The COVID-19 pandemic and resulting shelter-in-place measures led to widespread adoption of remote work policies and temporary business closures or operation curtailments, disrupting typical commuting patterns. This study investigates how these sudden shifts in traffic patterns affected near-road NO and NO₂ concentrations in California. We used (1) near-road air pollution data from the U.S. Environmental Protection Agency’s AirNow database, (2) passenger and heavy-duty traffic data from the Caltrans Performance Monitoring System, and (3) weather data from MesoWest between January 1 and April 30 during the years 2017–2020 to model NO and NO₂ concentrations as functions of highway traffic and meteorology. We then simulated NO and NO₂ under business-as-usual traffic conditions and compared modeled data to observed values. Weekday passenger traffic significantly declined in Northern and Southern California by 29% and 24%, respectively. As a result, Northern and Southern California near-road locations experienced statistically significant declines in NO concentrations of 35% and 32% and in NO₂ concentrations of 15% and 29%, respectively, compared to modeled estimates. As a natural experiment, our findings demonstrate that reduced vehicle activity significantly improved air quality, contributing to the body of evidence linking shelter-in-place measures and cleaner air.

中文翻译：

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在加利福尼亚州发生COVID-19大流行期间，近路NO和NO ₂浓度降低

COVID-19大流行以及由此产生的就地庇护措施导致远程工作政策的广泛采用以及临时业务关闭或运营缩减，从而扰乱了典型的通勤模式。这项研究调查了这些交通方式的突然变化如何影响加利福尼亚州的近路NO和NO ₂浓度。我们使用了（1）来自美国环境保护局的AirNow数据库的近路空气污染数据，（2）来自Caltrans Performance Monitoring System的客运和重型交通数据，以及（3）1月1日至4月的MesoWest气象数据在2017年至2020年的30年中，将NO和NO _2的浓度作为公路交通和气象函数进行建模。然后，我们模拟NO和NO ₂在一切照旧的流量条件下，并将建模数据与观察值进行比较。北加州和南加州的平日客运量分别大幅下降了29％和24％。结果，与模型估算值相比，加利福尼亚北部和南部加利福尼亚近郊道路的NO浓度分别下降了35％和32％，NO ₂浓度分别下降了15％和29％，具有统计学上的显着下降。作为一项自然实验，我们的发现表明，减少车辆活动可显着改善空气质量，从而为将就地避难所措施与清洁空气联系起来的证据做出了贡献。