Experimental Characterization of Atmospheric Diffusion in Complex Terrain with Land-Sea Interactions

The body of information presented in this paper is directed to scientists working in atmospheric dispersion research and model development. Two years of field measurements in the coastal area of Bilbao in northern Spain show that the diffusion behavior in this complex terrain can be classified into several well defined patterns, which correspond to certain meteorological conditions. The approach taken has been the systematic use of SO₂ remote sensors (COSPEC) and ground level monitors in moving platforms which are used to follow and document the flow of the air mass. Results to date show that complex reentry cycles can occur and that synoptically different flows may be indistinguishable by wind sensors at ground level (affected by channeling), and yet result in totally different observed pollution levels by a fixed monitoring network (affected by topographical effects). These results are being used to parameterize the cause-effect relationships and guide the modeling efforts in this area of complex terrain.     

Development of Federal Air Standards to Reduce Sulfur Dioxide Emissions from New Industrial Boilers

Federal new source performance standards to control air emissions of sulfur dioxide from new industrial boilers were proposed by EPA on June 19, 1986. These standards would require boiler owners to reduce SO₂ emissions by 90 percent and meet an emission limit of 1.2 lb/MM Btu of heat input for coal-fired boilers and 0.8 lb/MM Btu for oil-fired boilers. In developing these standards, several regulatory options were considered, from standards that could be met by firing low sulfur fuels to standards that would necessitate flue gas treatment. The environmental, economic, and cost impacts of each option were analyzed. National impacts were estimated by a computer model that projects the population of new boilers over the 5-year period following proposal, predicts the compliance strategy that will be used to comply with the particular option (always assuming that the lowest cost method of compliance will be selected), and estimates the resulting emission reductions and costs. Impacts on specific industries and on model boilers were also analyzed. This paper focuses on these analyses and their results. The Agency's conclusions from these analyses, which led to the decision to establish percent reduction standards, are provided, and the proposed SO₂ standards are summarized. The proposed standards also include an emission limit for particulate matter from oil-fired boilers (0.1 lb/MM Btu). However, this article focuses only on the SO₂ standards.     

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.     

Validation of Models for Predicting Formaldehyde Concentrations in Residences due to Pressed-Wood Products

This paper describes a laboratory project to assess the accuracy of emission and indoor air quality models to be used in predicting formaldehyde (HCHO) concentrations in residences due to pressed-wood products made with urea-formaldehyde bonding resins. The products tested were partlcleboard underlayment, hardwood- plywood paneling and medium-density fiberboard (mdf). The products were initially characterized in chambers by measuring their formaldehyde surface emission rates over a range of formaldehyde concentrations, air exchange rates and two combinations of temperature and relative humidity (23° C and 5 0% RH; 26°C and 60% RH). They were then installed in a two-room prototype house in three different combinations (underlayment flooring only; underlayment flooring and paneling; and underlayment flooring, paneling, and mdf). The equilibrium formaldehyde concentrations were monitored as a function of air exchange rate. Particleboard underlayment and mdf, but not paneling, behaved as the emission model predicted over a large concentration range, under both sets of temperature and relative humidity. Good agreement was also obtained between measured formaldehyde concentrations and those predicted by a mass-balance indoor air quality model.     

A Management Systems Review of the Superfund RI/FS: Opportunities for Streamlining

The Management Systems Review is an important component of EPA’s quality assurance program. MSRs enable managers to assess the effectiveness of environmental data operations and the quality assurance/ quality control activities designed to ensure that the results are of the expected quality. These reviews inform managers about aspects of the environmental data operation that are working well and those which may warrant some improvement. A recent review of the Superfund remedial investigation/feasibility study (RI/FS) has shown that the MSR is an excellent tool for providing a systematic definition of complex environmental data operations and for enabling a thorough analysis of these operations. The MSR utilized information gathered from interviews of Regional staff and management and from case studies of recently completed RI/FSs. The findings indicated that environmental data play an important role in most RI/FS decisions and that thorough and structured scoping is critical to the effectiveness of the RI/ FS. Analysis of the RI/FS process using a comprehensive flow model identified several opportunities for changes that may increase efficiency in data collection and the reliability of RI/FS decisions. These changes provide for more effective scoping activities, a streamlined feasibility study, and increased use of treatability studies during the RI. A pilot demonstration of these process changes is being planned for a Regional RI/FS.     

