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.     

Radiological Program of the Los Angeles County Air Pollution Control District

Abstract

One technology Geld tested under the SITE demonstration program was stabilization-solidification. The HAZCON process was one of those tested. It treats hazardous wastes, consisting of both inorganic and organic contaminants, by mixing it with portland cement, water and a proprietary additive called Chloranan in a modified cement mixer to produce a concrete mass. In evaluating the technology during the demonstration, two major criteria were investigated by using existing laboratory tests. These criteria were mobility of the contaminants before and after treatment and the long-term effect on mobility, and durability of the solidified masses. The former criteria was evaluated using various leaching tests, primarily the Toxicity Characteristic Leaching Procedure (TCLP) and permeability. The durability criteria was determined from weathering tests, wet-dry and freezethaw, unconfined compressive strength, microstructural analyses and sampling the prepared blocks from the demonstration twice at 9-month intervals. This paper describes the results of the field sampling performed 9 and 18 months after the initial field demonstration and relates it to the results obtained during the demonstration.

According to the data, little or no change in the chemical and physical properties of the blocks occurred. The technology is capable of immobilizing heavy metals. The organics were not immobilized and the treated material appears quite durable.     

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.     

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.     

Cyclic Trends in Los Angeles Fine Participates

Noontime visibilities in downtown Los Angeles, averaged over the smog season of June through November, show two cycles of general deterioration and improvement. The improvement since 1962 is confirmed by available high volume filter data and conditions in 1974/75 are at least as good as at anytime since observations were begun in 1933. The decrease in frequency of “rule 57” days suggests that the improvement of the last decade and perhaps the cyclic variation of the past 40 years has been primarily of meteorological origin.     

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.     

Methods of Organic Solvent Analyses Used in Los Angeles

The Los Angeles County Air Pollution Control District has enacted a solvent law termed Rule 66. It places limitations on both solvent emissions and formulations used within its jurisdiction. Two types of analytical procedures were developed in conjunction with the rule. For emissions, a total combustion method is used whereby organic source vapors are catalytically converted to CO₂ and reported in terms of carbon content. For liquid formulations, a column chromatographic screening analysis is first performed to measure categories of compounds: oxygenates, aromatics, olefins, and paraffins. This helps to select the starting conditions for the lengthier GC procedure which provides the ultimate analysis of individual compounds.     

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.     

A long-path infra-red study of Los Angeles smog

Gaseous air pollutants have been measured in Los Angeles smog by the method of long-path infra-red absorption spectroscopy. A Fourier transform spectrometer operated at 0.25cm⁻¹ resolution was used in conjunction with a 1260-m optical path folded along a base path of 23 m. Detection sensitivities were in the parts-per-billion range. Compounds measured included NH₃, CO, H₂CO, HCOOH, CH₃OH, HNO₃, NO, NO₂, O₃, peroxyacetyl nitrate, alkyl nitrates and various hydrocarbons. The rise and fall of pollutant concentrations is reported in detail for the smoggy two-day period of 26 and 27 June 1980. Reactive hydrocarbons and nitrogen oxides were oxidized during the daytime, yielding ozone, aldehyde, nitric acid and peroxyacetyl nitrate. The observed gaseous reaction products only accounted for about 20 % of the nitrogen oxides that disappeared during the day. It is deduced that the “missing” 80% of the nitrogen was removed heterogeneously into aerosol particles or on surfaces at ground level.     

Smog Chamber Simulation of Los Angeles Pollutant Transport

The body of information presented in this paper is directed to those individuals concerned with the effect of urban pollution on downwind areas. In the absence of any evidence, it has been widely assumed that increasing NO _x emissions have caused oxidant levels to increase downwind of Los Angeles, i.e., Riverside and San Bernardino. This smog chamber study simulated pollutant transport from Los Angeles to the downwind areas by irradiating a typical Los Angeles hydrocarbon/NO _x mixture for extended periods of time. The smog chamber experiments were extended to 22 hours to obtain an integrated light intensity equal to that which occurs in the Los Angeles area. The effects of variations of nitrogen oxide emissions on an aged air mass were examined. The results show that downwind oxidant levels are only slightly affected by large changes in NO _x emissions. However, it is clear that reduced nitrogen oxide emissions will lead to an increase in oxidant in downtown Los Angeles.     

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.     

Speciation of Arsenic in Ambient Aerosols Collected in Los Angeles

First-time measurements of the potentially toxic inorganic species of arsenic (arsenite arid arsenate) have been obtained in fine (<2.5 µm AD) and coarse (>2.5 µm AD) atmospheric particles in the Los Angeles area. A recently developed method that includes procedures for sample collection, preparation, and analysis was used in this study. Size-fractlonated aerosol samples were collected with a high-volume dichotomous virtual impactor that employed polytetrafluoroethylene filters. Results were obtained for the recovery of arsenic standards added to unexposed and collected filters. Data from this study, indicated that the recently developed speciation method can be used to determine concentrations of As(lll) and As(V) In atmospheric particulate matter samples.

Size-fractionated aerosol samples were collected in the city of Industry during January and February 1987. In most samples, As(lll) and As( V) were above the detection limit (approximately 1 ng m^-3 of either species) in both aerosol size fractions. A greater portion (about 75 percent) of the two species were observed in the fine particles. The As(lll)/As(V) ratio for both particle sizes was close to 1 (I.e., an equal mixture of both species). Comparison of total suspended particulate arsenic measured by the speciation method to that measured by a routine California Air Resources Board-approved procedure showed good agreement (r = 0.94), indicating both methods were approximately equivalent for the collection and analysis of aerosol arsenic.