Office of Air Quality Planning and Standards, U.S. EPA , Research Triangle Park, North Carolina 27711, United States.
Environ Sci Technol. 2015 Jan 6;49(1):186-95. doi: 10.1021/es504514z. Epub 2014 Dec 17.
In this work, we evaluate ambient ozone trends at urban, suburban, and rural monitoring sites across the United States over a period of decreasing NOx and VOC emissions (1998-2013). We find that decreasing ozone trends generally occur in the summer, in less urbanized areas, and at the upper end of the ozone distribution. Conversely, increasing ozone trends generally occur in the winter, in more urbanized areas, and at the lower end of the ozone distribution. The 95(th) percentile ozone concentrations decreased at urban, suburban, and rural monitors by 1-2 ppb/yr in the summer and 0.5-1 ppb/yr in the winter. In the summer, there are both increasing and decreasing trends in fifth percentile ozone concentrations of less than 0.5 ppb/yr at urban and suburban monitors, while fifth percentile ozone concentrations at rural monitors decreased by up to 1 ppb/yr. In the winter, fifth percentile ozone concentrations generally increased by 0.1-1 ppb/yr. These results demonstrate the large scale success of U.S. control strategies targeted at decreasing peak ozone concentrations. In addition, they indicate that as anthropogenic NOx emissions have decreased, the ozone distribution has been compressed, leading to less spatial and temporal variability.
在这项工作中，我们评估了美国城市、郊区和农村监测点在 NOx 和 VOC 排放减少期间（1998-2013 年）的环境臭氧趋势。我们发现，臭氧减少的趋势通常发生在夏季，在城市化程度较低的地区，以及臭氧分布的较高端。相反，臭氧增加的趋势通常发生在冬季，在城市化程度较高的地区，以及臭氧分布的较低端。在夏季，城市、郊区和农村监测站的 95%臭氧浓度每年下降 1-2 个 ppb，冬季每年下降 0.5-1 个 ppb。在夏季，城市和郊区监测站的臭氧浓度低于 0.5 ppb 的第 5 百分位数的臭氧浓度既有增加的趋势，也有减少的趋势，而农村监测站的臭氧浓度则下降了多达 1 ppb/yr。在冬季，第 5 百分位数的臭氧浓度通常每年增加 0.1-1 ppb。这些结果表明，美国针对降低峰值臭氧浓度的控制策略取得了大规模的成功。此外，它们表明，随着人为 NOx 排放的减少，臭氧分布已经被压缩，导致空间和时间变化减少。
