Sensitivity of summer ozone to precursor emission change over Beijing during 2010–2015: A WRF-Chem modeling study

Abstract

Beijing as the capital of China releases massive air pollutants and experiences the worsening summer O3 pollution recently. This study estimates Beijing ozone precursor emission, anthropogenic VOCs (AVOCs) being 325.3 kilotons in 2010, 231.8 kilotons in 2013 and 190.7 kilotons in 2015 and NOx being 211.3 kilotons in 2010, 238.3 kilotons in 2013 and 166.2 kilotons in 2015. Then, we conduct surface O3 simulation based on WRF-Chem through using different precursor emissions, to evaluate the influence of precursor control measures on Beijing O3. From 2010 to 2013, AVOCs reduction in Beijing would lead to O3 decrease in urban and suburban areas and O3 increase in some parts of northern rural areas; while from 2013 to 2015, AVOCs and NOx reductions would produce O3 increase in urban and northern suburban areas and O3 decrease in southern suburban and northern rural areas. Overall, the synergic reduction during 2010–2015 could effectively mitigate summer O3 pollution over Beijing, with daily maximum 1-h ozone (DAM1h O3) reduction exceeding 3 ppb. Finally, based on 2015 emission condition, 30% NOx and 30% VOCs emission reduction are further simulated to study O3-NOx-VOCs sensitivity over Beijing. The simulated DAM1h O3 reduction due to NOx- or VOCs-reduction shows that O3 is predominantly sensitive to VOCs in urban and northern suburban Beijing, but seems to be control more by the mixed chemistry in southern suburban and northern rural Beijing. However, NOx-sensitive condition is never found in rural Beijing. The distribution of simulated H2O2/HNO3 for the distinguished VOCs- and NOx-sensitive grids shows that 95th percentile for VOCs-sensitive distribution and 5th percentile for the NOx-sensitive distribution are 2.48 and 1.17 in all simulated days. According to the determined transition values, most Beijing is under VOCs-sensitive regime on the condition of 2015 precursor emission.