The Chemical and Meteorological Conditions Associated with High and Low Ozone Concentrations in Southeastern Michigan and Nearby Areas of Ontario

This analysis represents the first characterization of the photochemistry and transport of ozone in the Detroit metropolitan area and provides a basis for comparing data for Detroit to that for other cities. The characterization is based on a comprehensive set of meteorological and chemical measurements obtained at a site in the urban core of Detroit during the summer of 1981, together with measurements of O₃, nitrogen oxides (NO _X ), and nonmethane organic compounds (NMOC) from rural, suburban, and urban areas in southeastern Michigan and adjacent areas of Ontario.

For the quartile (23 days) with highest ozone maxima (97-180 ppb), the maxima occurred 10-70 km north-northeast of the city on days that were warm and hazy with light southsouthwest winds. On such days there was a marked accumulation of ozone precursors (NMOC and NO_X) in the early morning, as well as a rapid chemical removal of NO _X (NO _X half-life of ～5 h) from morning to midday. The timing of the daily ozone increase across the study region suggests that local photochemical generation in a moving plume was responsible for more than half of the ozone measured downwind. However, there was also evidence that ozone transported into Detroit as part of the regional background was a significant part of the O₃ maxima on high ozone days. The average contributions of photochemistry and transport for the 23 days with the highest ozone maxima were estimated to be 57 ppb and 47 ppb, respectively.     

Measurements of Sulfur Oxides,Nitrogen Oxides,Haze and Fine Particles at a Rural Site on the Atlantic Coast

During August, 1982 and January and February, 1983, General Motors Research Laboratories operated air monitoring sites on the Atlantic Coast near Lewes, Delaware and 1250 km to the east on the southwest coast of Bermuda. The overall purpose of this project was to study the transformations of the principal acid precipitation precursors, NO _x and SO _x species, as they transport under conditions not complicated by emissions from local sources. In this paper, the measurements of gas and particulate species from Lewes are described and the composition and sources of sulfate aerosol, which is the most important haze-producing species, are investigated.

On the average, the total suspended particulate (TSP) concentration was 27.9 μg/m³ while the PM₁₀ (mass of particles with a diameter less than or equal to 10 μm) concentration was 22.0 μg/m³ or 79 percent of the TSP. The PM₁₀ consisted of 6.1 μg/m³ of coarse particles (CPM, diameter = 2.5 ? 10μm) and 15.9 μg/m³ of fine particles (FPM, diameter < 2.5 μm).

On a mass basis the most important constituents of the fine particulate fraction were sulfate compounds, 50 percent, and organic compounds, 30 percent. The mean light extinction coefficient corresponds to a visual range of 18-20 km. Most of the extinction can be attributed to the sulfate (60 percent) and organic carbon (13 percent). Particle size measurements show that the mass median aerodynamic diameter for both species is 0.43 μm. This is a typical size for a hydrated sulfate aerosol. For carbon, however, this is a larger size than previously reported and results in a more efficient light scattering aerosol. Principal component analyses indicate that coal combustion emissions from the midwestern U.S. are the most significant source of sulfate in Lewes during the summer and winter.     

Spotting of Automotive Finishes from the Interactions Between Dry Deposition of Crustal Material and Wet Deposition of Sulfate

During the summer of 1988, General Motors Research Laboratories operated a mobile atmospheric research laboratory in Jacksonville, Florida to determine the cause of environmentally- related damage that occurs on automotive finishes In many parts of the U.S. The damage occurs as circular, elliptical, or irregular spots that appear as deposits or precipitates. The results of the present study show that a wetting event (rain or dew) is a prerequisite for damage to occur. Sulfuric acid contained in the rain or dew reacts on surfaces with drydeposited calcium which Is a common constituent of soli. As the droplets evaporate, a calcium sulfate precipitate forms on horizontal surfaces around the perimeter of the droplet. Subsequent washing of the surface may remove the precipitate, but on clearcoats, where the calcium sulfate was present, scars remain.     

Das Problem der Krebsverbreitung und Krebsbekämpfung

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