Theoretical considerations and empirical evidence indicate that atmospheric turbidity, a function of aerosol loading, is an important factor in the heat balance of the earth-atmosphere system. Turbidity increase over the past few decades may be primarily responsible for the decrease in worldwide air temperatures since the 1940's.

During fall and winter 1986/87, aerosol samples were collected with a 5-stage impactor in an urban, a suburban, and a rural area in Central Europe. The weak acid content of aerosol particles was characterized by buffer capacity titrations, and organic acids were determined by HPLC. C 4 -C 6 dicarboxylic acids were found to be the main constituents of aerosol organic acids, with the highest concentrations occurring during a winter-time smog period. Size distributions of single species showed a maximum in the accumulation mode, indicating that these compounds have gaseous precursors. It is suggested that these precursors are of anthropogenic origin.

No abstract

An evaluation of trends in air quality is a means to assess the net result of numerous interrelated factors that affect the quality of our air resource. Factors such as population growth, industrial activity, energy consumption, rural‐urban distribution of our population, the shape and size of our metropolitan areas, various social and economic changes, and the effectiveness of our efforts to control pollution at its source all play an important role in determining the resulting air quality. It must be noted that the trends in ambient levels of pollutants at any one place is a complex function of some or all of these factors and not merely the direct assessment of the degree of control applied to the various sources of pollution. We assess trends presumably because we would like to anticipate what is happening to us now, and we inject into this picture projections of potential pollution increases related to our nation's goals in population growth and standard of living, in order to anticipate some of the future consequences of trends in human activity. This also allows us to assess the need to control pollution and to undertake now the research and development required to bring such control about. It is to be noted that the subject of this article is by no means merely of scientific curiosity; rather, it is the basic building block on which our nation's need and program, to restore and protect our environment, is founded.

Carbon dioxide builds up in the eartht's atmosphere principally from increased use of fossil fuels. Estimates of the escalating uses of fossil fuels in the United States, especially for the generation of electric power and in the internal combustion engine, show that by the year 2000 emissions will have increased approximately eighteenfold from 1890. In the period 1965 to 1985 an emission-rate increase of around 4.0 percent per year compounded is expected. The expected intrusion and expansion of nuclear power will tend to lower the rates of increase of emission after 1985. Increases in emission rates in the rest of the world will probably equal or exceed the values projected for the United States.