Based on evidence that the rate of wet sulfate deposition in eastern North America is higher in the summer half of the year than in the winter haw, seasonal control of emissions is proposed as a means of minimizing acid deposition control costs. This paper evaluates the proposal that natural gas be substituted for coal and oil in electric power plants during April through September. A model is presented that simulates the substitution of natural gas for coal and oil in power plants in the eastern 31 state region, so as to minimize total costs with respect to deposition reductions at an Adirondack receptor. The results of the model show: 1) the increased effectiveness of seasonal versus year-round controls; 2) changes in fuel consumption levels as a result of substitution; and 3) the costs of achieving various levels of deposition reduction at an Adirondack receptor. The costs of seasonal gas substitution are compared to cost estimates for other proposed control methods. The conclusion is that seasonal gas substitution is cost-competitive with other control methods, at least in some plants and states.
Recently, several proposals have been advanced that move away from broad-lxisecl reduction of acid rain precursor emissions toward more efficient policies that recognize the spcitial relntionslzip between emission soiirces and t h e areas sensitive to the acid deposition caused by these emissions [ 1 -4 ] . This paper proposes that acid rain policy should step beyond the spatial relationship toward a recognition of the tern pord relationship between emissions and depositions; namely, that there are significant seasonal variations in deposition rates despite a relatively constant rate ofemissions. Just a s it is niore efficient to exert greater control of emissions from soiirces that are relatively close to sensitive areas, it is also more efficient to impose greater control of emissions at times when the deposition rates are highest.
Recent work in atmospheric niodeling has shown that differences in seasonal rates of sulfate deposition create the opportunity for seasonal control of sulfur emissions a s a inore efficient means of reducing annual amounts of sulfate deposition [ 4 ] . By electing to reduce SO, emissions in the suininer half of the year, there would result a larger reduction of annual deposition per ton of SO, I-einoved than if the same quantity were removed year-round. It may prove to he less expensive to reduce deposition by controlling emissions in the suininer half of the year, rather than year-round.