Odor Control In Los Angeles County

Abstract

Concentrations of 38 gas-phase organic air toxics were measured over a 2-yr period at four different sites in and around Pittsburgh, PA, to investigate spatial variations in health risks from chronic exposure. The sites were chosen to represent different exposure regimes: a downtown site with substantial mobile source emissions; two residential sites adjacent to one of the most heavily industrialized zones in Pittsburgh; and a regional background site. Lifetime cancer risks and non-cancer hazard quotients were estimated using a traditional and interactive risk models. Although study average concentrations of specific air toxics varied by as a much as a factor of 26 between the sites, the additive cancer risks of the gas-phase organic air toxics varied by less than a factor of 2, ranging from 6.1 × 10^-5 to 9.5 × 10^-5. The modest variation in risks reflects the fact that two regionally distributed toxics, formalde-hyde and carbon tetrachloride (CCl₄), contributed more than half of the cancer risk at all four sites. Benzene contributed substantial cancer risks at all sites, whereas trichloroethene and 1,4-dichlorobenzene only contributed substantial cancer risks at the downtown site. Only acrolein posed a non-cancer risk. Diesel particulate matter is estimated to pose a much greater cancer risk in Pittsburgh than other classes of air toxics including gas-phase organic, metals, polycyclic aromatic hydrocarbons, and coke oven emissions. Health risks of air toxics in Pittsburgh are comparable with those in other urban areas in the United States.     

Los Angeles Gasoline Modification: Its Potential as an Air Pollution Control Measure

A joint project of government and industry people who studied the possible effect upon air pollution in Los Angeles of variations in the composition of gasoline sold in Los Angeles is discussed.

No experimental automotive test work was undertaken in this project. However, prototype fuel blends were made and analyzed in order to simulate the effects certain changes would have upon photochemical smog formation.

It is apparent from the results of this study that the potential of reducing smog in Los ngeles by fuel modifications is quite small, even in the year of maximum effect. This potential decreases to a negligible level due to the effectiveness of mechanical control of evaporative losses required in California starting with the 1970 model cars.     

Control of Asphaltic Concrete Plants in Los Angeles County

Characteristics of maximum short-term ground level concentrations from an elevated point source, namely, the effective plume height, the critical wind speed, the distance to the point of maximum concentration, and the maximum concentration, are derived from the gaussian plume model. Both phases of plume development—before and after it has reached its final height—are considered. The plume rise treatment includes both thermal buoyancy and momentum effects. Certain limitations on critical wind speed are discussed. The dispersion model whose basis is established in this paper should be especially useful in applications where on site meteorological data are unavailable.     

Contaminant Concentrations in the Atmosphere of Los Angeles County

Sampling for nitrogen and sulfur dioxides was initiated at several National Air Sampling Network stations in 1959 using a sampler developed for that purpose. In 1961 the Gas Sampling Network was expanded to its maximum of 49 stations. Sampling equipment and collecting solutions are supplied and chemical analyses performed by the network laboratories. Sampling and analysis procedures are described briefly. Average and maximum 24-hour concentrations of nitrogen dioxide and sulfur dioxide observed at 48 stations during 1961-1963 are presented.     

Air Pollution Control Association Critical Reviews Program

This is the fourth in the series of Critical Reviews commissioned by the APCA Board of Directors. The first Critical Review "Regulations for the Control of Particulate and Sulfur Oxides Emissions" was published in 1974 and the topic is still timely. The second Critical Review "Regulations for the Control of Hydrocarbon Emissions (from Stationary Sources) and Odorous Pollutants" was published in 1975. In light of recent developments concerning hydrocarbon emissions from stationary sources, this Critical Review is again very timely. The third Critical Review "The Effect of Air Pollution Control Regulations on Land Use Planning" will soon be published in final form. Now we have the fourth in the series, "A Critical Review of Air Pollution Index Systems in the United States and Canada" and "Status Report on Federal Regulations for New Source Performance Standards".     

Effects of the Motor Vehicle Control Program On Hydrocarbon Concentrations in The Central Los Angeles Atmosphere

The body of information presented in this paper is directed to those individuals concerned with the effect of the motor vehicle control program on ambient hydrocarbon concentrations in a metropolitan area during peak traffic hours. The data used in this study are from gas chromatographic analyses of air samples taken in 1963-65, before implementation of the exhaust control program for new motor vehicles, and in 1971 and 1973, after several years’ application of this program. A brief history of the motor vehicle program in California together with emission standards for hydrocarbons are discussed and certain automobile-related hydrocarbons are identified and characterized. Frequency distributions were constructed for total hydrocarbons, non-methane hydrocarbons, methane, acetylene, and isopentane for 1963-65, 1971, and 1973 and the standard deviation (1 sigma) concentration limits are discussed for each of the subgroups mentioned above. The average concentration and relative percent comparisons for methane, ethane, n-butane, isopentane, C₃+ paraffin, eth-ene, propene, C₄ +olefin, acetylene, benzene, and toluene are shown and discussed in detail. These studies: 1) show hydrocarbon emissions from motor vehicles were reduced 47.6% during this time period; 2) indicate selective reduction of compounds; and 3) reveal a 51.8% reduction in the 1973 ambient total hydrocarbon concentration since 1963-65.     

