Abstract
Air pollution owing to fossil-fuel combustion has a long.history, but only since the 1950's has the long-range transport of gases, acids, and metals through the atmosphere to distant and hitherto uncontaminated lakes and streams been a matter of concern to scientists and citizens. Since the 1940's, radioactive fallout and a variety of new organic micropollutants have also spread to remote surface waters through the atmosphere. Only in the case of acid deposition has such long-range transport of air pollutants (LRTAP) been implicated unambiguously in damage to aquatic ecosystems and to the organisms that inhabit them. Nevertheless, contamination by radioactive fallout, and by trace organics and metals, may well be close to or above thresholds for such damage. There is, therefore, a need to determine such thresholds by a program of broad-scale surveys of aquatic ecosystems, local studies of population dynamics, paleoecological investigations, long-term monitoring, and long-term experiments upon whole lakes and streams, including a recovery phase.
