Harvard University , T.H. Chan School of Public Health, Boston, Massachusetts 02445, United States.
School of Civil and Environmental Engineering, Georgia Institute of Technology Atlanta, Georgia 30332, United States.
Environ Sci Technol. 2017 Dec 5;51(23):13797-13805. doi: 10.1021/acs.est.7b04109. Epub 2017 Nov 16.
Ozone production efficiency (OPE), a measure of the number of ozone (O) molecules produced per emitted NO (NO + NO) molecule, helps establish the relationship between NO emissions and O formation. We estimate long-term OPE variability across the eastern United States using two novel approaches: an observation-based empirical method and a chemical transport model (CTM) method. The CTM approach explicitly controls for differing O and NO reaction product (NO) deposition rates and separately estimates OPEs from on-road mobile and electricity generating unit sources across a broad spatial scale. We find lower OPEs in urban areas and that average July OPE increased over the eastern United States domain between 2001 and 2011 from 11 to 14. CTM and empirical approaches agree at low NO concentrations, but CTM OPEs are greater than empirical OPEs at high NO. Our results support that NO emissions reductions become more effective at reducing O at lower NO concentrations. Electricity generating unit OPEs are higher than mobile OPEs except near emissions locations, meaning further utility NO emissions reductions will have greater per unit impacts on O regionally.
臭氧生成效率（OPE）是衡量每排放一个一氧化氮（NO）分子所产生的臭氧（O）分子数量的指标，有助于确定 NO 排放与 O 生成之间的关系。我们使用两种新方法来估计美国东部地区的长期 OPE 变化：基于观测的经验方法和化学输送模型（CTM）方法。CTM 方法明确控制了不同的 O 和 NO 反应产物（NO）沉积率，并分别从道路移动源和发电单元源估算了广泛空间尺度上的 OPE。我们发现城市地区的 OPE 较低，并且 2001 年至 2011 年间，美国东部地区的 7 月平均 OPE 从 11 增加到 14。在低 NO 浓度下，CTM 和经验方法的结果一致，但在高 NO 下，CTM 的 OPE 大于经验 OPE。我们的结果表明，随着 NO 浓度的降低，NO 排放减少在降低 O 方面变得更加有效。发电单元的 OPE 高于移动源的 OPE，但在排放源附近除外，这意味着进一步减少公用事业部门的 NO 排放将对区域 O 产生更大的单位影响。
