Morphology, composition and mixing state of individual carbonaceous aerosol in urban Shanghai
1Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China
2Research Institute for the Global Environment Change, Fudan University, Shanghai 200433, China
3Environment Research Institute, Shandong University, Jinan Shandong 250100, China
4College of Environment and Life, Dalian University of Technology, Dalian Liaoning 116024, China
5Key Laboratory of Data Analysis and Applications, The First Institute of Oceanography, State Oceanic Administration, Qingdao, 266061, China
Abstract. A total of 834 individual aerosol particles were collected during October and November 2010 in urban Shanghai, China. Particles were sampled under different weather and air quality conditions. Morphologies, compositions and mixing states of carbonaceous aerosols were investigated by transmission electron microscopy (TEM) coupled with energy-dispersive X-ray (EDX). Structures of some particles were verified using selected-area electron diffraction (SAED). Among the aerosol particles observed, carbonaceous aerosols were mainly categorized into four types: polymeric organic compound (POC), soot, tar ball, and biogenic particle. Based on the detailed TEM-EDX analysis, most of the particles were coated with secondary organic aerosols (SOA), which commonly formed through condensation or heterogeneous reactions of precursor gases on pre-existing particles. Aged particles were associated with days with low wind velocities, showed complex structures, and were bigger in size. The internally mixed particles of sulphates, organics and soot were encountered frequently. Such internally mixed particles may be preferentially formed during a stagnated air mass during serious pollution events, such as on 13 November. Although relative number counts varied with different species, sulphates (38–71%) and soot (11–22%) constituted the most dominant species observed in the samples. However, soil-derived particles (68%) were relatively more frequently observed on the sample collected on 12 November during a dust storm.