Variance Design and Air Pollution Control

Confronted with shortages of low sulfur content residual fuel oil and, consequently, faced with the threat of social and economic upheaval, several air pollution control authorities in the Northeastern states were forced to relax hard-won air quality standards during the winter of 1972. The authorities did so by granting variances to their sulfur content standards for residual fuel oil. This paper examines the institutional characteristics of these variance policies from an economic incentive standpoint. After setting up desirable structural criteria for institutional design of such crisis policies, the authors examine the experience of the winter of 1972 and arrive at policy guidelines which recommend themselves for consideration in future periods of fuel oil shortages.     

Status and Problems of Regenerable Flue Gas Desulfurization Processes

Fourteen sulfur and/or sulfuric acid producing regenerate FGD processes were discussed at the 1974 FGD Symposium in Atlanta. During the period elapsed since then, considerable status change has occurred on many of these regenerable processes. Other regenerable processes which were not as well known during 1974 have surfaced in 1975. The problems of obtaining reducing gases (hydrogen sulfide, carbon monoxide, and hydrogen) for the reduction of sulfur dioxide product streams to elemental sulfur have become severe due to shortages of natural gas or other petroleum based feedstock. A new sulfur producing process which employs CO and H₂ directly (rather than the H₂S required for liquid and vapor base Claus reactions) is gaining attention. This paper discusses briefly: (1) the announced status of the many regenerable FGD processes, (2) the problem of reductant gas supply, and (3) the effect on FGD processes of using coal based reducing gas instead of reformed natural gas.     

Results of Field Measurements of Industrial Particulate Sources and Electrostatic Precipitator Performance

This paper presents results of source size distribution measurements over the size range from 0.1 μm to 5 μm for six classes of particulate sources and fractional efficiency measurements on five full scale electrostatic precipitators and one pilot scale precipitator. The precipitators all showed moderately high to high particulate collection efficiencies for particles having diameters larger than a few micrometers or smaller than a few hundredths of a micrometer and a minimum in collection efficiency for particles having diameters of a few tenths of a micrometer.     

Cooling Towers and the Environment

Measurements of natural draft cooling tower plume behavior, as well as meteorological variables, were obtained from aircraft flights near major power plants of the American Electric Power System. Persistence of the visible plume to great distances depends essentially on ambient humidity. Atmospheric stability at plume elevation was also important. Cooling tower-induced fog at ground-level was never observed in any of the tests, and aerodynamic downwash of the visible plume was absent also. The cooling towers did cause modification of natural clouds and they occasionally shadowed some local areas from the sun. Merging of the stack and cooling tower plumes was a common occurrence.     

Characterization of Particulates from Power Plants

The emphasis on participate control from industrial processes has been shifted recently towards fine particulates, having diameters less than 3 microns. There exists an urgent need for more scientific information of fine particle characterization.^1,2 Coal and oil fired power plants are among the largest anthropogenic point sources of particulate matter.³ Limited knowledge is available on particle size distribution and trace metal composition in power plant emissions.^4-7 The morphological properties of particle emissions have been largely neglected. In this report we present some information on particle characteristics for an oil-fired and coal-fired power plant.     

Weekday-Weekend Pollutant Studies of the Los Angeles Basin

Pollutant data from the Los Angeles Basin were analyzed for weekday-weekend differences for the smog months of June through September 1972 and 1973. The pollutants investigated were oxidant, NO, NO₂, total hydrocarbons (HC), CO, and particulates. In order to maintain the diurnal variation, the concentration percentiles were calculated for each weekday and weekend hour.     

The Formation of Mg3Ca(S04)4 during the Sulfation Reaction of Dolomite

Abstract

Inspection and maintenance programs for motor vehicles in the United States increasingly use loaded mode mass emissions testing (IM240). A method was developed to predict mass emission rates and mass emission changes, particularly from repair benefits, using a low-cost, portable four-gas non-dispersive infrared (NDIR) vehicle exhaust gas analyzer. A single vehicle was tested several times with the analyzer while on the dynamometer and undergoing successive repairs. Excellent correlations for CO and HC were observed. Five vehicles were measured using an on-road driving loop before and after emissions-related repairs, while another three vehicles were tested with no repairs performed. The on-road concentration data used to guide the repair process were converted to grams per gallon; when divided by estimated miles per gallon, this gave grams per mile emissions for comparison to IM240. Correlation coefficients (r²) of 0.87 for CO and 0.76 for HC were achieved for the 13 tests. The linear correlations between IM240 and emissions measured by this method would allow repair facilities to perform a relatively inexpensive test for diagnostic purposes and to estimate repair effectiveness without the need for a dynamometer.     