An Evaluation of the Effects of Ozone Injury on Radial Growth of Ponderosa Pine (Pinus ponderosa) in the Southern Sierra Nevada

Growth of ponderosa pines with visible symptoms of ozone injury was compared with that of asymptomatic trees in the southern Sierra Nevada, California. Time series analysis indicated that there was no significant reduction in annual radial increment of symptomatic trees during recent years compared to past growth and growth of asymptomatic trees. First order autocorrelation and climatic variables accounted for a large proportion of the variance in growth index, and winter precipitation was positively correlated with growth for all size and age classes. Although ozone concentrations are high enough to cause chlorosis and premature needle senescence in ponderosa pine, there has been no significant change in growth associated with ozone injury.     

Determination of Room Temperature OH Rate Constants for Acetylene,Ethylene Dichloride,Ethylene Dibromide,p-Dichlorobenzene and Carbon Disulfide

A relative rate procedure was used to measure hydroxyl rate constants at room temperature in the presence of oxygen. The photolysis of methyl nitrite in the presence of nitric oxide was used to generate OH radicals. The rate of loss of the test compounds was measured relative to that of ethane (k_OH = 2.74 × 10^-13 cm³ molec^-1 s^-1). The rates obtained at 297 ± 2 K are: acetylene = (7.8 ± 1.6) × 10^-13 cm³ molec^-1 s^-1,1,2-dichloroethane (2.8 ± Q.6) × 10^-13 cm³ molec^-1 s^-1, 1,2-dibromoethane (2.4 ± 0.5) × 10^-13 cm³ molec^-1 s^-1, p-dichlorobenzene (4.3 ± 0.9) × 10^-13 cm³ molec^-1 s^-1 and carbon disulfide (29 ± 6) × 10^-13 cm³ molec^-1 s^-1. Under a proposed EPA rule, this OH rate determination procedure could be used to determine if a given volatile organic will be subject to control for reduction of photochemical ozone.     

Transportation-Related Volatile Hydrocarbon Source Profiles Measured in Atlanta

Abstract

Samples representative of transportation-related hydrocarbon emissions were collected as part of the 1990 Atlanta Ozone Precursor Monitoring Study. Motor vehicle emissions were sampled in canisters beside a roadway in a tunnel-like underpass during periods of heavy traffic. Airport and aircraft emissions were approximated by canister samples obtained at a major airport facility. Three octane grades of gasoline were purchased from six major vendors in Atlanta. Canister samples were prepared using these fuels to approximate the whole gasoline and gasoline vapor composition of the fuels in use during the study. All samples were analyzed by gas chromatography/flame ionization detection (GC/FID) for their hydrocarbon content. Detailed speciated hydrocarbon profiles were developed from this source sampling and analysis program for use in the Chemical Mass Balance (CMB) model. Profiles presented and discussed here represent the hydrocarbon composition of emissions from a roadway, composite headspace gasoline at two temperatures, composite whole gasoline, whole gasoline at three octane grades, and an airport. The roadway profile is compared with similar profiles in the literature, and recommendations are made regarding its use in the CMB model. The roadway and fuel profiles are discussed in the context of the MOBILE5 model outputs. The headspace gasoline vapor profile presented here is compared with a headspace gasoline vapor profile calculated from the whole gasoline profile by means of Raoult’s law. Agreement between the measured and calculated headspace profiles is excellent. The airport profile demonstrates the importance of high molecular weight volatile hydrocarbons in airport and aircraft emissions.