SEASONAL, EPISODIC AND TARGETED CONTROL OF SULFATE DEPOSITION

The large differences in seasonal rates of wet sulfate deposition observed at many receptors in eastern North America imply that reducing SO//2 emissions only in the summer half of the year (April-September) would bring about greater annual wet sulfate deposition reductions than reducing emissions by the same amount year-round. Targeting the emission reductions to those source areas which contribute the bulk of summer depositions in ecologically sensitive areas would increase further the gain factor. In the northeastern U. S. , between 10 and 15 rain episodes deposit about 60 percent of the annual wet sulfate; reducing emissions in the dry periods preceding these heavy deposition episodes could further increase the gain factor.