Abstract. An inventory of anthropogenic primary aerosol emissions in China was developed for 1990-2005 using a technology-based approach. Taking into account changes in the technology penetration within industry sectors and improvements in emission controls driven by stricter emission standards, a dynamic methodology was derived and implemented to estimate inter-annual emission factors. Emission factors of PM 2.5 decreased by 7%-69% from 1990 to 2005 in different industry sectors of China, and emission factors of TSP decreased by 18%-80% as well, with the measures of controlling PM emissions implemented. As a result, emissions of PM 2.5 and TSP in 2005 were 11.0 Tg and 29.7 Tg, respectively, less than what they would have been without the adoption of these measures. Emissions of PM 2.5 , PM 10 and TSP presented similar trends: they increased in the first six years of 1990s and decreased until 2000, then increased again in the following years. Emissions of TSP peaked (35.5 Tg) in 1996, while the peak of PM 10 (18.8 Tg) and PM 2.5 (12.7 Tg) emissions occurred in 2005. Although various emission trends were identified across sectors, the cement industry and biofuel combustion in the residential sector were consistently the largest sources of PM 2.5 emissions, accounting for 53%-62% of emissions over the study period. The non-metallic mineral product industry, including the cement, lime and brick industries, accounted for 54%-63% of national TSP emissions. There were no significant trends of BC and OC emissions until 2000, but the increase after 2000Correspondence to: K. B. He (hekb@tsinghua.edu.cn) brought the peaks of BC (1.51 Tg) and OC (3.19 Tg) emissions in 2005. Although significant improvements in the estimation of primary aerosols are presented here, there still exist large uncertainties. More accurate and detailed activity information and emission factors based on local tests are essential to further improve emission estimates, this especially being so for the brick and coke industries, as well as for coalburning stoves and biofuel usage in the residential sector.

Secondary organic aerosol (SOA) produced by atmospheric oxidation of primary emitted precursors is a major contributor to fine particulate matter (PM2.5) air pollution worldwide. Observations during winter haze pollution episodes in urban China show that most of this SOA originates from fossil-fuel combustion but the chemical mechanisms involved are unclear. Here we report field observations in a Beijing winter haze event that reveal fast aqueous-phase conversion of fossil-fuel primary organic aerosol (POA) to SOA at high relative humidity. Analyses of aerosol mass spectra and elemental ratios indicate that ring-breaking oxidation of POA aromatic species, leading to functionalization as carbonyls and carboxylic acids, may serve as the dominant mechanism for this SOA formation. A POA origin for SOA could explain why SOA has been decreasing over the 2013–2018 period in response to POA emission controls even as emissions of volatile organic compounds (VOCs) have remained flat.