Exploring 2016–2017 surface ozone pollution over China: source contributions and meteorological influences

Abstract

<p><strong>Abstract.</strong> Severe surface ozone pollution over major Chinese cities has become an emerging air quality concern, raising a new challenge for emission control measures in China. In this study, we explore the source contributions to surface daily maximum 8-h average (MDA8) ozone over China in 2016 and 2017, the two years with the highest surface ozone averaged over Chinese cities in record. We estimate the contributions of anthropogenic, background, and individual natural sources to surface ozone over China, using the GEOS-Chem chemical transport model at 0.25° × 0.3125° horizontal resolution with the most up-to-date Chinese anthropogenic emission inventory. Model results are evaluated with concurrent surface ozone measurements at 169 cities over China and show general good agreement. We find that background ozone (defined as ozone that would be presented in the absence of all Chinese anthropogenic emissions) accounts for 90 % (49.4 ppbv) of the national March–April mean surface MDA8 ozone over China and 80 % (44.5 ppbv) for May–August. It includes large contributions from natural sources (80 % in March–April and 72 % in May–August). Among them, biogenic volatile organic compounds (BVOCs) emissions enhance MDA8 ozone by more than 15 ppbv in eastern China during July–August, while lightning NO<sub>x</sub> emissions and ozone transport from the stratosphere both lead to ozone enhancements of over 20 ppbv in western China during March–April. Over major Chinese city clusters, domestic anthropogenic sources account for about 30 % of the May–August mean surface MDA8 ozone, and reach 39–73 ppbv (38 %–69 %) for days with simulated MDA8 ozone > 100 ppbv in the Northern China Plain, Fenwei Plain, Yangtze River Delta, and Pearl River Delta city clusters. These high ozone episodes are usually associated with high temperatures, which induce large BVOCs emissions and enhance ozone chemical production. Our results indicate that there would be no days with MDA8 ozone > 80 ppbv in these major Chinese cities in the absence of domestic anthropogenic emissions. We find that the 2017 ozone increases relative to 2016 are largely due to higher background ozone driven by hotter and dryer weather conditions, while changes in domestic anthropogenic emissions alone would have led to ozone decreases in 2017. Meteorological conditions in 2017 favor natural source contributions (particularly soil NO<sub>x</sub> and BVOCs ozone enhancements) and ozone chemical production, increase thermal decomposition of peroxyacetyl nitrate (PAN), and further decrease ozone dry deposition velocity. More stringent emission control measures are thus required to offset the adverse effects of unfavorable meteorology such as high temperature on surface ozone air quality.</p>

Extending Ozone‐Precursor Relationships in China From Peak Concentration to Peak Time

“…There are other factors to be considered which introduce uncertainties (e.g., National Research Council, 1991). The standard deviation of the observed regional ozone peak concentrations is ~3 ppbv, similar to previous studies for longer periods (K. Li et al, 2019; Lu et al, 2019). The model‐simulated ozone systematic uncertainties are difficult to assess due in part to nonlinear chemistry (Liu et al, 2012).…”

Surface Ozone‐Meteorology Relationships: Spatial Variations and the Role of the Jet Stream

“…The O 3 ‐temperature relationship is varied equatorward of the midlatitudes; but, in the zonal mean, r ( T , O 3 ) decreases to negative values south of 30°N. Previous work by Rasmussen et al (2012) and Brown‐Steiner et al (2015) in the United States and Han et al (2020) and Lu, Zhang, Chen, et al (2019) in China showed a similar latitudinal gradient of r ( T , O 3 ). Despite the general tendency of a positive‐to‐negative relationship between O 3 and temperature with decreasing latitude, there are regions at low latitudes with significant positive correlations between O 3 and temperature (Central America, Sahel, the south coast of the Arabian Peninsula, Indo‐Gangetic Plain; Figure 3a).…”

Markedly Enhanced Levels of Peroxyacetyl Nitrate (PAN) During COVID‐19 in Beijing

“…The nested grid version of the model with a horizontal resolution of 0.25° × 0.3125° over eastern China (30–45°N, 108–125°E) was used. For anthropogenic emissions, we used the MEIC inventory (Zheng et al, 2018), which was developed by Tsinghua University (http://www.meicmodel.org/) and has been widely applied in simulating photochemical pollution (Gong & Liao, 2019; Hu et al, 2016; Lu et al, 2019) and haze events (Chen, Gao, et al, 2019; Chen, Zhu, et al, 2019; Qiu et al, 2017) in China.…”