A Wind Tunnel Study of Gaseous Pollutants in City Street Canyons

Steady state mean concentrations of tracer gas were measured in a 400:1 scale model of an idealized city with variable geometry placed within a wind tunnel at various orientations to the mean flow for a free stream velocity of 6.8 ft/sec. The tracer gas was released from two parallel line sources to simulate lanes of traffic in an effort to quantify the persistence of pollution as well as the mean values realized at street levels. An aerodynamically rough turbulent boundary layer of neutral thermal stratification was employed to simulate the atmosphere. Values of concentration measured in the model city were converted to prototype concentrations in ppm and compared to National Ambient Air Quality Standards. It was shown that single isolated structures may cause favorable mixing of pollution downwind but very high concentrations exist in the immediate leeward vicinity of the building. Two favorable geometries for city blocks tested were found to reduce pedestrian exposure to pollution both near heavy traffic congestion and downwind. It was concluded that the pollutant dilution was controlled by the mean flow rather than by turbulent diffusion and that the lateral spread of the plume was slight as one proceeded downwind of the line source. The combination of favorable geometry and higher dilution velocities may bring pollution levels down to existing Air Quality Standards. The body of information presented in this paper should interest city planners and air quality monitoring personnel, as well as those researchers attempting to study and model flow in city street canyons. It provides order of magnitude estimates on pedestrian and office worker exposure to pollutants under a wide range of conditions.     

The Impact of Gold Smelter Emissions on Vegetation and Soils of a Sub-Arctic Forest-Tundra Transition Ecosystem

Gold smelters near Yellowknife in Canada's Northwest Territories have emitted large quantities of sulfur dioxide and arsenic since inception of roasting in 1941. Although particulate wastes are well contained by baghouse fitters in the one remaining operating smelter, significant gaseous emissions continue. Soil and vegetation were sampled at 52 sites over an area of about 40 km radius from the source. Plant ecology was studied at 43 of those sites. After preliminary multi-element screening that indicated only arsenic was a serious persistent contaminant, x-ray fluorescence was used to measure arsenic content in sampled materials. The plant ecology data were synthesized into an Index of Vitality with numerical ratings of pertinent factors. In the marginal forests and rocky outcrops of the area, indicator species of vegetation permitted a division into zones of severe, moderate, mild, or no impact in order of increasing distance from the current center of emissions. Severe impact, including killing of trees, is local only. Analyses of foliage indicate little uptake of arsenic which, together with the presence of S0₂ symptoms, point to S0₂ as the main factor causing decline of vegetation. A separate study, abstracted here, supports this view by providing data that show a frequency of at least 2 significant fumigation episodes per growing season. Soil analyses indicate extremely high arsenic contamination near the stack. A monotonie pattern of dispersion yielded a function explainable in terms of rapid condensation of gaseous emissions. The relationship of arsenic in surface soil and vegetation to distance is approximately an inverse square.     

The Effects of Precipitation on Aquatic and Terrestrial Ecosystems: A Proposed Precipitation Chemistry Network

Precipitation is one of the most important factors determining the nature and productivity of terrestrial and aquatic ecosystems. Detailed historical and contemporary records are available indicating the amount of water deposited at thousands of locations throughout the world. Comparatively, however, knowledge of the changing chemistry of precipitation has developed only recently and is still very fragmentary. Our present ignorance of the total impact of changes in precipitation quality on the productivity and stability of ecosystems is especially profound. This paper has a fourfold purpose: (1) to describe the myriad of trace chemical constituents transferred from the atmosphere into the biosphere of the earth; (2) to define the range of beneficial and injurious ecological effects of perturbations in atmospheric deposition; (3) to explain the concepts of sensitive areas, life stages, and life forms; and (4) to describe briefly plans for a National Deposition Network and associated research on the terrestrial and aquatic ecosystems of the United States.