Influence of ship emissions on PM2.5 in Shanghai: From COVID19 to OMICRON22 lockdown episodes

Air quality has improved significantly in the recent 10 years, but there is still a wide gap compared to the WHO AQG level. The concentration of PM2.5 during OMICRON in 2022 was 21.7 μg m−3, which marked the lowest historical record under the lockdown status of the whole urban area, still exceeding the national Level 1 standard. PMF results have shown that the contributions of ship emissions increased from 2020 to 2022 during the historical OMICRON episodes, with growth rates of 9.7% and 10.7%, respectively. AIS data indicated an overall increase in shipping activities around Shanghai during the OMICRON22-2021 period. The strict control of urban activities during the silent period in 2022 reduced ship activities by 21.0% and 31.8% in the ChongMingMsa and WuSongMsa ranges close to Shanghai, respectively. However, significant growth was observed in the sea regions of ShanghaiMsa and ZhouShan-NingBoMsa, with growth rates of 44.2% and 33.7%, respectively. The total number of anchored ships in the sea region of YangShanGangMsa increased by 56.7%. CWT analysis indicated that the lockdown measures only changed the distributions of the ship emissions. More forceful measures for the reductions of the ship emissions should be considered. [Display omitted] •PM2.5 concentration under the lockdown status still exceeded the national Level 1 standard and WHO AQG level.•The concentration of ship emission marker-Vanadium decreased with the benefit of ECA,but increased after 2020.•No obvious reduction of ship activities and emissions were found around Shanghai during OMICRON episode.•Epidemic events changed the distributions of the ship activities and the related emissions.