Abstract
Abstract. Ozone formation regimes are closely related to the ratio of volatile organic compounds (VOCs) to NOx. Different ranges of HCHO/NO2 indicate three formation regimes, including VOC-limited, transitional, and NOx-limited regimes. Due to the unstable interactions between a diversity of precursors, the range of the transitional regime, which plays a key role in identifying ozone formation regimes, remains unclear. To overcome the uncertainties from single models and the lack of reference data, we employed two models, polynomial simulation and convergent cross-mapping (CCM), to identify the ranges of HCHO/NO2 across China based on ground observations and remote sensing datasets. The ranges of the transitional regime estimated by polynomial simulation and CCM were [1.0, 1.9] and [1.0, 1.8]. Since 2013, the ozone formation regime has changed to the transitional and NOx-limited regime all over China, indicating that ozone concentrations across China were mainly controlled by NOx. However, despite the NO2 concentrations, HCHO concentrations continuously exert a positive influence on ozone concentrations under transitional and NOx-limited regimes. Under the circumstance of national NOx reduction policies, the increase in VOCs became the major driver for the soaring ozone pollution across China. For an effective management of ozone pollution across China, the emission reduction in VOCs and NOx should be equally considered.
Highlights
With the significant improvement of PM2.5 pollution, surface ozone has become a major airborne pollutant across China since 2017 (Li et al, 2019a; Lu et al, 2020)
Due to the large area of China and potential spatial variations in ozone formation regimes, we respectively investigated ozone formation regimes in several major regions, including the North China Plain (NCP), Yangtze River Delta (YRD), Pearl River Delta (PRD), and Sichuan Basin (SCB), to explore the spatiotemporal variations in ozone formation regimes
To better understand the spatiotemporal variations in ozone formation regimes across China, we employed the thirdorder polynomial model and convergent cross-mapping (CCM) to estimate the range of the transitional regime from 2005 to 2019, the results of which were [1.0, 1.9] and [0.9, 1.9], respectively
Summary
With the significant improvement of PM2.5 pollution, surface ozone has become a major airborne pollutant across China since 2017 (Li et al, 2019a; Lu et al, 2020). In the past several years, spatiotemporal distribution of ozone concentrations (Wu and Xie, 2017; Shen et al, 2019a) and the influence of meteorological conditions (Chen et al, 2019c; Cheng et al, 2019, 2020) and anthropogenic emissions (Chen et al, 2019b; Cheng et al, 2018; Li et al, 2019a, 2020) on ozone concentrations have been massively studied. Due to the highly complicated ozone formation regime, effective ozone control remains challenging. Different from PM2.5, whose main precursors are NOx, volatile organic compounds (VOCs), and SO2, the formation and decomposition of ozone are closely related to two types of precursors, VOCs and NOx. There is a diversity of Published by Copernicus Publications on behalf of the European Geosciences Union
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