West J Jason, Ansari Asif S, Pandis Spyros N
a Departments of Civil and Environmental Engineering and Engineering and Public Policy , Carnegie Mellon University , Pittsburgh , Pennsylvania , USA.
b Department of Chemical Engineering , Carnegie Mellon University , Pittsburgh , Pennsylvania , USA.
J Air Waste Manag Assoc. 1999 Dec;49(12):1415-1424. doi: 10.1080/10473289.1999.10463973.
Reductions in airborne sulfate concentration may cause inorganic fine particulate matter (PM) to respond nonlinearly, as nitric acid gas may transfer to the aerosol phase. Where this occurs, reductions in sulfur dioxide (SO) emissions will be much less effective than expected at reducing PM. As a measure of the efficacy of reductions in sulfate concentration on PM , we define marginal PM as the local change in PM resulting from a small change in sulfate concentration. Using seasonal-average conditions and assuming thermodynamic equilibrium, we find that the conditions for PM to respond nonlinearly to sulfate reductions are common in the eastern United States in winter, occurring at half of the sites considered, and uncommon in summer, due primarily to the influence of temperature. Accounting for diurnal and intraseasonal variability, we find that seasonal-average conditions provide a reasonable indicator of the time-averaged PM response. These results indicate that reductions in sulfate concentration may be up to 50% less effective at reducing the annual-average PM than if the role of nitric acid is neglected. Further, large reductions in sulfate will also cause an increase in aerosol nitrate in many regions that are the most acidic.
空气中硫酸盐浓度的降低可能会导致无机细颗粒物（PM）产生非线性响应，因为硝酸气体可能会转移到气溶胶相中。在这种情况下，减少二氧化硫（SO）排放对于降低PM的效果将远低于预期。作为衡量硫酸盐浓度降低对PM影响效果的指标，我们将边际PM定义为硫酸盐浓度的微小变化所导致的PM的局部变化。利用季节平均条件并假设热力学平衡，我们发现，在美国东部冬季，PM对硫酸盐减少产生非线性响应的情况很常见，在所考虑的站点中有一半会出现这种情况，而在夏季则不常见，这主要是温度影响所致。考虑到昼夜和季节内变化，我们发现季节平均条件能合理地指示时间平均的PM响应。这些结果表明，与忽略硝酸作用的情况相比，降低硫酸盐浓度对降低年均PM的效果可能会低达50%。此外，大幅降低硫酸盐还会导致许多酸性最强地区的气溶胶硝酸盐增加。
