A comparative regional analysis of the status of aquatic resources with respect to acid deposition

Abstract

A national scale assessment of the effects of acid deposition on aquatic resources is currently unavailable for the United States. A more limited assessment has been performed in three potentially sensitive geographical regions the Adirondack Mountains of New York, the Southern Blue Ridge Province of North Carolina, Tennessee and Georgia, and the Upper Midwest of Minnesota, Wisconsin and Michigan. A series of questions organized the assessment, and historical and current data from each region were employed to address the questions. Where possible, independent data sets were used singly and in combination within a given case study area, to respond to the questions and to provide an estimate of confidence. Conclusions among regions were also compared. In general, the impact of acid deposition on aquatic resources is difficult to detect, but positive correlations between atmospheric deposition and effects do exist. Thus, there is evidence to suggest that acid deposition is at least partially responsible for the acidification of aquatic resources. The extent of acidification, however, varies from region to region. The Adirondacks appear to represent the region of greatest impact, but independent studies indicate that the area of acidified lakes is a small percentage of the total resource. Despite the observation of minimal damage, application of damage estimates from the Adirondacks to other regions would be inappropriate. Future Assessments will seek to predict the rate of acidification of watersheds with other regional characteristics under alternative loading scenarios.