Atmospheric Environment (1967)最新文献

Observations of lead $\text{206}\text{207}$ ratios and trace element concentrations in atmospheric aerosols at a rural location in Ontario, Canada confirm results of a previous study of urban aerosols that showed there are significant differences in the isotopic composition of lead from Canadian autos, Canadian smelters and eastern American sources. Lead measurements in fall 1984 and spring 1986 were apportioned to the respective sources as follows: for 1984 (55, 2, 43%) and for 1986 (69, 7, 24%). Lead isotopic and meteorological information point to In as the best elemental tracer of emissions from selected northern Canadian smelters.

Ozone concentrations were monitored above a 30 m Douglas-fir canopy at Cedar River, Washington from 1 April to 30 September in 1986 and 1987. Maximum average hourly ozone concentrations were similar in both years. Ozone concentrations exceeded 0.12 ppm on 2 days in 1986 and 1 day in 1987. Fifteen and 14 days had ozone concentrations greater than or equal to 0.08 ppm in 1986 and 1987, respectively. Ozone concentrations were positively related to daily radiation and maximum daily air temperature. However, only 46 per cent of the variance in ozone concentration in 1986 could be explained by solar radiation and even less was explained by maximum temperature (26%). In 1987, 51 and 54 per cent of the variation in ozone concentration was explained by solar radiation and temperature, respectively. Maximum average hourly ozone concentrations peaked near 1500 h (Pacific Standard Time) for days > 0.06 ppm with minimum values near 0600 h. Highest concentrations were observed when the wind was blowing from the northwest from the Seattle area indicating that photochemical oxidation of NO_x was a major source of elevated ozone. If the data represent current levels of ozone some potential for forest damage exists in Puget Sound forests.

The impact of a large NO_x point source on photochemical smog in Melbourne is examined through the use of a numerical model described by Hess. Over most of the Melbourne Airshed the NMHC/NO_x ratio is found to be less than 10, in agreement with the results of Evans et al. For these cases trajectories passing through the Newport Power Station exhibit a decrease in ozone (compared to background values) of about 0.02 ppm and an increase in nitrogen dioxide of about the same amount due to Newport's emissions. This result confirms a preliminary finding by Form and Substance (1982).

However, worst case scenarios have not been previously studied. Measurements indicate that any trajectory that links the high NO_x from Newport and the high NMHC from Pt Cook will result in a worst case. The windfield observations reported here show the existence of a topographically generated mesoscale eddy in the airshed, as proposed by Spillane (1978, Clean Air12, 50–56.), and its location tends to link Newport and Pt Cook. Simulation of two cases indicates that under worst case conditions Newport's emissions increase the ozone concentration by 0.01–0.04 ppm. These conditions are estimated to occur on one day in four to one day in three of high oxidant days in Melbourne.

This study was performed primarily to account for the differences between ice forming activity of fly ashes from different sources.

Ten samples of fly ash from ten various power plants on our territory were examined by X-ray powder diffraction to determine the contents of quartz, mullite and hematite. The quartz content varied in the range 5–17% depending on the type of coal and mullite contents varied from 0 to 22%.

The amounts of crystalline phases were compared with data about composition of ashes obtained by elemental chemical analysis. The distribution of silica and aluminia between crystalline phases and amorphous phase is discussed in connection with the origin of fly ash and with the differences observed in the ice forming activity. A direct relationship between the freezing temperatures and the contents of crystalline fractions in the samples does not exist but the presence of mullite and/or hematite in the concentrations found in samples could account for the observed freezing temperatures of droplets containing some of the samples.

The trend of annual average sulfate and nitrate ion concentrations in precipitation at 17 stations in eastern North America over 7 years 1979–1985 is estimated and compared with a modeled trend. The observed concentrations fluctuate from year-to-year about a mean value with a standard deviation of 12.7% on average. The average slope of a linear regression line at the 17 stations is −2.8% a⁻¹ for sulfate and −0.4% a⁻¹ for nitrate. The modeled trend at these stations, which assumes constant meteorology but a year-to-year varying emission inventory, is −2.4% a⁻¹ for sulfate and −0.9% a⁻¹ for nitrate.

An estimate is made of the emissions of the five main air pollutants resulting from combustion processes: sulphur oxides (SO_x), nitrogen oxides (NO_x), total suspended particles (TSP), CO and volatile organic compounds (VOC) which include gases. An initial estimate, intended to provide some indication of the emission time trend, covers the years 1976, 1980 and 1984. Here emissions are divided according to both large fuel-consuming sectors (industry, agriculture, thermal power plants, residential and commercial, transportation), and the type of fuel used (coal, lignite, natural gas, oil products).

A further estimate is made, with reference to 1980, in which identified emissions are related to individual Italian regions and to the large activity sectors. For the same year emissions are grouped with reference to the 150 km × 150 km EMEP grid.

The rotating shadowband photometer (RSP) is a simple, low-cost instrument that automatically measures the total, diffuse and direct solar illuminance. On clear days, the direct component yields a measure of the total column extinction. This extinction calculation compares favorably with an independent and more conventional determination of extinction. The column extinction measurements can be corrected for the effect of stratospheric aerosols, thereby yielding the lower atmosphere extinction coefficient. This extinction coefficient should be useful in assessing small changes in atmospheric visibility over the long term.

Taking into account the wind speed perturbations from the deterministic equation of conservation of the molecular species of the pollutant we obtained the corresponding stochastic differential equation. Because there is no mathematical reason to discriminate between its Ito and Stratonovich interpretations, we retained, on physical grounds, the Stratonovich interpretation and we derived the equation of the expected value of the pollutant concentration.

Dominant spatial and temporal theories of acid rain in the U.S. are identified, followed by brief comments on how historical data have generally been used in modern acid rain research. A frequently-cited 1982 article by E.B. Cowling is examined, one that has influenced much thinking on the history of acid rain. The article overlooks early American smelters, however, and the role they played in the true history and geography of acid rain in the United States. Continuing with this theme, a connection is established between acid rain and turn-of-the-century smelter smoke problems. Literature on the latter subject is discussed, and American and German examples are given. A beginning is then made on writing acid rain's neglected chapter, focusing on Tennessee's Copper Basin (Ducktown District) where copper smelting dates back to the 1850s. A short historical overview of this area's smelting operations is given, with particular attention to the air pollution and other environmental problems resulting from large emissions of sulfur dioxide. Five additional early smelter sites for potential study are mentioned as well. The paper concludes with some observations regarding the way in which expanded research of early smelter sites could affect the general perception of acid rain in the U.S. It is also suggested that such research might contribute to a better atmosphere for making decisions and policies pertaining to the phenomenon as it exists today.