ABSTRACT

Regional air quality models are widely being used to understand the spatial extent and magnitude of the ozone non-attainment problem and to design emission control strategies needed to comply with the relevant ozone standard through direct emission perturbations. In this study, we examine the manageable portion of ground-level ozone using two simulations of the Community Multiscale Air Quality (CMAQ) model for the year 2010 and a probabilistic analysis approach involving 29 years (1990–2018) of historical ozone observations. The modeling results reveal that the reduction in the peak ozone levels from total elimination of anthropogenic emissions within the model domain is around 13–21 ppb for the 90th−100th percentile range of the daily maximum 8-hr ozone concentrations across the contiguous United States (CONUS). Large reductions in the 4th highest 8-hr ozone are seen in the regions of West (interquartile range (IQR) of 17–33%), South (IQR 22–34%), Central (IQR 19–31%), Southeast (IQR 25–34%), and Northeast (IQR 24–37%). However, sites in the western portion of the domain generally show smaller reductions even when all anthropogenic emissions are removed, possibly due to the strong influence of global background ozone, including sources such as intercontinental ozone transport, stratospheric ozone intrusions, wildfires, and biogenic precursor emissions. Probabilistic estimates of the exceedances for several hypothetical thresholds of the 4th highest 8-hr ozone indicate that, in some areas, exceedances of such hypothetical thresholds may occur even with no anthropogenic emissions due to the ever-present atmospheric stochasticity and the current global tropospheric ozone burden.

Implications: Because air pollution is intricately linked to adverse health effects, National Ambient Air Quality Standards (NAAQS) have been established for criteria pollutants to safeguard human health and the environment. Areas not in compliance with the relevant standards are required to develop plans and policies to reduce their air pollution levels. Regional-scale air quality models are currently being used routinely to inform policies to identify the emissions reduction required to meet and maintain the NAAQS throughout the country. This paper examines the feasibility of the 4th highest ozone, which is used to derive the ozone design value for NAAQS, complying with various current and hypothetical 8-hr ozone thresholds over CONUS based on the information embedded in 29 years of historical ozone observations and two modeling scenarios with and without anthropogenic emissions loading.

摘要

区域空气质量模型被广泛用于了解臭氧未达标问题的空间范围和严重程度，并通过直接排放扰动设计符合相关臭氧标准所需的排放控制策略。在本研究中，我们使用 2010 年社区多尺度空气质量 (CMAQ) 模型的两次模拟和涉及 29 年（1990-2018）历史臭氧观测的概率分析方法，检查了地面臭氧的可管理部分。建模结果显示，在模型域内完全消除人为排放的臭氧峰值水平降低了约 13-21 ppb，在美国本土的每日最大 8 小时臭氧浓度的第 90-100 个百分位范围内（康纳斯）。西部（四分位距 (IQR) 为 17-33%）、南部（IQR 22-34%）、中部（IQR 19-31%）、东南（ IQR 25–34%) 和东北 (IQR 24–37%)。然而，即使消除了所有人为排放，该域西部的站点通常也显示出较小的减少，这可能是由于全球背景臭氧的强烈影响，包括洲际臭氧传输、平流层臭氧入侵、野火和生物前兆等来源排放。对第 4 高 8 小时臭氧的几个假设阈值超标的概率估计表明，在某些地区，

影响：由于空气污染与对健康的不利影响有着错综复杂的联系，因此制定了国家环境空气质量标准 (NAAQS) 来确定污染物的标准，以保护人类健康和环境。不符合相关标准的地区要制定计划和政策，以降低其空气污染水平。区域尺度的空气质量模型目前正被常规用于为政策提供信息，以确定在全国范围内满足和维持 NAAQS 所需的减排量。本文研究了第四高臭氧的可行性，用于推导出 NAAQS 的臭氧设计值，