration, population density, and distance from the center of the city. Physico-chemical models, which were developed using data collected during the summer of 1992, were excellent predictors of 24-h and mean summertime H⁺ concentrations measured during the summer of 1993. Models accounted for 78% of the variation in 24-h H⁺ levels. Results suggest that a single stationary ambient (SAM) monitor would be sufficient to estimate SO₄ ^2? exposures for populations living in Philadelphia. For H⁺, however, multiple monitoring sites or models should be used to determine the outdoor H+ exposures of populations living in urban environments, although a single SAM site may provide an excellent index of H⁺ variation over time.     

Effectiveness of Smokeless Ashtrays

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%.     

Controlled Exposures of Volunteers to Respirable Carbon and Sulf uric Acid Aerosols

Respirable carbon or fly ash particles are suspected to increase the respiratory toxicity of coexisting acidic air pollutants, by concentrating acid on their surfaces and so delivering it efficiently to the lower respiratory tract. To investigate this issue, we exposed 15 healthy and 15 asthmatic volunteers in a controlled- environment chamber (21°C, 50 percent relative humidity) to four test atmospheres: (i) clean air; (ii) 0.5-μm H2SO4 aerosol at =100 μg/m³, generated from water solution; (iii) 0,5-μm carbon aerosol at =250 μg/m³, generated from highly pure carbon black with specific surface area comparable to ambient pollution particles; and (iv) carbon as in (iii) plus =100 μg/m³ of ultrafine H2SO4 aerosol generated from fuming sulfuric acid. Electron microscopy showed that nearly all acid in (iv) became attached to carbon particle surfaces, and that most particles remained in the sub-μm size range. Exposures were performed double-blind, 1 week apart. They lasted 1 hr each, with alternate 10-min periods of heavy exercise (ventilation =50 L/min) and rest. Subjects gargled citrus juice before exposure to suppress airway ammonia. Lung function and symptoms were measured pre-exposure, after initial exercise, and at endexposure. Bronchial reactivity to methacholine was measured after exposure. Statistical analyses tested for effects of H₂SO₄ or carbon, separate or interactive, on health measures. Group data showed no more than small equivocal effects of any exposure on any health measure. One individual's responses were consistent with a clinically significant excess airway constriction from H₂SO₄ plus carbon, and 2-3 others showed slight excess responses to the combined pollutants, but all these observations might have reflected chance variations. We conclude that coexisting carbon aerosol did not increase respiratory irritancy of H₂SO₄, in most healthy and asthmatic subjects exposed for 1 hr under simulated "worst-case" ambient conditions.     

The Cost Estimation of Thermal and Catalytic Incinerators for the Control of VOCs

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.     

Rotary Kiln Incineration of Dichloromethane and Xylene: A Comparison of Incinerability Characteristics Under Various Operating Conditions

Comparisons are made, for the first time, between the combustion characteristics of dichloromethane and xylene in an industrial rotary kiln incinerator. The comparisons are made under different operating conditions, including variable kiln rotation rate and operation both with and without turbulence air. Continuous gas composition and temperature measurements and batch gas composition measurements were obtained from two vertical locations hear the exit region of the rotary kiln. The measurements show that there is significant vertical stratification at the exit of the kiln. Addition of turbulence air enhanced combustion conditions throughout the kiln during xylene processing. During dichloromethane processing, however, the addition of turbulence air had minimal effect and only promoted greater bulk mixing; chlorinated compounds transported from the lower kiln during operation with turbulence air were not efficiently processed in the upper kiln. Evolution of test liquids from the bed was not constant but rather was characterized by intermittent peaks. The field-scale data of this work suggest that the evolution rate of the test liquid was increased as kiln rotation rate increased. Many of the differences between xylene and dichloromethane processing during these experiments are explained by a simple stoichiometric analysis.