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It is especially difficult to obtain an overview of the literature on acid precipitation and its effects on freshwater ecosystems because this research covers disciplines in meteorology, chemistry, biology, geology, and hydrology. In addition, much of the work done in Scandinavia is not published in international journals and thus not included by major abstract services. Furthermore, many of these reports are written in Swedish and Norwegian and are, therefore, of little use to non-Scandinavian scientists.

Acid precipitation is altered by interaction with rocks, sediment and soil. A calcareous region buffers even the most intense loading at pH ~8; an alumino silicate region with unconsolidated sediment buffers acid loadings at pH ~6.5; alumino silicate outcrops are generally acidified. Either FeOOH or alumino silicates are probable H+ ion sinks in noncalcareous sediments. Glacially derived sediment is more important than bedrock in assimilation of acid precipitation in Shield areas. Toxic metal concentrations are dependent upon sediment metal concentrations and the pH of water.

The Cedar Creek Basin (39th N parallel 92nd W meridian) was studied for the period June 1952 through August 1954 to observe the effects of both continuous and periodic acid effluent flows on aquatic communities. The acid strip-mine effluent contained ferric and ferrous iron, copper, lead, zinc, aluminum, magnesium, titratable acid, and elevated hydrogen ion concentration, and was toxic to many of the aquatic organisms. In the areas of Cedar Creek, subjected to continuous acid flow, planktonic and benthic species had become adapted to the severe conditions and varied in abundance and...

Many soil processes and properties may be affected by a change in chemical climate such as that caused by acidification of precipitation. The effect of additions of acid precipitation depends at first on the extent to which this acid is really absorbed by the soil and on the changes in substances with actual or potential acidity leaving the soil. There is for instance the possibility that added sulphur dioxide or sulphuric acid may leave the soil either as sulphate ions or as gaseous hydrogen sulphide. In the latter case there is no net acidification. Acidity due to uptake of nitrogen...

Recent measurements of the pH of precipitation leave no doubt that rainfall is acidic. Evidence will be presented that precipitation is a weak acid system. The results of this research indicate the need to establish standard sampling procedures to provide uniform sampling of precipitation

The acidity of precipitation in rural, forested areas of the northeastern United States is dominated by the strong mineral acids, sulfuric and nitric. Weak acids have a negligible effect on the measured acidity (pH) of precipitation. These conclusions are based on total acidity titrations and detailed analysis of organic and inorganic components in precipitation.

Sequential rain and snow sampling has been performed at Burlington and Concord, Massachusetts. The samples have been collected during 1974 and 1975 in one-quarter inch and one inch rain equivalents and chemical analysis performed on the aliquotes. Meteorological data was documented at the time of collection.

The total annual emissions of sulfur oxides and nitrogen oxides in Canada are estimated to be 7.2 x 106 tons and 1.4 x 106 tons, respectively. These figures represent 5% and 2%, respectively, of the estimated worldwide anthropogenic emissions. Nearly two-thirds of the Canadian SO2 emissions come from primary smelters located in low population areas. The remainder originate from natural gas processing, pulp mills, fuel combustion and transportation in the more heavily populated areas. Transportation is the major source of oxides of nitrogen. No coordinated precipitation sampling has been...

The impact of acid precipitation reflects a usually deleterious balance between good and bad effects which may lead to serious and sometimes extreme degradation of aquatic as well as terrestrial ecosystems, particularly around metal smelters. Addition of hydrogen ions as sulfuric, nitric, and hydrochloric acid can alter and impoverish the species composition of biotic communities, and lead to severe leaching of beneficial metal cations such as calcium from ecosystems. Heavy metals and other trace elements which accompany acid precipitation may reach toxic levels, particularly where acid...

Extensive studies of precipitation chemistry during the last 20 years have clearly shown that highly polluted precipitation falls over large areas of Scandinavia, and that this pollution is increasing in severity and geographical extent. Precipitation in southern Norway, Sweden, and Finland contains large amounts of H+, SO4-2, and NO3-1 ions, along with heavy metals such as Cu, Zn, Cd, and Pb, that originate as air pollutants in the highly industrialized areas of Great Britain and central Europe and are transported over long distances to Scandinavia, where they are deposited in precipitatio...