Estimation of Size-Resolved Ambient Particle Density Based on the Measurement of Aerosol Number, Mass, and Chemical Size Distributions in the Winter in Beijing

• Published in: Environmental science & technology Vol. 46; no. 18; pp. 9941 - 9947
• Main Authors: Hu, Min, Peng, Jianfei, Sun, Kang, Yue, Dingli, Guo, Song, Wiedensohler, Alfred, Wu, Zhijun
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 18.09.2012
• Subjects: Aerosols; Aerosols - analysis; Air Pollutants - analysis; Air Pollution - analysis; Airborne particulates; Applied sciences; Atmospheric aerosols; Atmospheric pollution; China; Density; Exact sciences and technology; Measurement; Particle Size; Particulate Matter - analysis; Pollutants physicochemistry study: properties, effects, reactions, transport and distribution; Pollution; Seasons; Size; Winter; Asia; China; Beijing China; Particle size distribution; High atmospheric pollution episode; Winter; Megacity; Aerosols; Air pollution; Air quality; Chemical composition; Urban area; Particle number
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es204073t

Simultaneous measurements of aerosol size, distribution of number, mass, and chemical compositions were conducted in the winter of 2007 in Beijing using a Twin Differential Mobility Particle Sizer and a Micro Orifice Uniform Deposit Impactor. Both material density and effective density of ambient particles were estimated to be 1.61 ± 0.13 g cm–3 and 1.62 ± 0.38 g cm–3 for PM1.8 and 1.73 ± 0.14 g cm–3 and 1.67 ± 0.37 g cm–3 for PM10. Effective density decreased in the nighttime, indicating the primary particles emission from coal burning influenced the density of ambient particles. Size-resolved material density and effective density showed that both values increased with diameter from about 1.5 g cm–3 at the size of 0.1 μm to above 2.0 g cm–3 in the coarse mode. Material density was significantly higher for particles between 0.56 and 1.8 μm during clean episodes. Dynamic Shape Factors varied within the range of 0.95–1.13 and decreased with particle size, indicating that coagulation and atmospheric aging processes may change the shape of particles.