Characterization of Fe-containing particles in Chengdu, southwest China, using single-particle aerosol mass spectrometry

Abstract

Single-particle aerosol mass spectrometry was used to study the characteristics of Fe-containing particles during winter in Chengdu, southwest China. The mass concentrations of PM_2.5 and PM₁₀ during the study period were 64 ± 38 and 89 ± 49 µg/m³, respectively, and NO₂ and particulate matter were high compared with most other regions of China. The Fe-containing particles were divided into seven categories with different mass spectra, sources and aging characteristics. The highest contribution was from Fe mixed with carbonaceous components (Fe-C, 23.1%) particles. Fe was more mixed with sulfate than nitrate and therefore the contribution of Fe mixed with sulfate (Fe-S, 20.7%) particles was higher than that of Fe mixed with nitrate (Fe-N, 12.5%) particles. The contributions from Fe-containing particles related to primary combustion were high in the small particle size range, whereas aged Fe-containing particles and dust-related particles were mostly found in the coarse particle size range. The air masses mainly originated from the west and east of Chengdu, and the corresponding PM_2.5 concentrations were 79 ± 36 and 55 ± 36 µg/m³, respectively. The west and east air masses showed stronger contributions of Fe-containing particles related to biomass burning (Fe-B) and fossil fuel combustion (Fe-C and Fe-S) particles, respectively. The southwest area contributed the most Fe-containing particles. Future assessments of the effects of Fe-containing particles during heavy pollution period should pay more attention to Fe-C and Fe-S particles. Emission-reduction of Fe-containing particles should consider both local emissions and short-distance transmission from the surrounding areas.