1982 Stockholm Conference on Acidification of the Environment Through a glass selectively—or some governments saw what they wanted to see A new, and somewhat unexpected, international development concerning acid rain occurred last year. For the first time, a major industrial nation—a major polluter—joined the Scandinavian side in its views about the seriousness of the acidification problem. Until recently, West Germany vigorously defended the idea that not enough was known about the problem to warrant control actions. Now the West German government has adopted a diametrically opposite view and announced a new policy of reducing SO2 emissions by 50%. Switzerland also has changed its position and allied itself with those countries who favor near-term emission control at pollution sources. What persuaded these two countries to abandon their previous positions were disturbing revelations linking acid deposition, including the dry deposition of SO2, to "crown dieback" in forests over widespread areas of West Germany and to the almost complete destruction of large stands of trees in the neighboring high-altitude forests of Eastern Europe. This information was revealed and discussed intensively at the 1982 Stockholm Conference on Acidification of the Environment. The conference consisted of three related international meetings. The first two were expert meetings attended by scientists—one on ecological effects of acid deposition and the other on strategies and methods to control emissions of sulfur and nitrogen oxides. The third was a ministerial conference of government representatives. The attendees included over 100 scientists and nearly as many representatives from 21 countries, five international organizations, and observers from many nongovernmental organizations. The countries repre0013-936X/82/0916-0015A$01.50/0
Since 1965, nearly half the spruces have died on Camel's Hump in Vermont's Green Mountains. Mounting evidence suggests that acid rain may be the cause. sented were among the 34 signatories to the Convention on Long-Range Transboundary Air Pollution, an international agreement negotiated in 1979 by the United Nations Economic Commission for Europe (ECE). Before the Stockholm meeting began, many participants expected it
© 1982 American Chemical Society
to reveal little that was new and to emphasize what had been emphasized at previous meetings—namely, the very widespread acidification of lakes in Scandinavia. Instead, the conference focused on a different problem—more complete evidence strongly suggesting that ambient sulfur dioxide Environ. Sci. Technol., Vol. 17, No. 1, 1983
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Selected conclusions from the experts' meeting • "The main acidifying atmospheric pollutants are S 0 2 and N O x . " Within the industrialized region "man-made sulfur emissions exceed the natural emissions by a factor of five to twenty." • "Nitrate ions made available from atmospheric deposition play a minor role in water acidification today except during winter and early spring 'acid surges.' " • "Ammonia emissions also influ ence acidification. In Europe and North America domestic animals and fertil izers are thought to be its main sources with emissions comparable to those of NO x ." • "The atmospheric lifetime of 1/2 to 2 days for dry deposited S 0 2 cor responds to a mean transport distance of a few hundred km. Sulfate is re moved primarily by wet deposition and has a lifetime of 3-5 days. This cor responds to a mean transport distance of the order of a thousand k m . " • "If a general decrease in emis sions were to take place within a large industrialized region (of the order of a thousand km), specific areas within this region might experience signifi cantly smaller or larger decreases in deposition. However, the total depo sition over the whole industrialized
and acid deposition may be damaging trees in West Germany and other parts of Central Europe. The experts' meetings produced a consensus report that paid a great deal of attention to this research and summarized it as follows: "The recently reported forest damage in an estimated one million hectares of Central Europe seems to be related to (among others) the direct effects of gaseous pollutants and soil impoverishment, and toxicity arising from very large amounts of wet and dry deposition." This conclusion was drawn largely from the work of several West German scientists, but especially Professor Bernard Ulrich of Gôttingen University, who has been studying the effects of air pollutants on forests since 1966. In the paper he presented at the first experts' meeting, he offered the rather startling conclusion that, "No forest ecosystem, even forests on calcareous soils, can withstand the present [West German] air pollution without serious damage," and that "in the long run, trees will not get older than 30 to 40 or 16A
Environ. Sci. Technol., Vol. 17, No. 1, 1983
region would decrease approximately in proportion to the reduction in emis sions." • "Future acidification and reversal of present acidification of surface waters in sensitive areas receiving high sulfur deposition would be re duced by a decrease in the present level of sulfur deposition." • "Any reduction in acid deposition must be beneficial to aquatic ecosys tems under acid stress." • "Empirical data from Sweden, Norway, Canada, and the U.S. show that lakes in sensitive areas, with al kalinity < 5 0 μq/L· have in general not been acidified when the catchments receive a sulfur load of 0.5 gS/m 2 -y or less." • "In sensitive areas with deposi tion > 0 . 5 gS/m 2 -y, many surface wa ters have been acidified." • "In Ontario, Canada, about 50 000 lakes on granitic terrain re ceive > 0 . 7 gS/m 2 -y, and 2500 lakes surveyed in the area indicate that 2 0 % have alkalinity < 4 0 μeq/L. In Quebec the extent of sensitive lakes is even greater. Based on the Scandinavian experience, these lakes are expected to undergo acidification in the next several decades." • "Acidic groundwaters (some-
50 years, even under optimal soil conditions." Soil chemistry changes It has been known for many years that sulfur dioxide gas at high peak ambient concentrations causes direct damage to vegetation. What is new in Ulrich's and other related research is that the continuing deposition of comparatively low concentrations of SO2 and acid rain can cause indirect effects on forests, by gradually changing the soil chemistry over many years. According to Ulrich's work, forest damage occurs in four stages. In the first stage, trees benefit from the increased sulfur and nitrogen content in the rain and grow faster than they would without it. This stage is the one that has been most often observed in short-term studies. During the second stage, as the result of ion exchange and leaching progressing downward through the soil, the soil's neutralizing capacity is. impaired by the cumulative effects of
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