Air Quality Management in Los Angeles: Perspectives on Past and Future Emission Control Strategies

The 1988 Air Quality Management Plan was approved by the Board of the California South Coast Air Quality Management District in March 1989. The District comprises the counties of Los Angeles, Orange, and Riverside, and the non-desert portion of San Bernardino county. Emissions reductions in the past have lead to significant improvement in air quality despite large increases in growth. However, the District, largely because of continuous growth, currently violates the air quality standards for ozone, carbon monoxide, nitrogen dioxide, and respirable particulate matter (PM₁₀). Based upon the AQMP, reduction of approximately 80 percent in emissions of oxides of nitrogen and volatile organic compounds is required to bring the District into compliance with all air quality standards in the next twenty years.

Achieving compliance will necessitate the use of advanced technologies, as well as some changes in lifestyle and management practices. Advanced technologies, including the use of electric vehicles powered by batteries or fuel cells, the use of cleaner burning fuels and advanced combustion modifications, and treatment of surface coatings and solvents are included in the AQMP. The Technology Advancement Office in the District was created to work with industry, universities, research institutes, and other local, state and federal agencies to identify, evaluate, and promote low emitting fuels and technologies. In addition to electricity, fuels burning cleaner than conventional gasoline or diesel are being tested to obtain emissions and durability data so that rational choices can be made for the future. Compressed natural gas, methanol and liquefied petroleum gas are considered to be cleaner burning fuels for current applications. Ethanol, butane, and various oxygenated blends are being evaluated, and the broader application of solar energy and hydrogen are being investigated.

The impact of various cleaner burning fuels on air quality is being addressed. To date, methanol is the only fuel for which results are available. These results indicate that methanol use in vehicles—with control of formaldehyde emissions below 15 mg/mile for light-duty vehicles—can provide air quality benefits for all criteria pollutants and certain air toxics. These benefits are greater for M₁₀₀ than M₈₅.

Several District advanced technology programs are described, including a reduction in emissions from paints and coatings, and the demonstration of electric vehicles.     

The Utilization of Optimum Meteorological Conditions for the Reduction of Los Angeles Automotive Pollution

Advantage can be taken of optimum conditions of turbulent mixing to decrease the intensity of automobile-caused pollution in the Los Angeles Basin. Changing the summertime peak traffic hours—delaying the morning rush by one hour—will result in an improvement of 24 percent for an eight-hour day, in terms of oxidant concentrations. Greater improvements (up to 54 percent) are possible by use of seven or six-hour days, should they be found to be economically feasible.     

Lead Concentrations in Detroit,New York,and Los Angeles Air

Lead concentrations in air were measured at 12 sites in Detroit, New York and Los Angeles as part of a program to relate automobile emissions and polynuclear aromatic hydrocarbons in air. The information on lead is reported separately because of the current interest in lead as an air pollutant. Sampling was conducted by means of a large “absolute” filter and equipment contained in a step-van truck. A portion of the filter was macerated in nitric acid and the lead determined spectrographically. The combined annual average lead concentration for four sites in metropolitan Los Angeles was approximately 40% higher than the combined averages of either the five sites in metropolitan New York or the three sites in metropolitan Detroit. Concentrations ranged from 0.4 ug/M³ at Santa Monica, to 18.4 ug/M³ at a Los Angeles Freeway Interchange. Concentrations were generally highest in freeway areas, intermediate in commercial areas, and lowest in residential areas. They were about 40% higher in daytime than at night. Average lead concentrations were highest during autumn in New York and winter in Los Angeles reflecting an inverse relationship with wind speed. Correlation coefficients between lead and carbon monoxide, at all sites, were statistically non-zero with 99% confidence and varied from 0.75 to 0.96. Lead concentrations in this study were higher than concentrations reported by others for Detroit, New York, and Los Angeles, presumably because sampling in this study was closer to traffic. However, concentrations in this study were lower than in-traffic concentrations given in the literature.     

Fluorocarbons in the Los Angeles Basin

Ambient air concentrations of fluorocarbon 11 (fluorotrichloromethane) and fluoro-carbon 12 (dichlorodifluoromethane) have been measured using a gas chro-matograph equipped with a pulsed, electron capture detector. Air samples taken on a moderately smoggy day in July 1970, at several locations near Los Angeles gave average readings of fluorocarbon 12, 0.7 ppb and fluorocarbon 11, 0.56 ppb. These readings were contrasted with those taken in early February 1973 when the air was clear and marked with turbulence due to several seasonal rain storms. The readings of both fluorocarbon 1 1 and 12 averaged about 25% less during clear weather than those taken during moderate smog. The effects of weather conditions on the concentration were also dramatically pointed out by the February samples, in that as much as a tenfold change in concentrations of both fluorocarbons from location to location and from day to day at the same location was observed. A concentration versus altitude study clearly revealed that fluorocarbons are trapped by an inversion layer. Examination of air samples taken in the vicinity of factories known to be users of fairly large quantities of fluorocarbons revealed in part how large users contribute to the atmospheric concentrations of fluorocarbons. A comparison of fluorocarbon levels in homes and public buildings with ambient outside air levels revealed that the concentrations in some homes and buildings may be as much as several thousand times as high as levels in outside air. Inside the homes and public buildings, levels were as high as one-half of a part per million. Long term photolysis studies in simulated sunlight of both fluorocarbons 11 and 12 in ambient air samples and in air samples with 1 ppm of hydrocarbon and 1 ppm of nitrogen oxides revealed that the two fluorocarbons are photochemically stable even when photolyzed for several weeks.