Assessing the ecological risk of surface ozone and its impact on crop yields in China throughout the entire year of the COVID-19 pandemic in 2020

Abstract

In 2020, the outbreak of the novel coronavirus (COVID-19) spread across China and the globe. In response to this severe challenge, China swiftly enforced a series of rigorous lockdown measures, significantly improving air quality. However, O₃ levels increased, and their potential impact on ecosystems remains unclear. Therefore, this research systematically assessed the ecological risks from O₃ during the warm season of 2020 across China and further quantified its effect on the yields of major crops. The findings revealed that during the warm season of 2020, the values of the five ecological risk indicators across China were 42.1 ± 0.5 ppb for M12, 43.0 ± 0.5 ppb for M7, 32.5 ± 1.3 ppm h for SUM06, 22.1 ± 0.7 ppm h for AOT40, and 27.2 ± 1.0 ppm h for W126. The highest risks were observed in the Beijing-Tianjin-Hebei, followed by the Yangtze River Delta and Central China. During the main crop growing seasons, the national average AOT40 values were 9.3 ± 0.3 ppm h for winter wheat, 11.6 ± 0.6 ppm h for spring wheat, 10.2 ± 0.4 ppm h for single rice, 5.8 ± 0.4 ppm h for double-early rice, and 7.9 ± 0.4 ppm h for double-late rice. The projected ranges of O₃-induced national relative yield losses for wheat and rice were 20.4–32.9% and 3.1–9.7%, respectively. Correspondingly, the total national yield losses were 6.61 × 10⁷ metric tons and 1.37 × 10⁷ metric tons, respectively. Our findings reveal that O₃ posed significant harmful risks to ecosystems during the COVID-19 pandemic. These results not only highlight the threat of O₃ to agricultural production but also offer a scientific foundation to develop enhanced policies for controlling air pollution effectively.