Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States.
Department of Earth and Planetary Science, University of California, Berkeley, Berkeley, California 94720, United States.
Environ Sci Technol. 2022 Sep 20;56(18):12906-12916. doi: 10.1021/acs.est.2c03315. Epub 2022 Sep 9.
In China, emissions of ozone (O)-producing pollutants have been targeted for mitigation to reduce O pollution. However, the observed O decrease is slower than/opposite to expectations affecting the health of millions of people. For a better understanding of this failure and its connection with anthropogenic emissions, we quantify the summer O trends that would have occurred had the weather stayed constant by applying a numerical tool that "de-weathers" observations across 31 urban regions (123 cities and 392 sites) over 8 years. O trends are significant ( < 0.05) over 234 sites after de-weathering, contrary to the directly observed trends (only 39 significant due to high meteorology-induced variability). The de-weathered data allow categorizing cities in China into four different groups regarding O mitigation, with group 1 exhibiting steady O reductions, while group 4 showing significant ( < 0.05) O increases. Analysis of the relationships between de-weathered odd oxygen and nitrogen oxides illustrates how the changes in NO, in anthropogenic volatile organic compounds (VOCs), and reductions in fine particulate matter (PM) affect the O trends differently in these groups. While this analysis suggests that VOC reductions are the main driver of O decreases in group 1, groups 3 and 4 are primarily affected by decreasing PM, which results in enhanced O formation. Our analysis demonstrates both the importance of and possibility for isolating emission-driven changes from climate and weather for interpreting short-term air quality observations.
在中国，臭氧（O）生成污染物的排放已成为减排目标，以减少 O 污染。然而，观测到的 O 下降速度比预期的要慢/相反，这影响了数百万人的健康。为了更好地理解这一失败及其与人为排放的关系，我们通过应用一种“去气象化”观测的数值工具，量化了在天气保持不变的情况下夏季 O 趋势，该工具在 8 年内应用于 31 个城市区域（123 个城市和 392 个站点）。在去气象化后，234 个站点的 O 趋势具有统计学意义（<0.05），而直接观测到的趋势只有 39 个具有统计学意义（由于气象变化较大，因此只有 39 个具有统计学意义）。去气象化的数据允许将中国的城市分为四个不同的 O 减排组，其中第 1 组表现出稳定的 O 减少，而第 4 组则表现出显著的（<0.05）O 增加。对去气象化的奇数氧和氮氧化物之间关系的分析表明，NO 的变化、人为挥发性有机化合物（VOC）中的 VOC 变化以及细颗粒物（PM）的减少如何在这些组中对 O 趋势产生不同的影响。虽然这项分析表明，在第 1 组中，VOC 减少是 O 减少的主要驱动因素，但第 3 组和第 4 组主要受到 PM 减少的影响，这导致 O 形成增强。我们的分析表明，从气候和天气中隔离排放驱动的变化来解释短期空气质量观测结果的重要性和可能性。
