Fig. 4: Impact of emission sources on OA air pollution.
From: Substantial contribution of transported emissions to organic aerosol in Beijing
a–d, Concentration time series (a) and relative contribution of sources to OA at different pollution levels (b–d, daily averages). The measurement period is separated into winter (20 November 2019 to 25 January 2020, b), COVID lockdown (26 January 2020 to 30 April 2020, c), summer (1 May 2020 to 2 July 2020, d). The most prominent OA sources are disproportionately important during severe haze episodes, with solid fuel (especially secondary SFOA) comprising more than half of OA during wintertime haze events and aromatic-dominated SOA playing a major role during summertime haze events.
