Ozone production efficiency (OPE), a measure of the number of ozone (O₃) molecules produced per emitted NO_X (NO + NO₂) molecule, helps establish the relationship between NO_X emissions and O₃ 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 O₃ and NO_X reaction product (NO_Z) 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_Z concentrations, but CTM OPEs are greater than empirical OPEs at high NO_Z. Our results support that NO_X emissions reductions become more effective at reducing O₃ at lower NO_Z concentrations. Electricity generating unit OPEs are higher than mobile OPEs except near emissions locations, meaning further utility NO_X emissions reductions will have greater per unit impacts on O₃ regionally.

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美国东部近期和未来排放变化对臭氧的影响及其生产效率

臭氧生产效率（OPE）是对每个排放的NO _X（NO + NO ₂）分子产生的臭氧（O ₃）分子数量的度量，有助于建立NO _X排放量与O ₃形成之间的关系。我们使用两种新方法估算美国东部地区的长期OPE变异性：基于观测的经验方法和化学迁移模型（CTM）方法。CTM方法可明确控制不同的O ₃和NO _X反应产物（NO _Z）沉积速率，并从广阔的空间范围内从公路移动和发电单位来源分别估算OPE。我们发现，在城市地区和七月平均OPE 2001年和2011年之间增加了美国东部域从11至14 CTM和经验方法同意在低NO较低的OPE _ž浓度，但CTM的OPE比经验的OPE更大的高NO _ž。我们的研究结果表明，在较低的NO _Z浓度下，减少NO _X排放对于降低O ₃更为有效。除了在排放位置附近，发电单元的OPEs比移动OPEs高，这意味着进一步的公用事业NO _X减少排放量将对区域内的O ₃产生更大的影响。