Coal-Fired Power Plant Effects on Vegetation: TVA Experience

摘要

There have been only a few coal-fired power plants where occurrences of visible SO sub 2 effects on vegetation growing in their vicinities have been documented and even fewer documented cases of reductions in growth, yield, and quality. Nearly all the documented cases occurred near large plants with short stacks (less than or equal to 91 feet). Acute exposure to SO sub 2 concentrations of 1300 mu g/m exp 3 (0.5 ppM) or more for one or more hours may cause visible injury to the foliage of sensitive species, provided peak concentrations (for five minutes or less) equal or exceed 2600 mu g/m exp 3 (1.0 ppM). Reductions in growth, yield, or quality of crops and timber may occur when 5% or more of the foliage is injured. While some laboratory and greenhouse experiments indicate that permanent adverse effects may occur in the absence of foliar injury, such effects have not been demonstrated in the ambient environment even though attempts have been made to do so. It has not been demonstrated that chronic or long-term exposure to subthreshold dosages of SO sub 2 in the ambient environment cause detectable permanent adverse effect. Analyses of the air monitoring data and data for emissions from the power plants indicate that for power plants with tall stacks (greater than or equal to 152 m) and daily emission rates 5000 g/s or less, the probability for occurrence of injurious ground-level dosages approaches zero and that at the New Source Performance Standards (NSPS) of 1.2 lb SO sub 2 /10 exp 6 Btu, occurrences of effects, either visible or invisible, should be nonexistent. 5 figures, 5 tables. (ERA citation 08:005020)