Novel Method for Ozone Isopleth Construction and Diagnosis for the Ozone Control Strategy of Chinese Cities

Abstract

Ozone (O 3 ) isopleths describe the nonlinear responses of O 3 concentrations to changes in nitrogen oxides (NO X ) and volatile organic compounds (VOCs) and thus are pivotal to the determination of O 3 control requirements. In this study, we innovatively use the Community Multiscale Air Quality model with the high-order decoupled direct method (CMAQ-HDDM) to simulate O 3 pollution of China in 2017 and derive O 3 isopleths for individual cities. Our simulation covering the entire China Mainland suggests severe O 3 pollution as 97% of the residents experienced at least 1 day, in 2017, in excess of Chinese Level-II Ambient Air Quality Standards for O 3 as 160 μg•m −3 (81.5 ppbV equally). The O 3 responses to emissions of precursors vary widely across individual cities. Densely populated metropolitan areas such as Jing-Jin-Ji, Yangtze River Delta, and Pearl River Delta are following NO X -saturated regimes, where a small amount of NO X reduction increases O 3 . Ambient O 3 pollution in the eastern region generally is limited by VOCs, while in the west by NO X . The city-specific O 3 isopleths generated in this study are instrumental in forming hybrid and differentiated strategies for O 3 abatement in China.

Long-term ozone exposure associated cause-specific mortality risks with adjusted metrics by cohort studies: A systematic review and meta-analysis

“…50 This estimation was much higher than the 2019 GBD report: 0.31 (95% UI: 0.15–0.49) million, as had been highlighted in another recent study, 25 which should be attributed to the use of high HR value among all included studies. We had also found some other studies using one singular HR value for population risk estimations, 17, 74-77 but we would still encourage further relevant studies to consider multi-study pooled RRs, which could effectively reduce the potential biases from a single study. The adaptability of the pooled RRs could be verified from the coverage of exposure levels, as the 25 studies identified in our review had embraced a wide range of exposure concentrations (Supplementary Text S1) to encompass the global surface O 3 variability.…”

“…There were two major units used to quantify the surface O 3 concentrations, nmol mol -1 or parts per billion by volume mixing ratio (ppbV) more frequently used by atmospheric modelling researchers, 17, 18, 25 and milligram per cubic metre by mass concentration (µg/m 3 ) widely used by public health studies. 12 These two units are interchangeable to each other based on the ideal gas law PV n RT , if the air temperatures (T) and pressures (P) are given, as presented in eqs 1–4.…”

“…Surface O 3 , as a secondary photochemistry pollutant involving photolysis of NO 2 to trigger chains of radical reactions, has concentrations that will vary significantly between day and night-time, and between warm and cool seasons, as discussed by numbers of studies. 17, 28-31 Under this circumstance, various daily metrics to quantify the surface O 3 concentrations emerged due to series of considerations, which however brought in more difficulties to assimilate epidemiological evidences. The previous reviews simply pooled the reported risk association strengths without adjusting the diverse metrics, 15, 16 which we thought was a fatal defect requiring improvements.…”

“…Some deficiencies are spotted in the two reviews for long-term O 3 exposure-associated mortality risk studies, 15, 16 the primary issue of which is the inconsistent use of various O 3 exposure metrics; however, no other reviews are found to remedy these flaws. As a secondary photolytic gaseous air pollutant, the warm-season and diurnal concentrations of surface O 3 will be much higher than cool-season and nocturnal concentrations, 17, 18 and thus the average and peak metrics of O 3 concentrations shall be of drastically different realistic implications. 19 Under this circumstance, directly pooling the relative risks scaled in different metrics might lead to biases.…”

Trends and Variability of Ozone Pollution over the Mountain-Basin Areas in Sichuan Province during 2013–2020: Synoptic Impacts and Formation Regimes

“…Previous studies showed that the ozone chemical regime in most industrial cities in China is more likely to be VOC-limited while the rural area is in a NO x -limited or transition regime [13]. Studies also suggested that the formation regime in most areas in Sichuan Province except for Chengdu is NO x -limited [31]. In Chengdu, the ozone formation regime is categorized as VOC-limited for most of the time [32,33].…”