Critical Loads and Development of Acid Rain Control Options

The present paper describes the result of a demonstration project in which optimization models were used to identify efficient and equitable SO2 control strategies that satisfy environmental quality standards at sensitive receptor locations in Maryland. Notable in the modeling is the use of location‐specific critical‐load estimates. These estimates—the critical loads—represent maximum allowable sulfur‐deposition rates, that is, rates below which continued acidification and its attendant possible ecological consequences are believed not to occur. The analyses include scenarios that involve 10,000,000 t/yr SO2 reductions in the United States, uniform percentage‐reduction scenarios, and state‐level sensitivity analyses.