Recent international agreements for controlling atmospheric pollutant emissions have been based on the use of target loads that, require countries to develop national estimates of critical loads for the highest deposition of acidifying compounds that will not cause chemical changes leading to long-term harmful effects on ecosystem structure. The United States has proposed a uniform generic framework that allows critical loads to be developed using a variety of methods for different geographic scales. That framework is used here to qualitatively compare the critical loads estimates obtained by different modeling and mapping methodologies designed to predict the effect of acidic sulfate deposition on lake chemistry. The objective of the report is not to provide recommendations of critical or target loads that should be adopted, but to show the relative effects of using different methodologies to estimate critical sulfate loads.

"Parker J. Wigington, Jr." Includes bibliographical references. "February 1993." Microfiche.