Impacts of anthropogenic and non-anthropogenic factors on summertime ozone variation from 2015 to 2020 in the Yangtze River Delta, China
- 1Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, Nanjing University of Information Science & Technology, Nanjing, China (linli_413@163.
- 2Environment Research Institute, Shandong University, Qingdao, China (linli_413@163.com)
The variability of ozone (O3) concentration in China has received wide attention since the emission reduction policies were implemented in 2013. At present, it is still a great challenge to clarify the causes of O3 change in the Yangtze River Delta (YRD) region. In this work, we applied the Community Multiscale Air Quality (CMAQ) model to investigate the impacts of precursor emissions (such as non-methane volatile organic compounds (NMVOCs) and nitrogen oxides (NOX)) and meteorological conditions on the summertime maximum daily 8-h average (MDA8) O3 variation in Nanjing, a megacity in YRD between 2015 and 2020. The meteorological contribution was quantified by the difference between the sensitive scenario fixing the anthropogenic emission at 2015 level while remaining the meteorology unchanged in 2020 and baseline scenario in 2015. The impact of anthropogenic emissions was then estimated by the difference between the total change of observed MDA8 O3 and the meteorological contribution. Compared with 2015, the observed MDA8 O3 in Nanjing decreased by 19.1 μg/m3 during August in 2020, with the meteorological conditions and anthropogenic emissions contributing 8.4 μg/m3 (44%) and 10.7 μg/m3 (56%), respectively. The anthropogenic emissions of VOCs and NOX in Nanjing in August 2020 decreased by 7.8% and 11.7%. Temperature, relative humidity (RH) and wind filed are key meteorological parameters affecting the O3 formation. The lower temperature (30.3 ℃ in 2020 compared with 32.4 ℃ in 2015) and higher RH (76.9% in 2020 and 56.9% in 2015) in early August (especially in 4-5) as well as the clean air mass brought by the stronger wind (5.1 m/s in 2020 and 2.5 m/s in 2015) during August 13-14 in 2020 mainly resulted in a drop of O3. The longer hydroxyl radical (OH) chain length and higher ozone production efficiency (OPE) indicate that the reduction of anthropogenic emissions accelerated the NOX cycle and makes O3 more sensitive to NOX. Using the EKMA diagram, we estimated that O3 formation has shifted from VOCs-limited in 2015 to a transition regime jointly controlled by VOCs and NOX in 2020. Our study is consistent with previous ones that in reducing the urban ozone pollution, both the precursor emissions and meteorological conditions should be considered that with the benefit of meteorological conditions, reasonable emission reduction measures could have a positive effect on the reduction of O3 concentration in Nanjing during August in 2015 and 2020.
How to cite: Li, L., Li, J., Qin, M., Xie, X., and Hu, J.: Impacts of anthropogenic and non-anthropogenic factors on summertime ozone variation from 2015 to 2020 in the Yangtze River Delta, China, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-11130, https://doi.org/10.5194/egusphere-egu23-11130, 2023.
