Controlling acid rain

Abstract

High concentrations of sulfuric and nitric acid in raTn fn the northeastern USA are caused by the large scale combustion of fossil fuels within this region. Average precipitation acidity is pH 4.2, but spatial and temporal fluctuations of *1 pH unit have been observed. Amelioration of rain acidity requires significant reduction of precursor emissions--the oxides of sulfur and nitrogen. Such reduction of emissions from existing sources will be difficult and expensive. A pending legislativp proposal to reduce eastern U.S. emissions of SO2 by 10 Mty-' below the 1980 level of 22.5 Mty - 1 would reduce the acid sulfate deposition rate in the Adirondack mountains, an environmentally sensitive area, from 30 to 21.4 kg ha-ly-l. Based upon source/receptor modeling, an equal reduction of Adirondack sulfate deposition rate could be achieved by a 7 Mty- SO2 emission reduction if the reduction is allocated according to source proximity to the sensitive area. The cost of reducing 10 Mty - 1 SO2 emissions is estimated at $5 to $8 billion per year. Considerably lower costs could be realized in an emission control scheme that is the more stringent the nearer the sources are to the environmentally sensitive areas, and if novel approaches are implemented, such as seasonal or episodic emission reduction, NOx vs. SO2 emission control, emission redistribution, and least emission electricity dispatch. Substantial emission reductions will probably be achieved in the more distant future by employing new combustion technology, such as lime injected multistage combustion, fluidized bed combustion, coal gasifier combined cycle, magnetohydrodynamics, and- possibly others.