Significance of Regional Source Contributions to Urban PM-10 Concentrations

Based on data collected in St. Louis, Philadelphia and other eastern U.S. cities, we conclude that a significant fraction of the PM-10 concentration is "background." In these urban areas the background fraction ranges from 35 to 80 percent of the daily, monthly or annual concentration. The bulk of the background appears to be of regional origin. The average chemical makeup of eastern U.S. PM-10 is sulfate as SO₄, 21-34 percent; crustal material, 14-39 percent; "unknown" (carbonaceous matter, ammonium, nitrate and water), 36-51 percent, all of which is difficult to apportion to specific sources. Dispersion modeling using a local source inventory can account only for a small portion of the total PM-10 mass. Emission roll-back of local sources may have a limited effect on reducing total concentrations of PM-10.     

A Collaborative Effort to Model Plant Response to Acidic Rain

Radish plants were exposed three times per week to simulated acidic rain at pH values of 2.6 to 5.4 over the course of four weeks in trials performed at Argonne, Illinois; Ithaca and Upton, New York; Corvallis, Oregon; Oak Ridge, Tennessee; and Toronto, Canada. Uniform genotype, soil media and planting techniques, treatment procedures, biological measurements, and experimental design were employed. Growth of plants differed among trials as a result of variation in greenhouse environmental conditions according to location and facilities. Larger plants underwent greater absolute but lower relative reductions in biomass after exposure to the higher levels of acidity. A generalized Mitscherlich function was used to model the effects of acidity of simulated rain or dry mass of hypocotyls using data from three laboratories that performed duplicate trials. The remaining data, from three other laboratories that performed only one trial each, were used to test the model. When the laboratory by trial effect was removed (influence of different growth. conditions), lack of fit to the Mitscherlich function was insignificant. Thus, a single mathematical model satisfactorily characterized the relationship between acidity and mean plant response. The pH value associated with a 10 percent reduction in mass was 3.3 ± 0.3 for hypocotyls. No value was estimated for shoots because effects oh shoots were not significant. The results of this study demonstrate that a generalized exposure-response model can be developed in the presence of large variations in environmental conditions when plant culture and exposure to simulated rain are standardized among laboratories.     

Indoor/Outdoor Measurements of Volatile Organic Compounds in the Kanawha Valley of West Virginia

The Kanawha Valley region of West Virginia which is comprised of Charleston and surrounding communities Is the center of a heavily industrialized area known for its chemical manufacturing. As part of a larger study designed to investigate the Impact of the chemical industry on human exposures to volatile organic compounds (VOC), a study of the relationship between indoor and outdoor concentrations was conducted. Thirty-five homes were selected for monitoring from among volunteers; approximately ten in each of three distinct population-industry centers and four outside the Valley to act as controls. Monitoring was performed using passive, badge samplers with a three-week monitoring period. Two separate questionnaires were administered: one for characterization of the residence; and one to characterize source use during monitoring. Participants were also asked to keep a record of their activities with respect to in-home, outdoors and other Indoor environments. Analysis of the samplers was performed by solvent extraction followed by gas chromatography using a flame-ionization detector. Results suggest that indoor VOC concentrations are higher than outdoor concentrations. Additionally, certain ventilation-related parameters were identified that afforded some predictive power for indoor concentrations. No statistically significant differences between regions were identified.     

Stationary Combustion NOX Control A Summary of the 1989 Symposium

This paper summarizes information and results presented at the 1989 Symposium on Stationary Combustion NOX Control, held March 6-9, 1989 in San Francisco. Cosponsored by the Electric Power Research Institute (EPRI) and the U.S. Environmental Protection Agency, (EPA) the symposium was the fifth in a biennial series.     

Comparison of the Annular Denuder System and the Transition Flow Reactor for Measurements of Selected Dry Deposition Species

An intensive field study was conducted in Research Triangle Park, North Carolina in the fall of 1986. Ambient concentrations of the following constituents were obtained: nitric acid, nitrous acid, nitrogen dioxide, sulfur dioxide, ammonia, hydrogen ion, and particulate nitrate, sulfate, and ammonium. Results collected using the annular denuder system (ADS) and the transition flow reactor (TFR) are presented and compared.

Both types of samplers had operational detection limits on daily (22-hour) samples that were generally below 1 μg m_-3 suggesting that both samplers can provide sensitive measurements for most of the constituents of interest. Both the ADS and TFR show reasonable (>25 percent) within-sampler precision for most of the measured species concentrations, except TFR fine particulate nitrate measurements where results were frequently negative (The TFR fine particulate nitrate measurement is calculated using subtraction of positive numbers).

Comparison of ADS and TFR daily results showed good agreement for total particulate sulfate, the sum of total (coarse plus fine) particulate and gaseous nitrate, and ammonia. As a result of different inlet particle collection efficiencies, the ADS fine particulate sulfate exceeded the TFR (5 percent). In the absence of a filter to collect volatilized particulate ammonium in the ADS, the sum of total particulate and gaseous ammonium in the TFR exceeded that in the ADS. Of potentially more importance, ADS measurements of SO₂ and H⁺ exceeded those of the TFR, while TFR measurements of HNO₃ exceeded those of the ADS. Results of this study suggest that the TFR may provide biased measurements of SO₂, H⁺, HNO₃, and Fine NO₃ ^- that cannot be corrected without modifications to the fundamental design of the sampling system.     

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.     

A Field Intercomparison and Fundamental Characterization of Various Dust Samplers with a Reference Sampler

The European Economic Community Council Directive 80/779/EEC¹ describes air quality limit values and guide values for sulfur dioxide and suspended particulates. However, article 10, paragraph 1 does not define well enough the reference method required, amongst others, for the gravimetric measurement of suspended particulates. It is explicity stated in article 10, paragraph 5 of the directive, that “the commission shall, in selected locations in the member states and in cooperation with the latter, carry out studies on the sampling…of suspended particulates. These studies shall be designed in particular to promote the harmonization of methods of sampling and analysis of these pollutants.” Therefore, in a joint research program the Umweltbundesamt (grant #104 02263), the commission of European Communities (grant #84-B-6642-11-017-11-N) and the U.S. EPA (grant #2-43211-3580) funded the development of a reference dust sampler by the Fraunhofer-lnstitute of Toxicology and Aerosol Research (FhITA, in Hannover, Federal Republic of Germany) in order: ? to study the particle size distribution of ambient air aerosol at a number of selected sites;

? to compare the results obtained with the reference dust sampler with those of particle samplers operated in Europe and the United States;

? to verify the applicability of wind tunnel results to sampling behaviour in the free atmosphere.

     

A Combined Ca(OH)2/NH3 Flue Gas Desulfurization Process for High Sulfur Coal: Results of a Pilot Plant Study

The removal of SO₂ with atomization of a slaked lime slurry and supplemental injection of gaseous NH₃ were tested in a conventional spray dryer/baghouse system for SO₂ concentrations of 2000 ppm and 3000 ppm and a 30° F approach to saturation. Results at 3000 ppm of SO₂ showed an average SO₂ removal efficiency of 90.3 percent at a combined stoichiometric ratio of 0.95-1.10 and an average overall sorbent utilization of 91.6 percent. The overall molal ratio of NH₃/SO₂ reaction was found to be 2:1 under the test conditions Particle size analyses, and EP toxicity tests were conducted on the products of the reactions.     

Modeling Short Range Air Dispersion from Area Sources of Non-buoyant Toxics

A model based on K-theory has been developed for describing the short range air dispersion from area sources of non-buoyant toxics. Model parameter estimation is via boundary layer theory. Lateral dispersion by plume meander is considered but ail other sources of horizontal dispersion are neglected. The model can be applied on and near area sources and it can be adapted for predictions of downwind concentrations with a wide variety of meteorological Inputs.

The model has been evaluated by simulating the data obtained during atmospheric tracer studies and by comparison to vinyl chloride concentrations near the BKK landfill in southern California. The model appears to represent a useful and accurate tool for regulatory planning and risk assessment close to area sources of toxics.